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Archived

Avalanche Forecast

Jan 1st, 2015–Jan 2nd, 2015
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Mt Hood.

Watch for lingering wind slab from early in the week where the northeast winds redistributed snow mainly near ridges.

Detailed Forecast

A weak cold front will move northwest to southeast over the Olympics and Cascades Friday afternoon and night. This should cause increasing northwest winds at Mt Hood on Friday with cooling. But no precipitation is expected to reach Mt Hood on Friday through the end of the daylight hours.

This weather should not greatly change snow conditions at Mt Hood on Friday.

Watch for lingering wind slab from early in the week where the northeast winds redistributed snow mainly near ridges.

Sun crusts are also likely on steep south slopes where sun warmed snow from Thursday refreezes on Friday.

 

Snowpack Discussion

A storm system hit the Northwest last weekend with strong west to northwest winds. NWAC sites at Mt Hood picked up about 28 inches of storm snow with a good cooling trend.

However strong northeast winds hit at the tail end of the storm Monday and Tuesday. At Mt Hood this transported snow and formed some local wind slab near ridges which may be mainly on northwest to southeast aspects due to the northeast winds.

The Mt. Hood Meadows ski patrol found cracking and easy releases of storm slab on Monday.

NWAC observer CJ Svela reported on Tuesday that the main problem at Mt Hood is lingering wind slab near ridgetops. A private report via the NWAC Recent Observations also indicates easy compression tests at 25-30 cm due to areas of small wind slab near ridges.

An upper ridge tilted inland yesterday and today producing sunny weather with warming at Mt Hood. 

Right side up powder may probably lingers on sheltered shaded slopes. The warming and sunshine will likely cause some snowballing and small wet loose avalanches on steep slopes facing the sun.

A generally strong mid and lower snowpack is expected to be preventing deeper instabilities at Mt Hood.

 

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: South East, South, South West, West.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 1