Avalanche Forecast

A mostly dry but cloudy day is in store Friday with warming and increasing winds. The exception is the Mt Baker area where precipitation should increase from late morning or midday. A period of light to moderate rain and snow at rising freezing levels is expected again Friday along with strong S-SW  ridgetop winds. New storm related danger will continue Friday, especially near and above treeline as strong southwest wind loads lee slopes building new wind slab layers. Wind slabs will build on lee slopes, facing generally NW-NE.  Earlier formed wind slabs may still be reactive Friday and may add to the increasingly complex snow structure, by Thursday. Large cornices should form near ridges as well, requiring travelers to avoid overhead hazard.

Conservative terrain selection will be essential near and above treeline to avoid wind loaded terrain and features. Choose moderately angled terrain and avoid wind loaded slopes, choose the terrain void of overhead hazard such as wind slabs or cornices.

Non-avalanche hazard: Despite our seasonally, healthy snowpack, many creeks are open and difficult to cross due to the periodic warm temperatures and rain events.  

Weather and Snowpack

Very mild weather a week ago allowed for the formation of a strong melt-freeze crust, especially thick on solar slopes in most areas by Friday.

A series of active fronts have transited the region since Sunday, with fluctuating freezing levels and periods of very strong winds. The heaviest snowfall and precipitation occurred late Sunday and again late Tuesday. Total snowfall accumulations since late Sunday through Thursday afternoon have been about 2-3 feet at most sites along the west slopes. Some periods of rain have occurred below treeline at times as well, producing loose-wet avalanches.

The most significant transport winds were from the W-SW and seen early Sunday afternoon with gusts in the 40s or 50s below or near treeline with much stronger winds above treeline.

Wind slabs have formed near ridges most days this week, with daytime warming causing cold surface snow to settle and quickly form storm slabs. Mid and lower elevations have seen natural, loose-wet avalanches most days as radiation increases in early March. 

The mid and lower snow pack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

NWAC observer Tom Curtis was out on Jove Peak Monday. Jove Peak is NE of Stevens Pass and often overlaps snowpack characteristics of both the east and west slopes of the Cascades. Tom noted few instabilities in the upper snowpack until he observed a large natural wind slab avalanche (R2-D2) on the north side of Jove Peak that probably released Sunday night. The wind slab was 40 cm in depth and stepped down to a 2 mm buried surface hoar layer at 50 cm. The buried surface hoar was rounding, but clearly still sensitive to new loading. 

A stormy day on Tuesday limited observations, but one observation submitted via the NWAC observation page from behind Windy Ridge near Stevens Pass reported increasing instability and sensitivity to triggering with a large soft slab avalanche on a WNW aspect running well and entraining moist snow lower in the path. 

Both Wednesday and Thursday sunshine or daytime warming caused numerous natural point release, Loose-Wet avalanches on steep aspects, mostly below about 4500 feet, seen in the Alpental Valley and the Mt Baker backcountry.