2018-19 "Post-Season Report" 4/23/19 West Central Montana avy conditions.

[Scott]

Missoula Avalanche
Avalanche Advisory for March 16, 2019

moderate danger
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The avalanche danger is MODERATE for the West Central Montana backcountry. It is possible to trigger a slide on persistent weak layers in our snowpack. Look for wet loose activity to increase throughout the day on sun-exposed slopes. Identify wind drifted terrain. Carefully evaluate terrain and the snowpack to identify locations where hazards exist.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 16, 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 19 F to 21 F in the region. In the Bitterroot winds are 5 mph with gusts of 7 mph out of the S. In the northern part of the advisory area, winds are calm.

The primary avalanche problem is persistent weak layers. In isolated shallow snowpacks, we are still getting facets near the ground to propagate(video). In isolated sheltered and protected slopes look for buried surface hoar (video). Dig a pit to see if these layers are present and reactive.

The second is avalanche problem is loose wet on sun-exposed slopes and dry loose on north facing cold slopes. Today as temperatures rise and the sun comes out look for loose wet activity to increase on sun-exposed slopes. These two problems should not be a problem unless they knock you off your skis or machine and take you into a terrain trap. Look for roller ball activity on solar aspects and change aspects to colder ones as the snow surface gets saturated.

The third avalanche problem is small isolated wind slabs. There are small wind slabs on isolated slopes in the central and southern Bitterroot. Look for wind slabs at higher elevations. These formed from a wind event on March 14. Look for evidence of wind transport and identify slopes with wind slabs.

Bottom line: The snowpack is gaining strength. There are still avalanche concerns. Dig a pit before committing to avalanche terrain. Look for signs of wind loading. Change aspects when roller balls show up to a colder aspect. Avoid shallow snowpacks near rock bands and cliffs.

Avalanche and Weather Outlook

Today look for wet loose avalanches to increase throughout the day. Sunday look for cloud cover and freezing temperatures overnight. The avalanche danger will slowly decrease as our snowpack gains more strength. Look for loose wet activity in the afternoons. See the forecast.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

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[Scott]

Missoula Avalanche
Avalanche Advisory for March 19, 2019

moderate danger
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A MODERATE avalanche danger exists for the West Central Montana backcountry. Widespread loose wet avalanches can be expected later in the day and isolated hazards can be found in specific terrain. Evaluate slopes and the snow carefully to identify features of concern.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, March 19th, 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

The weather continues to go through a daily freeze-thaw cycle with temperatures warming to the 40’s during the day an then dropping below freezing and into the 20’s at night. However, Stuart Mountain snotel last night did not drop below freezing and could create some interesting conditions today. Mountain temperatures as of 5 am this morning are in the twenties at all other locations. Winds are light from the NE in the northern portion of the advisory area and the SE further south. Most locations have not received snow for the past few days but a stray dusting can be found in isolated locations.

Persistent weak layers continue to round and gain strength but can be problematic in isolated locations. In areas with a shallow snowpack and near rocky terrain, facets near the bottom of the snowpack continue to easily propagate in stability tests (profile)(video). This is a very isolated problem and won’t be found everywhere but will produce large avalanches. Due to the minimal distribution but high consequence nature of this layer it warrants taking a minute to dig a pit to check the total snow depth and if the weak layers are present and reactive.

Widespread loose wet activity can be expected on terrain that is exposed to direct sunlight with activity peaking in the afternoon. Small loose wet sluffs have consistently been observed for the past few days on solar aspects with some isolated larger slides from steep rocky terrain. Although mostly small remember that even a small slide can knock you over and take you for a dangerous ride if terrain traps are present. Carefully consider the consequences of even a small slide before committing to steep terrain. Warm temperatures are also causing cornices to lose strength. A handful of natural cornice failures have been observed over the past week and will become more problematic with warm and sunny days expected this week. Give cornices a wide berth as they tend to break back farther than expected and avoid traveling below them later in the day.

In shaded and north facing terrain cold snow can still be found above 7,000 feet. In the cold snow, pockets of wind drifted snow will be the greatest concern. Look for signs of wind loading in the softer snow and avoid likely trigger points like rollovers and just below ridges. Much like the persistent weak layers this problem is isolated and won’t be found everywhere but should be considered before committing to avalanche terrain.

