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Avalanche Forecast

Archived

Jan 18th, 2020–Jan 19th, 2020

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

Glacier.

Watch for windslab in exposed areas. These slabs may be sensitive to human triggering.

Weather Forecast

Scattered flurries with 4cm accumulation forecast for today accompanied by Southerly winds in the 20km/h range and a 700m freezing level. Cloudy with sunny periods and a rising freezing level to 1500m on Sunday accompanied by moderate Southerly winds. Monday looks very similar to Sunday with a shift to moderate winds out of the SW.

Snowpack Summary

Strong southerly winds have redistributed 15cm of new storm snow. Reactive wind slabs have formed in exposed areas above treeline. The Dec 27th surface hoar/ crust layer is buried approximately 100cm. The mid and lower snowpack are generally well settled and strong.

Avalanche Summary

Eight avalanches including one size 3 over the last two days in the highway corridor east of Rogers Pass. No new backcountry avalanches reported or observed.

Confidence

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.