Avalanche Forecast

Issued: Mar 17th, 2019 4:28PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Start and finish very early to travel when the snow is still cold, and be out of all avalanche terrain by the time the day heats up. We are seeing more and more avalanche activity each day with high danger levels at all elevations in the afternoons.

Summary

Weather Forecast

We expect a decent overnight freeze on Sunday night followed by rapidly rising freezing levels to near 3000 m on Monday afternoon, and slightly higher daytime temperatures on each of the following two days. Winds will remain light out of the N and W. No new precipitation is expected and the next few days look sunny and clear.

Snowpack Summary

Sun crusts or moist snow on solar aspects and moist snow at lower elevations. 15-50 cm of snow has accumulated since March 7. This sits over a mix of facets, sun crust and wind slabs above treeline, and over 30-50 cm of weak facets elsewhere. While a supportive mid-pack exists in thicker areas, weak facets to the ground are seen in many thin areas.

Avalanche Summary

Numerous natural and human triggered loose wet and slabs up to size 2.5 have been seen over the last two days at all elevations with several close calls and serious incidents. South aspects have been most active due to solar heating, but we are seeing increased activity on North aspects with cornice failures, wind slabs and skier triggered slabs.

Confidence

Freezing levels are uncertain

Problems

Loose Wet

Rapidly warming daytime temperatures and high solar inputs are causing loose wet avalanches to start by mid morning. Some of these are running long distances or triggering slabs along the way. Avoid exposure to these slopes when they heat up.

If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.Use extra caution on slopes if the snow is moist or wet.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2

Persistent Slabs

10-50 cm of snow since March 7 has formed slabs above treeline due to winds and warm temperatures and sits over a variety of weaker surfaces. Natural and skier triggering of this recent snow has occurred in the last several days on all aspects.

Watch for surface cracking and stiffer surface layers of snow.Use conservative route selection, stick to moderate angled terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

We are starting to see places where avalanches are failing on the basal weaknesses and scrubbing to ground. This is mostly occurring with large triggers in thin rocky areas but we expect this type of avalanche activity to increase with more heat.

Pay attention to overhead hazards like cornices which could easily trigger deep slabs.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 18th, 2019 4:00PM