Avalanche Forecast
Regions: Mt Hood.
Watch for mostly small wind-loaded pockets on steeper terrain, particularly above treeline. Approach ridges with caution and watch for firmer wind-transported snow.
Detailed Forecast
Continued sunny and mild weather is expected Wednesday with some moderate to strong crest level easterly winds.
This should allow for further settlement of the recent storm layers and cause an overall slowly decreasing danger.Â
Small wind slabs may exist on a variety of aspects, mainly on exposed lee slopes receiving any transported snow. The warming surface snow should limit or end further transport. Any remaining wind slabs are expected to be stubborn or difficult to trigger. Watch for small areas of firmer, wind-transported snow on isolated, lee terrain features.
Continue to watch for isolated, small, loose wet avalanches on steep sun exposed terrain during the late morning or afternoon, especially on unsupported slopes or near rocks.
Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.
Snowpack Discussion
Warm, wet weather before Thanksgiving caused wet snow and glide avalanches as well as significant snowpack settlement. There are no snowpack concerns below the Thanksgiving crust and new snow received post-Thanksgiving has reportedly bonded well.
A series of frontal systems produced snow over the week following Thanksgiving: NWAC stations at Mt. Hood received 20-23" of snow.
This includes the most recent snow accumulation for the 48 hours ending on Sunday, December 3 at NWAC stations of 7-8".
Winds at the top of Mt. Hood Meadows (Express Station), winds on Sunday were in the 20's with gusts mostly in the 50's to 70's. This built wind slab layers as evident Monday morning of a natural wind slab release sometime Sunday night. See image below
Observations
On Saturday, the Mt. Hood Meadows Ski Patrol reported 13†of increasing density snow over an impenetrable Thanksgiving crust. Tests gave no results on an east-facing slope at 6600 ft.
On Sunday, the Mt. Hood Meadows ski patrol found sensitive low-density 8-10" small, ski-triggered wind slab on specific, isolated ridge-top features near treeline.
On Monday, Patrol at Hood Meadows saw evidence of a natural wind slab that released after dark Sunday.
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Natural wind slab release sometime Sunday night, 12/3. ESE facing wind loaded slope about 6600 feet. Photo: Brian Murphy
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: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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