Avalanche Forecast
Issued: Jan 1st, 2020 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
Strong winds and new snow are building fresh wind slabs. These slabs may be poorly bonded to a saturated and frozen surface. Avoid steep lee slopes with freshly drifted snow. Evaluate the bond between new and old snow.
Summary
Discussion
New Year’s Day was a wet one on Mt Hood! Telemetry from the ski areas showed 4.0-4.5 inches of water in the last 24 hours! Most of that fell as rain or freezing rain Tuesday night and extended up to 7000’ or higher before cooling down and switching to snow Wednesday afternoon.
At low elevations, a rain saturated and re-frozen snowpack will make travel conditions the biggest concern.
Snowpack Discussion
New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.
Problems
Wind Slabs
Strong winds will build fresh wind slabs on lee slopes, at upper and middle elevations. New wind slabs will likely have a poor bond to the frozen, rain saturated snow surface below them. Avoid steep slopes with wind drifted snow and carefully evaluate the bond between new and old snow.
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: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 2nd, 2020 10:00AM
