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Avalanche Forecast

Archived

Mar 4th, 2020–Mar 5th, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead.

Minimize exposure to sunny slopes in the heat of the day, especially below cornices.

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

Dry sunny weather until a storm hits the region on Friday and Saturday...

WEDNESDAY NIGHT: Clear skies, light to moderate southwest wind, freezing level drops to valley bottom with alpine temperatures dropping to -10 C.

THURSDAY: Sunny, freezing level climbing from valley bottom to 1800 m in the afternoon, moderate southwest wind, alpine high temperatures around -1 C.

FRIDAY: Increasing cloud with light flurries in the afternoon bringing up to 5 cm of new snow, freezing level around 1500 m, moderate wind from the southwest, alpine high temperatures around -3 C.

SATURDAY: Stormy weather with 10-25 cm of new snow, moderate southwest wind, freezing level at valley bottom with alpine high temperatures around -5 C.

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. By midday Thursday warm sunny weather may melt the surface on south-facing slopes and below roughly 1800 m.

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

  • Cornices become weak with daytime heating or solar exposure.
  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches

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.