Avalanche Forecast

Issued: Feb 22nd, 2020 4:00PM

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

Avalanche Canada JSmith, Avalanche Canada

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The developing storm slabs are expected to be reactive to human triggers on Sunday. Careful terrain selection and route finding will be required to effectively manage risk.

Summary

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Weather Forecast

SATURDAY NIGHT: Cloudy, light southwest wind, alpine temperature -8 C, freezing level below valley bottom.

SUNDAY: 10-15 cm. snow, moderate to strong southwest wind, alpine temperature -6 C, freezing level 1000 m

MONDAY: Mostly cloudy with possible flurries; 0-3 cm, light west wind, alpine temperature -8 C, freezing level 900 m.

TUESDAY: Mix of sun and cloud, moderate southwest wind, alpine temperature -6 C, freezing level 1000 m.

Avalanche Summary

 On Friday, several skier triggered windslab avalanches up to size 2 were reported on steep, cross loaded features. Of note, two of these reportedly slid on the early February rain crust which are the first recent reports of avalanches on this layer. Numerous cornice falls over the last week had a variety of results. They mostly only entrained recent storm snow but a few did trigger slab avalanches up to size 2.5. Human triggered avalanches are expected to increase as the new snow settles into a cohesive storm slab over the fragile layer of surface hoar.

Snowpack Summary

5-10 cm of new snow has buried a widespread layer of surface hoar (size 5-20 mm.). This layer exists on all aspects and elevations except for steep solar aspects where it was melted by sun and windward alpine slopes where the layer was flattened by wind before being buried. Surface hoar sitting on a thin sun crust has been reported on lower angle solar aspects which is a particularly nasty combination. The new snow will likely become increasingly reactive as it settles into a cohesive slab. The early February rain crust down 60-80 cm. is another prominent layer in the upper snowpack that requires monitoring. The mid and lower snowpack is generally well settled and strong.

Terrain and Travel

  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Cornice failure may trigger large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

The new snow may be more reactive than expected; especially on slopes where it has been wind loaded and is sitting on a layer of fragile surface hoar.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 23rd, 2020 5:00PM

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