Avalanche Forecast

Archived

Feb 25th, 2023–Feb 26th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Watch for increasingly reactive conditions as snowfall accumulates on Sunday.

Avoid freshly wind loaded features.

Confidence

Moderate

Avalanche Summary

On Thursday small loose dry avalanche activity was reported.

On Wednesday a number of storm slab and wind slab avalanches were triggered with explosives and ski cutting, up to size 2 on various aspects and elevations.

A natural avalanche cycle occurred during stormy weather on Tuesday, with numerous storm slab releases up to size 2.5.

Snowpack Summary

Around 10 cm of low density storm snow will sit over wind affected surfaces at all elevations with deeper deposits expected in north and east facing terrain features.

The mid-snowpack is generally well settled, with no current layers of concern.

The lower snowpack includes a layer of weak sugary crystals and crusts near the ground. These facets are slowly gaining strength and have not produced recent avalanche activity. We continue to track the layer and watch for any signs that it could wake up and produce very large avalanches.

Weather Summary

Saturday Night

Cloudy overnight with flurries. Moderate to strong southwest winds. Freezing levels below valley bottom

Sunday

Snow begins early in the morning, delivering 5-15 cm over the day. Freezing levels rise to 1000 m. Alpine high of -5 °C with moderate to strong southwest winds easing over the day.

Monday

Another 5-10 cm possible overnight into Monday morning. Most cloudy day with moderate southerly winds easing. Freezing levels around 600 m. Alpine high of -7 °C. Snowfall eases in the morning with lingering flurries possible.

Tuesday

Cloudy with flurries bringing a few cm over the day. Light to moderate southwest winds. Freezing levels around 600 m. Alpine high of -7 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
Be especially cautious as you transition into wind affected terrain.
Recent wind has varied in direction so watch for wind slabs on all aspects.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.

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.