Avalanche and Weather Outlook

The forecast for the week calls for slightly warmer temperatures each day with clear skies as high pressure dominates the region. The avalanche danger will remain the same until a shift occurs in the weather which looks to develop sometime this weekend.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 19, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory
Posted: Mar 21, 2019 06:13 am
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Missoula Avalanche
Avalanche Advisory for March 21, 2019

moderate danger
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The avalanche danger for the West Central Montana backcountry remains MODERATE. Small loose wet avalanches are likely on sun-exposed terrain with potential for larger slides in extreme terrain. Larger dry avalanches are possible in isolated terrain and warrant careful evaluation of the snowpack before committing to avalanche terrain.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Thursday, March 21st, 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 again this morning at most locations are just below freezing. No new snow has been seen for nearly a week and winds are light out of the E in the northern portion of the forecast area. Stronger winds can be found in the Southern Bitterroot from the SSE at 12 mph with gusts up to 17 mph.

Loose wet avalanches are likely throughout the forecast area. Avalanche activity will increase through the day and will be concentrated on the southern half of the compass. Loose wet slides are primarily small but can be hazardous if terrain traps are present. Yesterday we found a handful of loose wet slides (Pic) that were able to entrain large amounts of snow (Video1). Again most loose wets will be small but be aware that in big steep terrain they have the potential to be large and destructive (video2). Warm temperatures are also resulting in cornices loosing strength and the formation of glide cracks. Give both a wide berth because they can be unpredictable and present another complex and hard to predict hazard.

The next hazard is persistent slabs. We again found depth hoar yesterday that easily propagated in stability tests in areas with shallow snow (profile). The weak faceted snow is gaining strength but is deep enough in the snowpack that the warm temperatures haven’t been able to accelerate the process, this means that this problem can linger for a while. The persistent slabs are very isolated and will not be found everywhere but will produce large avalanches if failures occur. Carefully assess the snowpack before committing to avalanche terrain because high consequences can be expected in any slide involving these weak layers near the ground.

Finally, isolated wind slabs can be found above 7,000 feet on cold or shaded aspects that have been wind-loaded (Pic). The lack of new snow and warm temperatures have slowed wind slab development and areas that have been loaded are gaining strength but the instability isn’t completely settled out yet. If you find yourself in soft snow, look for signs of wind loading before committing to steep terrain.

Avalanche and Weather Outlook

Warm and dry conditions will continue through Friday (forecast). Avalanche danger will continue to go through the daily cycle of a mid-day peak in activity before refreezing at night. Overall conditions will remain the same until this weekend when precipitation returns. Returning snow and rain will bump up avalanche hazard over the weekend.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 21, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Missoula Avalanche
Avalanche Advisory for March 23, 2019

moderate danger
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The current avalanche danger for the West Central Montana backcountry is MODERATE. Widespread small avalanches with isolated larger slides will give way to more widespread avalanche activity as the day warms. The danger could reach CONSIDERABLE by the afternoon making natural avalanches possible. Careful route-finding and cautious snowpack evaluation are critical for backcountry travel today.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Saturday, March 23rd, 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 early this morning are hovering right around freezing across the region. Winds are out of the West at 8 mph and gusting to 15 mph. No precipitation fell overnight for the forecast area.

Loose wet avalanches continue to be the most widespread and reactive problem today. Although temperatures will be slightly cooler today than earlier this week the warmer temperatures overnight have increased the reactivity of the surface snow. Widespread small loose wet avalanches will occur today with some potentially entraining large amounts of snow and becoming destructive. Avoid terrain traps and steep rocky areas or other trigger points in the mountains today.

The warm temperatures are now also creating wet slab avalanche problems. Wet slabs avalanches are a result of the snowpack becoming saturated and losing strength. The prolonged warm temperatures have finally reached a tipping point where the snowpack is saturated and susceptible to failure. Wet slabs are notoriously difficult to predict and have the potential to take the entire season snowpack out in a single slide. This is a particularly dangerous combination so if the snow surface is wet and heavy or the snow has become saturated seek out colder drier snow at higher elevations or colder aspects.

Bottom Line: Our luck has run out and we no longer have the cold overnight temperatures that were refreezing the snowpack. The good news is that this has diminished the wind slab and persistent weak layer concerns but has created a new problem of wet avalanches. Wet avalanches are very hard to predict and are best mitigated with timing and choosing appropriate terrain.

