Avalanche Forecast

Issued: Apr 11th, 2017 4:00PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Spring squalls may bring local variations in new snow amounts. If you are seeing more new snow than forecasted in your areas, the danger may be elevated!

Summary

Weather Forecast

Unsettled spring weather could bring as much as 5-10 cm of new snow on Wednesday with light SE winds and temperatures remaining cool. Freezing levels are forecast to stay below 1900m. Thursday could see another 5-10 cm of snow with freezing levels rising to ~ 2100m. Friday should bring a drying trend as a ridge builds over the coast.

Snowpack Summary

Small amounts of snow over the weekend have added up to about 20-40cm. This new snow is generally bonding well with some isolated pockets of wind slab in the alpine. Below tree line the surface snow is moist on solar aspects. At tree line and above a 120cm+ firm slab with few weaknesses overlies weaker basal facets in much of the region.

Avalanche Summary

No new avalanches observed or reported on Tuesday.

Confidence

Intensity of incoming weather systems is uncertain on Thursday

Problems

Deep Persistent Slabs

The snowpack is slowly gaining strength, but the weak basal facets continue to produce sudden collapse results and can produce large avalanches with large triggers. Stick to planar, supported slopes with a deeper snowpack if entering steep terrain.

Pay attention to overhead hazards like cornices which could easily trigger deep slabs.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Cornices

April is cornice failure season, and we continue to get reports of cornices failing and triggering deep slabs. Mature cornices can also break much further back than you expect, so give them a wide margin when traveling on ridges.

Stay well to the windward side of corniced ridges.Do not travel on slopes that are exposed to cornices overhead.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Apr 12th, 2017 4:00PM