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Archived

Avalanche Forecast

Jan 1st, 2020–Jan 2nd, 2020
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Mt Hood.

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.

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.

Avalanche 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: Likely

Expected Size: 1 - 1