Avalanche Forecast

Issued: Apr 17th, 2014 4:00PM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Deep Persistent Slabs, Loose Dry and Loose Wet.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Fresh snow has reset the ski conditions and overall we have a stable snowpack. When you plan your trip, remember that the basal weak layers are still present in thinner areas, and that we are not in full spring mode as of yet. SH

Summary

Weather Forecast

Freezing levels to 2000m on Friday with another 10cm in the alpine and possibly rain at lower elevations. Expect generally cloudy conditions and light winds gusting strong from the W. Sat and Sunday will see more solar input and freezing levels between 2400-2600m.

Snowpack Summary

15-20cm over last 24 hrs. bonding well to surfaces below. A supportive melt-freeze crust on all aspects to 2100m and higher on S and W aspects. The snowpack is well settled. The deep persistent weak layers are dormant, but may awaken if it warms up or you trigger the weak spot, as demonstrated 2 days ago on Mt. Whymper, (see avalanche table).

Avalanche Summary

Forecasters were very surprised 2 days ago after hearing a report of a size 3.5 skier remote avalanche on Mt. Whymper. The group heard a whumph and 30 seconds later the slide released taking out the whole slope the party had just climbed up from 70m away. Picture. Only loose sloughing in extreme terrain was noted today on a tour to Surprise Pass.

Confidence

Freezing levels are uncertain on Thursday

Problems

Deep Persistent Slabs

The basal layer is still a prominent feature of the snowpack in thin and variable areas. It is being well bridged and is unlikely to be triggered, but the consequences could be large if you hit the right spot.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Dry

With more snow and some wind in the forecast, watch out for power sloughing on steep slopes and gullies (40 deg +) as well as small pockets of wind slab near ridge crests.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Although the forecast is mainly cloudy for Friday, any period of sun will be intense enough to affect the new snow.

Start and finish early before the surface crusts melt.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 18th, 2014 4:00PM