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Avalanche Forecast

Archived

Feb 20th, 2020–Feb 21st, 2020

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

Regions

North Columbia.

Moderate southerly winds may create small wind slabs that are possible to trigger in steep, convex terrain below ridgetops.

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence.

Weather Forecast

THURSDAY NIGHT: Clear, moderate south wind, alpine temperature -13 C, freezing level below valley bottom.

FRIDAY: Mix of sun and cloud, moderate southwest wind, alpine temperature -8 C, freezing level 1100 m.

SATURDAY: 5-15 cm snow, moderate southwest wind, alpine temperature -9 C, freezing level 1000 m.

SUNDAY: Cloudy with flurries; 3-5 cm., light to moderate southwest wind, alpine temperature -11 C, freezing level 700 m.

Avalanche Summary

A couple small (size 1) skier triggered wind slabs were reported on northeast and east aspects on Wednesday. Several natural and skier triggered slab avalanches up to size 2 were reported on primarily east/southeast aspects at treeline and above on Tuesday. 

Snowpack Summary

30-60 cm of recent storm snow is gradually settling and gaining strength, but has shown some isolated signs of reactivity on wind loaded slopes, steep convexities in sheltered terrain (where the snow sits above small surface hoar or sun crusts), and steep gully features at low elevations (where the snow may be poorly bonded to the early February rain crust). These interfaces are unlikely to develop into a persistent problem, but for the next few days storm slabs could remain reactive on these isolated terrain features. The lower snowpack is generally well settled and strong.

Terrain and Travel

  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Cornice failure may trigger large avalanches.

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.