Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 5th, 2022–Dec 6th, 2022

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

Regions

Purcells, Dogtooth, East Purcell.

Fresh, reactive wind slabs are expected to form throughout the day. Watch for signs of instability such as whumpfing, cracking, and recent avalanches.

Concern remains for the persistent weak layers near the base of the snowpack. A conservative approach to terrain is advised.

Confidence

Low

Avalanche Summary

Explosive control on Sunday produced several small (size 1-1.5) persistent slab avalanches from North and Northwest facing treeline. These avalanches failed on the Mid-November surface hoar layer.

On Saturday, a small (size 1) skier triggered persistent slab avalanche occurred on a northwest aspect at treeline. A larger (size 2) natural slab avalanche was also observed from a distance on an east-facing alpine slope.

Last week, a small (size 1) natural persistent slab avalanche was observed at treeline on a steep, south-facing road bank. It failed on the sugary, faceted layer 25 cm deep.

We have very few eyes out there. If you do get out please consider reporting in the MIN.

Snowpack Summary

New snow and westerly winds may form fresh wind slabs in the alpine and treeline throughout the day. The upper snowpack has been redistributed by variable winds in the past week. In exposed terrain, slopes may have been scoured back significantly. In sheltered areas, 20-60 cm overlies a generally weak, sugary, facetted lower snowpack. A buried layer of surface hoar sits 25-60 cm deep and remains a layer of concern.

The overall height of snow is highly variable throughout the region with around 40-150 cm in the alpine.

Weather Summary

Monday night

Cloudy with light snowfall, less than 5 cm of accumulation expected. Westerly winds 25-40 km/h at ridgetop. Treeline temperatures drop to -16 C.

Tuesday

Cloudy with continued snowfall, up to 5 cm of accumulation expected. Westerly winds 25-40 km/h at ridgetop. An alpine temperature inversion may be present, with alpine temperatures around -10 C and valley bottom temperatures close to -15 C.

Wednesday

Cloudy with light snowfall, less than 5 cm of accumulation. Westerly winds 20-30 km/h at ridgetop. Treeline temperatures reach a daytime high of -10 C.

Thursday

Cloudy with snowfall, up to 5 cm of accumulation is possible. Southwesterly winds 30-60 km/h at ridgetop. Treeline temperatures reach a daytime high of -8 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.