Avalanche Forecast
Regions: Snoqualmie Pass.
Storm and wind slabs remain possible Tuesday, especially on lee aspects near and above treeline. Watch for wind transported new snow received Sunday and Monday, especially higher terrain.
Detailed Forecast
Little or no precipitation is expected early Tuesday, with light rain and snow increasing in the afternoon along the west slopes.Â
Shallow storm slabs formed Sunday and Monday may be poorly bonded to old surface crusts, especially near and above treeline on lee aspects.  Â
Snowpack Discussion
The weekend of Jan 24-25th, a warm and wet weather system caused high snow levels and rain and allowed for extensive snowpack settlement. Last week, high pressure aloft caused abundant sunshine and mild temperatures. This weather has now caused a thick, strong near surface crust. A series of weak frontal systems crossed the PNW on Sunday and Monday, producing generally light amounts of new snow along with moderate S - SW winds. This has likely built some areas of new wind and storm slab mainly near and above treeline. Mostly shallow wet snow conditions exist below treeline.
On Monday in the Stevens Pass area, shallow, but touchy loose wet avalanches were noted by NWAC observer Jeff Ward..Â
Prior to the Sunday's system, the snowpack was dominated by strong surface crusts, limiting the avalanche potential. There had been surface hoar growth last week on shaded terrain mainly below about 5000 feet, along with some near surface faceting(NSF) on non-solar slopes. Surface hoar/NSF were likely buried by the light snowfall and initial cool temperatures Sunday.Â
See Jeff's video from the Steven's Pass area below.
The snowpack west of the crest mainly consists of the generally shallow recent storm snow over stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
Avalanche Problems
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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: All elevations.
Likelihood: Possible
Expected Size: 1 - 1