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RegisterDec 10th, 2015–Dec 11th, 2015
Stevens Pass.
Recent storm concerns should decrease through the day Friday, but watch for sensitive wind slab, especially on lee N through SE slopes near and above treeline. Careful route-finding and snow evaluation will be essential.
Showers should diminish overnight through Friday morning. A low pressure system should glance the southern Washington Cascades with only light snow Friday afternoon while partly sunny skies should be seen further north.
Wind slab from Thursday and Thursday night on lee N through SE slopes will be the primary avalanche problem near and above treeline. Lingering storm slabs concerns are likely to diminish during the day.
Use extra caution if traveling into the above treeline zone (alpine) as there have not been any recent observations from this elevation band.
Snowfall over the west slopes the first week of December ranged from 1-4 feet with an overall warming trend. 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 has fallen along the west slopes through Thursday afternoon with some moderate showers Thursday PM.
Avalanche and Snowpack Observations
The recent setup led to widespread avalanches, both natural and human triggered beginning late Saturday with heavy snow and ending Tuesday with heavy rain as reports from Baker, Stevens, Crystal and Snoqualmie trickled in. There were a couple close calls with skiers caught and either completely or partly buried at Stevens and Alpental with new slabs failing on recently buried weak layers.
The upside to the wet and mild weather over the past few days has been to greatly stress the snowpack and flesh out lingering problem layers. Persistent weak layers in the Stevens and Snoqualmie zones should have been eliminated at lower and mid elevations and we have removed the persistent slab problem from the Passes moving forward.
Reports from the Mt Baker and Stevens Pro Patrols on Wednesday indicated stable, consolidating, wet, rounding grains well down into the snowpack. NWAC observer Lee Lazarra in the Baker backcountry Thursday indicated shallow storm and wind avalanche problems ramping up quickly with heavier precipitation in the afternoon in the below and near treeline zones. Due to the stormy weather, few observations from above treeline have been received across the west slopes.