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Avalanche Forecast

Archived

Dec 4th, 2020–Dec 5th, 2020

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

Regions

South Coast.

  

Above freezing temperatures up high over night and into the day Saturday will continue to stress the snowpack. Wet loose avalanches will be most likely to occur on solar aspects during the heat of the day.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

FRIDAY NIGHT: Clear / Moderate, southwest ridgetop wind / alpine low temperature 0 / Freezing level 3000 m.

SATURDAY: Sunny / Moderate, south ridgetop wind / alpine high temperature +8 / Freezing level dropping gradually to 2000 m.

SUNDAY: Mix of sun and cloud / Moderate, southwest ridgetop wind / alpine high temperature +3 / Freezing level 2000 m.

MONDAY: Rain; 35-45 mm. / Strong, southwest ridgetop wind / alpine high temperature +2 / Freezing level rising to 3000 m.

Avalanche Summary

No new avalanches were reported on Thursday. However, glide cracks did start to open up on the North Shore Mountains.

On Wednesday, numerous slab avalanches and loose wet avalanches were reported at treeline elevations and associated with the rapid warming. An older and larger natural avalanche cycle up to size 3.5 (from last week's storm) was also reported from alpine and treeline elevations. 

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 very warm alpine temperatures have had the greatest impact on the snowpack. This rapid warming likely increased slab development above 1300 m. Deep pockets of wind slab may linger on leeward slopes at upper elevations. 

Below 1200 m a soggy snowpack may exist. Cooler temperatures overnight may form a crust on all aspects and elevations but I suspect with the continued warming that crust will disappear quickly and make for a wet upper snowpack.

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

Terrain and Travel

  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Be careful as you transition into wind affected terrain.

Problems

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.

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.