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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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal.

Carefully assess steep lines for wind slab and limit exposure to slopes with cornices above. 

Confidence

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

Weather Forecast

THURSDAY NIGHT: High cloud increasing. Light westerly winds. Freezing level remains elevated at around 1300 m.

FRIDAY: Increasing cloud cover with light flurries in the afternoon. Light southwesterly winds. Freezing level remaining steady at 1400 m. Treeline temperatures around -1 C.

SATURDAY: Cloudy with snowfall, 5-10 cm of accumulation. Moderate to strong southerly winds. Freezing level around 1400 m. Treeline temperatures around -2 C.

SUNDAY: Cloudy with flurries, up to 5 cm of accumulation. Moderate to strong southwesterly winds. Freezing level 1000 m. Treeline temperatures around -4 C.

Avalanche Summary

A small skier-triggered wind slab was reported near Terrace on Wednesday (size 1). This avalanche occurred on a convex roll in the alpine and failed on slick melt-freeze crust. 

A few natural wind slab releases were observed in the Bear Pass area on Tuesday afternoon. These reached size 2 (large) and were limited to steep, wind-loaded features in the alpine. 

Looking forward to Friday, small but reactive wind slabs may exist in lee features in the alpine. Winds have varied in direction, so watch for wind slabs on all aspects.

Snowpack Summary

5-15 cm of new snow buried heavily wind-affected surfaces in open areas, the product of strong outflow wind early last week. In open areas, this new snow has been redistributed by easterly winds into small pockets of wind slab in lee areas. A crust will likely be found on steep solar aspects from warm temperatures and sun yesterday. Below 1200 m, a more widespread crust exists at or near the surface. Above 1200 m, 40 to 80 cm of settled storm snow is well bonded to another hard melt-freeze crust from late March.

Terrain and Travel

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

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.