Avalanche Forecast

Issued: Nov 23rd, 2012 4:55PM

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

snow safety, Parks Canada

Banff Yoho Kootenay.

Avalanche Control on Saturday for the Sunshine Road, please no climbing in the area. Considering control work for Bosworth and Stephen in Yoho and possibly Whymper in Kootenay on Sunday, stay tunned. (LP)

Summary

Weather Forecast

The mod to strong SW winds should abate by midnight and flip to a lighter NW flow & cooler temps (-10).Â Trace precip tonight. Unsettled tomorrow, with sunny periods.Â High pressure settles in Sunday with clearer skies forecasted.

Snowpack Summary

Since Nov 18th there has been 40-50 cm of new snow along the divide, lots still available for transport. Easy shears at the storm snow interface. There are mod shears on Nov 6 rain crust in the lower third of the pack.Â The crust exists throughout the region and can be found up to 2400 m.

Avalanche Summary

One notable skier cut size 2.5 avalanche in the Wizard chutes, NW aspect, at 2100 m, on 35-40 degree terrain - 60 cm thick soft slab, propagated 75-80 m, likely slid on the crust & ran 300 m. Generally poor visibility today for avy observations.

Confidence

Due to the number of field observations

Problems

Wind Slabs

20-40 cm thick soft and hard slabs, reactive to explosives and ski cuts and restricted to immediate lee's. Slab was stiffer today with longer propagations, but still in the size 2 range.

Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Storm Slabs

40-50 cm settled storm snow with an easy shear on the old snow surface. Primarily an issue on steep terrain features, especially if it's an open feature exposed to some wind effect. Give it a few days to settle and bond. See forecast details.

Avoid open slopes with any steepness over 30 degrees.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

May be reaching the tipping point for this layer. A size 2.5 was ski cut in the Wizard chutes on the backside of Wawa ridge near Sunshine. Thursday, a full depth release down to ice was noted on the Monarch Glacier (Sunshine backcountry).

Avoid open slopes with any steepness over 30 degrees.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Nov 24th, 2012 4:00PM