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Avalanche Forecast

Archived

Apr 9th, 2025–Apr 10th, 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 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.

Rising temperatures and sunshine will increase avalanche danger. Buried weak layers continue to produce large avalanches that may run to valley bottom.

Confidence

Moderate

Avalanche Summary

On Tuesday, there were several natural and rider-controlled wind slabs, mostly small, but some up to size 2. As well as some wet loose avalanches below treeline. There was also a recent large persistent slab (size 2.5) seen near Panorama that is suspected to have occurred in the past 3 days. From a northeast aspect in the alpine.

Snowpack Summary

Around 10 to 30 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 be wet and likely form into a crust.

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

Wednesday Night

Partly cloudy. 15 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Thursday

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

Friday

A mix of sun and cloud with up to 10 cm of snow ending in the morning. 20 km/h southwest ridgetop wind. Treeline temperature 0 °C.

Saturday

Mostly cloudy with 5 to 10 cm of snow. 10 km/h southwest ridgetop wind. Treeline temperature -3 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Even brief periods of direct sun could produce natural avalanches.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • 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

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.

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.