Avalanche Forecast

Archived

Feb 28th, 2025–Mar 1st, 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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Lizard-Flathead, Flathead, Lizard, Moyie.

Active persistent slabs and skyrocketing alpine temperatures are a bad mix. Time to back off from avalanche terrain entirely.

Confidence

Moderate

Avalanche Summary

We have an initial report of a natural size 3 avalanche in the Little Sand area on Friday. More details soon.

The field team saw five new persistent slabs in Corbin Thursday, part of an ongoing pattern of persistent slab activity that was mixed with storm and wind slabs earlier this week. Activity has been on a range of aspects, mainly in alpine.

A natural size 3 deep persistent slab was also seen Wednesday, suggesting isolated full-depth releases may occur during the warmup.

Snowpack Summary

A melt-freeze crust moist or snow now glazes the surface on solar aspects and potentially to mountaintop by Saturday afternoon. High overnight freezing levels mean crust recovery may be weak. This process will affect 30 to 60 cm of settling recent snow that is wind-affected in alpine. About half of this overlies a crust formed early in the storm. It otherwise overlies faceted snow.

A weak layer of preserved surface hoar or facets from late January is buried 80 to 130 cm deep. This weak layer is expected to stay reactive as warming tests the snowpack. The lower snowpack is generally well-settled, however a lone deep persistent slab observed Wednesday suggests isolated deep releases may occur during the warmup.

Weather Summary

Friday Night

Partly cloudy. 20 km/h southwest ridgetop wind. Freezing level remaining near 1800 m.

Saturday

Becoming sunny. 20 km/h southwest ridgetop wind. Freezing level rising to 3300 m, remaining high overnight. Treeline temperature 5 °C.

Sunday

Mainly sunny. 5 - 10 km/h southwest ridgetop wind, easing. Freezing level 2700 m - 3000 m. Treeline temperature 6 °C.

Monday

Cloudy with scattered flurries, negligible accumulation. 20 - 30 km/h northeast ridgetop wind. Freezing level 1500 m. Treeline temperature around 0 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be aware of the potential for large avalanches due to buried weak layers.
Even brief periods of direct sun could produce natural avalanches.
Avoid exposure to overhead avalanche terrain; avalanches may run surprisingly far.

Problems

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.