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Avalanche Forecast

Archived

Feb 23rd, 2023–Feb 24th, 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.

Sustained strong, easterly winds have created wind slabs in exposed terrain on all aspects and elevations.

Confidence

Moderate

Avalanche Summary

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

Recent snow continues to be redistributed by strong north to east winds at all elevations and has formed wind slabs throughout wind-exposed terrain.

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

The bottom of the snowpack consists of weak, sugary, basal facets and a crust.

Weather Summary

Thursday night

Mostly clear / Moderate northeast ridgetop winds, shifting from the southwest by Friday morning / Treeline temperatures -25 to -30 C.

Friday

Mostly sunny / Light southwest ridgetop winds / Treeline temperatures -25 C, warming to -15 C by the end of the day.

Saturday

A mix of sun and cloud / Moderate southwest ridgetop winds / Treeline temperatures -10 to -25 C.

Sunday

Cloudy, with snow beginning late in the day / Moderate southwest ridgetop winds / Treeline temperatures -5 to -10 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • 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.