Avalanche Forecast

Precipitation should end by early Tuesday as skies clear from the south and freezing levels climb.  Moderate northwest crest level winds should gradually ease through the day Tuesday.  This weather will help to settle and consolidate the large recent storm snow deposits and lead to a slowly stabilizing snowpack.  However warming and sunshine by late Tuesday may lead to some shallow wet snow conditions and possible loose-wet slides on steeper solar aspects.  

At elevations above treeline, earlier formed wind slab should be somewhat slower to stabilize so continued conservative decision making and cautious route finding will remain essential.  These earlier formed wind slabs near ridges in the alpine region should remain the greatest concern, most probably on north through southeast facing slopes.  Rather large wind slab releases may trigger more deeply buried weaknesses near or above old crust interfaces and this may lead to very large slides, though natural slides should become less likely and triggered slides should also become more stubborn to trigger, it remains a time to be extra cautious.

A nearly week long storm cycle began last Tuesday and should be waning Monday night as skies begin clearing under a return to high pressure. This major storm cycle has packed some fairly impressive numbers, especially for this season.  Five day storm snow amounts range on average from 60-150 cm both, with the lower amounts confined to lower Cascade passes where more rain occurred.  Most mid and higher elevation areas received 1-2 m of storm snow.  

Needless to day this produced several avalanche cycles producing numerous natural and triggered slides over the past few days.  Freezing levels fluctuated significantly and there were also periods of very very strong winds.  This culminated in some new denser layers or crust layers as well as buried weak lower density layers within the deep storm snow.  

Most recent avalanche activity either, natural, ski or explosive triggered has remained within storm snow layers, ranging from 15-60 cm. However, some slides released on a buried weak lower density layer above an earlier formed crust layer down some 60-120 cm or more depending upon locale.  Recent field obs from Sunday near Stevens Pass on a lee slope just above 5000 ft showed wind loaded storm snow of 1.2 m. The NWAC station at Paradise on Mt. Rainier became the first station this season to finally cross the 100 inch threshold during this storm.   

There were several reported soft slab releases Friday in the Mt Baker backcountry, felt to be releasing on a weaker lower density storm snow layer above a previous crust layer. However the snowpack has significantly changed with recent additional loading, warming as well as significant overall settlement helping move towards slow stabilization.  There were numerous new natural and triggered slides near Mt Baker on Shuksan arm and vicinity Sunday with slides on Shuksan estimated with Destructive potential 3 (destroy a wood frame house!).  Another natural release was reported early Sunday afternoon that likely released late morning during warming and heavy loading east of Stevens Pass.  The slide path is known as West Camp of Rock Mountain and was rated as D3/R2 N-SS, with a start zone about 5900 ft but poor visibility limited viewing.  

An NWAC observer in the Stevens Pass area Sunday reported sensitive storm slab with shooting cracks below treeline and good wind transport on higher N thru SE slopes.  

For the west slopes of the Cascades and Olympics, a generally favorable mid and lower snowpack exists, even if well below seasonal norms, consisting of various crust layers, rounded grains, and melt-freeze crystals.  

Sno-cat triggered 5' crown - E aspect - 5700 feet - White Pass In Area Sunday (Photo by Chris Talbot)

Shooting cracks in Storm Snow 4800' - SE Aspect - Stevens Pass (Photo by Dallas Glass)