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Avalanche Forecast

Archived

Apr 12th, 2025–Apr 13th, 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, Dogtooth, East Purcell, West Purcell, Bull.

If a thick, hard surface crust is present, avalanche activity is unlikely.Buried weak layers continue to produce sporadic large avalanches on high-elevation northerly slopes.

Confidence

Moderate

Avalanche Summary

Friday, a deep persistent slab was triggered by sledders east of Wasa (see photo below).Several wind slabs up to size 2 also occurred in the Western Purcells on lee alpine slopes.

Thursday, a few large cornice failures were triggered with warming, along with a large (size 2.5) wind slab on a northwest alpine slope.

A large persistent slab (size 2.5) failed on a northeast alpine slope near Panorama. It was suspected to have occurred early in the week.

Snowpack Summary

Around 10 to 30 cm of snow accumulated this week, with the highest amounts in the Western Purcells. Lower elevations and slopes that face the sun generally have a thick surface crust that can soften and become moist or wet with daytime warming. Shady alpine slopes likely still have dry snow and some lingering wind slabs.

Several persistent weak layers of crusts and/or facets can be found in the mid and lower snowpack. These layers remain a concern where there is no thick and supportive crust above them.

The base of the snowpack is generally faceted.

Weather Summary

Saturday Night

Mostly clear. 30 to 40 km/h northwest ridgetop wind. Treeline temperature -8 °C. Freezing level 1600 m, falling to valley bottom.

Sunday

Sunny. 10 to 20 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 1900 m.

Monday

Sunny. 5 to 15 km/h variable ridgetop wind. Treeline temperature +3 °C. Freezing level rising to 2500 m.

Tuesday

A mix of sun and cloud. 15 to 35 km/h west ridgetop wind. Treeline temperature +2 °C. Freezing level rising to 2300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avalanche activity is unlikely when a thick melt-freeze crust is present on the snow surface.
  • Be aware of the potential for large avalanches due to buried weak layers.
  • Wind slabs are isolated, but may remain reactive.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.