Avalanche Forecast

Issued: Feb 24th, 2021 4:00PM

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

Avalanche Canada ghelgeson, Avalanche Canada

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Stick to simple terrain free of overhead hazard as the next wave of storms breaks over the mountains. Up to 60 cm of aging storm snow from last weekend likely remains sensitive to human triggering and more snow with plenty of wind is incoming Wednesday Night into Thursday.

Summary

Confidence

Low - Uncertainty is due to the limited number of field observations. Forecast snowfall amounts are uncertain.

Weather Forecast

The territory continues to be in the storm track through the weekend.

WEDNESDAY NIGHT: Overnight low around -10 C, moderate to strong south/southeast wind, 3 to 8 cm of snow expected.

THURSDAY: Overcast, daytime high around -6 C, moderate northwest wind, 2 to 4 cm of snow expected.

FRIDAY: Clear skies at dawn with cloud cover building to broken throughout the day, daytime high around - 8 C, moderate southwest wind with potentially strong west wind at ridgetop, no snow expected.

SATURDAY: Broken cloud cover, daytime high around - 4 C, strong southwest wind, 2 to 5 cm of snow expected during the day with 5 to 15 cm Saturday night.

Avalanche Summary

There is evidence of a recent storm slab avalanche cycle to size 2, and slopes that have not yet avalanched are likely primed for human triggering.

This MIN report outlines conditions at the end of last weekend. 

Snowpack Summary

Last weekend's storm produced 60+ cm of new snow which rests on heavily wind affected and faceted snow in exposed terrain and perhaps a weak layer of surface hoar in sheltered areas, as found here and here. 

While our best weather stations are currently down, we have observations from Wednesday that suggest southwest wind has redistributed the aging storm snow into slabs in wind exposed terrain.

The lower snowpack is strong around White Pass, but inland areas like the Wheaton Valley likely have a thinner and weaker structure.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Stick to simple terrain or small features with limited consequence.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.

Problems

Persistent Slabs

An icon showing Persistent Slabs

The 60+ cm of aging storm snow rests on hard wind-affected snow, weak facets, and perhaps weak surface hoar in sheltered areas. This snow needs time to settle and stabilize before we can begin to trust it.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Storm Slabs

An icon showing Storm Slabs

4 to 8 cm of new snow is expected Wednesday night with strong south/southeast wind. Another 2 to 4 cm is forecast for Thursday as wind switches to the northwest. Fresh, shallow & sensitive storm slabs are likely to form.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 1.5

Valid until: Feb 26th, 2021 4:00PM

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