Avalanche Forecast

Archived

Dec 30th, 2015–Dec 31st, 2015

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland.

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Confidence

Moderate - Due to the number of field observations

Weather Forecast

The current ridge of high pressure will persist for the foreseeable future bringing mainly clear skies for the forecast period. Ridgetop winds will intensify throughout the day on Thursday, and remain strong and southwesterly until Saturday. An inversion is forecast for all 3 days with above-freezing temperatures expected in the alpine by Thursday afternoon.

Avalanche Summary

No recent avalanches have been reported. With solar radiation and warming forecast for the next few days, loose wet avalanches will become more likely on steep, sun-exposed slopes.

Snowpack Summary

Light amounts (10-15cm) of snow fell last weekend. Variable winds have likely shifted the new snow into wind slabs in upper elevation lee terrain. Although these wind slabs have likely gained strength, I'd remain cautious on steep, unsupported slopes in the immediate lee of ridge crests. Solar radiation has also come into play, and depending on the time of day, steep solar aspects may be moist or refrozen.We're still dealing with a thin, early-season snowpack for much of the Northwest Inland region. Between 80 and 100 cm of snow can be found at tree-line in the south and west of the region, with closer to 60 cm in the east. A weak basal layer probably exists in most areas, and I suspect that the ongoing cold temperatures have continued to promote faceting in the snowpack, especially in shallow, rocky areas.

Problems

Loose Wet

Loose Wet avalanches are the 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. 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.

Wind Slabs

Wind Slab avalanches are the 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.