Avalanche Forecast

Issued: Mar 15th, 2019 4:28PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

After the wind and later the sun triggered many avalanches today, cloudy skies and light winds are expected Saturday. Clearing Sunday however, marks the beginning of a significant warming trend that is expected to increase avalanche activity.

Summary

Weather Forecast

After a few patches of clear sky late in the day Friday, a return to more clouds seems likely for Saturday as winds diminish and temps stay largely static. Clearing skies midday Sunday looks to mark the beginning of a significant warming trend that will bring freezing levels to 3000m later in the week. An increase in avalanche activity is expected.

Snowpack Summary

15- 40cm has accumulated since March 7. Modertate to strong SW-W winds have redistributed this snow treeline and above. This snow sits over previous widespread wind effect in the alpine, suncrusts on steep S aspects and 30-50cm of sugary facets everywhere else. While a tough midpack exists in thicker areas, facets to ground are seen in many others.

Avalanche Summary

Fresh snow overnight, with moderate to strong winds led to a cycle Friday morning with slabs to sz 2.5 and loose dry avalanches to sz 1.5. As has been seen over the last week: the loose dry avalanches often entrain significant amounts of old faceted snow in steep terrain and continue to run until they hit lower angle terrain.

Confidence

Timing or intensity of solar radiation is uncertain on Sunday

Problems

Wind Slabs

New snow and strong SW-W winds have built wind slabs in open areas above treeline. In some cases, these slabs sit over the weak faceted snow and have been sensitive to triggering. In may cases, these slabs initiate a loose dry avalanche as well.

Watch for surface cracking and stiffer surface layers of snow.Even small avalanches may run a long ways under the current conditions.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Dry

The faceted snow is easily initiated as a sluff in steep terrain that will entrain all available loose snow until it hits lower angled terrain. If a windslab or cornice initiates these, expect increased width, mass, momentum and reach.

Good group management is essential to manage current conditions safely.Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Mar 16th, 2019 4:00PM