Avalanche Forecast

Archived

Feb 23rd, 2025–Feb 24th, 2025

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead, Flathead, Lizard.

Further heavy snowfall is expected overnight Sunday.

Avoid exposure to avalanche terrain as storm snow needs time to stabilize and persistent weak layers may be reactive to human triggers.

Confidence

Moderate

Avalanche Summary

On Sunday explosive control produced avalanches up to size 2 in the recent storm snow and on buried weak layers. Natural avalanches were observed on the persistent weak layers to size 2.5 from steep terrain features.

Activity is expected to continue with heavy snowfall Sunday night.

Snowpack Summary

By Monday morning storm totals are expected to reach up to 60 cm in the Lizard Range, and around 40 cm elsewhere. Moderate to strong southwest winds have likely redistributed this snow into deeper deposits at treeline and above. Lower elevations have received mostly rain, creating wet surface conditions or a crust.

A persistent weak layer of surface hoar or facets from late January is buried 70 to 100 cm deep. This layer is expected to be more reactive with the warming temperatures and new snow/ rain. The mid and lower snowpack is generally well settled.

Weather Summary

Sunday Night

Mostly cloudy with 15-20 cm of snow. Snowfall is expected to begin the night at 1500 m, and drop to 500 m by morning. Winds increase overnight to 50 km/h southwest at ridgetop.

Monday

Mostly clear skies. Southwest ridgetop wind eases to 25 km/h at ridgetop. Treeline temperature -3 °C. Freezing level rising to 1700 m.

Tuesday

Cloudy with up to 15 cm of snow. 30 to 40 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level rising to 1600 m.

Wednesday

Clearing skies with 20 to 30 km/h southwest ridgetop wind. Freezing levels rise to 2000 m, with treeline temperatures around 0 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
Avoid the runout zones of avalanche paths. Avalanches could run full path.
Even brief periods of direct sun could produce natural avalanches.

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.