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Avalanche Forecast

Archived

Jan 16th, 2024–Jan 17th, 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 avalanches possible, human triggered probable.
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, Dogtooth, East Purcell.

New snow and moderate southwest winds will build fresh slabs at higher elevations.

Deep instabilities are best managed through conservative terrain selection.

Confidence

Moderate

Avalanche Summary

On Monday, natural wind slab and loose dry avalanches were reported throughout the region to size 1.5

On Sunday, explosives control produced a few, size 3, deep persistent slab avalanches on reloaded bed surfaces.

If you go out in the backcountry, please consider sharing your observations on the Mountain Information Network (MIN).

Snowpack Summary

By morning 4 to 8 cm of snow has accumulated over faceted surfaces in many areas. In exposed terrain at treeline and above new snow overlies old wind slabs and wind-affected surfaces.

The mid and lower snowpack is generally weak with several layers of note. Of greatest concern are weak facets and/or depth hoar located at the bottom of the snowpack, particularly in alpine terrain.

Snowpack depths at treeline range from 70 to 160 cm.

Weather Summary

Tuesday

Mainly cloudy with isolated flurries, 2 to 4 cm of snow, west switching to southwest alpine wind 15 to 25 km/h, treeline temperature -14 °C.

Wednesday

Cloudy with scattered flurries, 4 to 6 cm of snow, southeast alpine wind 10 to 20 km/h, treeline temperature -17 °C.

Thursday

A mix of sun and cloud with no new precipitation, northeast alpine wind 10 to 25 km/h, treeline temperature -20 °C.

Friday

Mainly cloudy with isolated flurries, trace amounts of snow, southwest alpine wind 20 to 40 km/h, treeline temperature -15 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for signs of slab formation throughout the day.
  • Use appropriate sluff management techniques.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.