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Avalanche Forecast

Archived

Apr 4th, 2025–Apr 5th, 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 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.

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Another warm-up brings rising avalanche risk.

Uncertainty remains about cornice falls or surface instabilities stepping down to persistent weak layers.

 Read the new forecasters' blog.

Confidence

Moderate

Avalanche Summary

Two large natural persistent slabs (size 2) were naturally triggered from thin rocky northerly terrain near Panorama. Several dry loose and wind slabs also occurred naturally and skier-triggered in the region on Thursday.

Over the past 5 days, explosives were used to drop cornices, some of which triggered persistent slabs on the slopes below. The resulting avalanches were up to size 3 with crowns as deep as 3 meters.

Snowpack Summary

A diurnal melt-freeze cycle occurred in the past days. The surface is either moist or capped with a thin crust on all aspects and elevations except for high northerly slopes where up to 30 cm overlies a thick crust from late March.

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

Friday Night

Clear. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level around 1000 m.

Saturday

Sunny. 10 to 20 km/h southeast ridgetop wind. Treeline temperature +4 °C. Freezing level rising to 2500 m.

Sunday

Sunny. 10 to 20 km/h southeast ridgetop wind. Treeline temperature +6 °C. Freezing level rising to 3000 m.

Monday

Mix of sun and clouds. 20 to 40 km/h west ridgetop wind. Treeline temperature +4 °C. Freezing level around 2500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avalanche danger is expected to increase throughout the day.
  • Avoid areas with a thin or variable snowpack.
  • Limit exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

Problems

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.

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.

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.