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Avalanche Forecast

Archived

Nov 29th, 2022–Nov 30th, 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.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell, Moyie, St. Mary.

The snowpack is cold, thin, soft, and sugary. The best riding is where the snow is deeper and provides support. Riding safely in these deeper areas requires avoiding wind slabs: stick to moderate slope angles, seek out wind sheltered areas.

Confidence

Moderate

Avalanche Summary

Limited reporting from the field. The interesting thing about the one reported wind slab is that it scrubbed to the ground and ran quite far.Lack of avalanche activity suggests the general lack of a cohesive slab; don't interpret it as a sign of strength.

Snowpack Summary

Upper Snowpack: 20 to 30 cm of snow from the past week. In windy, alpine areas it may have been hardened into a slab, but generally it's soft and faceting (turning into sugar).

Lower Snowpack: Below the recent snow are a couple of surface hoar layers or extra faceted snow. But generally, it doesn't really matter because it's all mostly soft facets (in representative places that are out of the wind near treeline)

There isn't much holding everything together other than wind hardening. In most places the lack of structure doesn't support slab avalanche (only loose dry) but in wind loaded lee slopes where the snowpack is thicker and more cohesive the situation could be different.

In the alpine, snowpack depths range from 50-150 cm. At treeline there is around 50-100 cm. Below treeline is thin and scratchy. At all elevations there are many early season hazards like rocks and stumps.

Weather Summary

Tuesday Night

Light southwesterly wind, increasing to moderate as sunrise approaches. Trace to a few cm of snow. Temps around -15 to -20 C.

Wednesday

Moderate southerly wind, 5 to maybe 15 cm of snow, Temps in the minus teens.

Thursday

Southwest wind diminishing during the day and snow ending near sunrise. Temps steady in the minus teens. Mix of sun and clouds.

Friday

Dry, Mostly sunny. Continued cold temps. Light westerly winds.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.

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.