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Avalanche Forecast

Archived

Apr 7th, 2021–Apr 8th, 2021

Alpine
Natural avalanches possible, human triggered probable.
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.

Regions

Lizard-Flathead.

Forecast snowfall totals are uncertain. Dial back terrain choices where you find more than 20 cm of new snow as human-triggering avalanches may be likely.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Wednesday night: Cloudy, 5-15 cm of snow, moderate southwest wind, freezing level dropping to 1300 m.

Thursday: Mainly cloudy, 5-10 cm of snow, light west wind, treeline temperatures near -7 C, freezing level rising to 1500 m and dropping to valley bottom.

Friday: Increasing cloud, isolated flurries with trace accumulations, moderate southwest wind, treeline temperatures near -2 C, freezing level rising to 1600 m and dropping to valley bottom.

Saturday: Cloudy, 10-15 cm of snow, light west wind, treeline temperatures near -4 C, freezing level rising to 1500 m and dropping to valley bottom.

Avalanche Summary

On Monday and Tuesday, pinwheels and small loose wet avalanches were observed on steep sunny alpine slopes.

Snowpack Summary

Up to 25 cm of new snow may accumulate in favored areas in the region by midday on Thursday accompanied with moderate southwest winds. The combined snow and wind will likely form a new storm slab problem reactive to human triggering. Cornices are large, looming, and capable of triggering avalanches when they fail.

The mid-pack is firm and well settled. Some faceted snow and a decomposing melt-freeze crust can be found near the base of the snowpack. Snow line is slowly creeping up the mountains to roughly 1400 m in elevation. Check out this MIN report for more details on the access from common staging areas.

Glide cracks releasing as full depth glide slab avalanches become more common in the spring and are extremely difficult to predict. Best practice is to avoid slopes with glide cracks.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.