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Avalanche Forecast

Archived

Mar 2nd, 2025–Mar 3rd, 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, Esplanade, Dogtooth, East Purcell, St. Mary, West Purcell.

Time to reassess the snowpack. Tune into developing surface instabilities as new snow accumulates, but don't rule out persistent slabs lurking where surface crust is thin or absent.

Confidence

Moderate

Avalanche Summary

Saturday was another busy day for persistent slabs, with more natural, remote, and explosives-triggered releases failing on the same late-Jan crust, fitting a pattern of recent persistent activity, generally from size 2-3 and at treeline and above.

Skiers were caught in size 1.5 releases Tuesday and again on Friday with a partial burial.

Size 2 - 3 deep persistent slabs were also explosives-triggered Wednesday, showing the basal snowpack reacting to large triggers.

Snowpack Summary

New snow will begin to bury a melt-freeze crust or moist snow which makes up the surface on solar aspects and on all aspects below 2000 m. This crust tops the upper part of 20 to 45 cm of snow from last week, which was redistributed by strong southwest winds at treeline and above. In shelter, it 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 also exist at the base of the snowpack. These layers, particularly the late-January layer, remain a concern at higher elevations where strong surface crusts are absent.

Weather Summary

Sunday Night

Becoming cloudy. 0 to 15 km/h north ridgetop wind. Freezing level to 900 m.

Monday

Cloudy with scattered flurries bringing about 5 cm of new snow above 1600 m, continuing overnight. 5 to 10 km/h northeast ridgetop wind. Freezing level 1700 m. Treeline temperature around 0 °C.

Tuesday

A mix of sun and cloud with another 5 cm of new snow from overnight. 0 to 5 km/h southwest ridgetop wind, up to 30 km/h in alpine, increasing. Freezing level 1700 m. Treeline temperature around 0 °C.

Wednesday

Mainly cloudy with scattered flurries and less than 5 cm of new snow above 1600 m, light rain below. 5 to 10 km/h west ridgetop wind. Freezing level 1700 m, treeline temperature around 0 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large, destructive avalanches due to deeply buried weak layers.
  • Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.
  • Wind slabs are most reactive during their formation.
  • Avalanche activity is unlikely when a thick melt-freeze crust is present on the snow surface.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.