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Avalanche Forecast

Archived

Feb 2nd, 2023–Feb 3rd, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
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 unlikely, human triggered possible.
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.

Riders could trigger wind slabs at higher elevations.

Confidence

Moderate

Avalanche Summary

A few small (size 1) wind slabs were triggered by riders, naturally, and explosives out of steep alpine terrain on Thursday.

Looking forward, riders could trigger small wind slabs in lee terrain features from the recent snow and sustained southwest wind.

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

Snowpack Summary

Around 10 cm of recent snow is being redistributed into wind slabs in lee terrain features at higher elevations from southwest wind. This overlies previously wind affected snow and/or soft faceted snow above 1900 m and a melt-freeze crust below.

The mid-pack is consolidated in the Lizard Range with a robust melt-freeze buried 70 to 90 cm.

Outside of the Lizard Range, the snowpack is shallower and faceted. In these areas, deep weak layers formed early season are still a concern, especially in steep rocky terrain features.

Weather Summary

Thursday Night

Clear skies with no precipitation, 30 to 50 km/h southwest wind, treeline temperature -4 ºC.

Friday

Clear skies with afternoon clouds and no precipitation, 20 to 40 km/h southwest wind, treeline temperature -3 ºC.

Saturday

Cloudy with snowfall, accumulation 10 to 15 cm, 40 km/h southwest wind, treeline temperature -5 ºC.

Sunday

Cloudy with snowfall, accumulation 5 cm, 20 km/h southwest wind, treeline temperature -5 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.