Avalanche Forecast

Issued: Jan 4th, 2023 4:00PM

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

Avalanche Canada CG, Avalanche Canada

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We have a very weak, faceted, basal layer in our snowpack at Rogers Pass.

Avoid thin, rocky, unsupported features where one could sink into the sugary facets, potentially triggering the deeper persistent weak layers.

Summary

Confidence

Moderate

Avalanche Summary

Several natural sz 2 slab and loose avalanches were observed in the highway corridor on Tuesday and Wednesday. Most were from steep, rocky S aspects, with the exception of a larger slab from Macdonald Gully 10.

On Monday a size 2 avalanche was remotely triggered from a shallow snowpack area on Bruins Ridge. These are the spooky avalanches that are causing anxiety amongst avalanche forecasters! Stay away from thin, rocky areas!

Snowpack Summary

The top 30cm of snow is low-density and provides great powder turns. Steeper SW and W aspects have a thin sun crust on the surface. The Dec 23 facet interface, down ~70cm, is gaining strength. The Nov 17 facet/crust/surface hoar layer is still active in snowpack tests, exhibiting 'sudden collapse' or 'sudden planar' results.

Weather Summary

Clouds, flurries, and slightly elevated freezing levels (FZL) will be the norm for the next few days. No major storms in the foreseeable future. Darn, eh!?

Thurs: mainly cloudy, trace snow, Alp high -2*C, 1600m FZL, light S winds

Fri: cloud with scattered flurries, 5cm, Alp high -4*C, 1500m FZL, light/gusty SW winds

Sat: flurries, 5cm, Alp high -4*C, 1600m FZL, light SW winds

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Persistent Slabs

An icon showing Persistent Slabs

30-60cm of settled storm snow buries the Dec 23 facet interface. This layer will be a concern in steep terrain, on convex rolls, or areas where the snowpack is unsupported (pillows, hanging snow fields, etc.).

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

The Nov 17 layer, down 60-120cm, consists of facets, a rotting crust, and decomposing surface hoar. This layer still shows hard, sudden collapse/planar results in snowpack tests. Though becoming less likely to trigger, the resulting avalanche would be quite large.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Jan 5th, 2023 4:00PM