Avalanche Forecast
Regions: Cascades - West.
Shallow storm slabs are possible primarily on lee slopes above treeline Thursday.
Detailed Forecast
A few inches of new snow may accumulate along the west slopes above 4000-5000 feet Wednesday night through Thursday afternoon. The new snow along with a slight warming trend Thursday afternoon may make for locally unstable and shallow storm slabs, especially on lee slopes above treeline. Â
Watch for new snow bonding poorly to the old snow surface;Â likely a variety of surface crusts and older wind transported snow.Â
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.Â
Snowpack Discussion
Since the warm and wet start to February, fair weather through mid-February has led to generally thick surface crusts, as well as further deterioration of the snow cover below treeline.Â
A few weather disturbances passed through last Thursday and Friday, bringing a welcome few inches of snow near and above treeline. Winds veered to the east or northeast on Saturday, causing some new wind slab formation on non-traditional more westerly to southerly aspects mainly above treeline. A few reports of ski-triggered shallow wind slabs were reported from the west slopes over the weekend, generally found above tree-line. Â
Monday, NWAC observer Jeremy Allyn did some reconnaissance in the Alpental Valley, unfortunately, without the need for or possibility of travel on skis. The images below, simply recount the well known tale of the season.
The state of Snoqualmie Pass, Feb 23. The summer trail to Snow Lake Divide. Photo: Jeremy Allyn
The state of Snoqualmie Pass, Feb 23. Chair Peak and Snow Lake. Photo: Jeremy AllynÂ
The mid and lower snowpack west of the crest snow consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
Avalanche Problems
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1