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Avalanche Forecast

Archived

Jan 19th, 2021–Jan 20th, 2021

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

Regions

Banff Yoho Kootenay.

Forecasted extreme wind overnight on Tuesday has created uncertainty about wind slabs in the alpine and treeline. Investigate locally and approach cautiously until you get a feel for conditions. Great conditions expected on Thursday and Friday.

Weather Forecast

A wind event is expected to persist throughout the region tonight and into the early hours of Wednesday (Extreme from the West). A slight cooling trend will follow the wind event. Expect calm conditions and benign weather on Thurs/Fri.

Snowpack Summary

Up to 10 cm of snow over thin sun crust on steep solar aspects and over previously wind scoured terrain at treeline and above. Jan 11th interface down 20-35 cm producing mod to hard results. Dec 25th, 13th and 7th layers down 50-120 cm and generally produce hard or no results. A rain crust exists on surface below 1500 m in eastern areas.

Avalanche Summary

A large natural cornice fall was observed on Rockwall Peak. No slab was associated with the cornice fall on the fan below. Otherwise, no avalanches were observed or reported.

Confidence

Wind effect is extremely variable on Wednesday

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.

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.