Avalanche Forecast

The avalanche danger will peak Sunday night through Monday morning during the period of heaviest loading, slightly decreasing later in the day and tapering from north to south across the Cascades. The snow-line through this period will determine the sensitivity and depth of storm and wind slabs. Expect rising avalanche danger with an increase in elevation, and avoid traveling below paths connected to higher start zones. The most significant snowfall is expected at higher elevations of the near and above elevation bands, and moderate to strong W-SW winds will easily transport new snow to lee slopes. A locally lower snow level at Mt. Baker will increase the likelihood of storm slabs developing below treeline. Storm slabs may develop in the upper portion of the below treeline band from Stevens Pass and south to Mt. Rainier. 

Generally small loose wet avalanches are possible at lower elevations in steep terrain.  Be especially careful of even small loose wet avalanches around terrain traps. 

Remember that beneath any new snow received during this storm, a myriad of early season terrain hazards exist, especially at lower elevations. Expect terrain hazards with poorly covered rocks, vegetation and creeks, particularly on south-facing terrain, at lower elevations, and on exposed ridges where wind events have stripped much of the seasons snowcover.

After 12 long days of high pressure, the first frontal system in quite awhile crossed the Cascades on Friday. New snow accumulations Saturday morning ranged from 2-5 inches along the west slopes of the Cascades with a local maximum at the top of Alpental with 8 inches of new snow. Below this storm snow, a highly varied array of  snow conditions exist, including melt-freeze crusts, settled old storm snow, and a mix of recently formed surface hoar or near surface facets (sugary snow) at lower elevations and some shaded terrain.

Warm frontal moisture that arrived on Sunday brought light rain to 4000-4500 feet in the north Cascades, a battle between rain and wet snow at Stevens and Snoqualmie Passes with light snowfall accumulating at the top of Alpental, and a mix up to about 5500 feet in the south Cascades (Paradise, Crystal) through 4 pm Sunday.  No significant avalanche activity was reported. The warmer temperatures and light rain likely helped wet or potentially destroy recently buried persistent weak layers at lower elevations, especially in the Stevens Pass area.   

The overall snowpack of 2-5 feet along the west slopes is stable with settled old snow sitting over the strong Thanksgiving rain crust, buried about 1.5-2.5 feet.

Observations

North

Monday Morning Update: Baker Pro patrol is reporting widespread explosive and ski triggered 12-14" wind slab or storm slab above 3800" with shallower slabs entraining wet snow underneath at elevations below 3800". Approximately 18" new snow.

Central

Both Stevens and Alpental pro-patrol reported a few small loose wet avalanches localized to very steep terrain features, but otherwise no avalanche activity in area. 

Alpental pro-patrol reported sensitive but shallow 4-6" storm slabs during Saturday morning's avalanche mitigation. The storm slabs were easy to trigger but did not run far. Wind transported snow was noted near-treeline from N-NW winds Friday night.

There is a pertinent observation from the Yodelin area of Stevens Pass from Friday detailing recently buried surface hoar in an open location below treeline on the NWAC observations page.

South

Professional observer Jeremy Allyn was in the Crystal backcountry on Saturday.  He found variable snow with pockets of enjoyable dust on crust in smoother terrain. Very localized pockets of soft wind slab were unreactive. Plenty of early season terrain hazards exist on solar aspects, wind scoured terrain and at lower elevations.