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Avalanche Forecast

Archived

Feb 19th, 2024–Feb 20th, 2024

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.

A deep persistent slab problem remains where the near-surface crust is thin or absent.

Low-probability, high-consequence problems are best managed with conservative terrain choices.

Confidence

Moderate

Avalanche Summary

On Saturday, southeast of Golden, a small (size 1.5) deep persistent slab avalanche was reported in steep alpine terrain on a northeast aspect. It may have been triggered by a falling cornice. Facets deep in the snowpack continue to be a low-probability, high-consequence problem.

Over the weekend, several small (up to size 1.5) wind slab and loose avalanches were reported in steep alpine terrain, some triggered by humans, and some by the sun.

Snowpack Summary

Variable wind has created wind slabs on all aspects in alpine and open treeline terrain. Thin sun crusts have formed on steep slopes that face the sun.

In sheltered areas, 10 to 30 cm of settling snow sits over a frozen crust that formed in early February. This crust is generally supportive to the weight of a human below treeline, becomes breakable around treeline, and disappears as you ascend higher into the alpine.

The midpack is generally faceted.

The bottom 15-30 cm of the snowpack consists of weak faceted grains, depth hoar, and crusts that continue to produce sporadic, large avalanches.

Weather Summary

Monday Night

Mostly cloudy. A trace of new snow is expected. Light southwest ridgetop wind. Treeline around -4 °C. Freezing level 1000 m.

Tuesday

Mostly cloudy. 1 to 2 cm of snow is expected. Southwest ridgetop wind 30 to 50 km/h. Treeline high around -3 °C. Freezing level rising to 1200 m.

Wednesday

Partly cloudy. 0-1 cm of new snow is expected. Light southeast ridgetop wind. Treeline temperature around -2 °C. Freezing level rising to 1500 m. 

Thursday

Mostly cloudy. No new snow expected. Light southwest ridgetop wind . Treeline temperature around -2 °C. Freezing level rising to 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • 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.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Even a small avalanche can be harmful if it pushes you into an obstacle or a terrain trap.

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.