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Avalanche Forecast

Archived

Feb 21st, 2021–Feb 22nd, 2021

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

Regions

South Coast.

Avalanche danger will increase dramatically above the rain line, with human triggered avalanches likely on steep slopes.

 

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels. Forecast snowfall amounts are uncertain.

Weather Forecast

Cool dry weather after a cold front crosses Sunday night and delivers a final rain/snow mix to the South Coast mountains.

SUNDAY NIGHT: Another 20-30 mm of precipitation with snow levels somewhere around 1200 m, strong west wind, treeline temperatures near 0 C.

MONDAY: Clearing skies and dropping temperatures in the morning, gusty west winds, treeline temperatures around -2 C.

TUESDAY: Mix of sun and cloud, moderate northwest wind, treeline temperatures around -3 C.

WEDNESDAY: Mostly sunny, light wind, treeline temperatures around -3 C.

Avalanche Summary

Periods of heavy snowfall and wind will likely drive a natural avalanche cycle on Sunday night, while lower elevations may experience wet loose avalanches triggered by the rain. Preliminary reports from Sunday show some small reactive storm slabs during the early stages of the storm (MIN report). Human triggered storm slabs will remain likely at treeline and alpine elevations on Monday.

Snowpack Summary

Snowpack conditions will change dramatically with elevation. At lower elevations wet snow will be freezing into a hard surface crust throughout the day. Expect increasingly deeper deposits of new snow between 1000 and 1500 m, potentially up to 40 cm. The new snow should strengthen relatively quickly, but I'd carefully watch for signs on instability in areas with more than 20 cm of snow and avoid steep convex slopes. Alpine terrain could have upwards of 50 cm of new snow with heavily wind affected slabs in open terrain.

Terrain and Travel

  • Travel in alpine terrain is not recommended.
  • Choose simple, low-angle, well supported terrain without convexities.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Avoid freshly wind loaded terrain features.

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.