Avalanche Forecast

Issued: Jan 4th, 2019 4:00PM

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

lisa paulson, Parks Canada

Banff Yoho Kootenay.

A heavy snow fall (up to 70 cm) has overloaded a weak snowpack. Stay clear of avalanche terrain. Slopes that have not avalanched are ripe for human triggering.

Summary

Weather Forecast

The snowfall tapers off tonight & winds should also drop off slightly. For Saturday, there is a break in the weather with cloudy skies & cooler temperatures expected. A minor front crosses the region on Sunday bringing light flurries & higher winds. Beware - any additional load from wind transport may trigger slopes that have not yet avalanched.

Snowpack Summary

Up to 70 cm of storm snow with moderate to strong WSW wind has overloaded the persistent weak layers. In thicker snow pack areas, the Dec. 10th weak layer of facets & depth hoar is now down 100-150 m with a stronger snowpack below. In thin snowpack areas, the Dec.10th layer is mixed in with the basal facets and October crust.

Avalanche Summary

Over the past 24 hours, there has been a avalanche cycle up to size 3.5, some ran full path, and many have scrubbed to ground. Many steeper features at treeline & below have also avalanched. The natural activity should taper, but slopes will remain hair trigger with any further wind loading or by recreationalists on or near a slope.

Confidence

Problems

Storm Slabs

Up to 70 cm of storm snow has formed a touchy storm slab at all elevations. Numerous slopes & cutbanks below treeline have avalanched wall to wall or remain poised for human triggering.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Avoid all avalanche terrain

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1.5 - 3

Deep Persistent Slabs

The Dec. 10th layer of facets & surface hoar down 100-150 cm has been overloaded by recent storm snow. The snow pack needs time to adjust, be very conservative with route choices this weekend and avoid overhead exposure.

Be aware of the potential for wide propagations which could result in large avalanches.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 3.5

Loose Dry

With winds tapering tomorrow, there should be fewer loose dry avalanches, but they will still be a concern given the amount of snow we have received. Any increase in wind could trigger loose dry avalanches which in turn can trigger deeper avalanches.

Be very cautious with gully features.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Jan 5th, 2019 4:00PM