Avalanche Forecast
Regions: Mt Hood.
Watch for melting and weakening of surface snow on solar aspects. Avoid steep slopes at higher elevations suspected of wind deposited snow. Wind slab avalanches should become less sensitive, but remain possible to trigger on specific terrain features.
Detailed Forecast
Light winds, some sun breaks and moderate temperatures should allow for a further slow decrease in the danger Friday. In general, any recently formed shallow wind slabs overlying recently buried crusts should be less sensitive to skier triggering. In specific areas, small human-triggered slab avalanches could still be possible. Before committing to a slope, think about the consequences of the terrain if even a small avalanche occurred. Watch for wet snow conditions during sun breaks on solar aspects.
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Snowpack Discussion
About a week of fair weather was centered around the New Year. This allowed the significant snow that fell during a strong storm cycle, that ended about Christmas, to settle and stabilize.
By New Years Eve through the weekend moderate to strong east-northeast winds had significantly scoured or transported available surface snow onto lee west aspects, mainly in the near and above treeline elevation bands.
NWAC pro 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.
Surface snow sculpted by wind and active wind transport. Photo: Laura Green
On Monday the Mt Hood Meadows pro patrol reported warming and a widespread 1 cm freezing rain crust up to 7000 feet.
Laura was out again near the Mt Hood Meadows ski area on Tuesday and Wednesday and reported 5 inches of storm snow had formed small slabs, non-reactive to ski cuts, but some explosive triggered slides up to 10 inches were seen on steep slopes of varied aspects. These shallow slabs were becoming less sensitive by Wednesday as a result of warming temperatures.
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.
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: Unlikely
Expected Size: 1 - 1