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Avalanche Forecast

Archived

Apr 8th, 2025–Apr 9th, 2025

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

A cornice falling on a slope may trigger a large avalanche.

Avoid thin and rocky start zones where triggering the persistent problem may still be possible.

Confidence

Moderate

Avalanche Summary

Over the weekend, small wet loose avalanches were reported to size 1.

Avalanches on buried weak layers continue to be sporadically reported from thin and rocky terrain features. On Friday, a natural cornice fall triggered a large (size 2.5) slab on a northeasterly alpine slope.

Snowpack Summary

Around 10 to 15 cm of new snow, with the most on the west side of the region, sits over a crust or moist snow. Surface snow at lower elevations is expected to remain wet.

Several weak layers from early March, mid-February, and late January can be found in the mid and lower snowpack. These layers remain a concern where there is no thick crust above them.

The base of the snowpack is generally faceted.

Weather Summary

Tuesday Night

Cloudy with 0 to 5 cm of snow. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Wednesday

Mostly cloudy with 0 to 2 cm of snow. 20 to 30 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Thursday

Mostly sunny. 20 to 40 km/h south ridgetop winds. Treeline temperature 0 °C. Freezing level 2500 m.

Friday

Mostly cloudy with up to 20 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -1 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid areas with a thin or variable snowpack.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Be aware of the potential for large avalanches due to buried weak layers.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.