Avalanche Forecast

Issued: Feb 3rd, 2019 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

Increased reactivity of the Jan 17 surface hoar/crust layer is due to recent loading of storm snow. Distribution is spotty, so dig down to verify if this layer is present in your local area.

Summary

Weather Forecast

Thankfully, today is forecasted to be the coldest day. Temperatures will climb back to a somewhat reasonable level by tomorrow to about the -18 range in the valley. A clearing trend will ensue, and the wind will drop back to light from the West. No snow is forecasted for a while.

Snowpack Summary

30-45cm of recent storm snow is being redistributed into windslabs above treeline. Up to 65cm sits over the Jan.17 surface hoar which has been found up to 2300m. In shallower areas weak facets and depth hoar exist below the Dec 10 interface. In deeper snowpack this basal weaknesses is less pronounced

Avalanche Summary

No avalanches reported or observed today, however yesterday there were two skier accidental avalanches size 1.5. One was on Vermillion Peak (reported on the MIN) the other was at Bow Summit. Both were suspected to have slid on the Jan 17 Surface Hoar. No injuries or lost gear in either slide.

Confidence

Due to the number of field observations on Sunday

Problems

Wind Slabs

Wind was observed redistributing the recent storm snow in the alpine and creating fresh windslabs in lee areas. These slabs could be up to 70cm deep. For clarity, the storm slab problem has transitioned into the windslab problem.

Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

The Jan 17 layer is a combination of Surface Hoar and/or a melt freeze crust. Since the recent storm, it has become reactive to skier traffic and can generally be found down 50cm. Dig down, look and test this layer at tree line and below.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

The new snow load may start waking up the deep persistent facet weakness down 80-160 cm. This is of greatest concern in shallow snowpack areas where the basal facets are weakest.

Avoid thin, rocky or unsupported slopes.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Feb 4th, 2019 4:00PM