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Avalanche Forecast

Archived

Jan 15th, 2024–Jan 16th, 2024

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

Regions

Purcells, Dogtooth, East Purcell.

Dangerous avalanche conditions exist where increasing winds are building fresh wind slabs over weak layers.

Deep instabilities are best managed through conservative terrain selection.

Confidence

Moderate

Avalanche Summary

On Sunday, explosives control produced a few, size 3, deep persistent slab avalanches on reloaded bed surfaces. Wind slab avalanches, to size 2, were reported to be reactive to natural and human triggers in the region.

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

Snowpack Summary

Cold temperatures are slowly faceting the upper snowpack. Variable winds have redistributed 40 cm of low-density snow into wind slabs in exposed lees at higher elevations.

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 60 to 150 cm.

Weather Summary

Monday Night

Partly cloudy with no precipitation, northwest alpine wind 10 to 30 km/h, temperature inversion present with treeline temperature around -15 °C and valley bottom temperatures around -25 °C.

Tuesday

Mainly cloudy with isolated flurries, trace amounts of snow, westerly alpine wind 20 to 40 km/h, treeline temperature -14 °C.

Wednesday

Cloudy with scattered flurries, 6 to 12 cm of snow, southwest alpine wind 10 to 25 km/h, treeline temperature -18 °C.

Thursday

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

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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

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.

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.