Avalanche Forecast

Issued: Apr 17th, 2018 4:53PM

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 Loose Wet.

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

A surge of moderate to strong SW wind today created fresh windslabs and have loaded cornices. Choose conservative terrain and minimize exposure to overhead hazard until the snow has a chance to bond.

Summary

Weather Forecast

Temperatures will remain relatively cool, with cloudy skies and with freezing levels up to 1800m for Wednesday. Winds should diminish through the day as skies clear Wednesday evening and a high pressure builds in the region.

Snowpack Summary

Up to 50 cm of storm snow near the divide affected by moderate SW winds Tuesday afternoon. Several buried temperature crusts exist to 2000m on all aspects and to ridge tops on solar slopes, including the Mar 15 sun crust down 35-50 cm in the alpine. Moist snow at lower elevations, with the entire snowpack becoming moist near valley bottom.

Avalanche Summary

Touchy windslabs 10-40 cm thick developed Tuesday afternoon with moderate to strong SW wind.Â A few natural avalanches were observed and windslabs were reactive to ski cutting and explosive control.Â

Confidence

Problems

Wind Slabs

20-50 cm of storm snow has fallen over the past few days with the greater amounts near the divide. Increased SW wind Tuesday afternoon loaded lee terrain creating reactive windslabs.

Use caution in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

While it has been several days since there have been any confirmed events directly associated with the March 15 crust, other temperature crusts have now become buried in similar locations and are providing a good sliding layer for the new storm snow.

The storm slab may be more sensitive to human triggering on solar aspects where it sits on a crustBe cautious with convexities and steep slopes on solar aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Lower elevations may see loose wet avalanches start to occur later in the day with either temperature increases or with solar input as skies clear late Wednesday.

Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 18th, 2018 4:00PM