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Avalanche Forecast

Archived

Apr 20th, 2022–Apr 21st, 2022

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

North Rockies.

Carefully assess steep lines for wind slab and limit exposure to slopes with cornices above. Please consider filling out a Mountain Information Network report if you are recreating in the backcountry.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Wednesday night: Possibility of light flurries bringing trace amounts of new snow with light southerly winds. Low of -10 at 2000 m.

 

THURSDAY: A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light southerly winds. Freezing level rising to 1800 m.

Friday: Sunny with no new snow expected and light westerly winds. Freezing level rising to 2000 m.

Saturday: Sunny with no new snow expected. Moderate southwest winds and freezing levels rising to 2000 m in the north and up to 2300 m in the south.

Avalanche Summary

No recent avalanche activity has been reported. Information is limited at this time of year. Please consider submitting to the Mountain Information Network!

We suspect that small pockets of rider triggerable wind slab could be found in the alpine. As the sun comes out small wet loose avalanches are possible.

Snowpack Summary

Up to 10 cm of recent storm snow overlies old wind effected surfaces. Below this another melt-freeze crust can be found down up to 40 cm on all aspects to 2000 m and mountain tops on solar aspects. Moist snow will likely be observed on solar aspects as the sun comes out.

The late March crust layer is found 40-70 cm deep.

Cornices are very large and exposure to slopes beneath them should be minimized, especially if the weather is sunny, warm, or windy. The snowpack deteriorates rapidly at lower elevations.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.
  • Avoid sun exposed slopes, especially if snow surface is moist or wet.

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.

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.