Watch for windslabs formed by strong winds on Wednesday. Fresh slabs on south facing slopes will be especially sensitive to solar triggering when the sun comes out on Thursday.
10-15 cm of new snow coupled with strong winds are expected to form thin, touchy windslab over a temperature crust at most elevations. In the high alpine where the temperature crust does not exist, in addition to the new snow, previous storm snow will be available for wind transport. Expect thick windslabs in alpine lees such as below ridge crests.
Wednesday night: Cloudy with scattered flurries bringing 10-15 cm of new snow. Strong west winds.
Thursday: Sunny periods with cloud increasing and flurries beginning in the evening. Light variable winds. Alpine high temperatures around - 10.
Friday: Cloudy with flurries bringing 10-20 cm of new snow, totaling 20-40 cm with overnight accumulations, easing overnight. Light northeast winds. Alpine high temperatures around -5.
Saturday: Cloudy with continuing flurries bringing 5-15 cm of new snow, continuing overnight. Light southwest winds. Alpine high temperatures around -8.
A large natural storm slab avalanche cycle up to size 3.5 was reported in Bear Pass earlier this week. The cycle has subsided as a cooling trend set in late Wednesday, locking up the previously moist storm snow. The large loads provided by this cycle were a great test for reactivity of the persistent slab problem. An absence of reports of storm slab avalanches stepping down to the deeper layers indicates that the deep persistent slab may no longer be an avalanche problem.
With the forecast snow and strong wind over Wednesday night, thin, touchy wind slab forming over a crust will be the main concern. Also watch for solar triggering of newly fallen snow on steep south facing terrain features in the alpine.
10-15 cm of new snow fell amid strong winds and cooling temperatures Wednesday night onto a temperature crust at all elevations except the very high alpine. Below the well settled slab of recent storm snow, two layers of surface hoar are buried 70-150 cm deep. Reports from the Shames area suggest buried surface hoar can be found on all aspects, but is more prevalent on southeast to southwest aspects around 800-1400 m. Avalanche activity on this layer has not been reported for the past week, indicating that it has become dormant.
