2019-20 West Central Montana Avalanche Conditions---!!! CONSIDERABLE !!!---3/31/2020

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 04, 2020 07:01 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 4, 2020 View Full Advisory » The avalanche danger for the West Central Montana backcountry is CONSIDERABLE. Large dangerous avalanches are likely in the mountains today. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 4, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack We are currently under partly cloudy skies with mountain temperatures in the 20’s and winds gusting into the 40’s out of the south. Over the past 24 hours, we have had strong SW winds, accompanied by a couple of inches of snow in favored locations. The good news is that it is starting to look like winter in the mountains with skiing and riding conditions greatly improved over the past few days. The bad news is that avalanche conditions are currently hazardous. Numerous human triggered and naturally occurring avalanches have been reported over the past three days, and I would expect the same this weekend. Large dangerous avalanches on slopes above 5500 feet in elevation and over 30 degrees in steepness are likely today. Our primary avalanche concern is persistent slab avalanches. Since the new year, we have received 2-3 feet of heavy snow that is sitting on top of multiple weak layers. The first is depth hoar sitting near the ground, and the second is a surface hoar, crust, near-surface facet layer buried below 2-3 feet of dense snow. Strong winds and snow are forecasted today, further stressing these weak layers. Getting caught in a persistent weak layer avalanche would be deadly. Our secondary concern is wind slab avalanches. Winds have been strong since the new year and are forecasted to increase today. Keep an eye out for wind slabs which look like bulbous pillowy features throughout the mountains. The strong winds have also created large cornices, which have the potential to break back further than expected. While on ridge lines give cornices a wide berth, as a falling cornice can trigger wind slab avalanches or persistent slab avalanches. Bottom line: There is plenty of fun to be had skiing and riding on slopes below 30 degrees. Stay off of and well away from avalanche terrain as avalanches can be remotely triggered. This is a snowpack I do not trust, and getting caught in an avalanche today would be deadly. Avalanche and Weather Outlook This morning a cold front is rolling in with WSW winds 30-50 mph and gusts up to 80mph. 2 to 7 inches of snow is expected today. Mountain temperatures will be in the mid 20’s to low 30’s with wind chill values as low as -10 F. The avalanche danger will rise throughout the day with strong winds and more snow. Watch out for red flags such as cracking, collapsing, and recent avalanches. As always, if you make it out, please, feel free to share what you find on our public observations page. Ski and ride safe. The post Avalanche Advisory for January 4, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 07, 2020 07:07 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 7, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is HIGH on all slopes over 5500 feet in elevation. All other slopes the danger is CONSIDERABLE. New snow and winds are creating large dangerous avalanches. Travel in avalanche terrain is not recommended. Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for January 7, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures range from 26F to 33 F in the region. In the Bitterroot, winds are 7 mph with gusts of 17 out of the S. In the northern part of the advisory area, winds are 16 mph and gusting 27 mph out of the SW. Snotels are reporting between .6 and 2.1 inches of SWE for the last 24 hours for 6 to 12 inches of new snow. Yesterday a system of subtropical moisture entered the forecast area. Winds scoured many slopes over the weekend. The new snow from this system is loading leeward slopes and creating very dangerous avalanche conditions. Yesterday, Jeff and I were getting shooting cracks on wind loaded slopes. Overnight with the additional loading of snow, these wind slabs will be larger and more easily triggered. The new snow is falling on a poor snowpack structure that has the potential to create large avalanches. We are still getting propagations in our stability tests on the buried surface hoar crust combinations and a layer of depth hoar. The new snow will make these layers more sensitive today. The primary avalanche problem today is persistent slabs. There are two layers of concern in our snowpack, a layer of surface hoar and near-surface facets below a thin crust that the New Year’s storm buried about 2 to 3 feet deep. This layer failed several times, producing both natural and human triggered avalanches during the New Years’ cycle. The other is a layer of facets or depth hoar below a crust near the bottom of our snowpack. We are still getting these to fail in stability tests. There is the possibility of triggering the whole season’s snowpack in a very large slide on this layer near the ground. The second avalanche problem is wind slabs. Leeward slopes have been loaded and are easily triggered. Identify wind loaded terrain and avoid traveling on or below these slopes today. The third avalanche problem is new snow. Trigging storm slabs that step down into deeper buried weak layers today is possible. Avoid slopes over 30 degrees. Bottom line: There are very dangerous avalanche conditions today. Do not travel on or below wind loaded terrain. Travel in avalanche terrain is not recommended. Stick to lower angled sheltered slopes that are not connected to steep terrain because it is possible to trigger our buried weak layers remotely from the side, below, or above. The buried weak layers in our snowpack have the potential to create large dangerous avalanches, proof of this comes from observations of the natural and human triggered slides over New Years and the weekend(see public observations and report). Everyone in your group should have a beacon, shovel, and probe. Only one person on a slope at a time. Avalanche and Weather Outlook More snow and rising temperatures predicted today. Watch out for red flags such as cracking, collapsing, and recent avalanches. The avalanche danger will rise throughout the day with wind and more snow. See the forecast. Thank you to everyone who has been sending in public observations. As always, if you make it out, please, feel free to share what you find on our public observations page. Ski and ride safe. The post Avalanche Advisory for January 7, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 08, 2020 07:02 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 8, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is CONSIDERABLE. Dangerous avalanche conditions in the mountains exist and travel in avalanche terrain is not recommended. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 8, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures are in the low 20’s with increasing strong winds out of the WSW. In the past 24 hours favored locations have received a few inches of snow. Yesterday there was a fatal avalanche at Silver Mountain Ski Resort, a close neighbor to us in Kellogg, Idaho. Our deepest condolences go out to the avalanche victims and their friends and family. We have now had two separate avalanche accidents during the past week in and around our forecast area, totaling 4 deaths. The mountains are screaming at us to stay out of avalanche terrain. Before the New Year there was barely enough snow to ski or sled. On New Year’s Eve, it began snowing and has not stopped. We have received over 7 inches of Snow Water Equivalent (SWE) in some locations, which translates to 2-4 feet of heavy snow. This is a ton of weight, stressing multiple weak layers buried in our snowpack, primed for a deadly avalanche. Sometimes you cannot ski or ride in avalanche terrain, right now is that time. Our primary avalanche concern is persistent slab avalanches. There are two distinct buried weak layers in our snowpack capable of producing avalanches. The first is a surface hoar, crust, near-surface facet combo buried about 2-4 feet deep, and the second is weak sugary depth hoar and facets near the ground. Both of these layers have produced numerous natural and human triggered avalanches over the past week and will continue to do so. Our secondary avalanche concern is wind slab avalanches. It is forecasted to be windy and snowing today, creating wind slabs in leeward terrain. Wind slabs can be easily identified by looking for bulbous and pillowy features located on the leeward side of ridges or in cross-loaded terrain. Remember, even a small wind slab can step down and create a deadly persistent slab avalanche. Bottom line: If you are going out in the mountains today, stay out of and well away from avalanche terrain. Stay off of and far away from slopes approaching 30 degrees in steepness, as avalanches can be remotely triggered. Also, make sure you and all of your partners have a beacon, probe, shovel, and know how to use them. The kicker is that if you need to use this gear to dig out your partner, it will most likely be a body recovery. Avalanche and Weather Outlook Increasing WSW winds with gusts to 66mph are expected today. Average wind speeds are forecasted to be 20-30 mph with wind chill values below 0. 