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Avalanche Forecast

Archived

Mar 17th, 2025–Mar 18th, 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, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead, Flathead, Lizard, Bull.

Up to 60 cm of recent snow has formed reactive storm slabs.

These slabs will be most reactive on wind-loaded slopes and on sunny slopes during periods of strong solar radiation.

Confidence

Moderate

Avalanche Summary

On Sunday, numerous rider triggered size 1 storm slab avalanches were reported within the new snow at all elevations/aspects.

Additionally, several explosive triggered storm slab avalanches up to size 2 were reported primarily on northerly aspects in the alpine.

Snowpack Summary

Up to 60 cm of recent snow and southwest winds formed slabs reactive to human triggers.

In most areas, the storm snow rests on a melt-freeze crust, except for high elevation north and east facing slopes.

A persistent weak layer of surface hoar or facets from late January is buried 100 to 150 cm. Large avalanches occurred on this layer earlier in March. 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

Monday Night

Partly cloudy with isolated flurries, 0-3 cm snow, 10 to 20 km/h west ridgetop winds, treeline temperature -8 °C, freezing level valley bottom.

Tuesday

Mix of sun and cloud, 10 to 20 km/h west ridgetop winds, treeline temperature -6 °C, freezing level 1400 m.

Wednesday

Sunny, 10 to 20 km/h southwest ridgetop winds, treeline temperature -4°C, freezing level 1600 m.

Thursday

Cloudy with flurries, 5-10 cm snow, 15 to 30 km/h southwest ridgetop winds, treeline temperature -5 °C, freezing level 1500 m.

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.
  • Use small, low consequence slopes to test the bond of the new snow.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Even brief periods of direct sun could produce natural avalanches.
  • Avoid steep, sun-exposed slopes when the air temperature is warm or when solar radiation is strong.

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.

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.