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Avalanche Forecast

Archived

Jan 7th, 2023–Jan 8th, 2023

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 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.

Regions

Purcells, Dogtooth, East Purcell.

Human-triggered deep slab avalanches remain possible. Maintain a disciplined approach and avoid high-consequence terrain.

Read more about this winter's widespread persistent weak layers in our recent Forecasters Blog

Confidence

Moderate

Avalanche Summary

No significant avalanche activity has been reported in the last couple of days.

Please continue to share any observations or photos on the Mountain Information Network.

Snowpack Summary

The upper snowpack continues to settle and bond with mild temperatures. The mid and lower snowpack is generally weak and faceted, with a number of weak layers. Down 30 to 50 cm from the surface is a weak layer consisting of a crust, facets, and/or surface hoar, buried in mid-December. A layer near the bottom of the snowpack buried in November consists of large, weak facetted crystals.

Snowpack depths are roughly 60 to 150 cm at treeline.

Weather Summary

Saturday night

Cloudy with flurries, 0 to 2 cm. Light southerly winds. Treeline temperatures -5 to -10 C.

Sunday

Cloudy with flurries, 0 to 2 cm. Light southerly winds. Treeline temperatures -5 to -10 C.

Monday

Cloudy with sunny breaks and flurries, 0 to 2 cm. Light southerly winds. Treeline temperatures -5 to -10 C.

Tuesday

Mostly sunny, no precipitation. Light southerly winds. Treeline temperatures -5 to -10 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.

Problems

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.

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.