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Archived

Avalanche Forecast

Jan 7th, 2020–Jan 8th, 2020
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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.

Another round of heavy snow and wind will maintain very dangerous avalanche conditions. Look for signs of wind transported snow such as cornices and firm or textured snow surfaces. Avoid lee slopes steeper than 35 degrees where you find wind deposited snow.

Discussion

A significant freezing rain crust developed Monday night between about 5500-7000 feet. This ice layer will make travel conditions very difficult where it is not covered by new snow. New snow and wind transported snow may bond poorly to this icy surface.

Snowpack Discussion

New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.

Avalanche Problems

Wind Slabs

Another round of snow and strong winds will impact the area Tuesday night, building fresh wind slabs. The winds will be strong enough to develop new wind slabs at all elevations. Wind transported snow may bond poorly to the freezing rain crust which is the surface in many places. Look for signs of wind transported snow such as cornices, firm or textured snow surfaces, and drifts of snow adjacent to scoured areas. Where you see signs of wind transported snow avoid slopes steeper than 35 degrees.

No observations have been made recently above treeline due to the strong winds and limited visibility. It is possible that very large wind slabs exist at upper elevations. Avoid travel on or below wind loaded slopes above treeline.

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: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 1