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Avalanche Forecast

Archived

Feb 19th, 2020–Feb 20th, 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 possible, human triggered probable.
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

Northwest Coastal.

Overnight flurries and strong winds will build fresh wind slabs in the alpine and exposed treeline areas. Watch for wind loading around ridgecrests and steep rollovers.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Wednesday night: Flurries bringing around 10 cm new snow. Moderate west wind. Alpine low -10 C. Freezing level valley bottom.

Thursday: Mostly cloudy with a chance of isolated flurries late in the day. Moderate to strong southwest wind. Freezing level 800 m.

Friday: Flurries bringing 15-30 cm new snow. Strong southwest wind. Freezing level 800 m.

Saturday: Mostly cloudy with isolated flurries. Moderate south wind. Freezing level 600 m.

Avalanche Summary

Tuesday was a day of varied avalanche activity. Explosive control work produced size 2.5-3 cornices. A natural wind slab size 2 was observed on a southeast aspect and ran to valley bottom in a steep, confined feature. Glide slabs were also observed, where full depth avalanches slid on rock slabs along the highway corridor west of Terrace. 

Loose wet avalanches up to size 2 on steep solar aspects were observed on Monday. A few skier triggered storm slabs size 1-1.5 have been reported, on wind loaded features in the alpine, and running on surface hoar 40 cm deep at treeline.

Snowpack Summary

Overnight snow is being redistributed and loaded into lee features by strong winds at alpine and exposed treeline elevations. At treeline and below, recent snow may sit over patchy surface hoar in wind sheltered areas or crusts on solar aspects.

A thin layer of facets that formed during the January cold snap is now about 120-170 cm below the surface while an early season 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

  • Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

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.