Avalanche and Weather Outlook

Milder but still warm temperatures today will have a minor chance for sporadic snow flurries but will usher in more precipitation on Sunday (forecast). Any snow we get will add weight and stress to the snowpack and will have fairly high rain lines around 5-6 thousand feet. The avalanche danger will continue to trend upward throughout the weekend. Next week has the chance to bring freezing temperatures overnight again which will help to settle the snowpack.

With changing conditions public observations become crucial. If you are out in the mountains please share your observations on our public observation page.

Ski and ride safe.

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[Scott]

Avalanche Advisory for March 26, 2019

moderate danger
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The avalanche danger in the west central Montana backcountry is LOW this morning. Rain to 6000 feet will increase the avalanche danger to MODERATE. Pay attention to changing weather conditions which will increase the avalanche danger today.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 26, 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 28 F to 38 F in the region. Most snotel sites froze overnight except in the Rattlesnake. In the Bitterroot winds are 15 mph with gusts of 24 mph out of the SE. In the northern part of the advisory area, winds are 5 mph with gusts of 16 mph out of the SSE. A cold front is making its way into the area today with a rain line of 5500 feet to 6000 feet.

The primary avalanche problem is wet snow. At elevations, 7000 feet and below look for increased wet loose avalanche problems throughout the day. As the snow becomes saturated look for potential for wet slab avalanche problems. Wet slabs avalanches are a result of the snowpack becoming saturated and losing strength. Wet slabs are notoriously difficult to predict and have the potential to take the entire season snowpack out in a single slide. This is a particularly dangerous combination so if the snow surface is wet and heavy or the snow has become saturated with rain it is time to head home.

Bottom line: The avalanche danger will increase today with rain on snow to 6500 feet. The upper elevations will experience new loading events and potentially could reactivate weak layers in the snowpack. Look for changes in the avalanche danger with changing weather conditions.

Avalanche and Weather Outlook

The avalanche danger will increase throughout the day today. The cold front will decrease the rain line to 4000 feet overnight. Wednesday look for additional loading from snow which will keep the avalanche danger at moderate. See the forecast.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

 

[Scott]

Current West Central Montana Avalanche Advisory
Posted: Mar 28, 2019 06:26 am
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Missoula Avalanche
Avalanche Advisory for March 28, 2019

moderate danger
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The avalanche danger in the west central Montana backcountry is MODERATE.Wind slabs will be easy to trigger today on leeward slopes. Identify wind loaded terrain and avoid traveling on those slopes.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 28, 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 28 F to 30 F in the region. In the Bitterroot winds are 2 mph with gusts of 13 mph out of the E. In the northern part of the advisory area, winds are 5 mph with gusts of 16 mph out of the ENE. Look for winds to increase throughout the day. Snotels reported .3 to .5 inches of SWE in the last 24 hours. Continued snow is forecasted for today. Snow line is between 4000 feet and 5000 feet.

The primary avalanche problem is wind slabs. The cold temperatures have locked the springtime snowpack back up creating a slick sliding surface that small to large wind slabs are being deposited on(video). Wind slabs will be sensitive to human triggers today and have high energy. Identify leeward terrain and avoid traveling on these slopes. Shooting cracks from skis or machines will help to identify this problem. Look for scoured slopes to help identify leeward terrain.

The second avalanche problem is loose dry avalanches. Look for small loose avalanches today. These sluffs will be small and should not be a problem unless they carry you into a terrain trap. Use small test slopes to see how the new snow is bonding to old snow surfaces.

Bottom line: Today look for changing weather conditions that will lead to changing avalanche conditions. Wind slabs on leeward terrain will be high energy and easy to trigger. Avoid wind loaded terrain. Sluffs will be easy to trigger on the slick sliding surfaces of old snow.

Avalanche and Weather Outlook

More snow and strong wind gusts will keep the avalanche danger at moderate today. See the forecast.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 28, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory
Posted: Mar 30, 2019 05:57 am
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Missoula Avalanche
Avalanche Advisory for March 30, 2019

moderate danger
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The avalanche danger is LOW in the west central Montana backcountry this morning. Look for the danger to rise to MODERATE in the afternoon. Look for loose wet avalanches to increase throughout the day on sun-exposed slopes. Look for small isolated wind slabs on leeward slopes at elevations above 7000 feet near ridge lines on cold, dry North facing slopes.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 30, 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 17 F to 28 F in the region. In the Bitterroot winds are 2 mph with gusts of 5 mph out of the SSW. In the northern part of the advisory area, winds are 4 mph with gusts of 6 mph out of the NE.

