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Avalanche Forecast

Archived

Mar 31st, 2021–Apr 1st, 2021

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

Regions

South Columbia.

A forecast uptick in southwest winds should sustain wind slab problems at high elevations. Stay aware of cornices that formed fragile new growth during the storm.

Confidence

Moderate -

Weather Forecast

Wednesday night: Clearing. Moderate to strong southwest wind. Freezing level remaining near 1500 metres.

Thursday: A mix of sun and cloud with isolated flurries. Moderate to strong southwest wind, easing overnight. Alpine high temperatures around -2 with freezing levels to 1900 metres.

Friday: Mainly cloudy with isolated flurries, continuing overnight. Light southwest winds. Alpine high temperatures around -2 with freezing levels to 1800 metres.

Saturday: A mix of sun and cloud. Light to moderate southwest winds. Alpine high temperatures around 0 with freezing levels to 2000 metres.

Avalanche Summary

A widespread natural storm slab avalanche cycle was observed to have run during the storm size 3-3.5 in the Selkirks and in the Monashees to size 2.5. Several skier and explosive triggered size 1 wind slabs were reported Monday, and Tuesday. On Tuesday these slabs were reportedly more stubborn to trigger, while small natural dry loose releases were noted occurring in steep terrain at treeline and above. A skier triggered size 2.5 involvement in neighboring Glacier National Park resulted in lost gear and minor injuries.

Snowpack Summary

Thin new surface crusts have likely formed on solar aspects and below about 2000 metres. Forecast isolated flurries will add a skiff of dry snow to higher elevations while crusty surfaces below treeline become moist with daily rising freezing levels or light rain.

20-50 cm of recent snow in the Selkirk mountains and 10-20 in the Monashees has otherwise seen some redistribution by southwest to northwest wind, and seems to be bonding well with underlying surfaces.

At alpine and treeline elevations, a few layers of note are buried 50-100 cm deep including a layer of small surface hoar crystals on shady, wind-sheltered aspects and a series of crusts on solar aspects and below 1800 m. Overall the snow seems to be bonding well to these interfaces, although there have been a few isolated avalanches running on deeper crust layers in the past week.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Extra caution is needed around cornices under the current conditions.
  • Be alert to conditions that change with aspect and elevation.

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.