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Avalanche Forecast

Archived

Nov 29th, 2019–Nov 30th, 2019

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

Regions

Northwest Coastal.

Clear and cold conditions continue through the weekend. It is still possible to trigger avalanches where the wind has formed slabs at higher elevations.

Confidence

Moderate - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

FRIDAY: Mostly clear, light wind from the northeast, alpine high temperatures around -7 C.

SATURDAY: Sunny, light wind, alpine high temperatures around -6 C.

SUNDAY: Sunny with increasing cloud in the afternoon, light wind from the west, alpine high temperatures around -6 C.

MONDAY: Snow, accumulation 10-20 cm, strong southwest wind, alpine high temperatures around -4 C.

Avalanche Summary

A few small (size 1) naturally triggered avalanches were reported midweek. The main concern for human triggering is currently in areas where wind has blown surface snow into wind slabs.

Snowpack Summary

Recent wind from the southeast has likely left wind slabs on north and east facing slopes at higher elevations. The snow from last weekend appears to have settled and gained strength, as shown by this MIN report from the Shames area on Wednesday. A total of 30-80 cm of settled snow from last weekend sits above a widespread crust. The snow has likely bonded to this crust, however given the lack of field observations there is still some uncertainty about whether this could be an interface capable of producing large avalanches. The total snowpack depth is around 100 cm at 1200 m, and is still below the threshold for avalanches in many areas below treeline.

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.