Avalanche Forecast
Regions: Olympics.
A refreezing snowpack will cause decreased danger Wednesday in most areas. Watch for fresh but shallow new Wind Slabs near ridges at higher elevations. Older weak snow may still exist in the snowpack so avoid large open slopes that may still harbor this difficult to predict and manage avalanche problem. Give fresh Cornices a wide margin of safety.
Detailed Forecast
A strengthening surface crust will limit the avalanche danger Wednesday in the Olympics. Shallow new snow may be transported near ridges, especially above treeline where small wind slabs may be possible to triggered on steep lee slopes. Avoid steep open slopes showing signs of recent wind loading.
Recent warm weather and snowpack settlement has helped round and strengthen buried persistent weak layers. We have removed the Persistent Slab problem from the forecast problem list, however this does not mean it is impossible to trigger a persistent slab in isolated areas, especially with a larger trigger such as a cornice fall.Â
Avoid large open slopes, especially slopes below large overhanging cornices.Â
Snowpack Discussion
Sunshine and temperatures in the 40's to lower 50's over the past few days has allowed for significant snowpack settlement and for a variety of surface conditions to develop. Several melt-freeze cycles over the past few days has allowed for a strengthening snowpack.Â
The latest snowfall was 3-4 inches that fell Thursday night and early Friday. This shallow recent snow has undergone settlement consolidation over the past few warm and sunny days.Â
Older weak snow layers continue to be reported in the Olympics. On slopes that receive direct sun, several facet/crust layers may be found. A more widespread layer of weak sugary facets was found just above a very firm melt-freeze (2/8) crust formed in early February. The depth to this weak layer depends on aspect and elevation.
We have not received reports of recent avalanches in the Olympics other than small wet loose on steep sunny slopes.
There are no significant layers of concern below the 2/8 crust layer.
Observations
On Sunday as of 1 PM, NPS rangers reported generally small loose wet avalanches with one larger release caused by a partial cornice collapse.Â
On Saturday, Forecaster Robert Hahn and NPS Rangers found the 2/8 weak snow/crust interface in snowpits on a West aspect at 5300' and down 2.5 feet from the surface. No new avalanche activity was observed other than small wet loose avalanches on steep sunny slopes. North facing terrain still held drier settled powder.Â
On Wednesday March 7th, a NPS ranger traveled in the Victor Pass area and found many crusts with facets forming on south aspects. Near ridge-tops, the 2/13 weak layer was 8-12" down and 3 mm facets were observed. Mid-slope this layer was down 3-4 feet.
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, West, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1