Avalanche Forecast
Issued: Dec 8th, 2011 9:21AM
The alpine rating is Wind Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Fair - Intensity of incoming weather is uncertain on Sunday
Weather Forecast
Continued high pressure across the interior mountain ranges on Friday and Saturday. The ridge should break down on Sunday when a weak low pressure moves across the interior. There may be some strong winds in the alpine when the light precipitation starts on Sunday.
Avalanche Summary
Reports of a few small explosive released avalanches in the Dogtooth. We have dropped the danger rating in the alpine to moderate. It is still likely that you could trigger a windslab in steep terrain. Triggering a full depth release is getting less likely, but weak spots are sure to exist that may propagate a large avalanche. The snow pack is still relatively young and needs some time to mature. I am having a hard time dropping the treeline danger level to LOW because I think the snowpack is weaker and more variable in this region than it is to the west.
Snowpack Summary
There is not much change taking place. Previous problems are healing slowly. The overnight temperatures have been colder than I thought on the east slope, and they have probably been causing some depth hoar development, and some surface facetting. We suspect that surface hoar may be growing during the clear cold weather that has dominated over the past few days. Some steep south facing slopes may have developed a thin sun-crust. Windslabs continue to be a concern in the Purcells. Strong winds last week developed unstable slabs of transported snow on steep terrain in the alpine and at treeline. Snow depths are quite variable through the region. In the alpine there is 170- 250cm. At treeline there is anywhere from 130-150cm.The upper snowpack is tightening up forming a stronger mid-pack. A highlighted concern for the Purcells was the mid-November storms that created a heavy slab over a weak basal faceted base, resulting in a significant cycle of large avalanches running full depth.
Problems
Wind Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 10th, 2011 8:00AM