Avalanche Forecast

Archived

Jan 30th, 2023–Jan 31st, 2023

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

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

Watch for pockets of stiff wind slab at upper elevations from recent winds. These slabs may be in atypical areas due to reverse-loading.

Avoid shallow areas where the snowpack transitions from thick to thin and triggering deep weak layers is more likely.

Confidence

Moderate

Avalanche Summary

On Sunday, a few natural, size 1 to 1.5, wind slab avalanches were reported at higher elevations.

On Saturday several thin wind slabs, up to size 1.5, were reported to be reactive to natural and human triggers.

Please continue to share any observations or photos on the Mountain Information Network.

Snowpack Summary

15 cm of storm snow has been redistributed by variable winds in the alpine and at treeline. New snow sits over a crust on southerly slopes, previously wind affected surfaces in exposed areas and over a layer of surface hoar in sheltered areas.

A crust and facet layer from mid January, 2 to 15 cm thick at treeline sits 50 to 90 cm deep. Where it's thickest, it caps the settled and consolidated mid-snowpack.

The lower snowpack contains weak and facetted grains from November. The total snowpack depth ranges between 120 and 250 cm.

Weather Summary

Monday Night

Mainly cloudy with isolated flurries. Moderate northwesterly winds gusting 40 km/h. Alpine high of -17°C.

Tuesday

Cloudy with sunny periods and isolated flurries, trace accumulations. Westerly ridgetop winds 40 km/h. Alpine high of -13°C.

Wednesday

Cloudy with sunny periods and isolated flurries, trace accumulations. Westerly ridgetop winds 40 km/h. Alpine high of -8°C.

Thursday

Sunny with cloudy periods. Southwesterly ridgetop winds 40-60 km/h. Alpine high of -5°C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Recent wind has varied in direction so watch for wind slabs on all aspects.
Approach lee and cross-loaded slopes with caution.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.