Banff Yoho & Kootenay National Park Avalanche Forecast
Issued: Mar 7th, 2021 4:02PM
A good freeze Sunday has settled things down at lower elevations following last week's warm up but watch for a strong solar punch on Monday.
SW winds 35-45km/h midday Sunday should diminish by noon Monday as a ridge forms over the Rockies. Trace amounts of snowfall from convective activity can be expected overnight but skies will clear as the ridge builds. Expect freezing levels to reach 1500m but, as the sun comes out, and winds diminish, expect strong solar heating in the afternoon.
10-15 cm of new snow sits over a crust on solar aspects. Moderate SW winds are transporting this new snow at treeline ridge crests and above. 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.
Natural cornice, explosive, and some skier triggered avalanches, up to size 3, have been observed in the past week during the big warm up with most of these failing on one of the persistent layers. Sunday marked the first solid freeze. Freezing levels only reached 1500m with cloud. The ski hills reported working with only small, fresh wind 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.
- Pay attention to overhead hazards like cornices which could trigger the persistent slabs.
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
10-15 cm of recent snow is being redistributed by moderate to strong SW winds along treeline ridge crests and above. Expect soft new slabs in immediate lees. Previous strong winds created extensive wind effect in open areas and added cornice growth.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
As the sun comes out in the afternoon with the forecast light winds, expect a significant solar punch to moisten recent surface snow. This snow is already sitting on previous crusts and though small, these avalanches may run fast at far.
- Use extra caution on solar slopes if the sun is shinning or if the snow is moist or wet.
- Watch for moist surface snow over crust on steeper solar aspects.
Aspects:South, South West, West.
Elevations:Treeline, Below Treeline.
Valid until: Mar 8th, 2021 4:00PM
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