Avalanche Forecast

Issued: Apr 18th, 2018 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Loose Wet, Wind Slabs and Persistent Slabs.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Danger rating based on the highest rating of the day in relation to temperatures, and we expect an avy cycle on Thursday. Avalanche control on Mt. Whymper, Simpson, Vermillion, Wardle, and Mt. Bourgeau Thursday. No activities in these locations.

Summary

Weather Forecast

Mainly sunny conditions Thursday will see lots of solar input which will finally bring some spring temperatures to the region. Light winds and no snow in the forecast. Next week looks like a very warm week which will bring a dramatic spike in the avalanche danger. Stay tuned.

Snowpack Summary

Up to 50 cm of storm snow near the divide affected by strong SW winds Tuesday evening. 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

Some size 2 wind slabs reported at sunshine with explosives. Avalanche control on Mt. Bosworth Wednesday produced avalanches to size 3 with good propagations up to 200m wide, and further West a size 3.5 out of Emerald Lake slidepath occurred last evening.

Confidence

Freezing levels are uncertain on Thursday

Problems

Loose Wet

High solar input Thursday will increase the avalanche danger at all elevations. Watch locally for exposure to sun and how it is affecting the terrain you are on.

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

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

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 producing large results Wed. See avalanche discussion.

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

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

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.

Be cautious with convexities and steep slopes on solar aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Apr 19th, 2018 4:00PM