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Avalanche Forecast

Archived

Mar 21st, 2025–Mar 22nd, 2025

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.

Confidence

Moderate

Avalanche Summary

On Thursday, several naturally triggered size 2 persistent slabs were reported on northerly and east aspects in the alpine.

Additionally a sledder remotely triggered two size 1.5 storm slabs from 60 m. away. They occurred on a easterly aspect in a alpine bowl feature at treeline.

Snowpack Summary

5 to 15 cm of recent snow and southwest wind have formed small wind slabs on lee aspects at treeline and above.

30 - 50 cm of snow overlies a crust on sunny slopes and lower elevations, and surface hoar or facets on sheltered and shady upper elevations.

Several persistent weak layers consisting of a crust, facets, and/or surface hoar from February and January remain a concern. They are down 50 to 100 cm in most areas.

The bottom of the snowpack is composed of large facets in most areas. There is evidence that this layer is becoming reactive again, and some very large avalanches have failed on this layer recently.

Weather Summary

Friday night

Partly cloudy with 0 to 10 cm of snow. 10 to 20 km/h west ridgetop winds. Treeline temperature -8 °C. Freezing level valley bottom.

Saturday

Mix of sun and cloud. 10 to 20 km/h west winds. Treeline temperature -5 °C. Freezing level 1500 m.

Sunday

Mix of sun and cloud. 10 to 20 km/h southwest ridgetop winds. Treeline temperature -2 °C. Freezing level 1800 m.

Monday

Moslty sunny. 20 to 30 km/h west ridgetop winds. Treeline temperature 1 °C. Freezing level rapidly rising to 2100 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
  • Be aware of the potential for large, destructive avalanches due to deeply buried weak layers.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Even brief periods of direct sun could produce natural avalanches.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.