Avalanche Forecast

Archived

Feb 5th, 2020–Feb 7th, 2020

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 possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

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.

Regions

North Rockies.

Recent new snow and strong winds blowing from a variety of directions continue to build slabs at higher elevations. Some parts of the region have received up to 40 cm of new snow over the past few days.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

Wednesday Night: Mainly cloudy with scattered flurries. Alpine high temperature around -6 C. Moderate to strong northwest wind.

Thursday: Mainly cloudy with some sunny breaks. Alpine high temperature around -6 C. Moderate northwest wind.

Friday: Mainly cloudy with sunny breaks. Alpine high temperature around -7 C. Light to moderate west and northwest wind.

Saturday: Mix of sun and cloud. Alpine high temperature around -8 C. Moderate northwest wind.

Avalanche Summary

We are aware of an avalanche that occurred Sunday Feb 2 in the Upper Burnt area that is presumed to involve a snowmobiler. Preliminary information indicates that avalanche was a size 2.5 on a southeast aspect at 1600 m with a fracture line depth of 130 cm.

Snowpack Summary

Anywhere from 15-40 cm of new snow has fallen in the past two days throughout the region. This may now have obscure previous wind effect in exposed terrain an may be sitting on a rain crust that formed last weekend below 1600m approximately.

In the mid-pack there may still be a layer of surface hoar buried in late December. It's gaining strength, but may remain a concern. The warm wet storm on Feb 01 will have tested this layer in the short-term and will improve it in the longer-term; however, we're awaiting evidence before considering it dormant. This layer is found across much of the North Rockies region but our focus is around McBride and the McGregors/Torpy.

Terrain and Travel

Expect slab conditions to change drastically as you move into wind exposed terrain.
Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.

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.