Avalanche Forecast

Issued: Nov 18th, 2017 4:00PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Forecast snowfall amounts are uncertain but moderate to strong winds will be sustained; expect avalanche hazard to increase. Both natural and human triggered slabs have been reported near treeline.

Summary

Weather Forecast

A Southwesterly flow arrives midday Sunday favoring Northern areas. Models disagree on snow quantities but 10 to 25cm should be the range. Generally temps will remain in the -5 to -10C range but a brief spike in freezing level would not be a surprise with the arrival of this moist pacific air. Moderate to strong winds will continue through Sunday.

Snowpack Summary

Light flurries again today with moderate West winds. 15 to 25cm of storm snow in the last 72 hours. The alpine snowpack ranges from 50-100 cm across the region with the main feature to watch in the snowpack being a layer of facets now buried 25 to 40 cm . Below 2700m these facets sit above a temperature crust that was buried on Halloween.

Avalanche Summary

Continued reports of storm and wind slab activity are coming in; most notably a sz 2 slab at treeline just west of the Bourgeau Left ice climb reported by the Sunshine patrol. This slab was undoubtedly triggered by sustained wind loading late in the day Friday and is likely to have failed on facets over the Halloween crust.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Sunday

Problems

Wind Slabs

Strong West winds were again moving a great deal of snow today and treeline areas are also starting to be affected. These winds will continue through Sunday and, with more snow in the forecast, expect these slabs become even more developed.

Choose ice climbs that are not exposed to avalanches from above.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Storm Slabs

The snow that fell on Halloween became faceted by the early November cold snap. Soft slabs of snow now sit above this weak snow and have been reactive to skier traffic and small triggers such as sluffs out of rocky terrain.

Minimize exposure to steep, planar slopes.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Nov 19th, 2017 4:00PM