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Avalanche Forecast

Archived

Mar 18th, 2020–Mar 19th, 2020

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

Regions

South Rockies.

A cool, cloudy day is forecast for Thursday. Still apply caution when travelling near thin, rocky start zones.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

WEDNESDAY NIGHT: Cloudy, light north wind, alpine temperature -10 C.

THURSDAY: Cloudy, light northwest wind, alpine temperature -12 C.

FRIDAY: Clear skies, light to moderate northwest wind, alpine temperature -5 C, freezing level 1500 m.

SATURDAY: Clear skies, light northwest wind, alpine temperature -3 C, freezing level 1800 m.

Avalanche Summary

On Tuesday, explosives triggered small wind slabs, which stepped down to the faceted grains over the melt-freeze crust described in the snowpack summary. The avalanches were generally on west aspects and were large (up to size 2.5). The likelihood of similar avalanches on Thursday will decrease with cool, cloudy weather forecast.

If you decide to travel in the backcountry, consider sharing your observations with us and fellow recreationists via the Mountain Information Network (MIN) to supplement our data stream as operators are shutting down. Even just a photo of what the day looked like would be helpful.

Snowpack Summary

Sunny skies have formed a melt-freeze crust on sun-exposed slopes. The alpine consists of wind affected snow from easterly wind. This wind direction is atypical, so you may find small pockets of wind slabs in terrain features on south to west aspects.

A layer of faceted grains overly a melt-freeze crust from early February. This layer currently sits 40 to 80 cm below the surface. 

The base of the snowpack contains basal facets that are most prominent in shallow, rocky start zones.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.