Avalanche Forecast
Regions: Mt Hood.
Recent N-NE winds have created some wind slab on a variety of mainly southerly aspects, especially near ridges, so make sure to evaluate wind loaded terrain. Moderate avalanche danger means human triggered avalanches are possible! Watch for wet surface snow conditions on sun exposed slopes during the warmest part of the day
Detailed Forecast
Thursday should continue to be mostly sunny with light winds. Temperatures should remain warm. The main avalanche problem should be any areas of lingering wind slabs formed through Tuesday. More recent northerly winds likely redistributed snow on more southerly aspects above and near treeline. Warm temperatures and sunshine should again cause a chance of small wet loose slides on some steeper southerly facing slopes. good settled powder should persist on shaded slopes and wind protected slopes however.Â
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Snowpack Discussion
A storm system moved through the Northwest on Saturday and Saturday night delivering some much needed snowfall. West winds changed to northwest, with moderate to heavy snow and a cooling trend. Heavy snowfall continued Sunday and Sunday night with NWAC sites on Mt. Hood picking up about 25-30 inches of storm snow through Monday afternoon!
Mt. Hood Meadows pro patrol found cracking and easy releases of soft and generally shallow wind slab due to the rapid wind loading Monday.  Â
Moderate to strong northwest winds switched to easterly Monday and have persisted through Tuesday. This built new wind slab on westerly aspects. Due to the cold temperatures, soft storm slabs are not expected to be a widespread problem.  The below treeline zone now has enough snow for a loose dry avalanche problem on steeper slopes that are wind sheltered.
Mt Hood patrol observations from Tuesday indicated that new hard wind slabs had formed but in a highly varied pattern. Only a few locally released smaller slabs were noted with explosives. By Tuesday afternoon however, there was evidence of large new natural releases in the Newton-Clark creek drainages.  These start zones are well above the forecast zone near 9000 ft but show evidence of significant wind slab formation from very strong NE winds. Â
Winds eased significantly and temperatures warmed Wednesday. This should have allowed for recent slabs to settle and stabilize.Â
Warming and sunshine have likely allowed for surface snow melt on southerly facing slopes, where a new sun crust may form. Â
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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: South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Loose Wet
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1