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Avalanche Forecast

Archived

Mar 12th, 2025–Mar 13th, 2025

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.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead, Flathead, Lizard, Bull.

Before entering avalanche terrain assess how the new snow is bonding to the rest of the snow pack.

A persistent weak layer in the snow means avalanches could step down and become large.

Confidence

Moderate

Avalanche Summary

On Tuesday: A natural cycle of small (size 1 to 1.5) storm slab avalanches was reported in the alpine on north aspects.

Over the weekend, explosive avalanche control and natural cornice fall continue to produced numerous slab avalanches up to size 2 in north through east facing alpine terrain.

Avalanches on buried weak layers may be difficult to trigger, but if one is triggered, it is likely to be large and destructive.

Snowpack Summary

Up to 25 cm of new snow has been moderately redistributed by southwest winds.

Below 1900 m, and on solar aspects, this sits on a surface crust from recent sun and warming.

A weak layer of preserved surface hoar or facets from late January is buried 80 to 130 cm. This weak layer remains a concern where there is no thick, supportive crust under the recent snow.

The lower snowpack is generally well-settled and strong.

Weather Summary

Wednesday Night

Cloudy, with 5 to 10 cm of snow. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -2 °C.

Thursday

Cloudy, with 3 to 8 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Friday

Mix of sun and cloud, with up to 3 cm of snow. 10 to 25 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Saturday

Mainly cloudy, with 3 to 5 cm of new snow. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -1 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be alert to conditions that change with elevation, aspect, and exposure to wind.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
  • Be aware of the potential for large avalanches due to buried weak layers.

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.