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Avalanche Forecast

Archived

Dec 3rd, 2020–Dec 4th, 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.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

The heat is on! 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 - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

A warm air mass will invade the Sea to Sky region on Friday bringing warm temperatures and sunshine until Sunday.

Friday: A mix of sun and cloud. Ridgetop wind generally light with strong gusts from the South. Alpine temperatures +6 degrees and freezing levels 1500 m.

Saturday: Sunny with alpine temperatures near +7 degrees and freezing levels 2900 m. Ridgetop winds 25-40 km/h. from the southeast.

Sunday: Cloudy with light precipitation. Alpine temperatures 0 degrees. Ridgetop wind 20-30 km/hr and freezing levels falling to 1700 m.

Avalanche Summary

No new avalanches were reported on Thursday.

On Wednesday, a natural widespread wet loose avalanche cycle up to size 1 occurred. A cornice failure size 1.5 also occurred triggering a small surface slab on the slope below.

As warm air and sunshine hit the region again Friday and Saturday I expect more natural avalanche activity to occur. The longer the heat sticks around the deeper it drives into the snowpack potentially initiating larger avalanches. 

Have you been out and about in the mountains? If so please submit to the Mountain Information Network (MIN). It doesn't have to be technical it can be as simple as a photo. Photos are especially helpful! Sending out a big thank you to the already submitted MIN's this season. Thanks everyone!

Snowpack Summary

Recent sun and warm air well into the alpine likely had the greatest impact on the upper snowpack, showing signs of instability and promoting further slab development and cohesion. This may be most concerning where these slabs sit above an old thin crust on south aspects and feathery surface hoar crystals in wind-sheltered areas. New surface hoar formation can be found on slopes where it was protected from the warm temperatures, sunshine and wind. 

Northerly aspects will likely see fresh wind slab development at upper elevations on leeward slopes and melt-freeze conditions may exist especially on solar aspects at all elevations. 

The snowpack depth varies 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 just 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

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

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.

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.