Avalanche Forecast

Issued: Mar 21st, 2021 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada cgarritty, Avalanche Canada

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Touchy surface instabilities existed in the region before Sunday's storm - new snow and strong wind have just taken them up a notch. It's still winter up high!

Summary

Confidence

Moderate -

Weather Forecast

Sunday night: Cloudy with easing flurries and a trace to 10 cm of new snow. Moderate to strong southwest winds easing to light northwest by morning.

Monday: Cloudy with isolated flurries, increasing a bit overnight. Light northwest winds. Alpine high temperatures around -9.

Tuesday: Cloudy with flurries bringing about 10 cm of new snow, easing overnight. Strong southwest winds. Alpine high temperatures around -6.

Wednesday: Cloudy with isolated flurries. Light northwest winds. Alpine high temperatures around -7.

Avalanche Summary

A couple of recent MIN reports help to give a sense of conditions in advance of Sunday's storm. Snowfall and wind since these observations have been building on the avalanche problems described, particularly in the southwest of the region.

Saturday in Sinclair. This area is a bit more of a snow magnet than the Smithers area is, with touchy conditions quite a bit more widespread at the time of this report.

Wind slabs were clearly already affecting the Hudson Bay Mountain area on Friday, even before the storm rolled in.

Snowpack Summary

Weather stations so far suggest only about 5-15 cm of new snow (favouring the southwest of the region) accumulated during Sunday's storm. Up to 10 more cm (again favouring southwest) may accumulate over Sunday night. Elevated winds have almost certainly been using the new snow to form a regionally variable new wind slab problem in exposed terrain.

Collectively, our new and recent snow (20-30 cm of older storm snow near Smithers, closer to 70-100 cm in the southwest) overlies hard wind affected snow at alpine elevations, potentially surface hoar crystals on sheltered north aspects, or melt-freeze crust on south aspects and below treeline. Recent observations suggest warm temperatures have aided bonding at this interface. At lower elevations, recently rain soaked, now refrozen and crusty surfaces are buried by a bit more low density snow.

The mid and lower snowpack is reported as well settled and strong in most areas. However, weak facets exist at the base of the snowpack in the more shallow snowpack zones within much of the region and always have the potential of being triggered on steep, rocky slopes with a shallow or thin to thick snowpack; especially with large loads such as a cornice fall.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.

Problems

Wind Slabs

An icon showing Wind Slabs

New snow and elevated southwest winds have formed new surface instabilities that vary by location in the region. Expect thicker, more widespread storm slab formation in the snowier southwest of the region and wind slabs more confined to leeward terrain at exposed elevations closer to Smithers.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 22nd, 2021 4:00PM

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