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Avalanche Forecast

Archived

Apr 2nd, 2023–Apr 3rd, 2023

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

An unstable weather pattern will bring clouds, sun and flurries over the next couple of days. Sporadic flurries and wind will continue to promote wind slab formation at upper elevations.

Confidence

Moderate

Avalanche Summary

On Friday a size 3 naturally triggered avalanche was reported in the Dogtooth Range. While the failure plane is unknown the report mentions impressive propagation.

Snowpack Summary

New snow and wind have formed wind slabs at upper elevations. Surface hoar may exist below the recent snow, in wind sheltered and shaded terrain.

The mid snowpack may still contain a few persistent weak layers of surface hoar in sheltered treeline terrain. No recent avalanche activity has occurred on these layers suggesting the layers have gained strength.

The lower snowpack includes a widespread layer of large, weak facets and or depth hoar crystals. This weak layer was responsible for a number of very large and destructive avalanches through the season and right up to last week during a warm sunny period. This will continue to be a concern for the rest of the season.

Weather Summary

Sunday Night

Mostly cloudy with scattered flurries, accumulation 1-4cm. Light southwest wind. Alpine high of -7 °C. Freezing level at valley bottom.

Monday

Mostly cloudy with sunny breaks and scattered flurries, accumulation 1-5cm. Light northeast wind. Alpine high of -6 °C. Freezing level 1500 m.

Tuesday

Mostly cloudy with sunny breaks and scattered flurries, accumulation 1-5cm. Light east wind. Alpine high of -5 °C. Freezing level 1500 m.

Wednesday

Mix of sun and cloud. Light southwest wind. Alpine high of -3 °C. Freezing level 1700 m.

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 thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.