Avalanche Forecast
Regions: Cascades - South West.
Any light snowfall received Tuesday night should not be significant enough to cause an increase in the generally low avalanche danger in all areas.
Detailed Forecast
Mostly cloudy and cool Wednesday with an increasing chance of light showers, mainly after daylight hours. Â
As a result of further cooling and cloud cover, little threat of avalanches is expected.Â
The isolated shallow wind slab that may have formed over the weekend above treeline, on non-traditional westerly to southerly aspects, may persist on specific terrain features.
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. Â
On Saturday, NWAC observer reports from the Crystal Mt backcountry described a few inches of new snow bonding well to the old surface through mid-day. However, at Winchester Mt in the Mt. Baker area, new wind slab 10-40 cm thick was observed above treeline on multiple aspects with new NE wind transport in progress. A small loose wet slide was triggered on a south slope late in the day, even with the cold temperatures and wind.
On Sunday, a skier triggered a relatively shallow hard slab in the Nisqually Chutes on Mt Rainer and safely escaped the slide. The slab formed from the recent wind transport Saturday and appears to have formed in a steep terrain feature between rock outcrops. Dallas Glass at Skyline found the 10-15 cm of the most recent snow well bonded near treeline with minimal new wind transport.
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
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: South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1