Avalanche Forecast
Regions: Mt Hood.
An approaching storm Wednesday will load and stress the deep recent storm snow Wednesday. Watch for changing conditions and be prepared to alter tour plans and leave plenty of safety margin. Natural or triggered avalanches will become increasingly likely later Wednesday.
Detailed Forecast
An approaching storm will bring increasing clouds and strengthening winds through the morning Wednesday. Snowfall will arrive Wednesday morning and increase through the afternoon with warming.Â
The warming and beginning of the new snow loading Wednesday, will begin to stress the significant recent storm snow. Â The avalanche danger will increase through the afternoon Wednesday, however the significant loading and heavier precipitation rates are likely to hold off until Wednesday night and into Thursday.
If the approaching storm arrives sooner than forecast or with, initially heavy precipitation, the avalanche danger could increase more rapidly than expected. Watch for changing conditions and be prepared to alter plans accordingly.
Natural and triggered avalanches will become increasingly likely through the day Wednesday.
Snowpack Discussion
Weather and Snowpack
A strong storm cycle began Friday with 3-4 feet of snow recorded at the Mt Hood area stations on average, through Monday afternoon. A warming trend affected all areas Sunday. Moderate W-SW transport winds were recorded near and above treeline for much of the weekend. Strong westerly winds persisted Monday.
Light snowfall occurred Tuesday, depositing about 2-3 inches of new snow with fairly light winds.Â
Recent Observations
Mt. Hood Meadows pro-patrol had a busy day on Saturday with sensitive but generally shallow storm slabs easily releasing during control on a density change in the storm snow. Wind loaded NE slopes between 5500-6500 ft ran well during control work with crowns locally up to 2'. Â
On Sunday morning Meadows pro-patrol found storm slabs on all aspects of about 1 ft that were especially sensitive below treeline. E-NE aspects were being continuously loaded near and above treeline throughout the day.Â
By Tuesday, reports of settling storm snow made avalanche control work less exciting, as avalanches were very limited to isolated wind loaded pockets. This is a good indication of improving conditions, at least for Tuesday!
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: All elevations.
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: Likely
Expected Size: 1 - 1