Avalanche Forecast
Regions: Mt Hood.
Heightened avalanche danger should be specific to wind-loaded slopes at all elevation bands where recent east winds continue to build new wind slab.
Detailed Forecast
The recent clear weather should give way to increasing clouds and a return to a few light showers, especially late Sunday at moderating temperatures.Â
A heightened avalanche danger should apply to wind-loaded slopes near and above treeline where east-southeast winds continue to build new wind slab on a variety of aspects. If you find the right (or better put, wrong) wind loaded slope, it will remain possible to trigger a small slab avalanche. Look for recently transported snow further downslope from ridgelines than you might expect.
Snowpack Discussion
A cool and very snowy storm cycle brought 6-7 feet of snowfall to Mt Hood the week ending December 24th. Moderate additional accumulations in the past week have allowed the snowpack to slowly settle. A variety of surface conditions exist with firm windpack near and above treeline, scoured ridge-lines, sun crusts on solar aspects, and powder below treeline in sheltered terrain. Â
The Mt Hood Meadow pro patrol reported an overall right side up upper snow pack, good stability, limited wind effects below 7500 feet and good skiing on Tuesday. However, by Thursday and Friday, moderate to strong east-northeast winds had begun significant new snow transport onto lee westerly aspects mainly in the near and above treeline elevation bands.Â
NWAC observer Laura Green was in the Newton Creek drainage Friday and found good skiing in non-wind affected terrain. Even on wind loaded slopes near treeline, the denser wind slab was bonding to underlying snow and no natural or skier triggered avalanches were noted. Significant wind loading continued to occur on the upper mountain Friday and to lesser extent Saturday.
Other than well sun and wind protected slopes, mainly shaded slopes in the trees, most surface snow conditions have been transformed significantly by wind, sun and overall snowpack settlement over the past several days.  Exhibit photo a: surface snow sculpted by wind, active wind transport on ridge, center left: Photo: Laura Green
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, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1