The primary avalanche problem is loose wet avalanches. Loose wet avalanches will become more and more likely throughout the day. Look for roller balls ,and that is the queue to head to shadier and less sun-exposed slopes. Loose wet slides are primarily small but can be hazardous if terrain traps are present. Warm temperatures are also resulting in cornices loosing strength and the formation of glide cracks. Give both a wide berth because they can be unpredictable and present another complex and hard to predict hazard.

The second avalanche problem is wind slabs at elevations above 7000 feet on cold, dry north facing slopes. Look for wind slabs on isolated leeward slopes near ridges. These slabs will be small but will be sensitive to triggers.

Bottom line: The snowpack is refreezing overnight. This is creating a typical spring snowpack where timing is critical to avoid loose wet activity in the afternoon. Look for roller balls to give you the heads up that it is time to move to shadier aspects. North facing slopes have cold, dry snow which is relatively stable right now and producing good riding. Dig a pit on these slopes before committing to a big line.

Avalanche and Weather Outlook

We have a generally stable snowpack. Look for the avalanche danger to rise and increase loose wet activity on the southern half of the compass throughout the day. Once roller balls show up move to more shaded and drier slopes. Through the weekend look for the snowpack to refreeze at night and then loose wet activity to increase as the sun comes out and warms the snow surface. See the forecast. Expect the avalanche danger to be Low in the morning and then rise to Moderate in the afternoon.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

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[Scott]

Avalanche Advisory for April 2, 2019

low danger
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The current avalanche danger is LOW for the West Central Montana backcountry. Low danger does not mean no danger, small avalanches are possible in isolated terrain with increased danger in extreme terrain. Watch for unstable snow to develop on isolated terrain features as the snow warms today. The avalanche danger will trend towards MODERATE later in the day as natural loose wet cycles develop.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, April 2nd, 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

The snowpack continues to experience freezing temperatures overnight and this morning at 4am temperatures range from 24 to 28 degrees Fahrenheit. Winds are variable and light this morning at 3 mph with gusts up to 8 mph.

The greatest concern today are loose wet avalanches. Yesterday while touring in the central Bitterroot we observed widespread loose wet activity at all elevations and on every aspect but true north. This problem will increase through the day before peaking in the afternoon and will follow the sun across slopes. Although small and relatively slow-moving, loose wet sluffs have a lot of mass and can easily knock you down and take you for a traumatic ride. Avoid steep sun exposed terrain especially if terrain traps are present. If the snow starts to get wet and heavy move to a different aspect or call it a day.

The other concerns to keep an eye out for are persistent slabs and wind slabs. On a north facing slopes, we found preserved depth hoar above 7,000 feet in shallow snow near rocky terrain. This layer is very isolated but was reactive in stability tests. Shallow winds slabs will also be possible in cold snow on northern exposures. Again these problems are very isolated and unlikely to be triggered but if you find cold dry snow assess it carefully for wind loading and persistent weak layers before committing to steep terrain.

Avalanche and Weather Outlook

The forecast for today is scattered clouds and sun. No snow is expected and light winds from the Northeast will continue. The avalanche danger will increase through the day as the snow surface warms but isn’t in for any major changes until this weekend when the next round of precipitation arrives.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

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[Scott]

Avalanche Advisory for April 4, 2019

moderate danger
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The avalanche danger below 7,000 feet is MODERATE. Rain and warm temperatures have increased wet avalanche activity at mid to low elevations. At higher elevations, the avalanche danger is LOW trending towards MODERATE later in the day. Carefully assess routes and terrain in the backcountry today.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Thursday, April 4th, 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

Temperatures at snotels never dropped below freezing for the last two nights. As of 5 am mountain temperatures range from 32 to 36 degrees Fahrenheit. Winds continue to be calm to light out of the Southwest across the forecast area. Snotels have picked up between 0.1 and 0.4 inches of SWE. Most of the water added to the snowpack yesterday fell as rain and rain lines were observed as high as 7,000 feet.

Consecutive nights without freezing temperatures and rain falling on snow will increase the avalanche danger today. Free water added to the snowpack at mid and low elevations is decreasing the strength of the snowpack. Expect to see loose wet activity transitioning towards wet slabs and formation of new glide cracks or full-blown glide avalanches primarily between 4,500 and 7,000 feet. The instability created by water that has been added to the snowpack is not always obvious and the only indications of weakening snow are natural failures and glide cracks. Don’t commit to avalanche terrain if you are unsure if the conditions are primed for wet failures as they are hard to predict and dangerous. Avoid traveling near or under cornices today especially later in the day because the lack of freezing temperatures have significantly weakened them. Remember that cornices tend to fail further back than expected so give them a wide berth.

