Avalanche Forecast

Issued: Dec 5th, 2017 4:00PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

The wind has gotten to high alpine areas, but good ski conditions can still be found in sheltered locations. The hazard will increase on Thursday if the freezing level forecasts come true.

Summary

Weather Forecast

A strong high pressure system is building in the region. Winds will ease to light from the NW on Wednesday. Temperatures are rising, and freezing levels are forecast to hit ~1500m on Wed, and 2000 - 2500m on Thursday and Friday. We may see an inversion set up towards the end of this period.

Snowpack Summary

Above 2500m, the surface snow has been blown into windslabs in exposed areas. Below 2500m, 30 -50 cm of snow lies over the Nov 27th and Nov 23rd crusts. Both of these now overly the Halloween crust/ facet layer that sits 30-50cm above the ground. This lower layer is a facet layer above 2500m and a crust below. Some surface hoar is forming below TL

Avalanche Summary

Some small loose dry avalanches were observed in steep terrain triggered by wind on Mt Fairview. Additionally, a couple size two slabs were observed near the Pulpit area on the Icefields Parkway. These were on steep NE facing terrain and likely triggered by windloading and sluffing. .

Confidence

Freezing levels are uncertain on Thursday

Problems

Persistent Slabs

Natural avalanche activity has tapered, but concern remains for human triggering on the weak snow on this layer. Previously, slab avalanches have been triggered above ~ 2400m where the Nov. 23rd crust fades out. Shallow alpine areas warrant caution.

Avoid shallow snowpack areas where triggering is more likely.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Wind Slabs

Recent moderate to strong winds have created variable windslabs in exposed alpine areas along the divide. These are mostly stubborn, but because they are of variable stiffness, they are difficult to manage on skis

Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 6th, 2017 4:00PM