Avalanche Forecast
Regions: Mt Hood.
Moderate to strong winds and high snow levels will combine to create the potential for windslabs in the above treeline terrain. Watch for areas with more significant snow accumulation and wind transport. Otherwise light rain will fall on a mostly stable snowpack, with shallow new snow. Watch for early season terrain hazards, rocks, creeks etc.
Detailed Forecast
A complex storm system will bring increasing rain and snow, rising snow levels and moderate to strong W-SW winds on Sunday. By Sunday morning the snow levels will rise to 6000 ft, so new snow loading will be confined to the above treeline terrain and wind slabs will develop here as the day progresses. See the mountain weather forecast tab for more details.
If in areas receiving greater new snow, watch for wind transport building shallow wind slabs near ridges, particularly on NW-SE slopes. This new snow may combine with shallow storm from Friday's storm to run on harder melt-freeze interfaces formed during the prolonged dry spell.
Rainfall falling on recent shallow snowfall should not be a concern on Mt. Hood because there won't be enough volume of snow to create a hazard.
The recent warm, sunny weather has melted much of the early season snowpack and exposed terrain hazards, especially lower elevations. Expect terrain hazards with poorly covered rocks, vegetation and creeks, particularly on south-facing terrain, at lower elevations, and on exposed ridges where wind events have stripped much of the seasons snowcover.
Snowpack Discussion
The most recent storm brought light amounts of new snow to Mt. Hood, with most areas receiving approximately 3" of new snow that fell on a crust which formed during a brief period of light rain followed by light snow accumulations during the afternoon and overnight hours Friday. The brief period of rainfall likely washed out most persistent grain types which were observed prior to Friday's storm.
The warm and sunny weather over the past 12 days has done a number on the early season snowpack throughout the region, returning many areas to very shallow early season conditions. The most consistent snowpack remains on shaded northerly aspects in the upper below treeline to near treeline where 3-6 feet remain.
The overall snowpack is stable with settled old snow sitting over the strong Thanksgiving rain crust, buried about 1-3 feet.
No human-triggered avalanches have been reported in over a week.Â
Observations
On Wednesday afternoon, Mt. Hood Meadows Pro Patrol reported consolidated snow and no avalanche concerns with some corn developing on south-facing aspects.
NWAC pro-observer Laura Green traveled in the Mitchell/White River drainage on Monday between 5300 and 6600 feet and found many variations in the surface snow but overall a settled and well bonded snowpack with few avalanche concerns in the terrain she covered. She observed surface hoar up to 3-4 mm on non-solar ENE-facing slopes.Â
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, South, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1