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Avalanche Forecast

Archived

Mar 26th, 2020–Mar 27th, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies.

Limited observations are keeping forecast confidence low. Steady winds are redistributing loose snow and building wind slabs.

Confidence

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

Weather Forecast

Thursday night: Increasing cloud coverage. Alpine low temperature -9 C. Moderate west winds.

Friday: Cloudy with isolated flurries, up to 5 cm. Alpine high temperature -3 C. Moderate to strong southwest winds.

Saturday: Cloudy with scattered flurries, up to 5 cm. Alpine high temperature -5 C. Moderate gusting to strong southwest winds.

Sunday: Cloudy with scattered flurries, 5-10 cm. Alpine high temperature -1 C. Moderate gusting to strong southwest winds.

Avalanche Summary

No new avalanches were reported from Tuesday's storm, but observations have been minimal. Recent new snow is expected to remain reactive over the near term, especially on steeper south facing slopes and in areas where wind loading has occurred or will occur.

Snowpack Summary

About 15-25 cm of new snow accumulated during Tuesday's storm. Sun has encouraged settlement and produced moist slopes on steep solar aspects at lower elevations. Increasing southwest winds are redistributing loose surface snow. 

The recent new snow sits above a melt-freeze crust on sun-exposed slopes and on previously wind-affected snow in other areas, so new slabs may take some time to bond to these surfaces. 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.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

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.