Avalanche Forecast

Issued: Feb 9th, 2015 5:55PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Loose Wet and Deep Persistent Slabs.

brian webster, Parks Canada

Banff Yoho Kootenay.

Avalanche control will be conducted on Mt. Stephen, Mt. Dennis, and on Mt. Hector on Tuesday. Please no skiing or climbing in these areas.

Summary

Weather Forecast

A weak freeze overnight with freezing levels rising to 1800m on Tuesday. Some flurries forecasted but little in the way of accumulation.

Snowpack Summary

45 - 70 cm of recent storm overlies a crust from January 30th. The recent heavy precipitation, and warmer temperatures have created very touchy storm slabs over top of the January 30th crust interface. Despite a weak freeze last night isothermal conditions persist at treeline and below.

Avalanche Summary

Avalanche control over the past three days in Banff, Yoho Park and Koorenay Park have produced numerous avalanches up to size 3. Many of the avalanches started dry and turned wet at lower elevations. Also, evidence of a widespread cycle up to size 3.5 throughout the forecast region. Some avalanches running close to full path.

Confidence

Freezing levels are uncertain

Problems

Storm Slabs

Fifty to 90 cm of storm snow exist on the January 30th crust interface. A poor bond exists at this interface and large avalanches have been observed running on this layer. Huge propagations are still possible.

Avoid freshly wind loaded features.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Loose Wet

A weak temperature crust overlies isothermal conditions at treeline and below elevations. Many loose wet avalanches that have gouged down to ground have been observed in past 48 hours.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Deep Persistent Slabs

The base of the snowpack remains weak due to basal depth hoar/facets. Additional snow load, or a storm slab failure may trigger large to very large avalanches in thin snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Feb 10th, 2015 4:00PM