Avalanche Forecast

Archived

Jan 9th, 2023–Jan 10th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

While the likelihood of triggering a deep persistent layer may be decreasing, it is very difficult to predict where you will or will not trigger a large avalanche.

Continue to take a conservative approach while traveling in avalanche terrain.

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. Of significant concern is a layer down 30 to 50 cm from the surface consisting of a crust, facets, and/or surface hoar. And a layer of large facets and a crust down roughly 50 to 110 cm from the surface. The snow below this deeper weak layer is unconsolidated and weak.

Snowpack depths remain highly variable, ranging from 60 to 150 cm at treeline.

Weather Summary

Monday night

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

Tuesday

Mostly cloudy, with no precipitation. Light southwest ridgetop winds. Treeline temperatures -5 to -10 C.

Wednesday

Mostly sunny, with no precipitation. Light southwest ridgetop winds. Treeline temperatures -5 to -10 C.

Thursday

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

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Uncertainty is best managed through conservative terrain choices at this time.
Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
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.