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Avalanche Forecast

Archived

Feb 22nd, 2020–Feb 23rd, 2020

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

Regions

Northwest Coastal.

Recent snow rests on a weak layer so may take longer than usual to bond to old surfaces and will likely remain reactive to human traffic. Continue to make conservative terrain choices while storm snow settles and stabilizes.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Saturday night: Light snowfall, accumulation up to 5 cm. Moderate to strong southwest wind. Alpine low -5 C. Freezing level 500 m.

Sunday: Light snowfall, accumulation trace. Light wind southeast switching to northwest. Alpine high -3 C. Freezing level 500 m.

Monday: Mix of sun and cloud with isolated flurries. Light northwest wind, alpine high -5 C. Freezing level valley bottom.

Tuesday: Moderate snowfall, accumulation 10-20 cm. Strong southwest wind, alpine high -1 C. Freezing level 500 m.

Avalanche Summary

A widespread natural storm slab cycle up to size 2.5 occurred during the storm Thursday night and Friday. Skier accidental and remote triggered storm slabs were reported up to size 1.5, releasing on the underlying surface hoar. The slabs were 30 to 50 cm deep and on north to east aspects.

Snowpack Summary

40 to 70 cm of new snow has likely formed storm slabs at all elevations. The slabs are likely deepest in lee terrain features, as the snow fell with strong south to west wind.

These slabs may slide easily where they overly a couple layers of surface hoar that may be found in sheltered terrain at and below treeline or a melt-freeze crust on sun-exposed aspects. You may find these layers around 50 and 80 cm deep.

A thin layer of weak and sugary faceted grains that formed in January may be found about 120 to 170 cm deep, and an early-season melt-freeze crust lingers at the base of the snowpack. These layers produced a few large natural avalanches in early-February but have recently been unreactive.

Terrain and Travel

  • Be aware of the potential for human triggerable storm slabs at lower elevations, even on small features.
  • Be especially cautious as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.