Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Mar 18th, 2024–Mar 19th, 2024

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

Regions

Purcells, Dogtooth, East Purcell.

Very large persistent slab avalanches remain likely to human trigger, especially at treeline and above.

Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

Confidence

Moderate

Avalanche Summary

Numerous naturally triggered persistent slab and deep persistent slab avalanches up to size 3.5 (very large) were reported on all aspects and elevations on Sunday.

Snowpack Summary

A weak surface crust forming overnight will break down quickly throughout the day.

A widespread, hard crust down 40 - 110 cm with weak facets above continues to be the primary layer of concern for natural and human triggering of very large persistent slab avalanches.

Cornices have become large and looming, and are more likely to fail during periods of warming.

The bottom of the snowpack is generally weak and faceted, with the potential to produce very large avalanches. The most likely areas to trigger this deeply buried weak layer are steep, rocky areas in the alpine with a shallow or thin to thick snowpack.

Weather Summary

Monday Night

Clear skies. 10 to 20 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level 1000 m.

Tuesday

Mix of sun and cloud. 10 to 20 km/h southwest ridgetop wind. Treeline temperature 3 °C. Freezing level 2400 m.

Wednesday

Mix of sun and cloud with isolated flurries, 0 to 3 cm of snow (above 1700 m). 10 to 20 km/h west ridgetop wind. Treeline temperature -1 °C. Freezing level 2000 m.

Thursday

Mix of sun and cloud with isolated flurries, 3 to 5 cm of snow (above 1400m). 10 to 20 km/h west ridgetop wind. Treeline temperature -3 °C. Freezing level 1700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be aware of the potential for large, deep avalanches to run full path or even longer.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Cornice failure may trigger large avalanches.

Problems

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.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.