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Avalanche Forecast

Archived

Mar 20th, 2023–Mar 21st, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

The snowpack in Yoho is generally stronger than the snowpack further east, towards Banff. Areas like Mt. Field and the west side of the Wapta have a deeper and mostly well-consolidated snowpack. With the clear skies and sun this week, watch carefully for signs of instability as the day warms up.

Confidence

Moderate

Avalanche Summary

There was a late-day loose wet avalanche cycle on Sunday, with temperatures reaching up to 11 degrees in the valley bottom. As of 4 pm on Monday, no new avalanches have been observed. We continue to expect deep persistent avalanches with almost any change in the weather, but so far this week no significant new ones have been reported.

Snowpack Summary

Above 1600 m the surface is 10-25 cm of soft, settled snow with minimal wind effect. Suncrusts are forming on steep solar slopes and are more widespread below 1400 m. The middle of the snowpack holds several crust layers that continue to produce avalanches, and the base of the snowpack is weak facets that appear their strongest in deep snowpacks such as in Little Yoho.

Weather Summary

A ridge of high pressure is dominating the weather picture until mid-week. Expect a few clouds in southern areas, but otherwise clear skies, light winds and freezing levels reaching 1800 m. Expect the sun to pack quite a punch in sheltered areas.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.