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Avalanche Forecast

Archived

Mar 7th, 2014–Mar 8th, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Inland.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Saturday: Cloudy with periods of snow – 5-15 cm. The freezing level is around 1000 m in the north and 1500 m in the south. Winds are moderate to strong from the S-SW. Sunday: Cloudy with flurries. The freezing level is around 1000-1400 m. Winds are moderate to strong from the S-SW. Monday: Mainly cloudy with a chance of flurries and sunny breaks. The freezing level is around 1000 m. Winds are moderate S-SW.

Avalanche Summary

No new avalanche activity has been reported. Expect the likelihood of triggering slab avalanches to increase this weekend.

Snowpack Summary

5-10 cm of dry new snow sits on a layer of surface hoar and/or a thick layer of facetted snow on shady slopes at all elevations. The new snow is likely sitting on a sun crust on steep solar aspects and various wind affected surfaces in exposed terrain. The early February weak layer of facets, crusts, and surface hoar is buried down about 35-80 cm. Cold temperatures have not settled the snow above this weak layer into a cohesive slab, and the cold has preserved the weak layer and associated crusts. This layer could become reactive in the next couple days with additional loading and significantly warmer temperatures. Basal facets and depth hoar remain a concern in areas with thin or variable snow cover.

Problems

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.