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Avalanche Forecast

Archived

Dec 22nd, 2020–Dec 23rd, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

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

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

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.