Avalanche Forecast
Regions: Olympics.
Shallow wind slabs may linger in wind exposed terrain above treeline. In some areas, firm surface crusts will make for difficult travel conditions so be prepared to self-arrest and think about the sliding hazard before crossing steeper slopes.
Detailed Forecast
On Thursday, mild temperatures will be accompanied by increasing morning clouds and a chance of very light rain on Thursday afternoon.Â
Lingering shallow wind slabs should continue to become far less sensitive to triggering on Thursday and confined to higher terrain. Continue to watch for areas of recently wind transported snow such as fresh cornices, snow drifts, and uneven snow surfaces. Identify and avoid locations where recent wind loading occurred.
Wind slabs can be deceptively difficult to manage in the terrain. Take a moment and read our recent blog post by NWAC Pro Observer Jeremy Allyn on wind slabs.
In some areas, firm surface crusts will make for difficult travel conditions so be prepared to self-arrest and think about the sliding hazard before crossing steep slopes. Â
Early season hazards still exist. Many creek beds have still not filled in for the winter.
Snowpack Discussion
Mild weather seen Sunday through Wednesday has allowed lingering wind slabs to gain strength.
On 12/29, snow levels rose to crest level by afternoon before dropping snow levels and SW winds Friday night redistributed post-frontal new snow, forming shallow wind slabs on lee slopes at higher elevations above a crust. This resulted in a variety of snow surfaces including soft unconsolidated snow, wind scoured slopes, rain crust, and firm wind slabs.Â
The 12/16 mid-December crust can still be found 2-3 feet down within the snowpack.
Observations
NWAC pro observer, Matt Schonwald visited Hurricane Ridge on Friday, 12/29 and stressed that this is a different snowpack than the Cascades! He visited W-NW-N-NE aspects and found the 12/16 crust and 1-2 mm facets down 2.5 feet. Several PST tests failures, self-arrested, but propagated through most of the column along the 12/16 layer. This PWL will mostly likely be found below ridgelines and will have to be watched moving forward.Â
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, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1