Avalanche Forecast

Archived

Jan 31st, 2023–Feb 1st, 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 wind slabs that have developed in sheltered terrain due to the recent strong winds.

Avoid shallow, rocky snowpack areas where triggering the deep persistent weak layer is still possible.

Confidence

Moderate

Avalanche Summary

On Monday, a skier-triggered, size 1 wind slab was reported.

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

Winds continue to redistribute recent snow into wind slabs in open terrain features at treeline and alpine elevations. These wind slabs are developing over variable surfaces of wind-pressed snow, spotty surface hoar, and soft, faceted snow.

The mid-pack is well consolidated in the Lizard Range with a robust melt-freeze crust formed around Christmas down 50 to 90 cm deep. In the north of this region, the snowpack is gaining strength but is much shallower with a more faceted snowpack.

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

Weather Summary

Tuesday Night

Mainly cloudy, trace accumulations, 30 to 40 km/h westerly winds, treeline temperatures -12 ºC

Wednesday

Mainly cloudy, trace accumulations, 30 to 40 km/h westerly winds, treeline temperatures -11 ºC

Thursday

Partly cloudy, no new snow, 5 to 10 km/h southwest winds, treeline temperatures -10 ºC

Friday

Mostly clear skies with increasing overnight, 1 to 3 cm of new snow, 5 to 10 km/h southwest winds, treeline temperatures -10 ºC

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

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.