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Avalanche Forecast

Archived

Mar 28th, 2021–Mar 29th, 2021

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

Regions

North Columbia.

Moderate winds shifting northwest overnight will continue to redistribute recent storm snow into deep slabs. Give the new snow time to settle and stabilize before pushing into bigger terrain. Crusty surfaces below treeline will make for low hazard but difficult travel conditions.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Sunday night: Flurries bringing around 5 cm. Moderate northwest wind. Freezing level drops to valley bottom. Alpine temperature -13.

Monday: Mix of sun and cloud. Moderate northwest wind. Freezing level valley bottom. Alpine temperature -15

Tuesday: Mostly cloudy. Light westerly wind. Freezing level 1400 m. Alpine temperature -7.

Wednesday: Sunny. Light southwest wind. Freezing level 2000 m. Alpine temperature -1.

Avalanche Summary

We are still awaiting reports of avalanche activity from the weekend's storm. A widespread natural cycle is likely to have occurred Sunday.

Recent avalanche activity has primarily been small (size 1-1.5) wind slab and dry loose, with a few reaching the 2-2.5 size range. One notable size 3 slab avalanche was observed northeast of Revelstoke on Wednesday. The avalanche failed on the ground on a south aspect at 1600 m. In neighboring Glacier National Park and South Columbia regions, several natural cornice falls triggered deep slab avalanches size 2-3. As temperatures rise mid week, keep in mind that the springtime heat penetrates down to layers buried deep in the snowpack

Snowpack Summary

The weekend's storm dropped 20-40 cm over the southern Selkirk mountains and 5-10 cm elsewhere. This snow has likely been redistributed by strong wind, switching from southwest to northwest Sunday night. Crusty surfaces exist below treeline.

At alpine and treeline elevations, a widespread crust exists (except on north-facing slopes above 1800 m) buried 50-100 cm deep. Overall the snow seems to be bonding well at this interface, although there have been a few isolated avalanches running on crust layers over the past few week.

Terrain and Travel

  • Be careful to keep storm day fever from luring you out into bigger terrain features.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.