Archived

Avalanche Forecast

Dec 31st, 2018–Jan 1st, 2019

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

Happy New Year! New Years day looks to be cold and windy, but by the time you've recovered from New Years Eve, we should be into another storm cycle!

Weather Forecast

A ridge will bring cold dry conditions for the first day of 2019, and an incoming system will bring strong NW winds in the alpine. Fortunately, this system will also bring snow on Wednesday/Thursday. Precipitation amounts will start light, but forecasts are calling for 20-30 cm on Thursday, with the greatest amounts to the west and north.

Snowpack Summary

Wind effect exists in the alpine and at treeline. Below treeline, the surface is faceted powder. This overlies the Dec. 10th layer of facets and depth hoar which is down 60-100 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

No new avalanches observed on a field trip on the Icefields Parkway today, but good visibility highlighted more naturally triggered avalanches up to size 2.5 out of steep alpine terrain from the storm on Dec. 29th. These seemed to be on all aspects, and running on the Dec. 10th layer and stepping down to the ground in thin areas.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Thursday

Avalanche Problems

Deep Persistent Slabs

A stiff slab overlying a weak lower snowpack comprised of facets and depth hoar can be found in most areas of the region (generally central and eastern) where a shallow snowpack exists. Give this weak snowpack some time to adjust to the storm load.

Watch for signs of instability such as whumpfing, or cracking. Be wary of slopes that did not previously avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 2.5

Wind Slabs

Strong SW winds blew mid-storm on Dec. 29th creating touchy new slabs. While the cold temperatures that have followed have diminished the sensitivity of these slabs, they are still reactive with explosives in steep terrain.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2