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Avalanche Forecast

Archived

Mar 23rd, 2020–Mar 24th, 2020

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

Regions

South Rockies.

There is uncertainty in the forecast due to a lack of data available at this time.

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.

Weather Forecast

MONDAY NIGHT: Cloudy with flurries, accumulation trace to 10 cm, moderate to strong southwest wind, alpine temperature -8 C.

TUESDAY: Cloudy with flurries, accumulation 5 to 10 cm with locally higher amounts possible, moderate southwest wind, alpine temperature -8 C, freezing level 1000 m.

WEDNESDAY: Cloudy with flurries, accumulation 5 to 10 cm, light southwest wind, alpine temperature -7 C, freezing level 1000 m.

THURSDAY: Clear skies, light southwest wind, alpine temperature -6 C, freezing level 1500 m.

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 new snowfall and wind forms fresh slabs.

Snowpack Summary

Snowfall and southwest wind are forecast for the coming days, which will form wind slabs in exposed terrain. Expect the slabs to be thickest and most reactive in lee terrain features adjacent to ridge lines. The slabs will sit on a melt-freeze crust on sun-exposed slopes or previously wind-affected snow, so these 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.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
  • 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.