Avalanche Forecast

Issued: Jan 12th, 2021 4:00PM

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

Avalanche Canada MBender, Avalanche Canada

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Snow and strong wind Tuesday evening into Wednesday will likely form fresh storm and wind slabs at upper elevations. There is uncertainty with forecast snowfall amounts. If local snow amounts overnight are greater than 25 cm then avalanche danger will be High.

Summary

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

Weather Forecast

Tuesday Night: Snow, 10-20 cm, strong southwest wind, alpine high -4, freezing level 1400 m.

Wednesday: Flurries, 5-10 cm, moderate to strong southwest wind, alpine high -5, freezing level 1300 m.

Thursday: Cloudy with sunny breaks, light to moderate northwest wind, alpine high -8, freezing level 600 m.

Friday: Isolated flurries, moderate to strong southwest wind, alpine high -7, freezing level 600 m.

Avalanche Summary

Expect to see an increase in storm and wind slab avalanche activity on Tuesday in the after math of new snow accumulating with strong southwest winds.

Snowpack Summary

New snow accumulating Monday through Tuesday night has fallen on wind affected surfaces at upper elevations, surface hoar in wind sheltered areas and a thin crust on solar aspects. Winds are likely redistributing new snow into wind slabs and growing cornices.

A couple of persistent weak layers exist in the upper to mid snowpack:

  • The upper layer, found 50-80 cm down, is a spotty layer of surface hoar at treeline and below. 
  • The lower layer, found 90-150 cm down, is widespread and can present as surface hoar and/or a crust.

Avalanche activity on these layers has dwindled since last week and snowpack tests results have generally indicated the weak layers are gaining strength. Incoming snowfall early this week will add additional load to these layers and may shed some light on whether they will remain a concern.

Terrain and Travel

  • Watch for signs of slab formation throughout the day.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs are most reactive during their formation.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.

Problems

Storm Slabs

An icon showing Storm Slabs

New snow and strong winds are likely forming fresh storm and wind slabs at upper elevations. Expect to find deepest deposits in lee terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

A couple of weak layers exist in the mid snowpack, buried 50-80 cm and 90-150 cm below the surface. They are highly variable in form and distribution and have not been associated with avalanche activity in recent days. Incoming snowfall in the forecast for this week will add additional load to these layers and may shed some light on whether they will remain a concern.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 13th, 2021 4:00PM