Avalanche Forecast

Issued: Nov 13th, 2018 4:00PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

A big winter storm is approaching and conditions will change starting Wednesday. Potentially 30-50 cm of new snow plus strong winds by Thursday. Modify your plans accordingly and avoid exposure to avalanche terrain for the next several days.

Summary

Weather Forecast

A significant storm enters the region starting at midnight on Wednesday and continues through Thursday night; it will be a snowy few days. There is much uncertainty in the models, but some are predicting up to 30cm on Wednesday and another 20cm on Thursday - most of this is expected at Lake Louise and north, accompanied by strong westerly winds.

Snowpack Summary

Storm and windslabs will develop on the snow surface starting Wednesday and continue to build through the storm with 30-50 cm in the forecast. These slabs overlie 50-70 cm of weak facets with a melt-freeze crust in the middle (Oct. 26 crust). Overall the snowpack is weak due to its early season nature and could become overloaded by this storm.

Avalanche Summary

No new avalanches observed today on the Banff-Jasper highway area or on Observation Sub-Peak. Both Sunshine Village and Lake Louise ski patrols reported no significant new avalanches today - but we are all anticipating the next 24-48 hours to see how much new snow will result from the storm.

Confidence

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

Problems

Wind Slabs

This problem will develop and become worse through the day on Wednesday, perhaps being widespread by the end of the day. Watch out for all wind loaded slopes as these avalanches will trigger easily as they overlie facets and will bond poorly.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

This problem is found in most north facing (shaded) terrain up to 2800m, and will become more reactive as the storm deposits more load. Recommend avoiding all steep alpine terrain for the next few days.

Whumpfing is direct evidence of a buried instability.If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2.5

Valid until: Nov 14th, 2018 4:00PM