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Avalanche Forecast

Archived

Feb 26th, 2024–Feb 27th, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Purcells, Dogtooth, East Purcell.

Maintain a conservative approach, recent storm snow still needs time to stabilize and bond to surfaces below.

Confidence

Moderate

Avalanche Summary

Over the weekend, explosive control work in the north of the region produced several storm and wind slab avalanches up to size 2 on various aspects and elevations.

Snowpack Summary

As much as 50 cm of new snow in areas has been redistributed by recent strong winds.

A variety of pre-existing surfaces exist below the new snow, including sun crusts on south-facing slopes and faceted snow or surface hoar in sheltered north-facing terrain.

A widespread crust formed in early February is buried roughly 40 to 80 cm. This crust may be less prominent or not exist at high alpine elevations.

The mid and lower snowpack is largely faceted with depth hoar and a crust found at the bottom of the snowpack in many areas.

Weather Summary

Monday Night

Mostly cloudy with 1 to 5 cm of snow. 10 to 20 km/h west ridgetop wind. Treeline temperature -15 °C.

Tuesday

Mix of sun and cloud. 10 to 30 km/h west ridgetop wind. Treeline temperature -17 °C.

Wednesday

Mostly cloudy with 0 to 8 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -4 °C. Freezing level 1700 m.

Thursday

Mostly cloudy with 2 to 10 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level 1400 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Good day to make conservative terrain choices.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.