Avalanche Forecast

Archived

Mar 15th, 2025–Mar 16th, 2025

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead, Flathead, Lizard, Bull.

Update 7:10 am: New snow & wind are building reactive slabs.

Avoid avalanche terrain during periods of heavy snowfall and strong wind.

Confidence

Moderate

Avalanche Summary

Fri: Explosive control produced a few storm slabs to size 2 on northeast facing slopes.

Thurs: A widespread natural cycle was observed in the Lizard Range with storm slabs up to size 2.5. Explosive control also produced numerous small storm slabs.

Wed: Explosive control produced dry loose and storm slab avalanches to size 2 on north through east facing slopes.

Looking forward: Natural and human-triggered avalanches will be likely on Sunday.

Snowpack Summary

30 to 40 cm of recent snow previously formed widespread storm slabs. An additional 20 to 30 cm is forecast to fall overnight and through Sunday, with wet snow or rain at lower elevations. Moderate to strong southwesterly winds are expected to build especially reactive slabs on lee north through east facing slopes near ridgetops.

A persistent weak layer of surface hoar or facets from late January is buried 90 to 150 cm. This layer triggered large avalanches earlier in March, and remains reactive in snowpack tests. The greatest concern for this weak layer is on upper-elevation northerly and easterly slopes. The lower snowpack is generally well-settled and strong.

Weather Summary

Saturday Night

Cloudy, with 5 to 15 cm of snow. 30 to 40 km/h southwest ridgetop wind. Treeline temperature -8 °C.

Sunday

Cloudy, with 5 to 15 cm of snow, possible rain below 1300 m. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level rising to 1600 m.

Monday

Partly cloudy, with up to 3 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level rising to 1500 m.

Tuesday

Mostly cloudy, with up to 3 cm of snow. 15 to 30 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level rising to 1500 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.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.
As the storm slab problem worsens, the easy solution is to choose more conservative terrain.
Use conservative route selection. Choose simple, low angle terrain with no overhead hazard.

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.