Avalanche Forecast

Issued: Dec 22nd, 2020 4:00PM

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

Avalanche Canada mconlan, Avalanche Canada

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South Coast.

A rapid rise in the freezing level is expected over the day, which could activate the recent snow.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

TUESDAY NIGHT: Clear skies, 10 km/h northwest wind, treeline temperature -4 C, freezing level 600 m.

WEDNESDAY: Mix of sun and cloud, 10 km/h northwest wind, treeline temperature 0 C, freezing level 500 m rising to 2300 m over the day.

THURSDAY: Clear skies, 20 km/h southeast wind, treeline temperature 4 C, freezing level 2500 m.

FRIDAY: Cloudy with rain or snow, accumulation 10 mm or 10 cm, 20 km/h southeast wind, treeline temperature 2 C, freezing level 1600 m.

Avalanche Summary

Monday's snow was described as being moveable on the hard melt-freeze crust, forming small avalanches. Check out these MIN's from the North Shore mountains for a few photos: here and here.

Snowpack Summary

Around 20 cm of snow came out of Monday's storm, which fell onto a hard melt-freeze crust up to around 1500 m. The concern for Wednesday is this snow turning into touchy slabs that could slide easily on the crust. At the mountain tops, the snow may have been blown into wind slabs on all slopes due to variable wind directions.

The remainder of the snowpack is well-settled and hosts numerous other melt-freeze crusts.

Terrain and Travel

  • Closely monitor how the new snow is bonding to the crust.
  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Watch for areas of hard wind slab on alpine features.
  • Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

Problems

Storm Slabs

An icon showing Storm Slabs

Around 20 cm of snow overlies a hard crust. A warming trend may add slab properties to this snow and make it easy to trigger. If triggered, it should slide easily on the crust.

At the mountain tops, thicker wind slabs may be found on all aspects due to variable wind directions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 23rd, 2020 4:00PM

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