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Avalanche Forecast

Archived

Mar 22nd, 2023–Mar 23rd, 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.

A stronger and deeper snowpack exists in the Yoho zone. Remain watchful for daytime heating and exposure to large triggers above slopes, such as cornices.

Confidence

Moderate

Avalanche Summary

On Wednesday, only loose snow avalanches to size 2 were reported by field teams and ski hill snow safety teams. On Tuesday, there was a deep persistent slab reported on Observation peak and Sunshine patrol reported observing two size 2.5 deep slabs in the surrounding backcountry. One on Fatigue Mountain and one near Mt. Ball. Also on Tuesday, Lake Louise patrol reported triggering two old hard wind slabs size 1.5 in the White Horn gullies with explosives.

No other avalanches were observed or 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

Thursday - will start clear with cloud building in the afternoon. We may see more solar induced avalanche activity, but it will depend on the incoming cloud an how warm it gets. Overall expect a cooler day (alpine highs of -4C) and westerly ridge top winds of 20-30 km/hr.

Friday - scattered flurries becoming more widespread in the afternoon, but only trace amounts are expected. Winds will generally be light westerly 10-20 km/hr. Overnight, along the eastern slopes, we may see up to 15 cm by Saturday morning, but there is variation between weather models, and we may not see that much.

Saturday - another upslope flow with another 5-10 cm possible on the Eastern slopes by Sunday.

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.