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Avalanche Forecast

Archived

Feb 29th, 2024–Mar 1st, 2024

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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 possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Purcells, Dogtooth, East Purcell.

Danger avalanche conditions persist. The recent storm snow has buried a touchy weak layer and human triggering remains a serious concern. Conservative decision-making remains critical.

Confidence

High

Avalanche Summary

Numerous natural, skier, and explosive-triggered avalanches up to size 3 have been reported in the past few days throughout the region. All avalanches slid on layers in the upper snowpack.

While natural activity should begin to taper off on Friday, human triggering is expected to remain a serious problem.

Snowpack Summary

Up to 60 cm of new snow has fallen in the past 2 days and over 1 m has accumulated in the past week. This new snow has formed touchy slabs, especially in wind-exposed terrain.

The new snow has also buried a weak layer of facets, surface hoar, and/or a crust from mid-February which remains reactive.

A widespread crust formed in early February is buried roughly 70 to 120 cm deep and extends up to 2400 m. Facets have been found above this crust. This layer has produced many concerning avalanches across the province.

The mid and lower snowpack is largely faceted with depth hoar and a crust found at the bottom of the snowpack in many areas.

Weather Summary

Thursday Night

Some clearing overnight with flurries of up to 5 cm. 20 to 40 km/h southwest alpine wind. Treeline temperature -12 °C.

Friday

Mostly cloudy with scattered flurries up to 5 cm. 15 to 30 km/h southwest alpine wind. Treeline temperature -6 °C.

Saturday

Mostly cloudy with scattered flurries up to 3 cm. 20 to 40 km/h south alpine wind. Treeline temperature -8 °C.

Sunday

Mostly cloudy with trace amounts of new snow. 10 to 20 km/h southwest alpine wind. Treeline temperature -6 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.

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.

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.