Avalanche Forecast
Regions: Mt Hood.
Storm related avalanche problems could escalate quickly in the near and above treeline bands Friday with new snow and shifting winds.
Detailed Forecast
Light to occasionally moderate snowfall is possible for the Mt. Hood area Thursday night and Friday morning, with shallow yet unstable storm slabs developing by mid-day.Â
As winds shift from westerly to easterly Friday afternoon, the potential for new wind slab and cross-loaded slopes will become more likely, especially near and above tree-line. Â
Expect increasing storm related avalanche concerns in the near and above treeline bands on Friday if you travel into avalanche terrain. Â
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.Â
Snowpack Discussion
Since the wet start to February, fair weather through mid-February has led to generally thick surface crusts, as well as further deterioration of the snow cover below treeline. Weak weather disturbances passed through in NW flow aloft last week producing light snowfall but no new avalanche concerns.Â
New snowfall at NWAC Mt. Hood stations from Wednesday night through Thursday afternoon ranged from less than 1 inch at Meadows to a soggy 3 inches at Timberline with likely higher accumulations and some loading of easterly aspects above treeline. No avalanche reports were received on Thursday. Â
The mid and lower snowpack at Mt Hood snow consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
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: All aspects.
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