2-7 inches of snow are expected today with a few more inches tonight. The avalanche danger will rise with new snow and more wind. Pay attention to red flags such as cracking, collapsing, wind transported snow, and recent avalanches. Any and all observations are greatly appreciated. If you get out in the mountains please send us information here. Thank you very much to those of you who have been sending in observations as it is very helpful. Ski and ride safe. The post Avalanche Advisory for January 8, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 09, 2020 06:38 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 9, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is CONSIDERABLE. Dangerous avalanche conditions today. Human triggered avalanches are likely, and natural avalanches are possible. Sticking to simple low angle terrain is critical for the complex problems we have today. Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for January 9, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures range from 11 F to 22 F in the region. In the Bitterroot, winds are 8 mph with gusts of 11 out of the SSW. In the northern part of the advisory area, winds are 11 mph and gusting 19 mph out of the W. Snotels are reporting between .2 and .4 inches of SWE overnight for 2 to 4 inches of new snow. The snowpack is trying to adjust to the new load of snow. Yesterday, we saw evidence in natural slides from the last two days that our buried weak layers can still not be trusted. We are still getting propagations in our pit tests. The weight of a skier or rider on a steep slope(>30) is likely to be the tipping point to cause a large dangerous avalanche. The primary avalanche problem is persistent slabs. The buried surface hoar is now 3 to 4 feet deep in our snowpack. We got a report of a natural slide yesterday that released in the upper 2 feet of new snow and then stepped down to this layer. The depth hoar near the bottom of the snowpack is still reactive in our pit tests. The second avalanche concern is wind slabs. There were strong winds yesterday, and we saw active wind loading of leeward slopes. Avoid wind loaded slopes. Even a small wind slab can tip the scales and step down into the persistent weak layers and cause a large dangerous avalanche. The last avalanche problem is storm slabs. New snow takes time to bond to old snow surfaces. These slabs, if triggered, can step down into deeper weak layers and cause a large dangerous avalanche. The avalanche problems we have today are complex, so choose simple terrain. The choice for today are slopes less than 30 degrees that are smooth, without likely trigger points(rocks, cliff bands, and convexities) and sheltered from the wind. The bottom line: The snowpack structure can not be trusted. The buried weak layers are capable of producing large dangerous avalanches. Choose slopes less than 30 degrees that are not connected to steeper terrain. You can trigger an avalanche from below, the side, or from a ridge. You can trigger an avalanche from flat ground if the slope is connected to steep terrain (> 30 degrees). The riding is good on simple low angle slopes. Get the forecast. Carry a shovel beacon and probe. Only have one person on a slope at a time. Take a class, here is a link to our events and classes. Avalanche and Weather Outlook Banded snow showers today with gusts in the 30 mph above 6000 feet. See the forecast. A short break from snow on Friday. The avalanche danger will rise with new snow and more wind. Pay attention to red flags such as cracking, collapsing, wind transported snow, and recent avalanches. I will issue the next advisory on January 11, 2020. Any and all observations are greatly appreciated. If you get out in the mountains please send us information here. Thank you very much to those of you who have been sending in observations as it is very helpful. Ski and ride safe. The post Avalanche Advisory for January 9, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 14, 2020 06:57 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 14, 2020 View Full Advisory » The avalanche danger for the West Central Montana backcountry is CONSIDERABLE in terrain above 6500 feet and is MODERATE in non-wind loaded terrain below 6500 feet. Approach avalanche terrain with caution as triggering an avalanche would be unsurvivable. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 14, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures currently range from the single digits to teens with light winds out of the SW. Snotel sites report .1-.3 inches of SWE in the past 24 hours or about 2-4 inches of new snow accompanied by wind. The best way to describe our snowpack is untrustworthy. Since the New Year, we have been bombarded with snow and wind. This has put a tremendous amount of stress on the underlying weak snowpack. We have multiple faceted weak layers buried below a thick and heavy slab of snow. Numerous avalanches this past week have produced impressive results. These include: A natural slide in the Southern Missions that propagated across a ridge line, over 500′ wide, and stepped down 3-4 feet to buried surface hoar A skier triggered 2+ feet deep avalanche that ran on a 32º slope in the central Bitterroot. A ski cut triggered slide at Lost Trail, over 100′ wide that ran at ground on basal facets. This slab was around 4 feet thick. A skier triggered slide in the southern Missions. 500′ wide with a 7′ crown at the deepest part. It stepped down twice, to a crust/facet layer 18″ from the ground and then to ground. It was triggered from under 30º on the 8-foot thick section, and the upper bed surface was 31º. It was not preceded by whumphing and took place on a slope with trees that did not have flagging. This is just a list of reported avalanches. Numerous avalanches have occurred since the New Year, but are hard to identify due to poor visibility, wind and snow covering up avalanche activity. Triggering a large avalanche is still a concern. Our primary concern is persistent slab avalanches. This avalanche problem is most pronounced in upper elevation terrain above 6500 ft on slopes over 30 degrees in steepness. Avoid runout zones of avalanche paths as remotely triggering an avalanche is a concern. This avalanche problem is becoming harder to predict as red flags such as cracking and collapsing are becoming less frequent. If you get caught in a persistent slab avalanche, it will be unsurvivable. Our secondary concern is wind slab avalanches. Yesterday the winds were whipping from multiple directions creating wind slabs. Today snow and winds are forecasted, creating fresh wind slabs. Be on the lookout for stiff feeling snow, cracking, and collapsing in your travels. These are signs of wind effected snow. Wind slabs are bulbous and pillowy and are found on the leeward side of ridges or in cross-loaded terrain. Any small wind slab has the potential to step-down, creating a deadly persistent slab avalanche. Bottom line: Give the snowpack some time to heal up. We have a complex and dangerous snowpack that makes me shudder when thinking about being near upper elevation wind-loaded avalanche terrain. A mentor of mine told me not to try and outsmart a persistent slab avalanche problem, and you may have a long life in the mountains. Avalanche and Weather Outlook Today we are expecting increasing winds out of the W with 5-9 inches of snow through this evening. See the forecast here. Any new snow and wind will make the avalanche danger rise. Pay attention to red flags such as cracking, collapsing, wind transported snow, and recent avalanches. Any and all observations are greatly appreciated. If you get out in the mountains please send us information here. Thank you very much to those of you who have been sending in observations as it is very helpful. Ski and ride safe. Education Opportunities: Tomorrow January 15th, our friends at LB Snow will be hosting us for an Avalanche Awareness Talk from 6-7:30pm. Feel free to swing by and brush up on your avalanche knowledge. More details can be found here. Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for January 14, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 16, 2020 06:50 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 16, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is CONSIDERABLE in wind loaded terrain above 6500 feet and stout MODERATE in all other terrain. Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for January 14, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Up to a foot of low-density new snow is being blown around by moderate to strong winds, creating windslab on a variety of surfaces. These are forming slabs that are sensitive to triggering and likely to be triggered by skiers and snowmobilers. Mostly smaller in size, D1-D2, these wind slabs could step down to deep, persistent weak layers that continue to plague our snowpack. The base of our snowpack is still rotten, unsupportive, and weak. It is getting buried deeper and harder to trigger, but still showing a high propensity for propagation. The slab on top is getting thicker and harder, which means that if these weak layers fail, avalanches will be bigger and more destructive. It is going to require care and patience for a while still. Warning signs such as whumphing and cracking on this layer have mostly disappeared, which could lead to a false sense of security. If it fails, it will likely be without warning. While the likelihood of triggering a slide on this layer is slowly decreasing, the consequences are increasing. Remember, moderate means it is possible to trigger an avalanche. If you find the weak spot or trigger point, the resulting avalanche will most likely not be survivable. This slide at Lost Trail shows what this layer can do. The bottom line: Large deadly avalanches are possible, and their predictability is decreasing. Be very cautious in the backcountry, stick to simple terrain, mostly under 30º, and investigate the snowpack for depth hoar. Assess snow depth, shallow areas may be easier to trigger. Avoid steep wind loaded terrain. Enjoy powder in meadows and low angle trees. Always carry your safety equipment — beacon, probe, and shovel. If you want to increase your competence in avalanche terrain, check out our education page. Help us understand the snowpack, submit your observations here. Ski and ride safe The post Avalanche Advisory for January 16, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 18, 2020 07:05 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 18, 2020 View Full Advisory » The avalanche danger for the West Central Montana backcountry is MODERATE. Approach avalanche terrain with caution as triggering a massive avalanche is possible. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 18, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures are currently in the single digits to teens with wind chill values below 0 F. Ridge top winds are predominantly out of the WSW with averages in the teens with gusts up to 20 mph. A skiff of snow has fallen overnight in favored locations. We are in the midst of a break in the action with snowfall. Since the New Year, we have received a tremendous amount of new snow that made avalanche conditions spike. During the past few days, snow has tapered off, giving the snowpack a chance to adjust. The snowpack is starting to stabilize but the green light is not on just yet. There is a possibility of triggering a catastrophic avalanche, so play your cards wisely. Our primary concern is persistent slab avalanches. Since the New Year, we have had numerous natural and human triggered avalanches failing on buried weak layers. The last report of a persistent slab avalanche was from 1-14-20 in the Southern Bitterroot. Signs are pointing towards a strengthening snowpack, but it is still possible to trigger a persistent slab avalanche. Snowpit scores in some areas are showing that the weak layers are gaining strength. We are no longer experiencing red flags, which can trick you into thinking the snowpack is safe. Therefore, you must do your homework and dig snow pits to look for instabilities. There is a possibility of triggering a persistent slab avalanche, and likely spots would be thinner rocky areas or on rollovers. Another likely trigger spot would be an area with a thinner snowpack, about 3-4 feet deep. Deciding to ski or ride in avalanche terrain safely takes into account many factors to deem the slope is stable. If you make the wrong call, it would be catastrophic, do not blow it. Bottom Line: Do not just jump into steep, complex terrain. First, check out some lower consequence slopes around 30 degrees. Dig multiple snow pits to the ground, look for buried weak layers such as depth hoar, surface hoar, and crusts in the lower portion of the snowpack. If you find any of these layers, see how they are reacting. Just remember if you do trigger an avalanche failing on a buried weak layer, it could release the entire season snowpack. Avalanche and Weather Outlook Today mountain temperatures are expected to be 20-30F with winds in the teens and gusts up to 30mph on the highest ridge tops. There will be snow showers with up to a couple inches of snow by this evening. A ridge of high pressure is moving in on Sunday and Monday with warming temperatures. Our next chance of light snow is expected on Tuesday. Any observations are much appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. If you have taken a Level 1 avalanche course and want to get more avalanche knowledge. We still have spaces on our Level 2 avalanche course next weekend located at Yurtski in the Swan Range! Take a look here for a full list of courses. The post Avalanche Advisory for January 18, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 21, 2020 06:45 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 21, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is stout MODERATE in areas with a shallow snowpack. Areas with a thick base are less touchy. Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for January 21, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. In areas of shallower snowpack, roughly 5 feet or less, there is a higher likelihood of triggering avalanches on the persistent weak layers at the base of the snowpack. A remotely triggered slide Sunday near Lost Trail ski area tells us these layers are still active. This ran on depth hoar, near the ground with a four-foot slab, in trees. The southern Bitterroot has the shallowest snowpack in the forecast area and, as a result, has the highest avalanche likelihood. Mid elevation slopes throughout the forecast area where the snowpack is thinner may have similar probability. In areas with a thick base, such as the central Bitterroot and Seeley lake zone, the snowpack has stabilized, and the likelihood of triggering an avalanche is getting lower. In some places, the snowpack is up to 7 feet deep. However, the possibility to trigger a slide in these areas may still exist, especially near rock outcroppings and thin areas. Freezing levels are forecast to rise to 5500 feet today and may create a thaw instabilities, increasing the likelihood of avalanches. Take extra caution if you notice dripping trees, rollerballs, or packable snow. With the freezing level forecast to rise to 6500 feet Wednesday night, and precipitation throughout the week, expect avalanche danger to increase. Conditions such as this may reawaken the depth hoar layer and result in large avalanches. Always carry your safety equipment — beacon, probe, and shovel. If you want to increase your competence in avalanche terrain, check out our education page. Join us for an avalanche awareness talk from 7:00 to 8:00 pm Wednesday the 22nd at Trailhead. Your avalanche, snowpack, and weather observations help us keep the public informed and assist us when generating the advisory. Please help us continue to better understand the snowpack, and submit your observations here. Ski and ride safe The post Avalanche Advisory for January 21, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 23, 2020 06:42 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 23, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is MODERATE. Areas with a shallow snowpack and thin spots are of higher concern for triggering an avalanche. Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for January 23, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. In areas of shallower snowpack, roughly 5 feet or less, there is a possibility of triggering avalanches on the persistent weak layers at the base of the snowpack. A remotely triggered slide Sunday near Lost Trail ski area tells us these layers are still active in specific locations. This ran on depth hoar, near the ground with a four-foot slab, in trees. Yesterday in the Rattlesnake and southern Missions, we found depth hoar in several locations, and it is safe to assume that it is present under most of the snowpack in the forecast area. This persistent weak layer showed increased strength in stability tests since last week, indicating it is slowly gaining strength. However, the structure remains very poor and capable of sustaining a propagation if a collapse is triggered. Thin areas where wind scouring has occurred, near buried trees and bushes, and rock outcroppings are the most likely places to trigger it. In the past 24 hours, we received a few inches of snow throughout the forecast area. It was accompanied by moderate to strong winds, and wind slabs have developed on leeward aspects. Steep wind-loaded pockets were cracking and shifting when tested yesterday, and wind slabs released naturally in the last 24-48 hours in both the Rattlesnake and Southern Missions. Continued snow and wind will build more wind slab over the next couple of days. It is possible to trigger windslab in steep leeward terrain near ridge tops. Conditions vary quite a bit throughout the forecast area, mostly based on snow depth. Some spots have been favored with snow, and others haven’t. Here’s a quick breakdown of what we’ve seen: The Southern Bitterroot, around Lost Trail, has the shallowest snowpack in the area and the worst structure. There have been three slides to ground here in the past 12 days, that we know of. Widespread surface hoar was reported this last weekend, so new snow and wind slabs may be sitting on this persistent weak layer. I would take the greatest care in this area The Central Bitterroot, Twin Lakes to around the Gash, has received quite a bit more snow, with depths to 6+ feet, and has better structure as a result. It is unlikely to trigger a slide in the deep areas. However, we are still seeing propagation propensity in thin spots, and with the base structure, there is a possibility these could propagate to deeper areas if triggered. No recent slides on the basal facets that we know of. Wind slab has been building, and at least one released in the last week on steep, unsupported terrain. Warm temps have done the low elevation snowpack some good, consolidating it and making it more supportive. Lolo has been getting its share of snow. Lower elevations where the snowpack is thinner showed a possibility of propagation this past weekend, while higher deeper areas showed lower propagation likelihood. Warm temps have likely put a crust on most surfaces due to the low elevation. The Rattlesnake has a shallow snowpack relative to other areas, ranging from 3-5 feet. There has been considerable consolidation in the snowpack in the past week and widespread wind effect. Except for isolated wind slab, I didn’t find any concerning layers in the upper snowpack yesterday. The depth hoar is present everywhere. It’s faceting further in thin areas and rounding a bit where it’s deep. It’s still not inspiring much confidence, avoid steep slopes and obvious avalanche paths. The southern Missions and Swan are stacked up deeper than the Rattlesnake and at higher elevations likely have some of the deeper snow in the area. Depth hoar can still be found, the structure is poor, but it proved difficult to trigger a propagation yesterday. That said, thin spots exist, and snowmachines can trench down to deep weak layers. Due to warm temperatures, there is a melt-freeze crust to around 6500’ and 6800’ on steep southern aspects. Near-surface facets have developed underneath it, and it may become a problem with future loading. Currently, it is a minor inconvenience to ski. Snow, wind and warming temps are in the forecast. Expect wind slab to build further and become touchier. The freezing level may rise to 7000 feet tonight, increasing the likelihood of thaw instabilities. The bottom line: It is possible to trigger large, deep avalanches, especially in shallow faceted areas. Wind slabs are a concern in steep 35º+ leeward terrain. Wet loose avalanches will become possible today. In areas with deeper snow, it may be appropriate to cautiously step out into steeper terrain. Do your due diligence first. Check the depth of the snow throughout your tour and conduct stability tests. Avoid thin areas and convexities. Choose planar slopes without terrain traps. Follow safe travel protocols. Always carry your safety equipment — beacon, probe, and shovel. If you want to increase your competence in avalanche terrain, check out our education page. Your avalanche, snowpack, and weather observations help us keep the public informed and assist us when generating the advisory. Please help us continue to better understand the snowpack, and submit your observations here. Ski and ride safe The post Avalanche Advisory for January 23, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 25, 2020 06:54 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 25, 2020 View Full Advisory » The avalanche danger for the West Central Montana backcountry is MODERATE. Approach avalanche terrain with caution as triggering a large avalanche is possible. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 25, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures are hovering around the freezing level, with the highest peaks recording temperatures around 20 F. Winds are light to moderate out of the WSW, with upper elevation ridgetop winds gusting over 30MPH. Over the past 24 hours, Snotel sites have picked up .3 to .4 inches of SWE and about 3-6 inches of snow in upper elevation terrain. The past few days have been rather warm, with snow levels rising to about 6000 to 6500 feet. It feels more like late spring than mid winter right now, but you take what you can get. Plenty of fun can still be had in upper elevation low angle terrain. You have the possibility of triggering a large avalanche on 35+ degree slopes above about 6000 feet in elevation. Our primary concern is persistent slab avalanches. The likelihood of triggering a large persistent slab avalanche is decreasing, but the consequences are not. We have multiple buried weak layers in our snowpack capable of producing large dangerous avalanches. Likely places that you could trigger this type of avalanche would be in thin rocky areas, around cliff bands, or on convexities. I would also be cautious in the runout zones of avalanche paths, as remotely triggering a persistent slab avalanche is possible. Throughout our forecast area, we have varying snowpack depths. Areas with a deeper snowpack (4+ feet deep) are less prone to persistent slab avalanches than areas with a shallow snowpack (less than 4 feet deep). The kicker is, if you ski or ride over a thin spot in a deeper snowpack, you have the possibility of triggering a large avalanche. I know it is a tricky situation right now. Where do you ski or ride? A safe bet would be in low angle terrain. Bottom line: Some winter seasons, you can ski or ride most slopes safely. So far this winter, we have not had that option. You are rolling the dice if you ski or ride in avalanche terrain. Just know, if you hop into avalanche terrain today and do not trigger an avalanche, you might be lucky, not smart. Avalanche and Weather Outlook Today mountain temperatures will be rather warm with average temperatures between 6000-8000 feet ranging from 24-37 F. A few inches of snow is expected in favored locations. Winds will be light to moderate out of the SW, with upper elevation exposed terrain gusting into the high 30’s. We keep hoping that our snowpack will stabilize, but this has not happened yet. Expect avalanche conditions to remain the same for the foreseeable future. Any observations are appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for January 25, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Jan 28, 2020 07:00 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for January 28, 2020 View Full Advisory » The avalanche danger for the West Central Montana backcountry is MODERATE. Approach avalanche terrain with caution as triggering a large avalanche is possible. