Avalanche Forecast

Issued: Mar 13th, 2017 4:00PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

Warm temperatures today have moistened the surface of the snowpack, and we expect this will have contributed to increased slab formation. The snowpack will remain tricky this week with continued light snow and warm temperatures.

Summary

Weather Forecast

A SW flow continues across BC and Alberta bringing continues precipitation and warm temperatures this week. Expect another 5cm on Tuesday, but up to 20cm by the end of the week. Temperatures on Tuesday will reach 0 degrees at treeline with freezing levels extending upwards to 2000m. Moderate winds overnight on Monday will calm down for Tuesday.

Snowpack Summary

10cm of soft surface snow became moist on Monday afternoon at lower elevations. This overlies a 40cm settled slab that produces sudden planar shears and is the main concern in the upper snowpack. Deeper in the snowpack, the facets from mid-December continue to plague us with sudden collapse test results in large, weak depth hoar grains.

Avalanche Summary

Size 2.5 avalanche ran over the ice climb, Rogan's Gully today (you could expect a similar occurrence on Cascade). Lake Louise and Sunshine ski areas reported 10-20 cm size 1 windslab avalanches from Sunday night's winds, and Lake Louise got one size 2 in the deep facets from an explosive in Elevator Shaft. Generally poor visibility today.

Confidence

Problems

Wind Slabs

A 40-50cm cohesive windslab exists at higher elevations, and in specific wind effected areas near treeline. This slab reacts easily to tests and its expected that skiers could trigger it.

Be aware of the potential for wide propagations.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

The entire snowpack is built upon a structurally weak base, which can produce very large avalanches. Recently, large deep persistent slabs have been observed. This situation will be slow to improve.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Mar 14th, 2017 4:00PM