Avalanche Forecast

Archived

Dec 4th, 2023–Dec 5th, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Lizard-Flathead, Akamina, Flathead, Lizard.

Travel in avalanche terrain is not recommended as an intense storm loads a weak snowpack. A natural avalanche cycle is likely to occur.

Confidence

High

Avalanche Summary

Many storm and wind slabs released on Sunday within the snow that overlies the weak layer of surface hoar described in the Snowpack Summary. The avalanches were generally small to large (size 1 to 2) and triggered by riders and explosives at treeline and alpine elevations.

Looking forward, natural and human-triggered avalanches are very likely as an intense storm impacts the region.

Snowpack Summary

An intense and warm storm will rapidly load the snowpack with new snow and rain. A weak and feathery surface hoar layer buried about 20 to 30 cm will rapidly destabilize with the added load. This layer may be associated with a hard melt-freeze crust.

The remainder of the snowpack is weak and faceted. Snowpack depths are approximately 60 to 80 cm at treeline, which rapidly tapers with elevation below treeline.

Weather Summary

Monday Night

Cloudy with snow switching to rain below approximately 2500 m, accumulation 5 to 15 cm of snow possible at the highest elevations. Southwest alpine wind 40 km/h. Treeline temperature 0 °C. Freezing level rising from 1300 m to 2500 m.

Tuesday

Cloudy with rain or snow, 20 to 40 cm snow accumulation possible above the rain-snow line near 2100 m. Southwest alpine wind 20 to 40 km/h. Treeline temperature 2 °C. Freezing level 2500 m.

Wednesday

Cloudy with rain or snow, 10 to 20 cm snow accumulation possible above the rain-snow line near 2000 m. Southwest alpine wind 20 to 40 km/h. Treeline temperature 1 °C. Freezing level 2200 m.

Thursday

Cloudy with rain switching to snow, 20 to 50 cm snow accumulation possible above the rain-snow line near 1500 m. Southwest alpine wind 20 to 40 km/h. Treeline temperature 0 °C. Freezing level 2000 m dropping to 1300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid avalanche terrain during periods of heavy rain.
Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
If triggered loose wet 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

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.