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Avalanche Forecast

Archived

Feb 5th, 2025–Feb 6th, 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.

Start on small slopes and retreat to mellower terrain if you find signs of instability like whumpfing, shooting cracks, or recent avalanches.

Check out our blog about Conservative Mindset.

Confidence

High

Avalanche Summary

On Monday, a few human-triggered size 1 wind slab avalanches were reported in north facing alpine and treeline features. Avalanche control produced several explosive-triggered persistent slab and dry loose avalanches, up to size 1.5.

A size 2 natural wind slab avalanche was observed in northeast-facing alpine terrain.

We expect unconsolidated snow will remain reactive to skier traffic on Thursday in steep terrain. Carefully manage sluffing.

Snowpack Summary

Storm snow totals range from 30 to 50 cm, with deeper deposits in wind-loaded areas. The new snow is bonding poorly to old surfaces, which include melt-freeze crusts on sun-exposed slopes, surface hoar or facets on shaded slopes, and wind-affected snow at higher elevations.

A weak layer of surface hoar or facets may be found 30 to 60 cm deep. Where this layer is preserved it may be reactive to human triggering.

A weak layer of facets from early December is 60 to 120 cm deep.

The base of the snowpack consists of a thick crust with facets or depth hoar in many areas.

Weather Summary

Wednesday Night

Clear. 15 to 30 km/h west ridgetop wind. Treeline temperature -20 °C.

Thursday

Sunny. Light variable ridgetop wind. Treeline temperature -17 °C.

Friday

Sunny. Light variable ridgetop wind. Treeline temperature -17 °C. Possible temperature inversion above 1700 m.

Saturday

Mostly sunny. 5 km/h southwest ridgetop wind. Treeline temperature -17 °C. Possible temperature inversion above 1700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for remote triggering and large avalanches due to buried surface hoar.
  • Keep in mind that human triggering may persist as natural avalanches taper off.
  • Be especially cautious as you transition into wind-affected terrain.
  • Recent wind has varied in direction, so watch for wind slabs on all aspects.

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.