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Avalanche Forecast

Archived

Apr 18th, 2022–Apr 19th, 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.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Inland.

Continuous light flurries might bring just enough new snow to create a small wind slab problem to manage. Monitor new snow amounts and reactivity as you travel on Tuesday.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

MONDAY NIGHT: Cloudy with flurries bringing a trace to 5 cm of new snow. Moderate east winds, easing into the morning.

TUESDAY: Mainly cloudy with continuing isolated flurries and a further trace of new snow. Light east or southeast winds. Treeline high temperatures around -6.

WEDNESDAY: Cloud diminishing over the day with another trace to 5 cm of new snow from the overnight period. Light east or southeast winds. Treeline high temperatures around -4.

THURSDAY: Cloud increasing again with isolated flurries and a trace of new snow. Light southeast winds. Treeline high temperatures around -3.

Avalanche Summary

One recent cornice fall that did manage to trigger a slab was reported from a flight over the Telkwa range on Friday. On Saturday a few small loose dry avalanches were observed in steep, solar, rocky terrain. Otherwise, no new avalanches have been reported in the past few days.

On Thursday, explosives triggered wind slabs up to size 2 on south-south east aspects. On Wednesday, glacial icefall (serac) triggered a large persistent slab avalanche (size 3). This avalanche occurred on a northeast aspect in the alpine and is suspected to have failed on a crust from early April. This avalanche was only possible with an extremely large load and is not suggestive of general conditions in the region as a whole.

Looking forward, minimal flurries likely won't be enough to form a substantial wind slab problem. Isolated, small but reactive slabs may still form in pockets of leeward terrain.

Snowpack Summary

Light snowfall has begun to bury heavily wind-affected surfaces in exposed terrain, the product of an intense wind event early last week. In sheltered areas, flurries may add to limited stashes of soft snow. A widespread melt-freeze crust can be found 20 to 50 cm deep in most areas, and up to 80 cm in the snowiest parts of the region. This crust is near the surface below 1200 m.

Terrain and Travel

  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Wind slabs are most reactive during their formation.

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.