Avalanche Forecast

Issued: Mar 11th, 2019 6:47PM

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

Conrad Janzen, Parks Canada

Banff Yoho Kootenay.

New snow and strong winds will form slabs over the previous weak facet layer resulting in a rising hazard level. We have seen a few slides run further than expected. Make conservative terrain choices until more is known about how this new snow reacts

Summary

Weather Forecast

Upper elevation winds will remain strong Monday night then slowly diminish during the day on Tuesday becoming light by Tuesday night. 5-10 cm of new snow is forecast for Monday night and into Tuesday. Alpine temperatures will hold steady Monday night near - 10'C and begin dropping on Tuesday. Valley bottoms will see high temperatures near freezing.

Snowpack Summary

Strong SW winds Monday have redistributed recent snow into wind slabs in open areas above treeline. This recent snow sits over weak facets, previous wind effect or sun crusts on steep solar aspects. The mid pack varies from supportive in thicker snowpack areas to weak and completely faceted in thin areas.

Avalanche Summary

Small natural avalanches and spindrift avalanches were observed in the alpine Monday afternoon as the winds increased. Some of these traveled long distances entraining facets and running full path. Several skier triggered slabs have occurred in the last couple days, and avalanche control Sunday produced slabs up to size 2.5 running to treeline.

Confidence

Intensity of incoming weather systems is uncertain on Tuesday

Problems

Wind Slabs

New snow and strong SW winds are building slabs in open areas above treeline. These slabs are sitting on the weak, faceted snow that was previously on the surface and as a result can run further than expected when triggered.

Watch for surface cracking and stiffer surface layers of snow.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Loose Dry

Previous cold temperatures created weak, faceted surface snow. In steep terrain, these facets remain easily triggered and can gain enough mass to affect skiers and climbers. Narrow gullies are where this is most concerning.

Good group management is essential to manage current conditions safely.Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 12th, 2019 4:00PM