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 28, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures are currently in the high teens to mid 20’s F. Winds are light out of the WSW, with ridgetop winds gusting into the 20’s. During the past 24 hours, favored locations have picked up .2-.3 inches of SWE, equating to a few inches of snow. This season has been rather scary in regards to our avalanche problems. We have been plagued by persistent weak layers buried in our snowpack, with the possibility of triggering an avalanche that may take out the entire seasons snowpack. Based on recent observations, it seems that our snowpack is gaining strength. We are starting to see a more stable snowpack in many locations, while others we are not. The chances of triggering a large avalanche are decreasing, but the consequences are not. Play your cards wisely if you decide to hop into avalanche terrain. Our primary concern is wind slab avalanches. With a decent amount of new snow today accompanied by wind, be on the lookout for active snow transport. The new snow and wind may cause wind drifts, which look like bulbous or pillowy like features found on the leeward side of ridges or in cross-loaded terrain. This type of avalanche problem will most likely be found in open terrain or near ridge tops. Use caution when approaching steep terrain as wind slabs are most sensitive during and or soon after being transported. Another thing to keep in mind is that we have a widespread slick melt-freeze crust buried just below the surface of the snow. The melt-freeze crust could work as a good sliding surface, making wind slabs more reactive and much larger. Keep a close eye on how the new snow is reacting today. Our secondary concern in persistent slab avalanches. Throughout the winter, we have had numerous human and natural triggered persistent slab avalanches. During the past few days, observations have been showing that our buried weak layers are beginning to heal. We are not fully there yet in all locations, but things are moving in the right direction. A likely spot to trigger a persistent slab avalanche would be in areas with a shallow snowpack (3-4 feet or less). Other places you are most likely to trigger this type of avalanche would be in thin rocky terrain, around cliff bands, or on convexities. Remember, if you do trigger a persistent slab avalanche, it may break to the ground, taking out the entire seasons snowpack. Bottom line: Today is a storm day, so pay attention to any changes with the new snow. Look out for red flags such as cracking, collapsing, recent avalanches, and wind transported snow. Approach avalanche terrain with caution as triggering a large avalanche would take out the entire seasons snowpack. Avalanche and Weather Outlook Today through this evening, the mountains are expected to get up to a foot of new snow accompanied by moderate winds. Mountain temperatures will range from 24 to 37 F, with SW winds in the teens and gusts up to 31MPH. Snow is expected to taper off on Wednesday, followed by more snow later this week and a cold front later this weekend. Stay tuned. Expect avalanche conditions to rise during or shortly after any rapid changes in regards to wind and new snow. Our snowpack is beginning to heal but could be reactivated by new snow and wind. Any observations are appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for January 28, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for January 30, 2020 View Full Advisory » The avalanche danger for the West Central Montana backcountry is MODERATE. Approach avalanche terrain with caution as triggering a large avalanche is possible. Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for January 30, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures are currently in the upper teens to mid 20’s F. Winds picked up late yesterday and overnight and are gusting up to 50 mph on ridgetops, with wind chills currently below 0ºF. Overnight we picked up .2 inches of SWE in favored locations or up to 4 inches of snow. Our primary concern is persistent slab avalanches. While this problem is becoming less of a concern, it is still ever-present. Snowpit results in thin areas (3 to 5 feet or less in depth) are still showing signs of propagation, failing near the ground on depth hoar and facets. Deeper areas (5 or more feet deep in depth) are not propagating. What this means is you are less likely to trigger an avalanche in terrain with a deep snowpack. The catch is that there are thin trigger points, buried just below the surface of the snow in deeper areas. If you decide to ski or ride in avalanche terrain you need to do your homework. Avoid likely trigger points, such as thin rocky areas, around cliff bands, in shallow snowpack areas, and on or near convexities in terrain 35 degrees or steeper. You need to dig pits and walk around with a probe poking for snow depths. Our secondary concern is wind slab avalanches. With the recent increase of winds and easily transportable snow, wind drifts will be sensitive today. Wind drifts are easily identified by looking for bulbous or pillowy like features near ridgetops and on cross-loaded features. Bottom line: Some years, it is safe to ski and ride many slopes, but this is not the year. Our main concern is weak faceted snow buried near the ground, which, if triggered, could take out the entire seasons snowpack. Don’t let the sunny skies today lure you into being complacent and making bad decisions. Side note: On 01-28-2020, just outside our forecast area in the Flint Creek Range there was a 3-4 feet deep and 700 foot wide remotely triggered avalanche. The slide was on an east facing aspect at about 8000 feet in elevation which failed on basal facets below a crust at the ground. The snowpack in the Flint Creek Range is very similar to the snowpack in our forecast area. Avalanche and Weather Outlook Today will be a beautiful sunny day with mountain temperatures in the mid 20’s to high 30’s. Winds will be out of the WSW, averaging 10-14 MPH with gusts up to 31mph. Our nice sunny day is going to be short-lived, with a warm and windy storm moving in this evening, dropping a few inches of dense snow by Friday afternoon. Expect the avalanche danger to rise later this week with warming temperatures and the chance of new snow and rain up to 6000 feet. If you are in the mountains and it is raining, its a good clue to head home because rain and snow do not mix well in regards to avalanches. Any observations are appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for January 30, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 01, 2020 06:40 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 1, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is MODERATE. Wind slabs on leeward slopes are possible to trigger today. It is possible to trigger a persistent slab on depth hoar in thin shallow snowpacks. Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche forecast for February 1, 2020. Today’s forecast is brought to you by ON X Maps. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures range from 26 F to 37 F in the region. In the Bitterroot, winds are 16 mph with gusts of 30 out of the South. In the northern part of the advisory area, winds are 12 mph and gusting 32 mph out of the SSW. Snotels are reporting between 0 and .1 inches of SWE for the last 24 hours for a trace to 1 inch of new snow. Snowpack At A Glance: The snowpack is healing in deeper areas greater than 5 feet. In thin shallow snowpacks less than 4 feet, it is suspect. The depth hoar near the bottom of the snowpack is producing propagations in our pits. Moderate to strong winds over the last couple of days have created small to large wind slabs on leeward terrain. Cornices are starting to get quite large and should be given a wide berth. Most snotels did not freeze overnight. Warming temperatures at elevations below 7000 feet will produce loose wet conditions today. Avalanche Problems: The primary avalanche problem is wind drifted snow. Look for small to large wind slabs at higher elevations on leeward slopes. Identify this terrain. Watch for blowing snow and rounded, textured, drifts. Shooting cracks are a sign of unstable wind slabs. These slabs are sensitive to human triggers. Seek more wind-sheltered terrain to avoid this hazard today. The second avalanche problem is persistent slabs. The basal facets or depth hoar near the bottom of the snowpack can not be trusted in shallow snowpacks. We are still getting propagations in our ECT’s in snowpacks less than 3 feet. Dig a pit to find this problem. Use your probe to get an idea of the variability in snowpack depths across slopes. Avoid likely trigger points(cliff bands, rocky areas, and steep convexities). Choose more uniform slopes that do not have sharp changes in slope angles. The likelihood of triggering this layer is going down, but the consequences are high. The third avalanche concern is wet