Avalanche Forecast
Issued: Mar 8th, 2021 4:09PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
Tim Haggarty,
Two large avalanches on opposite ends of the region over the past 24 hours likely involved the persistent slab problem. Events such as these may be low likelihood but would yield consequence and should be carefully weighed in decision making .
Summary
Weather Forecast
With mainly clear skies, a strong freeze is expected Monday night. As west winds pick up to the moderate range in the alpine Tuesday, minimal heating is expected despite clear skies. Clouds will develop overnight Tuesday leading to milder morning temperatures and the potential for flurries through the day Wednesday. Clearing overnight into Thursday
Snowpack Summary
Since Friday, up to 30 cm of recent snow sits over solar crusts and wind effect in open areas. New solar crusts on isolated steep slopes formed on Monday. Two persistent facet layers (Feb 19 & Jan 27) are down 30-80cm and still producing sudden shears in some locations. In thin areas the basal depth hoar/crust from Nov is still quite prominent
Avalanche Summary
Two large events were observed in the past 24 hrs. A size 3 cornice triggered slab ran between the 4rth and 5th buttresses of Rundle Sunday, and a large powder cloud was observed off of Mt. Lefroy into the Death Trap from Lake Louise Monday. Both of these events seem to have involved the persistent layers.
Confidence
Problems
Persistent Slabs
Two layers of facets and/or sun crust in the top meter of the snowpack have been active in the past week. Cooler temps and surface crusts now formed may reduce the likelihood of triggering on solar aspects but little change is apparent otherwise.
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
- Pay attention to overhead hazards like cornices which could trigger the persistent slabs.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
10-15 cm of snow that fell Fri / Sat was redistributed by moderate to strong SW winds along treeline ridge crests and above Sunday. While the 10cm that arrived Monday has seen little wind, expect increasing winds Tuesday to contribute to these slabs.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 9th, 2021 4:00PM
