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Avalanche Forecast

Archived

Feb 25th, 2025–Feb 26th, 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 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.

Regions

Purcells, Esplanade, Dogtooth, East Purcell, St. Mary, West Purcell.

Strong sunshine may trigger natural avalanches, and storm snow likely remains reactive to human triggers.

Don't let sun and clear skies tempt you into consequential terrain.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity was observed during the recent storm to size 3. Explosive control since, has produced similar results. Avalanches were triggered within the storm snow and on buried weak layers.

Several avalanches were remotely triggered (from a distance) a clear sign of instability.

While natural activity is expected to taper off, human triggering remains a concern.

Snowpack Summary

Storm snow totals 20 to 45 cm. Moderate to strong southwest winds have redistributed snow into deeper deposits at treeline and above. Strong sunshine on Wednesday is expected to create moist snow on sun-exposed slopes and moist snow is also present at lower elevations due to recent warm temperatures and rain.

Storm snow sits over a surface hoar or crust layer from mid-February. Two more weak layers exist: a layer of facets, surface hoar, or crust from late-Jan buried 30 to 50 cm deep, and a layer of facets from early Dec, buried 70 to 120 cm deep.

In many areas, facets or depth hoar exists at the base of the snowpack.

Weather Summary

Tuesday Night

Clearing skies. 10 to 20 km/h southwest ridgetop wind. Freezing level drops to 500 m.

Wednesday

Clear skies. 20 to 30 km/h west ridgetop wind. Treeline temperature 0°C. Freezing level rising to 2000 m.

Thursday

Partly cloudy. 40 to 50 km/h southwest ridgetop wind. Treeline temperature 0°C. Freezing level rising to 2100 m.

Friday

Mostly clear skies. 10 to 20 km/h southwest ridgetop wind. Treeline temperature +3°C. Freezing level rising to 2500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
  • Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.

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.