snow. The snowpack below 7000 feet did not freeze overnight. Look for warming temperatures to produce loose wet problems. Rollerballs on slopes are a sign to choose a different aspect. With prolonged warm temperatures and rain around 300 pm, today be heads up on your descent to lower elevations today and look for signs of a warming snowpack. Bottom line: Today is going to be warm and windy, with rain starting around 300 pm. The weather today will increase the avalanche hazard. Pay attention to changing weather conditions like warming temperatures, new precipitation (rain or snow depending on elevations), and wind speeds and direction. Dig a pit. Check snow depths. Avoid shallow rocky areas and cliff bands. Carry a beacon, shovel, and probe. Practice safe travel by exposing only one person to a slope at a time. Pay attention to red flags: recent avalanches, shooting cracks, collapsing, and warming temperatures. Avalanche and Weather Outlook Rain and strong winds with gusts into 60 mph or more are expected to enter the forecast area today around 300 pm. See the forecast. Warm Temperatures in the 30’s and 40’s today. Later tonight, a cold front hits and will drop temperatures creating snow to the valley floor. over a foot of new snow overnight with strong winds will increase the avalanche danger for tomorrow. The new snow will land on a variety of old snow surfaces. With the predicted snowfall, look for storm slabs, wind slabs, and persistent slabs as the avalanche problems tomorrow. This weather system will be a rapid change for the snowpack. Pay attention to how the snowpack adjusts. Any observations are appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for February 1, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 04, 2020 06:17 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 4, 2020 View Full Advisory » The avalanche danger for the southern Bitterroot and Rattlesnake mountain ranges is MODERATE. It is possible to trigger a persistent slab avalanche. In the central Bitterroot, southern Missions, and southern Swan mountain ranges, the avalanche danger is LOW. Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 04, 2020. Today’s advisory is sponsored by ON X Maps. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures range from 3 F to 12 F in the region. In the Bitterroot, winds are 7 mph with gusts of 14 out of the WSW. In the northern part of the advisory area, winds are 16 mph and gusting 21 mph out of the West. Snotels are reporting between 0 and .2 inches of SWE for the last 24 hours for a trace to 2 inches of new snow. Rattlesnake and southern Bitterroot The Rattlesnake and southern Bitterroot have the shallowest snowpacks. In these two areas, we are getting propagations on the depth hoar near the ground. The primary avalanche problem is persistent slabs. The depth hoar near the ground is still reactive in pit tests. Dig a pit. Avoid likely trigger points (e.g., cliff bands, rocky areas, and steep convexities). The likelihood of triggering this layer is going down, but the consequences are high. Southern Missions, southern Swans, and central Bitterroot The southern Missions, southern Swan and central Bitterroot have deeper snowpacks. The basal facets or depth hoar has become dormant in these ranges. We are not getting propagations in pit tests. The last reported avalanche was over a week ago. Normal caution is the avalanche problem. Continue to practice safe travel protocols in case you find an exception to a generally stable snowpack. Travel one at a time in avalanche terrain, carry a beacon, shovel, and probe, and stay alert for signs of instability. Bottom line: Overall the snowpack is healing. In the Rattlesnake and southern Bitterroot, avalanche danger is heightened in shallow snowpacks on steep slopes. Avoid likely trigger points (e.g., cliff bands, rocky areas, and steep convexities). The likelihood of triggering the weak layers near the ground is going down, but the consequences are high. Dig a pit. Check snow depths. Avoid shallow rocky areas and cliff bands. Carry a beacon, shovel, and probe. Practice safe travel by exposing only one person to a slope at a time. Pay attention to red flags: recent avalanches, shooting cracks, collapsing, and warming temperatures. Avalanche and Weather Outlook Over the weekend, we had an extreme wind event and warm temperatures. There are a variety of old snow surfaces left in the aftermath of this event. Tonight a Northwest flow enters our area. This weather pattern will lead to continued moisture and precipitation through the weekend. See the forecast. New loading and winds will elevate the danger rating. Look for the new snow to take time to bond to old snow surfaces. I will issue the next advisory on Thursday, February 6, 2020. Any observations are appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for February 4, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 06, 2020 06:29 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 6, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is CONSIDERABLE on wind loaded slopes and MODERATE on all other slopes. New snow and wind have created dangerous avalanche conditions on leeward slopes. It is likely to trigger a avalanche on wind loaded slopes today. Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 06, 2020. Today’s advisory is sponsored by ON X Maps. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Mountain temperatures range from 21 F to 30 F in the region. In the Bitterroot, winds are 16 mph with gusts of 21 out of the WNW. In the northern part of the advisory area, winds are 32 mph and gusting 41 mph out of the WNW. Snotels are reporting between .8 and .9 inches of SWE for the last 24 hours for 6 to 10 inches of new snow. New snow and wind slabs are the two avalanche problems for today. The new snow is bonding well to the old snow surfaces. There is a crust that was buried on 02/02/2020 from the warm temperatures over the weekend.(see video) Winds have transported the new snow to leeward slopes. The depth hoar near the base of the snowpack is healing. We have not had a report of this layer avalanching in over 2 weeks. The depth hoar is unreactive in pit tests. We are taking persistent slabs off the avalanche problems today. The primary avalanche problem is new snow. The new snow is bonding well to the old snow surfaces. Look for loose snow avalanches on steep slopes(>35 degrees). These should not be a problem unless they knock you off your machine or skis and carry you into a terrain trap. Look for storm slabs with continuing loading of new snow throughout the day. Use small test slopes to see how the new snow is bonding. Use hand pits and pole tests to assess the new snow. Look for cracks from your skis or machine to identify storm slabs. The second avalanche concern is wind slabs. Yesterday throughout the advisory area, active transport of new snow created wind slabs. These slabs will be sensitive to human triggers today. Look for small to large wind slabs at higher elevations on leeward slopes. Identify this terrain. Watch for blowing snow and rounded, textured, drifts. Shooting cracks are a sign of unstable wind slabs. Bottom line: Pay attention to changing weather conditions today. Look for red flags: recent avalanches, shooting cracks, collapsing, rapid loading, and warming temperatures. Dig a pit. Use small test slopes to see how the new snow is bonding. Carry a beacon, shovel, and probe. Practice safe travel by exposing only one person to a slope at a time. Avalanche and Weather Outlook Snow and moderate to strong winds are forecasted for today. See the forecast. Look for more snow and winds to elevate the avalanche danger. Any observations are appreciated. If you get out in the mountains, please send us your observations here. Thank you very much to those of you who have been sending in observations, as it is incredibly beneficial. Ski and ride safe. Education Opportunities: Want to learn more about avalanches? We still have spaces available on Avalanche Courses throughout the winter. Take a look here for a full list of courses. The post Avalanche Advisory for February 6, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 08, 2020 06:45 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 8, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is CONSIDERABLE on wind loaded slopes and MODERATE on all other slopes. New snow and wind are creating dangerous avalanche conditions on leeward slopes, where it is likely to trigger an avalanche today. Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for February 08, 2020. