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Archived

Avalanche Forecast

Jan 15th, 2016–Jan 16th, 2016
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Mt Hood.

Back country travel in avalanche terrain at Mt Hood is not recommended on Saturday. An avalanche warning has been issued Mt Hood for Saturday.

Detailed Forecast

Active weather and avalanches should be seen this weekend!

A front will approach the Northwest Saturday morning and should cross the Northwest Saturday midday. This will cause increasing winds and moderate to heavy rain or snow with warming on Saturday. A change to rain or snow showers should be seen following the front Saturday afternoon and night.

This weather will build generally upside down snow layers of increasing density near the surface and snow may also change to rain in some areas. Up to about a foot of upside down snow should be seen at Mt Hood especially in the higher terrain bands by late Saturday.

New wind slab will be very likely mainly on lee north to east slopes on Saturday.

New storm slab due to the warming trend is also very likely on varied aspects where winds are lighter and snow rapidly accumulates to deeper than a few inches.

Avalanches releasing in near surface layers on Saturday may entrain previous snow producing large avalanches.

 

Snowpack Discussion

The latest period of snowfall has been from about January 12-15th with about 20 inches at Mt Hood.

A very active day on avalanche control was seen at Mt Hood Meadows today. The pro patrol reported explosively triggered widespread 1-4 foot slab avalanches on north to east slopes above treeline releasing on a crust from last weekend. Ski cuts were deemed to be too dangerous to undertake along with shooting cracks and some remote triggering by snow cats. Below treeline  had storm slab and loose dry avalanches that were easy to trigger and running a more recent crust from about 2 days ago.

 

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.

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 1

Storm Slabs

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.

 

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

 

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 1