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Avalanche Forecast

Archived

Dec 14th, 2020–Dec 15th, 2020

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

Regions

South Rockies.

The primary concern for Tuesday is in steep, wind-loaded terrain features near ridges. Sheltered terrain will likely offer the softest riding conditions.

Confidence

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

Weather Forecast

MONDAY NIGHT: Cloudy with isolated snowfall, 30 to 50 km/h west wind, alpine temperature -9 C.

TUESDAY: Cloudy with snowfall, accumulation 5 cm, 40 to 80 km/h west wind, alpine temperature -8 C.

WEDNESDAY: Mix of sun and cloud with isolated flurries, accumulation 5 cm, 20 to 40 km/h west wind, alpine temperature -6 C.

THURSDAY: Cloudy with snowfall, accumulation 10 to 15 cm, 30 to 60 km/h southwest wind, alpine temperature -4 C.

Avalanche Summary

Small (size 1 to 1.5) wind slab avalanches were observed out of steep terrain on Sunday and Monday, being triggered naturally and by riders.

Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter.

Snowpack Summary

The snowpack depth varies substantially in the region and has been described as thin, wind-hammered, variable, and tapering rapidly at lower elevations. The average snowpack depth at treeline is approximately 100 cm.

Up to 30 cm of snow from last week overlies a hard melt-freeze crust formed in early December at least up to 2000 m. To date, this layer has not been an avalanche concern but use caution if you find cohesive snow above the crust, particularly if there are weak, sugary faceted grains or feathery surface hoar crystals above the crust. Strong wind from the southwest is forecast on Tuesday along with a bit of new snow, which may form new wind slabs above this crust.

The middle of the snowpack has been reported as being well-consolidated and may host another hard melt-freeze crust.

The base of the snowpack consists of a hard melt-freeze crust from early-November that may have faceted grains around it. There has not been recent avalanche activity on this layer but it remains on our radar. The most likely spot to trigger it would be on thin and rocky slopes.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Avoid areas where the snow feels stiff and/or slabby.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.