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Avalanche Forecast

Archived

Feb 29th, 2020–Mar 1st, 2020

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

Regions

Lizard-Flathead.

A warm to cold pattern has reduced our avalanche problems to cornices and wind slabs at the highest elevations.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Warmer funky weather is with us for the forecast period.

SATURDAY NIGHT: Freezing level returning to valley bottom, light variable wind, a trace of snow possible.

SUNDAY: Scattered cloud cover in the morning with some afternoon clearing, freezing level beginning at valley bottom rising to 1500 m during the day, light variable wind, no significant precipitation expected.

MONDAY: Clear skies at dawn building to broken cloud cover in the afternoon, freezing level beginning at valley bottom rising to 1600 m during the day and then staying there until Wednesday night, light southwest wind at lower elevations, strong west/northwest wind at mountain top, no precipitation expected.

TUESDAY: Mostly cloudy, freezing level holding around 1800 m, moderate to strong west/southwest wind, no significant precipitation expected.

Avalanche Summary

Temperatures warmed up in a big way Friday leaving a crust on the surface that extends from valley bottom to somewhere around 1900 m. For the short term, this crust should serve to neutralize the wind slab problem (except for the highest elevation slopes near ridge crest) but, cornices are still a problem. 

There was a report of a natural cornice failure on Saturday.

Snowpack Summary

Friday was quite warm which allowed for further settlement of the upper snowpack. 20 cm of well settled snow rests on a variety of old surfaces including a firm crust on solar aspects, soft faceted snow, possibly a spotty surface hoar layer and old wind slabs near ridge crest. Wind slabs are unlikely to be a problem, except in the highest elevation and more extreme terrain near ridge crest. 

A thick rain crust that has facets associated with it sits 30-60 cm below the surface and can be found up to ridge top. We have only seen one avalanche on this layer since February 17th.

The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.

Terrain and Travel

  • Large cornice falls are dangerous on their own.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

Problems

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.