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Archived

Avalanche Forecast

Jan 8th, 2018–Jan 9th, 2018
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
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
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.

Light showers, moderate alpine winds and a cooling trend on Tuesday should slightly increase the avalanche danger as shallow new wind slabs build above treeline. Watch for signs of active wind loading onto lee aspects throughout the day and avoid obviously wind loaded slopes. If more snow materializes than forecast, be on the look out for shallow storm slabs or wind slab lower in the terrain.

Detailed Forecast

Light showers, moderate alpine winds and a cooling trend on Tuesday should slightly increase the avalanche danger as shallow new wind slabs build above treeline. Watch for signs of active wind loading onto lee aspects throughout the day and avoid obviously wind loaded slopes. If more snow materializes than forecast, be on the look out for shallow storm slabs or wind slab lower in the terrain.

Early season hazards still exist. Many creek beds have still not filled in for the winter.  

Snowpack Discussion

Warm temperatures on Sunday and Monday and occasional spits of light rain or snow did little to change the overall low avalanche danger on Mt. Hood. On Saturday, temperatures cooled and winds eased but there was little new snow at the tail end of Friday's system. 

Several 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

On Sunday, the Mt. Hood Meadows patrol reported that the surface crust was softening at all elevations in their area. 

NWAC pro-observer Laura Green was in the Bennett Pass area of the White River drainage on Saturday up to 6100 ft.  Laura found challenging travel conditions with a surface crust of variable strength and no notable layers of concern in the upper snowpack.  No new avalanche activity was observed. 

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: North, North East, East, South East, North West.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 1