Avalanche Forecast
Regions: Mt Hood.
A strong storm has created very dangerous avalanche conditions. Natural avalanches are likely and human triggered avalanches very likely in terrain near and above treeline where travel in avalanche terrain is not recommended Wednesday.
Detailed Forecast
Continued very strong winds overnight Tuesday and Wednesday with increasing light to moderate snow overnight and early Wednesday will maintain widespread unstable snow conditions. Natural or triggered avalanches are very likely in exposed terrain near and above treeline.Â
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Snowpack Discussion
Weather and Snowpack
The most recent warm and wet SW storm arrived on Valentines Day 2/14 and formed the uppermost very strong rain crust in our snowpack.Â
About 2 feet of snow accumulated at the NWAC Mt Hood stations from Sunday, 2/19 through Wednesday 2/22.Â
Weak weather systems Sunday and again Monday, deposited about another foot of low density snow by Monday evening with light to moderate westerly transport winds near and above treeline
A stronger than forecast storm late Monday through Tuesday deposited an additional 2-2.5 feet of snow by Tuesday evening! The latest heavy snow has arrived with very strong crest level winds with 7300 ft elevation, wind instruments averaging 50+ MPH all day Tuesday with gusts over 100 MPH.  Â
Recent Observations
Several contacts with the Mt Hood pro patrol through the day Tuesday reported widespread natural and triggered wind and storm slabs Tuesday morning, especially near and above treeline. Avalanches were occurring even on relatively low angled terrain. Over 2 feet of new snow had accumulated by early Tuesday with more snow received through the day. Low visibility limited additional observations, however, by Tuesday afternoon large hard wind slabs were developing above treeline and several sympathetic avalanches were triggered. The recent relatively stable snowpack has quickly become very dangerous avalanche conditions.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