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Avalanche Forecast

Archived

Feb 3rd, 2023–Feb 4th, 2023

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

Regions

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

630 am update: New snow and wind are elevating avalanche hazard.

Natural and human triggered avalanches can be expected in wind loaded features. This MIN from the Flathead is a great example of the type of terrain where the wind slab problem can be found. Evaluate snow conditions as you transition into open terrain features, and be on the lookout for signs of instability like shooting cracks.

Confidence

Moderate

Avalanche Summary

Natural and rider-triggered (size 1 to 1.5) wind slabs continue to be reported at treeline and alpine elevations. This MIN from the South Rockies field team is a good example of terrain where wind slabs are more likely to be triggered.

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

5 to 10 cm overnight will be redistributed by moderate to strong winds developing wind slabs at treeline and alpine elevations. This overlies previous wind slabs that may still be reactive and a melt-freeze crust below 1900 m

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 more faceted. In these areas, deep weak layers formed early season are slowly gaining strength but are still a concern, especially in steep rocky terrain features.

Weather Summary

Friday Night

Cloudy with overnight snow, 5 to 10 cm of accumulation, 10 to 15 km/h southerly winds, treeline temperatures -2 ºC

Saturday

Mainly cloudy, continued flurries through the morning 2 to 5 cm accumulation, 10 to 20 km/h southwest winds, treeline temperatures -4 ºC.

Sunday

Cloudy with flurries, 2 - 4 cm accumulation, 30 to 40 km/h southwest wind, treeline temperature -5 ºC.

Monday

Cloudy with flurries, accumulation 2 to 4 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.