Avalanche Forecast

Archived

Feb 7th, 2020–Feb 10th, 2020

Alpine

Natural avalanches unlikely, human triggered possible.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

North Rockies.

A break in the storm is welcome and will probably reduce the likelihood of avalanches. The factor that could change that is the sun - best avoid steep sunny slopes if the sun feels hot.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Friday night: Flurries. Moderate northeasterly winds. Treeline temperatures around -10C.

Saturday: Dry with sunny periods. Light northwesterly winds increasing to moderate in the afternoon. Daytime high temperatures around -7C.

Sunday: Flurries. Strong to extreme northwesterly winds. Daytime high temperatures around -7C.

Monday: Flurries. Strong westerly winds. Daytime high temperatures around -3C.

Avalanche Summary

A skier triggered a size 1.5 wind slab avalanche on a northwest aspect at around 1750 m on Thursday. Also on Thursday, several storm slab avalanches up to size 2.5 were triggered on northerly aspects.

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

Approximately 30-60 cm recent storm snow sits above a thin rain crust from the warm, wet storm on Feb 01. This rain crust has been reported to exist up to treeline elevations around 1700 m. Initially this layer was described as reactive and was the focus of a number of avalanches. However, it now appears to be gaining strength and probably won't end up being a significant long-term weak layer.

In the mid-pack there may still be a layer of surface hoar buried in late December. It's gaining strength, but should remain a concern since snowpack tests still demonstrate this layer has the potential to slide, albeit in isolated areas and/or with very large triggers.

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

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.