Avalanche Forecast

Issued: Jan 13th, 2018 4:14PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

This is a good time to be conservative in your terrain choices and minimize exposure to avalanche terrain. The chances of human triggered avalanches are quite high and as temperatures increase we will start to see more natural activity as well.

Summary

Weather Forecast

The winds will decrease on Sunday afternoon and the gradual warming continues as the high pressure system arrives. On Monday and Tuesday we expect an inversion to build with alpine temperatures forecast to be just above freezing. Valley bottom temperatures will remain at or below freezing. No significant precipitation is expected.

Snowpack Summary

Moderate to strong W winds and warming temperatures are forming wind slabs in the alpine. There is 30-50 cm over the Dec.15 persistent weak layer of facets and surface hoar. This Dec 15th layer is becoming reactive to skiers at treeline and above and producing easy to moderate sudden collapse results. Below this is a heavily faceted snowpack.

Avalanche Summary

Several small skier triggered slabs on the Dec 15 interface were reported on Saturday in the Rock Isle Lake area. A few small wind slabs from ski cutting and explosive work were seen at the local ski hills. Sluffing was observed in the alpine due to strong West winds. Lots of reports of whumphing and cracking in open glades at treeline and above.

Confidence

Due to the number of field observations

Problems

Wind Slabs

New wind slabs have formed during the last 24 hrs in the alpine and near ridge crests at treeline. Watch for the changing feel of the snow under your feet and be wary of areas with denser surface snow over weaker snow.

Use caution in lee areas. Recent wind loading has created wind slabs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

There is a dangerous weak layer down 30-40 cm and the slab overlying it is becoming stiff enough for avalanches to occur. Be very careful with this layer and travel conservatively even if you observe no avalanches.

Choose conservative lines and watch for clues of instability.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Jan 14th, 2018 4:00PM