Avalanche Forecast

Issued: Mar 14th, 2017 4:00PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

A widespread avalanche cycle is underway with many small and large avalanches observed on Tuesday. Avoid exposure to all avalanche terrain. We have published our forecast early today to get this message out there.

Summary

Weather Forecast

Strong westerly flow continues as another storm crosses the area starting Tuesday afternoon. By Wednesday end of day we should see 20 cm of additional snow. Freezing levels will remain near 2000m until Wed afternoon when the air will slowly begin to cool. Alpine winds are forecast to be moderate to strong through the period.

Snowpack Summary

Additional snowfall and warming temperatures have tipped the snowpack and an avalanche cycle is underway now. A 50 cm dense slab has overloaded two prominent weaknesses in the snowpack; one down 40cm and the other in facets near the base of the snowpack. We expect the cycle to persist while the temperatures remain warm over the coming days.

Avalanche Summary

Two skier triggered avalanches on the Wapta on Monday evening, and then a flight along the Bow Valley Tuesday morning revealed dozens of fresh avalanches ranging from size 1 to size 3. There is an avalanche cycle underway now.

Confidence

Due to the number of field observations on Tuesday

Problems

Deep Persistent Slabs

The entire snowpack is built upon a structurally weak base, which is producing very large avalanches. Large deep persistent slabs have been observed on Tuesday and some are running into the valley bottom.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 4

Wind Slabs

A 40-50cm cohesive windslab exists at higher elevations, and in wind effected areas near treeline. This slab reacts easily to tests and is producing avalanches now.

Be aware of the potential for wide propagations.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 3

Valid until: Mar 15th, 2017 4:00PM