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Avalanche Forecast

Archived

Mar 5th, 2020–Mar 6th, 2020

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

Regions

Lizard-Flathead.

We're not expecting much overnight re-freeze Thursday night which may allow for increasingly sensitive cornices Friday. Watch for changing conditions late in the afternoon, a bit of precipitation and wind are expected before sunset.

Confidence

Low - Uncertainty is due to the timing of the incoming weather system.

Weather Forecast

Dramatic weather through the forecast period.

THURSDAY NIGHT: Freezing level around 2200 m, moderate to strong southwest wind, no precipitation expected.

FRIDAY: Overcast, freezing level around 1900 m, late in the day moderate to strong southwest wind will pick up and 5 to 15 mm of precipitation is possible, falling as rain at lower elevations and snow up high.

SATURDAY: Overcast, freezing level returning to valley bottom just before sunset and then staying near valley bottom all day, light variable winds at lower elevations, strong southwest wind in the alpine, 10 to 25 cm of snow possible.

SUNDAY: Overcast in the morning clearing off a little bit to broken cloud cover after lunch, freezing level near valley bottom, light to moderate southwest wind, no significant precipitation expected.

Avalanche Summary

A few small loose avalanches were observed on sun-exposed slopes on Tuesday and Wednesday. Over the weekend a few small wind slab avalanches (see this MIN report) and size 2 cornice falls were reported. The cornice falls did not trigger any slabs on the slopes below.

Snowpack Summary

Alpine terrain is heavily wind affected. A crust can be found near the surface up to 2000 m on solar aspects and up to 1700 m on all other aspects. 

A thick rain crust that has facets associated with it sits 30-60 cm below the surface and can be found up to ridgetops. 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

  • Firm cornices can pull back into flat terrain at ridgetop if they fail.
  • Stay in tune with the physical environment, conditions may change throughout the day.

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.