Avalanche Forecast

Issued: Dec 24th, 2016 4:00PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

A final round of Avalanche Control on Mt Dennis today produced good results both with slabs and loose dry avalanches failing of the December 19 facets that ran fast and far. Have a Merry - and safe - Christmas!

Summary

Weather Forecast

Snowfall will taper tonight as light winds from the North bring cooler, drier air for Sunday. Expect alpine temperatures in the - 20 to -15C range. A Westerly flow reasserts itself on Monday with moderate winds, light precip and a bit of an increase in alpine temperatures to start the week.

Snowpack Summary

10-40 cm sits over the very weak Dec.19th facets. Wind slabs up to 60cm have been observed over this same layer in alpine areas. The new snow / facet interface has proven touchy with avalanche control work over the last 5 days and will persist for some time. The Nov crust is 30-80cm deep and a few isolated observations indicate it to be reactive.

Avalanche Summary

Explosive control this week resulted in avalanches up to size 2.5-3. The largest involved windslabs that failed on the persistent Dec.19th facets. Notably, ski hills triggered a couple of size 2's with bombs that initiated on the Nov 12 crust on solar aspects where both a thin snowpack and pronounced crust exist. Limited natural activity seen

Confidence

Due to the number of field observations

Problems

Persistent Slabs

New snow and strong winds have created wind-slabs on exposed slopes that can be easily triggered. These slabs sit over a very faceted snowpack creating a weak interface that will last for some time.

Be careful with wind loaded pockets while approaching and climbing ice routes.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Loose Dry

New snow amounts have slowly piled up, especially in Eastern areas with the influence of an up-slope flow. The weak Dec 19 facets do not provide much support for this snow and once a sluff is initiated in steep terrain, it can run a long distance

Good group management is essential to manage current conditions safely.Be very cautious with gully features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Valid until: Dec 25th, 2016 4:00PM