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Avalanche Forecast

Archived

Apr 21st, 2022–Apr 22nd, 2022

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

Regions

Lizard-Flathead.

We are getting back into a seasonal spring trend with cool nights, warm days, and highly variable snow conditions with elevation and aspect changes. Be on the lookout for signs that suggest unstable snow.

Confidence

High - The snowpack structure is generally well understood.

Weather Forecast

THURSDAY NIGHT: Partly cloudy with no precipitation, 10 to 20 km/h southwest wind, alpine temperature -5 C.

FRIDAY: Mix of sun and cloud with no precipitation, 10 km/h west wind, alpine temperature -1 C, freezing level rising to 2100 m.

SATURDAY: Early-morning snowfall then mix of sun and cloud, accumulation 5 cm, 10 km/h northeast wind, alpine temperature 0 C, overnight freeze and daytime freezing level rising to 2200 m.

SUNDAY: Mix of sun and cloud with no precipitation, 10 km/h southwest wind, alpine temperature 1 C, overnight freeze and daytime freezing level rising to 2400 m.

Avalanche Summary

We received a report of a rider-triggered avalanche in a north-facing steep chute. The slab was 20 cm thick and reportedly ran a long distance. Otherwise a few small wet loose avalanches were observed.

Please consider posting your observations to the Mountain Information Network to supplement our data stream and help fellow recreationists.

Snowpack Summary

Around 10 to 20 cm of snow since Tuesday formed wind slabs in lee terrain features at treeline and alpine elevations. Below treeline and on sun-exposed slopes, the snowpack is moist and consolidated. At ridge top, remember that cornices are large and looming at this time of year.

The remainder of the snowpack is strong, consisting of hard snow and various melt-freeze crusts.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

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.