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Avalanche Forecast

Archived

Mar 24th, 2020–Mar 25th, 2020

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

Regions

South Rockies.

Forecast confidence is low due to a lack of field observations. New and reactive wind slabs should be expected in higher elevation terrain.

Confidence

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

Weather Forecast

Tuesday night: Mainly cloudy with possible isolated flurries. Light to moderate west winds.

Wednesday: A mix of sun and cloud with possible isolated flurries. Light west winds. Alpine high temperatures around -8.

Thursday: Sunny. Light to moderate west winds. Alpine high temperatures around -6.

Friday: A mix of sun and cloud. Light to moderate west or southwest winds. Alpine high temperatures around -5

Avalanche Summary

A few small (size 1) loose wet avalanches were observed in the region on Monday when the sun poked through the clouds. 

Looking forward, wind slab activity may increase as continuing light snowfall and increased wind form new slabs.

Snowpack Summary

Continuing light snowfall and elevated southwest wind are expected to form new wind slabs in exposed terrain. The new snow will sit on a melt-freeze crust on sun-exposed slopes or previously wind-affected snow, so new slabs may take some time to bond to the snowpack.

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

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Make conservative terrain choices and avoid overhead hazard.

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.

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.