Near 7,000 feet most locations initially received snow that transitioned to rain, but higher up wet snow was accumulating. Snow totals are small, but the high SWEs are adding a good load to the snowpack. This layer will need a day to bond to crusts on solar aspects and may be the catalyst needed to activate the deep persistent weak layers on cooler aspects. Although still unlikely be aware that large dry avalanches can be triggered from start zones or rocky areas above 7,000 feet on northern aspects.

Avalanche and Weather Outlook

Warm and mostly cloudy conditions are forecasted for today. A round of light precipitation looks to develop by Friday morning with rain lines approaching 7,000 feet again. Saturday will bring a more impactful storm for the weekend. Overall the avalanche danger will slowly trend upwards over the next few days with more rain and snow.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

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[Scott]

Avalanche Advisory for April 6, 2019

moderate danger
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The avalanche danger is MODERATE. Wet avalanches will be possible across West Central Montana backcountry as a result of warm temperatures and significant rain. Carefully evaluate snow and terrain before traveling on steep slopes or onto likely trigger points.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Saturday, April 6th, 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

Overnight temperatures cooled a bit and rain and snow showers continued. Above about 5,500 temperatures briefly dropped below freezing early this morning creating a light freeze. Mountain temperatures this morning are hovering right around freezing and range from 28 to 33 degrees Fahrenheit. Showers yesterday brought rain to a good portion of the advisory area and to upper elevations. Overnight the rain line dropped bringing heavy snow that fell onto rain-saturated snow. Snow water equivalents for the past 24 hours range from 0.1 to 0.6 inches of water. Winds are primarily out of the west to southwest and are sustained in the upper teens with gusts into the low thirties.

A few days with above freezing temperatures and rain to upper elevations combined with very light freeze last night and continued rain transitioning to wet heavy snow will increase wet avalanche activity today. Wet avalanches can be challenging to predict and won’t give you many red flags. Look for increased loose activity or roller balls to identify areas of increased potential. Avoid likely starting zones like rocky terrain, rollovers, and saturated or runneled snow.

The wet and heavy new snow will need a day or two to bond to the old snow surface. Loose wet avalanches will be widespread and easily triggered in steep terrain today. Cornices will continue to lose strength as temperatures climb above freezing again today. With yesterdays high elevation rain (approx 8,000 feet) expect to see an increase in glide cracks. The snowpack is wet and lubricated and primed for gliding at any elevation now. Glide avalanches are extremely difficult to predict and can release without warning, steer clear of slopes that have glide cracks and avoid traveling below them or on adjacent terrain as it likely has a similar structure and bed surface necessary for glide avalanches.

The bottom line is that rain yesterday, a very light overnight freeze, wet new snow and temperatures well above freezing will all increase the avalanche danger today. Avalanche activity will increase through the afternoon and requires anyone in the mountains to stay aware of rapidly changing conditions as the day progresses.

Avalanche and Weather Outlook

Diminishing showers this morning will make today a bit drier than yesterday. Light and scattered shower potential will again develop later today but snow and rain totals will be minimal (forecast). The avalanche danger today will increase with emphasis on solar aspects and locations that experience rain showers today. Sunday will bring a significant increase for snow as a moist system moves into the region. Snow levels will drop and several inches of new snow is possible.

We will conclude our regular forecasts next week as this storm cycle ends but will continue to post updates as necessary after that. Observations on our public observations page will continue to get posted and shared with the community so keep sending in what you find.

Ski and ride safe.

The post Avalanche Advisory for April 6, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for April 8, 2019

considerable danger
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Rain, wind, and heavy snow have increased the avalanche danger to CONSIDERABLE. Human triggered avalanches are likely. Warm temperatures and saturated snow with more moisture today are creating dangerous conditions that require conservative decisions and astute route-finding.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Monday, April 8th, 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 this morning are in the low thirties. Winds have subsided overnight while rain and snow continues to fall across the region. Snow lines have oscillated up and down through the storm complicating things. Upper elevations have received 6-10 inches of snow as of this morning while mid elevations have 2-5 inches mixed with rain and lower elevations have seen entirely rain. All of which adds up to over an inch of SWE in the past 24 hours.

