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Avalanche Forecast

Archived

Dec 1st, 2020–Dec 2nd, 2020

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

The snowpack doesn't respond well to rapid change. The impact of the afternoon sun and warm temperatures could bump up the avalanche danger to HIGH. Watch for signs of instability and be conservative with your terrain selection.

Confidence

Moderate -

Weather Forecast

Wednesday: Sunny with some cloudy periods. Ridgetop winds 15-25/h km fromthe southeast and alpine temperatures + 9 degrees. Freezing levels 3500 m.

Thursday: A mix of sun and cloud. Ridgetop winds 10-20 km/hr from the southeast and alpine temperatures near + 5 degrees. Freezing levels 3000 m.

Friday: A mix of sun and cloud. Ridgetop winds light from the southeast and alpine temperatures + 9 degrees. Freezing levels 3000 m.

Avalanche Summary

Wednesday we may see storm slab avalanches due to rapidly warming temperatures and sun in the afternoon. They may be especially reactive where recent snow sits over a crust. Loose wet avalanches are likely, especially on steep solar aspects at all elevations.

Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

Last week's snowfall dropped near 30 cm of snow at upper elevations. Strong southwest winds have formed fat pockets of storm slab in lee features above 1400 m. 

Forecast sun and rising freezing levels well into the alpine will have the greatest impact on the recent snow promoting slab development. Below 1200 m, most of the recent snow fell as rain on a soggy snowpack. Cooler temperatures overnight may form a thin surface crust on all aspects and elevations.

The snow line currently sits at around 900 m. Snowpack depth rapidly changes with elevation. The snowpack rapidly jumps to around 100 cm deep above 1000 m and between 150 to 200 cm near the mountain tops.

Terrain and Travel

  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • Be cautious of buried obstacles especially below treeline.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.