Avalanche Forecast
Regions: Mt Hood.
Backcountry travel is not recommended near and above treeline Sunday on Mt. Hood. Below treeline, choose conservative terrain such as lower angled slopes while watching for firmer wind transported snow down into the below treeline band during the afternoon.
Detailed Forecast
More snow is on the way Saturday night and Sunday with a gradual cooling trend forecast. W-SW transport winds will continue on Sunday and are forecast to become very strong on the upper mountain Sunday afternoon. Â
Despite a slight cooling trend, new and recently formed storm slabs should still be sensitive Sunday. While storm slabs are most likely to release within the most recent storm layers, various crusts are capable of providing bed surfaces for larger avalanches.Â
We've highlighted more traditional lee easterly aspects on the elevation/aspect diagram, but be aware that strong winds on the upper mountain Sunday afternoon may create unusual loading patterns as well as load lee aspects much further downslope than usual. Large natural and human triggered wind slab avalanches will be possible on lee aspects near and above treeline. Â
Backcountry travel is not recommended near and above treeline Sunday on Mt. Hood. Below treeline, choose conservative terrain such as lower angled slopes while watching for firmer wind transported snow down into the below treeline band during the afternoon. Â
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Snowpack Discussion
Weather and Snowpack
Strong NE-E winds were seen Wednesday and Thursday with very cold temperatures. Fresh, touchy wind slabs formed with large plumes of snow visibly transporting loose snow from exposed terrain.
A storm cycle began Friday with generally 1Â foot of snow accumulating at NWAC stations on Mt. Hood. Except for a band of freezing rain on the lower mountain Saturday morning, snow levels gradually warmed into the 4000-5000 foot range by Saturday afternoon. Â Moderate W-SW transport winds were recorded near and above treeline for much of Friday night and Saturday.
Recent Observations
NWAC pro-observer Laura Green was out near Barlow Pass on Friday at 4100-5200 feet and found limited wind transport, low quality shears in tests in the upper snowpack and no direct signs of instability.Â
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
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, 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: Likely
Expected Size: 1 - 1