Avalanche Forecast

Snow will begin by late morning and increase in intensity throughout the day. In addition, there should be a gradual warming trend as snow levels peak near 3000 feet in the north and 3500-4000 feet in south in late afternoon and early evening. Combined with increasing southerly transport winds in the afternoon, there will be an increasing avalanche risk through the daylight hours. 

Storm slabs should become more sensitive and likely to trigger in the afternoon, particularly away from Passes which should stay cooler through the daylight hours.

Wind slabs should also become easier to trigger as they build on NW through E lee slopes throughout the day, expanding to westerly aspects mainly near the Passes.  

Expect deteriorating snow stability as the day progresses and the storm really takes hold. Travel conservatively by staying off steeper slopes and avoiding wind loaded terrain near and above treeline, especially later in the day. 

Be aware of early season hazards below treeline. The heavy rains from last week have left many creeks open at lower elevations. 

Snowfall over the west slopes the first week of December ranged from 1-4 feet. An atmospheric river arrived early in the week and heavy rain fell over the west slopes, with water amounts ranging from about 5 to 8.5 inches in just 2 days ending Wednesday morning!  Since Wednesday mid-day, 6 -12 inches of new snow fell along the west slopes through early Thursday morning. 

Avalanche and Snowpack Observations

It's worth remembering the setup last weekend led to widespread avalanches, both natural and human triggered beginning late Saturday with the heavy snow and ending on Tuesday with heavy rain throughout the west slopes. There were a couple close calls with skiers caught and either completely or partly buried at Stevens and Alpental over the first weekend in December, with slabs failing on recently buried weak layers formed in late Nov.

The upside to the wet and mild weather earlier this week was it really stressed the snowpack, fleshing out lingering problem layers. Persistent weak layers in the Stevens and Snoqualmie zones should have been eliminated and we have removed the persistent slab problem from the Passes moving forward.  

Reports from Pro Patrols mid-week indicated consolidating, wet, rounding grains well down into the snowpack. Observations from the Baker area Thursday indicated shallow storm and wind avalanche problems ramping up quickly with heavier precipitation in the afternoon. However by Friday, NWAC observers in the Stevens Pass and Baker backcountry reported no natural or skier triggered avalanches within the new snow with a generally right-side up layered upper snowpack near and below treeline. Crystal patrol reported significant loading from SE winds near and above treeline Thursday, but little instability in the way of control results Friday AM.