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Avalanche Forecast

Archived

Feb 18th, 2012–Feb 19th, 2012

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

Regions

Northwest Inland.

Confidence

Fair - Timing of incoming weather is uncertain on Sunday

Weather Forecast

Sunday: Light snowfall / moderate southwest winds increasing to strong in the evening / freezing level @ 500m Monday: light snowfall / moderate southwest winds / freezing level @ 700m Tuesday: moderate snowfall / strong southwest winds / freezing level @ 700m

Avalanche Summary

No new avalanches have been reported.

Snowpack Summary

About 15cm of snow that fell over the past week sits over a variety of old surfaces: melt-freeze crusts exist on all aspects at lower elevations as well as on south-facing slopes higher up, and well-settled powder is found on shaded aspects in the alpine. Weak surface hoar crystals (size 3-4mm) are sandwiched between the old surfaces and the newer snow. The distribution of the surface hoar seems to be up to treeline on all aspects and on sheltered features in the alpine. This upper snow pack structure will be the big thing to watch as the overlying slab develops. I expect to see gradually increasing reactivity in the surface hoar interface with incremental loading and higher winds forecast for this week. Check out our Forecaster's Blog for some thoughts on incremental loading. The mid and lower snowpack is generally well settled and strong.

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.