Avalanche Forecast

Issued: Dec 4th, 2014 5:10PM

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

tim haggarty, Parks Canada

Waterton Lakes.

With 55cm at Little Prairie there is sufficient snow for travel on trails at lower elevations. While there is over one meter at Treeline coverage remains poor Below Treeline with early season hazards presenting a real threat to skiers and riders.

Summary

Weather Forecast

Warming Friday with a few flurries and a freezing level reaching Little Prairie at 1700m Southwest winds increasing to moderate. 5 to 10cm on Saturday with a steady freezing level and winds increasing to Strong. Freezing levels to drop to townsite Sunday at 1300m with few flurries as winds back off to moderate. Significant warming begins Monday.

Snowpack Summary

At Treeline from the ground: 5cm of mid-Nov facets sit on 30cm of crusts formed early in November. Rain at the start of the storm on Nov 26 created a 7cm crust over the facets before cooler temps Nov 27 and 28 dropped up to 1m of snow. Wind effect can be found in open areas at treeline however this looks to be much more advanced in the alpine.

Avalanche Summary

At least two large avalanches occurred near the end of the recent storm: a size 3 hit Cameron Lake and another large crown was seen above Forum Lake. A fracture line profile on Forum ridge today found the November 28 crust to be the bed surface and we suspect very soft snow at the base of the newly formed slabs was the failure plane.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Thin windslabs can now be found at treeline and can also be seen at lower elevations around our ice climbs. Extensive wind transport is evident in the alpine areas.

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.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

At high elevations cooler temps will have only allowed thin crusts to form above the weak November Facets which may remain a possibility for triggering for some time. Use caution until more is know about alpine areas.

Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

These slabs taper radically with elevation. Large slides resulted from failures in the recent storm snow over the crust that extends into the alpine.

The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 7th, 2014 4:00PM