Avalanche Forecast

A slightly weaker front should cross the area Wednesday night through Thursday morning with an uptick of west to southwest winds during this time period as well. 

Warmer temperatures and a relative break in new loading Wednesday afternoon helped new storm snow instabilities settle, but new loading Wednesday night will reintroduce new storm and wind slab.  

Rain at lower elevations will also load and weaken surface snow layers and may cause wet loose avalanches in the lower below treeline zone, likely below 3500 ft.

Natural avalanches will be less likely on Thursday, but large avalanches in specific areas sensitive to skier/rider triggering remains likely.

With the passing of each storm system, the possibility of deeper and more dangerous slabs grows for slopes that have not yet avalanched, potentially releasing to or entraining snow down to near the late Jan crust.  Exercise caution tomorrow and through the rest of the storm cycle by choosing more conservative terrain.    

Note the avalanche danger is locally lower in the Crystal Mountain and south region and over in the Olympics. 

The moisture tap turned back on this week across the Pacific Northwest and we are in the midst of what will likely be at least a week long storm cycle more typical of a PNW winter with quick moving frontal systems arriving roughly every day.  What is not as typical is the variety of weak layers buried underneath the newest storm snow. Sustained cold tempeartures last week lead to new surface hoar formation, near surface faceting and preserved the generally light amounts of low density snow that fell during last week.  The cold weather also helped to break down crusts in the upper snowpack. Moderate east winds late last week helped form touchy wind slabs.    

Generally 2 - 4 inches of water weight has been added to the snowpack on the west slopes, with 1 to 2.5 ft of new, higher density snow. The higher amounts were seen at Mt. Baker and upper Alpental and Stevens NWAC stations.  Natural avalanches Monday night and again Tuesday night were reported throughout the west slopes with the exception of near Crystal Mtn.  In the near and above treeline zones, colder temperatures and strong westerly winds transported new snowfall and built new wind slab on lees slopes.  A period of easterly flow at Stevens and Snoqualmie Passes helped crossload slopes before a switch to westerly Wednesday morning. 

Near Mt. Baker, Mt. Baker ski patrol reported a natural cycle down below 5000' with the warming and slides up to 2'.  Some slides reached SR 542 Tuesday night. Alpental ski patrol reported a healthy avalanche cycle Tuesday night as well throughout their uncontrolled terrain with most slides initiated within the new storm snow but reaching down to a localized freezing rain crust was formed Sunday, 2/9. Perhaps the trickiest snowpack continues to be in and near the Stevens Pass area. DOT professionals reported slides 1-2.5 ft with control work Tuesday morning failing on faceted crystals just above the late Jan crust.  A similar weak layer was involved in a skier triggered avalanche on Big Chief Mtn just outside the ski area boundary Tuesday afternoon around 5000 ft on a NW aspect and resulted in an injury.  NWAC observer Jeff Ward has a great video from Tuesday demonstrating the touchy new storm slab failing on near surface facets and triggering a remote slide near Stevens Pass near treeline and of high quality shears for an increasingly deeply buried layer of surface hoar at lower elevations on a north aspect.   

Note the avalanche danger is locally lower in the Crystal Mountain and south region and over in the Olympics where there has been less new snow and due to reports of better bonding between old and new snow surfaces in the Crystal Mountain area. 

NWAC observer Jeff Hambelton sent this photo of a storm slab triggered on a test slope at Mt Baker from 10 Feb.

Limited snow at the lowest elevations will limit the avalanche danger there. The mid and base pack should still consist of mostly stable crust and melt form layers from periods of warm weather earlier this winter.