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Avalanche Forecast

Archived

Apr 2nd, 2025–Apr 3rd, 2025

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Persistent slabs are possible to trigger in areas where the snowpack transitions from thick to thin or by a falling cornice

Evaluate terrain and avoid travelling below cornices

Confidence

Moderate

Avalanche Summary

Over the past 3 days explosives were used to drop cornices, some of these cornices triggered persistent slabs on the slopes below. The resulting avalanches  were up to size 3 with crowns as deep as 3 meters.

On Tuesday several remote and naturally triggered cornice failures were reported. Some of these pulled slabs on the slopes below.

Snowpack Summary

By mid day on Thursday up to 10 cm of new snow could have accumulated with moderate southwest wind. This new snow will overlie a crust on all aspects and elevations, except for north facing terrain in the alpine, Where up to 30 cm overlies a crust from late March. Below these crusts, the upper snowpack is moist.

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 a thick crust isn’t present above.

The base of the snowpack is generally faceted.

Weather Summary

Wednesday Night

Mostly cloudy with 0 to 3 cm of snow. 15 to 30 km/h west ridgetop wind. Treeline temperature -9 °C.

Thursday

Mix of sun and cloud with 0 to 3 cm of snow. 15 to 30 km/h northwest ridgetop wind. Treeline temperature -6 °C.

Friday

Sunny. 10 to 20 km/h northwest ridgetop wind . Treeline temperature -2 °C.

Saturday

Sunny. 20 to 40 km/h west ridgetop wind. Freezing level rising to 2300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Keep in mind that human triggering may persist as natural avalanches taper off.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid areas with a thin or variable snowpack.

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.