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Archived

Avalanche Forecast

Nov 25th, 2016–Nov 26th, 2016
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
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Mt Hood.

Human triggered avalanches will possible above treeline in areas that experience significant wind loading. Use caution while navigating avalanche terrain and take it slow, the season is just beginning! 

Detailed Forecast

A warm front lifting north Friday night should bring light to moderate precipitation to the Mt. Hood. Along with the precipitation, there should be a moderate warming trend through Saturday morning. 

Mild temperatures and time will help the most recent snow settle and recent storm slabs should become less reactive to human triggering. Rain below treeline should have a limited effect on the avalanche danger due to the shallow snowpack and abundance of terrain anchors. 

Shallow wind slabs found near and above treeline should be the most sensitive avalanche problem on Saturday. Strong winds above treeline will transport snow to lee aspects, loading mainly NW through SE aspects.  

Use caution at lower elevations where creeks, rocks and other early season terrain hazards lurk just below the surface; your body and equipment will thank you!  

Snowpack Discussion

Mt. Hood NWAC sites picked up about an inch and half of water over the last 3 days, but snowdepths near and below treeline are still quite shallow. Mt. Hood Meadows found pockets of shallow storm slabs sensitive on Thanksgiving Day above treeline, but the avalanche danger overall is muted by the early season shallow snowpack and an abundance of terrain anchors. 

It's early season and the forecasts are based on limited field observations. Keep that fact in the forefront of your mind if entering avalanche terrain this weekend. 

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, North West.

Elevations: Alpine, Treeline.

Likelihood: Possible

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: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1