Rain lines were around 6,500 feet yesterday and may creep further upslope today after lowering slightly overnight. 36-hour SWE totals of up to almost 3 inches can be found in the Bitterroot Range with plenty more on the way. Widespread wet avalanches will be seen for the next few days. Below rain line, free water in the snow will decrease the strength of the snowpack and make it susceptible to human triggers and some natural failures. Above rain line, dense snow and strong winds are creating a heavy load of surface snow that is stressing the snowpack. Wet avalanches will be widespread and possible on all aspects and elevations with the largest slides possible at mid-elevations.

Strong wind accompanied the initial snowfall and will make wind drifted snow easy to trigger. Sundays winds moved a good amount of new snow and has created small windslabs at upper elevations that were easily triggered yesterday in the rattlesnake. Newly drifted snow may be sitting on crusts or at a wet snow interface and have poor bonding. Avoid steep wind loaded terrain above 6,000 feet where avalanches will easily be triggered by humans today.

Bottom Line: The heavy load of dense snow and rain have destabilized the snowpack and will continue to do so for the next few days. This is likely the catalysts that will kick off the first significant springtime avalanche cycle.

Avalanche and Weather Outlook

A very moist system continues to impact the region with plenty more to come (forecast). Snow and rain will continue today further enhancing the avalanche danger. However, snow levels look to drop Tuesday and transitions to more snow than rain. The avalanche danger will continue to increase as the storm progresses and avalanche problems may even change as precipitation transitions from rain to snow.

We will conclude our regular forecasts later this week as the storm cycle ends but will continue to post updates as necessary after that. Observations on our public observations page will continue to get posted and shared with the community so keep sending in what you find.

Ski and ride safe.

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[Scott]

Avalanche Advisory for April 9, 2019

considerable danger
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The avalanche danger for the West Central Montana backcountry is CONSIDERABLE. Wind slabs are easily triggered at upper elevations and move quickly on solid bed surfaces. At mid-low elevations, saturated snow is failing from the recent load of water and continues to be reactive. Carefully evaluate the snowpack before entering avalanche terrain as human triggered avalanches are likely today.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, April 9th, 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

An atmospheric river continues to impact the forecast area adding another 0.3 to 0.8 inches of water to the snowpack over the past 24 hours. Mountain temperatures range from 34 to 36 degrees Fahrenheit as of 5am this morning. Winds continue to be unremarkable with Deer Mountain reporting 9 mph from the SSW with gusts up to 16 mph but stronger ridgetop winds are likely.

Yesterday we toured in the Central Bitterroot and found a reactive snowpack. Above 7,000 feet small wind slabs were easily triggered. Although initially small they were able to entrain large amounts of snow and create sympathetic releases, quickly developing into very large slides which were able to run far and fast on dense snow and crusts (pic). Wind slabs continue to grow as more snow and wind affects the region. Wind drifted snow will easily fail with human triggers and traveling below them is not recommended with how far and fast they were moving yesterday. Carefully assess the snowpack for signs of wind loading before venturing into avalanche terrain.

Rain to just below 7,000 feet yesterday has saturated the snowpack producing widespread loose wet slides and wet slabs. Multiple natural wet avalanches were observed up to about 8,000 feet and loose wet slides and roller balls were easily triggered on rollovers and in steep terrain. Wet activity will be concentrated between approximately 5,000 and 7,000 feet but should be considered on any slope with saturated snow.

Bottom line: Avalanches will easily be triggered today, the key is determining which problems are the greatest concern where and how to appropriately manage the hazards. Avoid wind loaded terrain and remember that wet avalanches can be challenging to predict so avoid starting zones that are saturated if you don’t want to roll the dice.

Avalanche and Weather Outlook

The atmospheric river will continue to supply plenty of moisture to the region before subsiding late Wednesday and transitioning to showery conditions for the end of the work week. Lots of additional water is expected over the next two days but will transition towards more snow than rain. Rain lines are dropping and should be around 5,500 feet today and by Wednesday will be around 4,000 feet (forecast). The avalanche danger won’t drop until the precipitation subsides.

We will conclude our regular forecasts later this week as the storm cycle ends but will continue to post updates as necessary after that. Observations on our public observations page will continue to get posted and shared with the community so keep sending in what you find.

Ski and ride safe.

