Avalanche Forecast
Regions: Snoqualmie Pass.
Detailed Forecast
The ridge which has been around so much over the US west coast this month will build a bit and shift east over the Northwest on Wednesday. This should cause a day of partly cloudy or partly sunny weather and mild above freezing temperatures through the daylight hours in the Olympics and Cascades. This weather and the low sun angle should cause little change in snow conditions.
There are no major concerns. Watch for old wind slab on previous lee slopes in the upper alpine. Small wet loose snow avalanches might be seen on steep solar aspects.
A front will begin to spread clouds and moisture to the area Wednesday night. Some light rain or snow may reach the Olympics and north Cascades Wednesday night.
Snowpack Discussion
An extended cold and dry period was seen earlier this month that caused faceting of the shallow snowpack at the surface and at the ground in most areas.
The last storm cycle that brought significant snow was about 20-23 December. This caused 1-2 feet of heavy snow in the alpine and some very wet snow and rain near and below treeline. Widespread sensitive wind slab was reported by ski patrol at Mt. Baker and a size 2 natural wet slab was reported by a professional guide near Chair Peak at Snoqualmie Pass.
Otherwise the weather since mid December has been characterized by minor wet snow and rain and periods of mild and routinely above freezing temperatures. Faceted snow from early in December has been largely eliminated or de-activated near and west of the crest.
Snow reports from NWAC pro observers for near and west of the crest lately mainly indicate and consolidated stable snow pack with alternating layers of crusts and rounded grains. A photo below illustrates crusts identified in a snowpit dug by NWAC pro observer Jeff Hambleton at Table Mountain on a south aspect at 5500 feet near Mt. Baker on 29 December.
There were some small wet loose avalanches reported on solar aspects until a couple days ago but none lately. Back country skiers are also reporting plenty of hard or icy slopes.
A weak front is crossing the area on Tuesday. Some light snow or light rain should do little to change conditions. The avalanche danger will continue to be low at the lower elevations due to the meager snowpack.
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.
Likelihood: Unlikely
Expected Size: 1 - 1