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Archived

Avalanche Forecast

Dec 21st, 2024–Dec 22nd, 2024
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Flathead, Lizard, Lizard-Flathead.

Overnight snow and wind may form fresh, reactive slabs. Back off if you encounter signs of instability.

Confidence

Moderate

Avalanche Summary

A widespread natural avalanche cycle took place during the storm last Wednesday.

A notable sled-triggered wind slab was reported at Coal Creek from a ridgetop, wind-loaded feature. More details can be seen here.

A MIN report from Saturday suggested that wind slabs remained touchy below ridges and tree bands.

Snowpack Summary

Up to 15 cm of new snow will add to 40 cm of recent storm snow, with deeper deposits accumulating in lee-facing terrain at higher elevations due to southwest winds.

The mid and lower snowpack is generally well-settled and stable. However, there is some uncertainty about a potential surface hoar layer buried 50 to 80 cm deep, which could be reactive on isolated, steep, sheltered slopes around treeline and below.

Snow depths at treeline range from 120 to 180 cm.

Weather Summary

Saturday Night

Cloudy with 5 to 15 cm of new snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Sunday

Cloudy with up to 1 cm of new snow. 25 to 50 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Monday

Cloudy with up to 5 cm of new snow. 20 to 50 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Tuesday

Cloudy with up to 2 cm of new snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -1 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Approach steep and open slopes at and below treeline cautiously, as buried surface hoar may exist.

Avalanche Problems

Storm Slabs

Newly formed and reactive slabs are expected to form in wind-loaded terrain.

Take a cautious approach to steep openings at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2.5