Avalanche Forecast

Issued: Feb 5th, 2016 4:00PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

We expect a natural avalanche cycle to occur in the alpine overnight Friday and into Saturday. Minimize your exposure to large alpine slopes and watch for small wind loaded slopes at lower elevations.

Summary

Weather Forecast

10-20cm of snow is forecast for Saturday in most areas with very strong alpine winds out of the West. Temperatures will gradually drop into the -10 to -15'C range as the weather begins to clear late on Saturday. Light flurries and moderate West winds are expected for Sunday.

Snowpack Summary

New wind slabs forming in the alpine and tree line areas which are easy to trigger. The Jan 6 surface hoar/facet/sun crust layer, down 30-60cm, is becoming less reactive to skier triggering, however sudden collapse results persist on the Jan 6 and Dec 3 layers. Isolated whumphing on mid-pack facets/surface hoar have been observed this past week.

Avalanche Summary

Several new natural wind slab failures were observed Friday up to size 2 in the Lake Louise area as the winds began to increase and the temperatures warmed up. We expect a substantial increase in natural activity over the next 24 hours as the storm arrives.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Problems

Wind Slabs

10-20 cm of new snow is expected by Saturday accompanied by strong West winds. This will result in rapid loading of lee slopes and a substantial increase in natural avalanche activity especially in alpine areas.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Avoid avalanche terrain during periods of heavy loading from new snow and wind.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 3

Loose Dry

The new snow and wind will cause loose dry avalanches to occur in alpine areas. These loose dry sluffs have potential to trigger larger avalanches below. Ice climbers in particular should avoid areas exposed to sluffing over the next couple of days.

The new snow will require several days to settle and stabilize.Avoid travelling under cliffs that are exposed to sluffing from above.

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

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

An average of 30-60 cm overlies the Jan 6 layer of surface hoar, facets and sun crust. Test results on this layer show it has become stubborn to trigger, but potential for wide propagation remains. The new snow will increase the likelihood of this.

Avoid open slopes and convex rolls where buried surface hoar may be preserved.Use careful route-finding and stick to moderate slope angles with low consequences

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Feb 6th, 2016 4:00PM