Avy Forecast 3.12.X
Backcountry Avalanche Forecast for Front Range
Issued 03/12/2010 8:07 AM by Simon Trautman
Highlights
Snowfall stopped, but winds increased from the north. New slabs have formed on E-S-W aspects up high. You will find pockets of drifted snow formed since Sunday, and some older drifts from the end of last week. They could be a problem on very steep slopes. As usual this winter, persistent weak layers near the ground keep deep slabs a possibility on the same steep slopes.
An avalanche fatality occurred on March 10, 2010 in the backcountry west of Arapahoe Basin Ski Area. A male snowboarder triggered and was caught in an avalanche in Steep Gully #1. The victim died of trauma after being carried into a stand of trees at the terminus of the path. This is the fourth avalanche fatality in Colorado this season.
Avalanche Danger
In the Front Range Zone the danger is CONSIDERABLE on steep E-S-W aspects near and above treeline where new snow has formed reactive wind slabs. There are pockets of CONSIDERABLE danger near and above treeline on NW-N-NE aspects, where windslabs formed Monday and Tuesday. Human triggered avalanches are probable on slopes steeper than 35 degrees where recent snow has drifted into stiff, variable slabs. Persistent weak layers near the ground keep deep slab avalanches a possibility on the same steep slopes.
The danger is MODERATE on all aspects below treeline.Human triggered avalanches remain possible.
Snow & Avalanche Discussion
It is still winter in the mountains. Continued cold temperatures, snow, and wind have not let our snowpack strengthen sufficiently. There have been four skier triggered avalanches across the state in the last 48 hours. All of these slides ran to the ground. One resulted in a fatality, one a partial burial that required partner rescue, and the other two sound like solid near misses. The snow is still cold, weak, and thin in many places. Don't let the mild spring weather cloud your judgment this weekend.
Snowfall tapered off on Thursday, but the wind has been strong form the NNW for the last 24 hours. The storm total was ~12" so there has been plenty of snow to move onto leeward aspects. Since Friday, winds have come from almost every direction. You will find soft to stiff slabs and drifts on most terrain near and above treeline, but with the overnight north winds be especially careful of E-S-W aspects.
Mild weather last week helped settle and strengthen the upper portion of the old snowpack. Stout, mostly supportable crusts were created on south and west aspects, many of these will now be covered with new wind slab at higher elevations. The upper snowpack in the alpine is highly variable, with multiple crossloaded layers. Thin, weak faceted layers are present on the southerly slopes under the recent wind slabs. On shady, or more northerly aspects, there are thicker layers of surface facets, or "recycled powder', below the newer snow. Recently loaded southern faces that did not have snow 3 days ago will be very reactive to human traffic.
Observers report that deeper weak layers above 12000' are still reactive. Recent storm cycles, regardless of snow amounts, have brought on avalanche cycles on these old, deep weak layers. Remotely triggered, human triggered, and natural avalanches have spiked upwards with just a little snow. Continue to play conservative. Triggered avalanches have the potential to be deep and large near and above treeline.