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Avalanche Forecast

Archived

Nov 30th, 2020–Dec 1st, 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.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Avalanche danger will increase in the afternoon as temperatures rise at upper elevations. Use extra caution where recent snow is experiencing sun and rapidly warming temperatures for the first time.

Confidence

Moderate -

Weather Forecast

Monday night: Clear, light northwest wind, freezing level 500 m.

Tuesday: Sunny, light northwest wind, freezing level 1000 m with an above freezing layer developing 1500-2500 m.

Wednesday: Sunny, light southeast wind, freezing level 3000 m.

Thursday: Increasing cloud, light south wind, freezing level 1000 m.

Avalanche Summary

Natural, skier triggered and explosive triggered storm and wind slab avalanches were reported size 1.5-2.5 during and after the storm on Monday. Crown depths generally ranged 20-50 cm, with a 120 cm deep crown observed in a heavily wind loaded feature.

Tuesday we may see more 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 or surface hoar. Loose wet avalanches are also be possible, especially on steep solar aspects.

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

15-25 cm of recent snow sits over a thin melt-freeze crust on south aspects and surface hoar in wind sheltered areas around treeline. Fat pockets of wind loaded snow may be found in lee features at upper elevations.

The snowpack depth varies substantially with elevation. Below treeline 30 to 70 cm, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.

The mid to lower snowpack contains a series of crusts, the most notable of which is also the deepest, sitting 30 cm above the ground at elevations above 1500 m. This crust may have a thin overlying layer of weak faceted grains and/or surface hoar crystals, especially in sheltered areas around treeline. There is uncertainty as to whether these layer will be a concern going forward. 

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.