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Avalanche Forecast

Archived

Dec 1st, 2020–Dec 2nd, 2020

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

Regions

South Columbia.

  

Things are looking HOT up high for the next couple days. Naturally triggered wet loose avalanches are possible on all aspects and especially likely on solar aspects. Overhead hazards will be a primary concern.

Confidence

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

Weather Forecast

  

TUESDAY NIGHT: Clear / Light, north ridgetop wind / alpine low temperature 0 (temperature inversion, -12 in valleys) / Strong temperature inversion with above freezing air 2000-3500 m.

WEDNESDAY: Sunny / Light, south ridgetop wind / alpine high temperature +6 / Strong temperature inversion with above freezing air 2000-3500 m.

THURSDAY: Sunny / Moderate, southwest ridgetop wind / alpine high temperature +6 / Strong temperature inversion with above freezing air 2000-3500 m.

FRIDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature 0 / Temperature inversion with above freezing air 2000-3000 m.

Avalanche Summary

There have been very few reports of avalanches in the region, however, observations are very limited at this time. 

Several recent MIN reports from neighboring Glacier National Park have reported human triggered avalanches on small surface hoar below the recent storm snow.

Data is very sparse in this region. Please submit your observations to the Mountain Information Network!

Snowpack Summary

  

On Monday, 10 cm of new snow and moderate northwest winds formed small wind slabs on lee features at treeline and above. Last week’s strong southwest winds created wind slabs that are still lingering on lee features at treeline and above. These wind slabs may be surprisingly reactive in areas where they are sitting on a layer of small surface hoar. There are a couple of crusts in the mid snowpack, from mid and early November. The most prominent of these is from early November, and it has been reported that there are weak, sugary facets above and below this crust. It is down approximately 70-100 cm, and is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky, snowpack areas in the alpine.

Terrain and Travel

  • Avoid exposure to overhead hazards when solar radiation is strong.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.