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Avalanche Forecast

Archived

Apr 22nd, 2023–Apr 23rd, 2023

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

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

Cornices are currently very large and guard many ridgetops like gargoyles.

Cornice falls may trigger large avalanches on the slopes below.

Confidence

Low

Avalanche Summary

The warm temperatures and sunshine triggered numerous wet loose avalanches up to size 1.5 on all aspects/elevations on Friday. See MIN

Observations are limited at this time of year, please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

Cornices are very large and loom over slopes below like gargoyles. Cornice falls may trigger large avalanches on the slopes below.

Recent wind has varied in direction so watch for lingering wind slabs on all aspects at upper elevations.

A robust crust exists on all aspects up to approximately 1400 m and to ridgetop on sunny aspects.

A weak layer of surface hoar/crust/facets buried in early January is now around 100 cm down in most areas. A significant warming event or a large trigger (like a falling cornice) are the most likely things to activate this layer.

Weather Summary

Saturday Night

Cloudy with isolated flurries; 0-3 cm / 20 km/h southeast ridgetop wind / Temperature at treeline around -2 C / Freezing level 800 m

Sunday

Cloudy with isolated flurries; 0-10 cm / 20 km/h southeast ridgetop wind / Temperature at treeline around 2 C / Freezing level 1400 m

Monday

Mix of sun and cloud with isolated flurries; 3-5 cm / 40 km/h south ridgetop wind / Temperature at treeline around -1 C / Freezing level 900 m

Tuesday

Mix of sun and cloud / 30 km/h southwest ridgetop wind / Temperature at treeline around -2 C / Freezing level 800 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Cornice failure may trigger large avalanches.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Carefully evaluate steep lines for wind slabs.

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.

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.