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Avalanche Forecast

Archived

Apr 19th, 2022–Apr 20th, 2022

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

Regions

North Rockies.

Carefully assess the wind slab hazard as you gain elevation. Field data is limited in the region so please consider filling out a Mountain Information Network report.

Confidence

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

Weather Forecast

Tuesday night: Low of -10 at 1700 m. Light flurries bringing around 5 cm of new snow with light variable winds.

 

WEDNESDAY: Mostly cloudy with light flurries bringing trace amounts of new snow. Light southeast winds and freezing levels rising to around 1500 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 1900 m.

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

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!

Snowpack Summary

Up to 10 cm of new snow overlies old wind effected surfaces. Below this a melt-freeze crust can be found down up to 40 cm on all aspects to 2000 m and mountain tops on solar aspects. Another prominent 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

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the old surface.
  • Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

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.