Avalanche Forecast

Tuesday night: Mostly cloudy, a trace of new snow, light southwest winds, alpine temperature -5 C, freezing level dropping to valley bottom.

Wednesday: Mostly cloudy, 2-5 cm of snow, moderate southwest winds, alpine temperature -2 C, freezing level around 1300 m.

Thursday: Mix of sun and cloud, light west winds, alpine high temperature -1 C, freezing level around 1500 m.

Friday: Mix of sun and cloud, isolated flurries with trace accumulations, moderate southwest winds, alpine high temperature 2 C, freezing level rising above 2000 m overnight.

Over the past several days, there have been reports of natural, human-triggered, and explosive triggered avalanches up to size 2.5 breaking in the new storm snow, specifically where it has been drifted by wind into stiffer slabs on northwest through northeast aspects. A couple of these avalanches have been reportedly triggered by cornice fall. See this MIN report for a helpful illustration of these wind slab avalanches.

Southwest winds continue to drift 20-30 cm of recent snow into slabs on lee and cross-loaded terrain features at upper elevations. This combination has also contributed to cornice growth, increasing the need for vigilance with overhead hazard. A temperature crust formed Friday at least as high as 1600 m.

The stout upper snowpack continues to settle in mild temperatures. Several crust layers exist in the mid-pack as a result of previous warming and rain events. These have not been identified as bed surfaces or failure planes in recent avalanche activity.

The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. Although inherently weak, this basal layer has not been an active avalanche problem in the region since December.

• Be alert to conditions that change with elevation, aspect and exposure to wind.
• Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
• Pay attention to cornices and give them a wide berth when traveling on or below ridges.