Avalanche Forecast

Issued: Jan 3rd, 2019 4:00PM

The alpine rating is extreme, the treeline rating is extreme, 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.

Time to stay out of avalanche terrain. Weather models predict another 30-75 cm with strong winds, if this storm continues as forecasted through tomorrow the hazard will be into Extreme for Friday.

Summary

Weather Forecast

Another 30-70 cm of snow is expected before the storm ends Friday night with the greatest amounts on the Wapta. Most weather models are in agreement. The system is accompanied by warm temperatures & moderate to strong westerly winds = a perfect recipe for large avalanches stepping down into our persistent weak layers!

Snowpack Summary

25-45 cm of storm snow so far with moderate to strong WSW wind is overloading the Dec. 10th weak layer of facets and depth hoar which is down 80-120 cm. In thin snowpack areas, the Dec.10th layer is mixed in with the basal facets and October crust. In thicker areas, it is a distinct layer, with a stronger snowpack below.

Avalanche Summary

Although visibility was obscured today, a wide spread natural avalanche cycle is occurring with avalanches running well into the run out zones with avalanches up to size 3.5. We expect the cycle to continue through Friday with the ongoing storm. Continued wind transport on Saturday will keep the hazard elevated.

Confidence

Problems

Storm Slabs

Another 30 cm is forecasted for Emerald adding to the 35 cm already received. This will certainly form a touchy slab. Any avalanches initiated here are likely to step down to the deeper Dec. 10th layer.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1.5 - 3

Deep Persistent Slabs

The Dec. 10th layer of facets and surface hoar down 80-160 cm continues to be rapidly loaded by an ongoing intense storm. Any avalanche that initiates almost certainly to step down to this layer and run well into the run outs below treeline.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

2 - 3.5

Loose Dry

Loose snow avalanches are occurring and is very likely to initiate a larger avalanche on the Persistent slab layer described above.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 2.5

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