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Avalanche Forecast

Archived

Jan 8th, 2023–Jan 9th, 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 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.

Regions

Purcells, Dogtooth, East 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. 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 weak layer of facets and a crust buried in November is down roughly 50 to 110 cm from the surface. The lower snowpack below this November weak layer is weak and highly facetted to the ground.

Snowpack depths are roughly 60 to 150 cm at treeline.

Weather Summary

Sunday night

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

Monday

Cloudy with sunny breaks and flurries, 0 to 5 cm. Mostly light southwest ridgetop winds. Treeline temperatures -5 to -10 C.

Tuesday

A mix of sun and cloud, flurries in the morning, 0 to 2 cm. Light southwest ridgetop winds. Treeline temperatures -5 to -10 C.

Wednesday

Mostly sunny, no precipitation. 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.

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.