Avalanche Forecast

Issued: Feb 8th, 2015 6:34PM

The alpine rating is high, the treeline rating is high, 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.

Very warm temperatures have weakened the snowpack and turned it isothermal in many locations. Avalanche terrain should be avoided until cooler temperatures return.

Summary

Weather Forecast

Cloudy with scattered flurries forecast for Monday. Freezing levels to valley floor on Sunday night and then rising to 2000 m on Monday. Winds are light from the south-west turning to moderate west late in the day on Monday.

Snowpack Summary

45 - 70 cm of recent storm overlies a crust from January 30th. The recent heavy precipitation, wind and warmer temperatures have created storm slabs which will put an enormous amount of stress on the January 30th crust interface. Isothermal conditions exist at treeline and below.

Avalanche Summary

Avalanche control today in Yoho Park and Koorenay Park 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

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 3

Loose Wet

Isothermal conditions exist at treeline and below. Many loose wet avalanches that have gouged down to ground have been observed below 1800 metres.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 4

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 - 4

Valid until: Feb 9th, 2015 4:00PM