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Since the start of the storm on Tuesday, February 04, we’ve received an average of 2.8 inches of snow water equivalent (SWE). The crust that formed with the warm temps and winds on Saturday, February 01, is now buried over 2 feet deep. Temperatures have been mild throughout the storm, and freezing levels rose to about 6400’ Thursday and Friday. Strong westerly winds accompanied the start of the storm and picked up again last night, reaching 61mph. Westerly gusts to 50mph are forecast for today, and another 5-10 inches is expected to fall by evening. The strong winds are creating wind slab on leeward slopes that will build throughout the day. These are likely to be triggered by the weight of a single skier or snowmobile. Wind loaded pockets >35º, near ridgetop, are the most likely place to trigger an avalanche. However, cross-loading may create windslab lower on slopes. Be wary of stiff pillows of hollow sounding snow, and the leeward side of ridges. Storm slab is also a concern. Warm temps mid storm created a density break in the new snow that was showing a propensity for propagation, in some locations, a foot below the surface yesterday. This will gain strength quickly; however, it is getting buried deeper and poses a risk on steep convex or unsupported terrain, especially if there are terrain traps present. At lower elevations, less than 5800’ at Lolo Pass, a thin crust was formed mid-storm, but new snow seems to be bonding well to it. Loose snow avalanches may be a problem on steep terrain. The Bottom Line Strong winds and plenty of new snow available for transport will be building dangerous wind slabs throughout the day. The likelihood of triggering a windslab will increase as the day progresses. Storm slabs are also possible on 35º+, convex, and unsupported slopes. Terrain traps will increase the consequences of either of these problems. Travel with partners, avoid steep convex or wind-loaded terrain. Be on the lookout for red flags. Always carry a beacon, shovel, and probe. As always, we welcome all public observations of avalanche conditions, please submit them here. If you’d like to increase your avalanche knowledge and competence, check out our course offerings. Ski and ride safe. The post Avalanche Advisory for February 8, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 11, 2020 06:45 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 11, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is MODERATE on wind loaded slopes and LOW on all other slopes. The southern Bitterroot is MODERATE in all terrain. Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for February 11, 2020. Today’s advisory is sponsored by LB Snow. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack It’s been quite a week. After record warm temps and winds on Saturday, February 1, the weather switched gears, and the area has been consistently snowed on for 6 days. Anyone who has been out in the past few days knows how good the riding is. Since Tuesday, February 4, we’ve received up to 5.1 inches of snow water equivalent (SWE) and averaged 3.5 inches of SWE throughout the forecast area. This translates to more than 3 feet of new snow. We measured snow depths up to 110 inches in the Rattlesnake yesterday. Despite arriving with strong winds, the bulk of the storm was relatively calm. Mostly light winds, with long calm stretches, moved much less snow than was anticipated, despite some strong gusts. Wind slab did not develop to the extent that we expected. Isolated, steep, high elevation terrain is where it is possible to trigger a wind slab avalanche. Cornices grew considerably and are a hazard as well. Overall the storm snow has bonded surprisingly well. Mid storm density breaks that were showing some instabilities on the 7th have healed well. The February 1 crust has also bonded well and does not seem to be an issue. Storm slabs may be found in isolated spots, and overall, are unlikely to slide. Loose snow avalanches or sluffs can be a problem in steep terrain, >38º. While mostly manageable they become more hazardous if they can push you into terrain traps. The only place showing significant red flags in the forecast area is the southern Bitterroot around Lost Trail. On Saturday there was a natural avalanche, to ground, in the depth hoar that was plaguing us through January. Everywhere else in the forecast area has received enough snow for that layer to gain strength. The southern Bitterroot has received the least snow in the forecast area, and in thin spots, it is still possible to trigger a persistent slab avalanche in that area. It’s been 24 days since we’ve had a report of a slide on this layer, highlighting the unpredictability of this problem. The Bottom Line In most of the forecast area, the avalanche hazard is low, and it is unlikely to trigger an avalanche. Low hazard does not mean no hazard; do your due diligence. Dig a pit, test the snow, watch for red flags. Avoid steep wind loaded terrain near ridge tops. Give cornices a wide berth. Ski one at a time. The southern Bitterroot requires more caution as the depth hoar is still active. Check snow depths throughout tours; shallow areas are more likely trigger points. Sticking to lower angle simple terrain is still the best approach to this problem. Always carry your beacon, shovel, and probe. As always, we welcome all public observations of avalanche conditions, please submit them here. If you’d like to increase your avalanche knowledge and competence, check out our course offerings. Ski and ride safe. The post Avalanche Advisory for February 11, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 13, 2020 06:45 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 13, 2020 View Full Advisory » The avalanche danger for the west central Montana backcountry is MODERATE on wind loaded slopes and LOW on all other slopes. The southern Bitterroot is MODERATE in all terrain. Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for February 13, 2020. Today’s advisory is sponsored by LB Snow. This danger rating does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack Over the past couple of days the weather mellowed out a bit, but was thankfully still bringing us snow. We’ve had mixed skies and periods of moderate wind. The area has averaged 0.6” of snow water equivalent (SWE). Snowbowl reported 4” of new snow yesterday, Lolo had 6” of low-density new snow, the southern Missions got around 8″, the central Bitterroot up to 10″ and southern Bitterroot 6″. This has been landing on a surface free of instabilities and we expect that it will bond well. The sun hasn’t been out full time, but it has been strong enough to affect snow surfaces. South faces are denser and stiffer than nonsolar aspects. Solar warming triggered some small sluffs on steep south aspects yesterday, and at lower elevations could lead to crusts forming. The wind has continued to periodically load start zones at higher elevations near ridge top. It is possible to trigger a wind slab avalanche in steep, high elevation, wind loaded terrain. Cornice fall is still a concern. Storm slab is mostly not an issue. Last week’s snow has bonded well. Yesterday’s new snow was too low density to form a slab and should bond well as it settles. Storm slabs may be found in very isolated spots, and overall, are unlikely to slide. Loose snow avalanches or sluffs can be a problem in steep terrain, >38º. While mostly manageable they become more hazardous if they can push you into terrain traps. The southern Bitterroot still has the persistent slab problem. On Saturday, February, 8 there was a natural avalanche, to ground, in the depth hoar that was plaguing us through January. It had been 24 days since we’d had a report of a slide on this layer, highlighting the unpredictability of this problem. The Bottom Line In most of the forecast area, the avalanche hazard is low, and it is unlikely to trigger an avalanche. Low hazard does not mean no hazard; do your due diligence. Dig a pit, test the snow, watch for red flags. Avoid steep wind loaded terrain near ridge tops. Give cornices a wide berth. Ski one at a time. The southern Bitterroot requires more caution as the depth hoar is still active. Check snow depths throughout tours; shallow areas are more likely trigger points. Sticking to lower angle simple terrain is still the best approach to this problem. Always carry your beacon, shovel, and probe. As always, we welcome all public observations of avalanche conditions, please submit them here. If you’d like to increase your avalanche knowledge and competence, check out our course offerings. Ski and ride safe. The post Avalanche Advisory for