Avalanche Forecast

Archived

Feb 20th, 2023–Feb 21st, 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 avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

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, Elkford East, Elkford West.

Heavy snow and strong wind created very dangerous avalanche conditions on Tuesday.

Stick to low-angle terrain while avoiding overhead hazards, like cornices and large slide paths.

Confidence

Moderate

Avalanche Summary

With ongoing wind and heavy snow overnight, surface slabs are expected to remain reactive through Tuesday.

Over the weekend, several natural and skier-triggered size 1 loose dry avalanches as well as a few small pockets of wind slab.

The deep persistent slab problem continues to be a concern for parts of the region. In the nearby Bull River area, this very large older avalanche was observed on Friday by the Avalanche Canada field team which is expected to have occurred on Wednesday.

Snowpack Summary

New snow continues to accumulate burying heavily wind-affected surfaces in exposed terrain and a sun crust on south. aspects.

The middle of the snowpack is well consolidated and sits on a thick crust. The bottom of the snowpack still consists of weak, sugary crystals that are slowly gaining strength in areas with a deeper snowpack.

Deep persistent slab avalanches should still be on your radar in thinner snowpack areas outside of the Lizard Range such as the Elkford area, and the Flathead range.

Weather Summary

Monday night

Heavy snowfall, 15 to 40 cm. Strong southwest alpine winds shifting to the northeast by Tuesday morning. Treeline temperatures -5 to -10 C.

Tuesday

Cloudy with snow, 5 to 15 cm. Strong northeast alpine winds. Treeline temperatures -10 to -20 C.

Wednesday

Cloudy with sunny periods and no precipitation. Moderate to strong northeast alpine winds. Treeline temperatures -20 to -25 C.

Thursday

Cloudy with sunny periods and no precipitation. Moderate to strong northeast alpine winds. Treeline temperatures -20 to -25 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
Expect slab conditions to change drastically as you move into wind exposed terrain.
Be careful to keep storm day fever from luring you out into bigger terrain features.
Avoid traveling through runout zones during stormy periods when large avalanches are likely.

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.

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.