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Avalanche Forecast

Archived

Dec 23rd, 2024–Dec 24th, 2024

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.

Regions

Lizard-Flathead, Flathead, Lizard.

Increasing winds on Tuesday will create new and reactive wind slabs.

Confidence

Moderate

Avalanche Summary

On Sunday, numerous wind slab avalanches up to size 2 occurred, including both natural and explosive-triggered. These avalanches were observed in alpine and treeline terrain on various aspects, with depths ranging from 10 to 40 cm.

An encouraging observation is that none of these avalanches triggered a step-down avalanche on layers deeper in the snowpack.

Snowpack Summary

Strong winds on Tuesday will further redistribute the recent 20 cm of snow from the weekend, promoting wind slab development in lee and cross-loaded terrain.

Settled powder snow remains in wind-sheltered terrain, while a thin melt-freeze crust exists below approximately 1600 m.

The mid and lower snowpack is generally well-settled and stable.

Snow depths at treeline range from 120 to 180 cm.

Weather Summary

Monday Night

Mostly cloudy. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Tuesday

Cloud building through the day with 0 to 2 cm of snow. 50 to 70 km/h southwest ridgetop wind. Treeline temperature -1 °C.

Wednesday

Mostly cloudy. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -7 °C.

Thursday

Mostly cloudy with 2 to 5 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid lee and cross-loaded slopes in the alpine.
  • Wind slabs are most reactive during their formation.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.

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.