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Avalanche Forecast

Archived

Feb 22nd, 2025–Feb 23rd, 2025

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Lizard-Flathead, Flathead, Lizard.

Dangerous avalanche conditions are developing as new snow and rain accumulates throughout the storm.

Travel in avalanche terrain is not recommended.

Confidence

Moderate

Avalanche Summary

Numerous size 1 to 2 dry and wet loose avalanches, both natural and rider-triggered occurred over the week.

Thursday, a size 1.5 naturally-triggered wind slab was reported in the Lizard Range.

Tuesday, there were two reports of size 1.5 skier and sled triggered persistent slabs in the alpine. See details in this MIN here and this MIN.

Looking forward, we expect avalanche activity to rapidly increase as snow starts to accumulate along with strong winds and warming.

Snowpack Summary

Around 25 to 45 cm of new snow is expected to fall overnight and through Sunday, with the highest amounts forecast for the Lizard Range. At lower elevations this will fall as rain. The combined storm snow is covering old wind-affected surfaces in open areas, and 20 to 30 cm of settling snow overlying facetted snow in wind-sheltered areas. A persistent weak layer of surface hoar or facets from late January is currently buried 40 to 60 cm. There is significant concern for this layer becoming active with the incoming precipitation and warming. The mid and lower snowpack is generally well settled, with no other layers of concern.

Weather Summary

Saturday Night

Cloudy with 10 to 30 cm of snow / possible rain below 1800 m. 30 to 50 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 1900 m.

Sunday

Mostly cloudy with 5 to 15 cm of snow / possible rain below 1800 m. 35 to 45 km/h southwest ridgetop wind. Treeline temperature 1 °C. Freezing level rising to 2000 m.

Monday

A mix of sun and cloud. 25 to 45 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level rising to 1700 m.

Tuesday

Cloudy with 2 to 10 cm of snow / possible rain below 1200 m. 30 to 40 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level rising to 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.
  • Avoid the runout zones of avalanche paths. Avalanches could run full path.
  • Storm slab size and sensitivity to triggering will likely increase through the day.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.