Avalanche Forecast
Issued: Jan 3rd, 2018 11:44AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
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.
Summary
Detailed Forecast
Continued mild temperatures with lowering clouds and increasing light rain and high elevation snow are expected on Thursday.
Lingering wind slabs should continue to be far less sensitive to triggering on Wednesday 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.
Despite all this new snow, 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. A variety of snow surfaces exist including wind scoured snow, crusts, and likely stubborn to unreactive wind slabs. No recent avalanche activity has been observed.
A variety of rain and freezing rain crusts are sandwiched in the upper snowpack depending on elevation. Current observations do not suggest these layers to be reactive.
Observations
Laura Green was in the Mt. Hood Meadows area on Thursday and reports slide for life conditions and very thin, unreactive wind deposits on non-solar slopes. On solar slopes, corn formed from the base to 7,300 ft. Stability tests on a SSE aspect at 6100 feet showed no reactive layers.
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
Expected Size
Valid until: Jan 4th, 2018 11:44AM
