Avalanche Forecast

Due to the high likelihood and variety of avalanche problems expected, the high avalanche danger forecast will continue along the west slopes of the Cascades Sunday. 

Another front will bring more moderate rain and snow to the Cascades Sunday, beginning in most areas by mid-morning and turning to moderate showers in the afternoon. The heaviest precipitation will likely focus on the volcanoes and areas favored by southerly flow. A confusing mix of wandering snow levels should be seen again Sunday, with areas west of the crest warming initially during the morning, and the Passes only slightly warming in the evening with a subtle switch to westerly winds.

This weather will generally cause upside down snow layers of increasing density near the surface and snow may also change to rain in some areas west of the crest and at lower elevations. Up to about a foot of upside down snow should be seen along the west slopes by late Sunday afternoon.

This snow will load the January 3rd and January 11th persistent weak layers were they exist along the Cascade west slopes. This could produce natural or human triggered avalanches that could be remotely triggered, propagate around terrain features and bury, injure or kill.

New wind slab will continue to build mainly on lee northwest to east slopes near and above treeline but should be more varied aspects in the Cascade passes. As the same lee aspects continue to load Sunday, larger avalanches will become possible. 

New storm slab due to the warming trend is also very likely on varied aspects where winds are lighter and snow rapidly accumulates to deeper than a few inches Avalanches releasing in near surface layers on Sunday may entrain previous snow producing large and powerful avalanches.

Loose wet avalanche will again be possible below treeline in areas that see initial snow turn to rain Sunday, mainly on steeper slopes below treeline, although this will not be listed as a primary avalanche problem. 

Deep storm snow that fell during mid-late December is well settled, homogeneous and has stabilized so the current avalanche danger focus will be on the upper snowpack. Fair weather over the New Year caused extensive surface hoar and near surface faceted snow. This was buried by about light to moderate snowfall along the west slopes from about January 3rd-6th. Another fair weather period was seen from about January 7-10th. Surface hoar and near surface faceted snow formed again in many areas during this period. 

A parade of weather systems this week has added moderate amounts of new snowfall along the west slopes. The latest frontal system on Saturday brought 8-12 inches along the west slopes through 5 pm Saturday, with rain mixing up to roughly 5000 feet outside the Cascade Passes, from Mt. Baker down to Mt. Rainier. 

Avalanche and snowpack observations 

From a combination of  reports from the Mt Baker pro patrol and the NWAC Observations page, a 2-3 foot slab was remotely triggered Thursday at about 5500 feet on the north side of Shuksan Arm. A phone report from the Mt Baker pro patrol to the NWAC indicated the persistent January 11th layer.

NWAC Pro observer Lee Lazzara was near Mt Baker on Thursday and above 5000 feet on W-N-E aspects found 30 cm of snow over a 2 cm think layer of surface hoar buried on January 11th. He was able to trigger this persistent slab with a cornice test and snow pit tests gave easy results indicating propagation. He also noted pockets of wind slab over the same persistent January 11th layer.

A solo ski tourer in Silver Basin near Crystal Mountain Friday triggered a 40 cm slab on a west aspect at about 6600 feet that released on the persistent January 11th layer. This skier was caught and and sustained minor injuries.

NWAC Pro observer Dallas Glass found the buried surface hoar layer well intact 45-50 cm down on a west aspect of Kendall Peak Saturday.  Natural avalanches he observed were limited to recent storm snow, with storm slabs averaging around 8-12 inches (20-30 cm).  Mt. Baker pro-patrol found storm slabs to reactive with ski cuts this morning in the 8-10 inch range before a change to rain. They also reported an 18" storm slab that caught but did not bury a snowshoer on a steep but short NW slope outside the ski area. 

Make sure to check out the Professional observer avalanche and snowpack photos in the film strip!