Avalanche Forecast
Regions: Mt Hood.
New storm and wind slab may become increasingly sensitive and widespread Saturday due to additional light loading. Continue to assess snowpack stability throughout the day and dial back your plans if you experience signs of increasing instability.
Detailed Forecast
Another round of light to moderate snow showers Friday night should be followed by increasing shower activity Saturday afternoon and evening. Look for a relative break in precipitation from Saturday mid-morning through mid-day. Mt. Hood has already moderated temperature-wise and snow levels should remain steady on Saturday.  Â
Look for sensitive new wind slab near and above treeline on lee aspects. Storm slabs should become increasingly sensitive Saturday due to additional loading of denser snow overlying weaker snow formed prior to this storm cycle. Continue to assess snowpack stability throughout the day and dial back your plans if you experience signs of increasing instability.Â
Even though the lower part of the below treeline band is filling in, watch for early season travel hazards such as barely covered rocks and open creeks.
Snowpack Discussion
Weather and Snowpack
An active and cool weather pattern has resulted in a snowy December thus far with Mt. Hood NWAC stations recording about 2-4 feet of lower density snow.
Cold and fair weather was in place midweek allowing near surface faceting and/or surface hoar to become widespread. Beginning Wednesday night and continuing through Thursday, considerable wind transport from easterly winds occurred near and above treeline.Â
Moderate easterly winds shifted to the west along with a rapid warming trend Thursday night along with about 7 inches of new snow through early Friday morning. An additional few inches fell through the day on Friday. Â
Prior to this new snow, the snowpack in non-wind affected terrain was generally right side up with low density snow at the surface and no problematic layers in the lower snowpack. A freezing rain crust that formed and was buried December 2nd has had been identified in snowpack up to 7000 ft, but no new or recent avalanche activity has been reported on this layer.Â
Recent Observations
During the day on Wednesday the Mt. Hood Meadow pro patrol reported light winds that were not causing wind transport. The upper snowpack was generally right side up with good skiing and riding conditions. Some surface hoar was noted in wind sheltered locations.
On Thursday shifting winds was producing significant wind transport of recent low density snow near and above treeline on Mt. Hood. Despite a rapid warming trend, shifting winds and new snowfall Thursday night, widespread avalanche activity was not reported Friday morning from the Mt. Hood Meadows pro-patrol. Pro-observer Laura Green found sensitive storm layers in the below and near treeline bands in snowpack tests, but experienced no direct signs of instability. No observations were received from above treeline where lee aspects should have been continuously loaded throughout the day.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.
Elevations: Alpine, Treeline.
Likelihood: 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