The post Avalanche Advisory for April 9, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Special Update – Spring Snow and Weather – April 11, 2019

norating danger
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This is Logan King with the end of the season update for the West Central Montana Avalanche Center. It doesn’t feel like spring in the mountain as copious snow has fallen over the past week but it’s not uncommon for large snow events this time of year. Whether we are ready for it or not spring is here and it necessitates a different set of skills and approach to recreating in the mountains.

Yesterday, while touring in the Rattlesnake we found full on mixed spring conditions with a mix of dry and wet avalanche problems. The name of the game is now adjusting to conditions as they rapidly change throughout the day. Keep in mind that spring can bring dry avalanches in the form of storm slabs, and wind slabs or more challenging hazards like wet avalanches and cornice failures.

At upper elevations or in dry snow watch for wind slabs failing on interfaces of old snow or crusts. Also, stay aware of storm slabs following storms that bring snow to the region. Carefully assess the new snow for how well it is bonding to the old snow surface. New or wind drifted snow on crusts can result in easy failures that have a lot of pop that rapidly accelerate on slick crusts.

Long days, warm temperatures, and sunshine will result in the loss of strength within the snowpack. Wet avalanche problems are all a function of timing. Get in and get out before the snow loses enough strength to fail. When snow becomes wet and starts to form roller balls move to a different aspect or call it a day. Wet slabs are challenging to predict but are best identified by lack of overnight freezes and free water in the snowpack. Remember that the harder or deeper the freeze overnight the more time you will have the following day before conditions turn. Wet slabs and glide avalanches are to be expected this time of year, wet slabs are a challenge to predict and glides are nearly impossible. With glide avalanches being so unpredictable its best to avoid them altogether if you see glide cracks don’t travel below them and find different terrain free of cracks in the snow. Finally, remember cornices will continue to lose strength as well. Give cornices plenty of space as they can break back farther than anticipated.

There is plenty of moisture still on tap for the foreseeable future and we will continue to post updates as the season draws to a close. We will continue to post public observations as we receive them.

All of us at the WCMAC would like to express our appreciation for all of the amazing support that we receive from the community. It has been a great season and we wouldn’t be able to do what we do without the outstanding support from all of you. Thanks again for another great season.

Ski and Ride Safe!

The post Avalanche Special Update – Spring Snow and Weather – April 11, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Special Update – Spring Conditions – April 23, 2019

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Good morning this is Logan King from the West Central Montana avalanche center with an end of season conditions update for Tuesday, April 23rd, 2019.

Mid-week will bring warm and dry conditions that cap off a handful of days which resulted in a significant warming of the snowpack. This extended period of warm weather may spell the end for cold dry snow for the season. There is still plenty of corn snow to enjoy out there and the season isn’t over yet but the time has come for you to become your own forecaster. The first step is to know your foe.

Saturated snow from warm temperatures, solar radiation, and rain or wet snow events will continue the transition from dry avalanche problems to wet avalanche problems. The main concerns are wet slab avalanches, glide avalanches, and loose wet avalanches. Likely trigger points are slope transitions or rock outcrops and can be dependent on elevation, aspect, and time. If the snow is starting to get wet and sloppy and you are sinking more than a few inches down its time to get out or move to a safer location. Don’t forget that cornices will continue to be suspect for the remainder of the season until they have all broken down. Wet avalanche problems are more difficult to predict and require more skill, experience, knowledge and planning to avoid them.

Before you travel into the mountains take the time to go over the weather for the past few days and determine if conditions have refrozen overnight and if so, how hard of a freeze did the snow undergo? Trip plan accordingly, this may mean leaving or getting down early, avoiding certain aspects and elevations and avoiding traveling under or onto cornices at certain times of the day. There is a multitude of resources available to help with trip planning that can either help you map out your routes or keep tabs on weather and conditions. Familiarize yourself with local telemetry resources, cameras, and apps that can be used to monitor conditions. Do your due diligence to minimize the uncertainty that is associated with wet avalanches before venturing out. Enjoy the corn, and if you get out, feel free to share what you find on the public observation page, we will continue to post reports as long as they are coming in.

Finally, I would like to extend our thanks to the amazing community that supports the center and makes all of the forecasts and educational opportunities possible. Thanks to all of our supporters, sponsor, donors, partners, and our wonderful board who has helped to make the center what it is today.

Ski and ride safe.

The post Avalanche Special Update – Spring Conditions – April 23, 2019 appeared first on Missoula Avalanche.