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Avalanche Forecast

Archived

Apr 3rd, 2022–Apr 4th, 2022

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

Regions

Northwest Coastal.

Slabs may be most reactive around ridges and steep, unsupported features or where they have formed over a crust.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Sunday night: Unsettled with isolated flurries and starry breaks, up to 5 cm. Moderate southeast-east wind. Ridgetop low -9 C.

Monday: Cloudy with isolated flurries and sunny breaks, trace to 10 cm. Moderate to light southwest wind. Ridgetop high 0 C.

Tuesday: Flurries starting late Monday evening, 5-15 cm. Moderate southwest-west wind. Ridgetop high -4 C.

Wednesday: Snow, 15-25 cm. Moderate south wind. Ridgetop high -4 C.

Avalanche Summary

Explosives triggered storm slab avalanches to size 2 (and one 2.5) late Saturday and early Sunday morning in the northern end of the region.

On Thursday, wind slabs to size 1.5 were reactive to skiers, reported on northerly aspects with crown depths 15-40 cm. On Wednesday, explosives in the north of the region triggered storm slabs to size 2.

Snowpack Summary

Around 20 cm fresh snow fell by Sunday morning with strong overnight winds, building slabs in the alpine and tree line and more reactive deposits in lee terrain. Now down 20-50 cm, a crust can be found on all aspects and elevations except high elevation north-facing terrain. In the north of the region, small surface hoar may be found above this crust. 

A weak layer of surface hoar from mid-March buried 70-120 cm deep can still be found but is considered dormant around the Terrace area. However, in the far north of the region, it produced large avalanches last weekend and continues to display poor (sudden fracture characteristics) results in snowpack tests.

Terrain and Travel

  • Make conservative terrain choices and avoid overhead hazard.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • 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.