February 13, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 15, 2020 06:31 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 15, 2020 View Full Advisory » Today’s avalanche danger is rated CONSIDERABLE on wind loaded slopes and MODERATE on all other slopes in the southern Bitterroot. Avalanche danger is MODERATE on wind loaded slopes and LOW on all other slopes in the Central Bitterroot, Rattlesnake, and Seeley Lake areas. Good morning, this is Andrew Schauer with the West Central Montana avalanche advisory for Saturday, February 15, 2020. Today’s advisory is sponsored by LB Snow. This advisory does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack After a brief break in the action, the faucet is turning back on throughout our advisory area. In the last 24 hours, we received 4-8 inches of new snow in the Bitterroot, with a trace to 2 inches in the Rattlesnake and Seeley Lake areas. This morning, winds are blowing 10-20 mph out of the west and southwest, and mountain temperatures are in the low 20’s. Today we can expect to see 2-4 inches of new snow, with slightly higher totals in the Seeley Lake area. Mountain temperatures will get into the high 20’s to low 30’s and winds will be 15-25 mph out of the west with gusts reaching 50 mph. Snow will pick up this afternoon through tomorrow, and we will see 6-10″ of new snow by tomorrow morning, with higher totals at higher elevations. As the storm unfolds, our primary concern will be triggering fresh wind slabs, which can be found on steep, wind-loaded slopes. These avalanches can be up to 3’ deep, and will be big enough to bury a person (video, photo, photo). The best way to manage a wind slab problem is to avoid steep, wind-loaded terrain. You can recognize a fresh wind slab by sticking your pole in the snow, or hopping off your sled to look for dense snow that is deeper than the storm totals in the area. Cornices and wind-affected surfaces are also good indicators of unstable wind slabs. A wind slab will be easy to identify in a snow pit, and it will be likely to propagate in a stability test. You do not need to dig deep to identify this problem since it will only exist in the upper 2-3 feet of the snowpack. With more snow stacking up, we will also be dealing with a storm slab problem. Storm slabs will be up to a foot deep, and can be recognized by looking for shooting cracks or recent avalanche activity. While these avalanches may not always be large, they can still be dangerous in consequential terrain. If a storm slab is reactive, it will be possible to identify the problem by doing a quick stability test. Jeff was in the southern Bitterroot yesterday, and he found weak, faceted snow near the ground that was still failing in stability tests. This layer is not present in the rest of our advisory area. It has now been one week since the last reported avalanche that failed on this weak layer (photo), and it is becoming less likely to trigger an avalanche deeper in the snowpack. However, new snow and moderate winds will apply a load that will push this weak layer closer to its breaking point. Translation: we have a deep persistent slab problem in the Southern Bitterroot. Before committing to steep terrain, take the time to dig a pit and look for that weak, sugary snow near the ground. Keep in mind these deep weak layers will not always fail in stability tests, and you might not see any red flags like collapsing or shooting cracks before triggering a large avalanche. If you notice poor structure, stick to slopes less than 30 degrees that are not connected to steeper terrain. Avoid slopes that have been previously scoured, areas with rocks poking out of the snow, and slopes that have avalanched earlier this season. The Bottom Line With more snow and wind in the forecast today, it is important to take the time to dig a pit and do a quick test before committing to avalanche terrain. Stick to slopes that have not been recently wind loaded, and keep an eye out for red flags like recent avalanches, shooting cracks, and collapsing in the snowpack. If you are planning on getting out in the Southern Bitterroot, be sure identify and avoid slopes with weak, sugary snow deep in the snowpack. Your observations are extremely helpful! If you get out, please take a minute to fill out the observation form on our website (missoulaavalanche.org), or shoot us a quick email at info@missoulaavalanche.org. We offer a variety of avalanche courses throughout the winter. Our education calendar is posted on our website. We will be running two avalanche awareness lectures at Lost Trail this Sunday, Feb 16 (details). The post Avalanche Advisory for February 15, 2020 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory Posted: Feb 18, 2020 06:18 am Is this email not displaying correctly? View it in your browser.

Avalanche Advisory for February 18, 2020 View Full Advisory » Today’s avalanche danger is rated CONSIDERABLE on all wind-loaded slopes, and MODERATE on all other slopes in the advisory area. Good morning, this is Andrew Schauer with the West Central Montana avalanche advisory for February 18, 2020. Today’s advisory is sponsored by LB Snow. This advisory does not apply to operating ski areas, expires at midnight tonight, and is the sole responsibility of the U.S. Forest Service. Weather and Snowpack We received 10-18 inches of new snow since Saturday. The storm favored the northern half of the advisory area, dropping 13” of new snow and 1.5-2.5” of water in the Seeley lake and Central Bitterroot areas. Winds have been blowing 10-30 mph from the west to southwest. This morning, temperatures are in the teens F, and winds are blowing 10-25 mph out of the west and southwest. Temps will reach the mid- to upper 20’s F today, and winds will be 10-15 mph out of the west. We can expect to see 1-2″ of new snow throughout the day. Heavy snowfall and strong winds have built sensitive wind slabs that will be easy to trigger. These avalanches will be up to three feet thick, and can be large enough to bury a person (photo). The good news is that you can easily recognize them by looking for a dense layer of snow on the surface, and avoid them by staying off steep, wind-loaded slopes. With over a foot of new snow since Sunday, it will be possible to trigger storm slabs on slopes steeper than 35 degrees. Yesterday my partners and I were able to trigger these avalanches 1-2’ deep on a small test slope in Gash Creek (photo). I do not trust larger slopes, or anything above terrain traps like gullies, road cuts, rocks, and trees. This problem will heal quickly without any more new snow, but it still needs another day. The trickiest problem today will be persistent slab avalanches. In the past week, we have gotten reports of pockets of surface hoar buried 2-3’ deep in the central Bitterroot (video, profile). Yesterday, Travis and Jeff found weak facets near an ice crust buried 1-2’ deep in the Rattlesnake (photo, profile). Although these weak layers may be hard to spot with the naked eye, they will easily show up in stability tests. In the Southern Bitterroot, there is still a thick layer of depth hoar on the ground (photo). This layer is widespread in the southern portion of our advisory range, and it will not always be possible to get it to collapse in a stability test. When dealing with a problem like this, I will avoid steep slopes entirely. If you want to commit to avalanche terrain, do your homework. Dig in a shallow spot (2 m or less), and look for weak, sugary snow at the ground. If you find it, choose another slope to ski or ride. The Bottom Line Today’s avalanche equation is simple. New snow and strong winds have built thick slabs on the surface, which are pushing weak layers closer to their breaking point. Avoid wind-loaded slopes, and dig a pit to see if you can get any weak layers to propagate in stability tests. If you are getting out in the southern Bitterroot, be aware of weak layers lurking deep in the snowpack, and avoid any shallow areas where you can trigger a large avalanche. Your observations are extremely helpful! If you get out, please take a minute to fill out the observation form on our website (missoulaavalanche.org), or shoot us a quick email at info@missoulaavalanche.org. We offer a variety of avalanche courses throughout the winter. Our schedule may be found at the course offerings page on our website. We still have two spots left on our Level 1 course at Lolo Pass at the end of this month (2/27-3/1). If you are interested in enrolling, you can find info here, or email us with questions. The post Avalanche Advisory for February 18, 2020 appeared first on Missoula Avalanche.