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Avalanche Forecast

Archived

Dec 1st, 2021–Dec 2nd, 2021

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.
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

Lizard-Flathead.

Continued precipitation overnight may create fresh wind slabs in the alpine and loose wet avalanches in the alpine and treeline. Approach avalanche terrain cautiously as we assess the impacts of several large storms.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Wednesday overnight: 2500m freezing levels will begin to descend reaching ~1800m by morning. Another 20-40mm can be expected, initially falling as rain, and eventually falling as snow at higher elevations. Winds will continue to be strong to extreme from the southwest. 

Thursday: A clearing trend! Up to 10mm of mixed precipitation can be expected in the early morning, with freezing levels sitting around 1700m. Throughout the day we will see clearing skies, gradually lowering freezing levels and winds steadily decreasing into the moderate to strong range from the west. 

Friday: A brief period of high pressure prevails. A mainly sunny day with light winds from the southwest and freezing levels at valley bottom. High cloud may develop in the afternoon with another front approaching.

Saturday: Another system is upon us. 10-30cm of snow is expected throughout the day accompanied by strong westerly ridgetop winds. Freezing levels starting the day at near valley bottom rising up to 1300m.

Avalanche Summary

There have been very few reports in the past 24 hours. On Wednesday, Island Lake Lodge reported several size 1.5 wet loose avalanches out of steep alpine terrain and a Size 2 Natural Storm Slab on at NE aspect at 1900m. I suspect a widespread natural avalanche cycle has occurred in the region in conjunction with Wednesday's storm. 

Reports in the region remain limited. If you go out in the mountains, please share your observations and/or photos on the Mountain Information Network! 

Snowpack Summary

Heavy rain has soaked the snowpack to mountaintop in most areas. In the high alpine (above 2300m) up to 50cm of wet snow accumulation is possible. Until temperatures cool, this will result in a wet, heavy, and unstable upper snowpack.

Below 40cm of saturated storm snow lies a thick mid-November rain crust which has been the suspected bed surface of a few recent step-down avalanches. Moist snow is still found below the crust and to the ground.

Snowpack depths range from 20-50cm at treeline elevations. Expect to find a deeper snowpack at higher elevations and in previously wind-loaded areas. Snowpack decreases rapidly below 1900m.

Terrain and Travel

  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
  • Be alert to conditions that change with elevation and wind exposure.
  • Watch for newly formed and reactive wind slabs 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.