Avalanche Forecast

Issued: Dec 11th, 2020 4:00PM

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

Avalanche Canada jcoulter, Avalanche Canada

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Recent snow may still be sensitive to human triggers, especially where they've been stiffened by the wind and sit on the widespread crust. Use small low consequence slopes to test the bond of the new snow before committing to your line.

Summary

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Expect partly cloudy skies overnight, light north east wind with a chance of light flurries and a low of -8. On Saturday, cloudy with sunny periods with alpine high of -8 with light south west wind at ridge top. On Sunday we could see flurries develop again and wind will increase and be from the south west. Monday the chance of isolated flurries continues.

Freezing levels should remain at valley bottom through out the forecast period.

Avalanche Summary

At the time of writing, there have been no new avalanche observations reported since December 9th.

On Wednesday, the new storm snow saw a poor bond to the underlying crust. Natural and human triggered avalanches were widespread and up to size 2 at treeline and above. Limited propagation was reported, however; these avalanches were running far and fast down the path as the snow slid on the crust.

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Snowpack Summary

Up to 30 cm of recent storm snow sits on top of the December 8th crust in much of the Lizard Range. I suspect it could be similar in the Flathead start zones. Snowpack test results suggest that the recent storm slab may still be sensitive to human triggering in alpine like features, especially where it might have been stiffened by wind. In sheltered spots, loose dry sluffs running on the crust are more likely.

Rain from early in the last storm seems to have destroyed most of the surface hoar from the last dry spell and has left the December 8th crust in its place. Let us know it the Mountain Information Network if you have found any buried surface hoar.

Deeper in the snowpack, depending on your location, there may be couple of crusts from November. Although we haven't had any recent avalanches on these layers, they have reacted in some snowpack tests, so this "potentially" problematic snowpack structure remains on our radar moving forward.

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Closely monitor how the new snow is bonding to the old surface.
  • Use small low consequence slopes to test the bond of the new snow.

Problems

Wind Slabs

An icon showing Wind Slabs

Initially, the recent storm snow was not bonding well to the crust. I suspect the bond has improved, however; slabs may be still reactive to human triggering where snow has been wind stiffened. Loose dry sluffs may run fast from your boards or sleds in steep sheltered terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 12th, 2020 4:00PM