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Avalanche Forecast

Archived

Apr 16th, 2021–Apr 17th, 2021

Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Banff Yoho Kootenay.

We expect to see a lot more avalanche activity on Saturday as this is the hottest day of the spring so far. Avoid all avalanche terrain once the snowpack heats up and be aware that a forecast inversion may be heating upper elevations faster.

Weather Forecast

An inversion is forecast Friday night with above freezing temperatures all night in the alpine. The clear skies and warm weather will continue until Saturday evening when a cooling trend starts with some precipitation expected on Sunday. Saturday could be "the day" for avalanches. This is the biggest warm up so far this year.

Snowpack Summary

Surface crusts present on solar aspects and all aspects up to 2200 m in the morning, quickly turning to wet snow as the day warms up. High elevation north aspects still holding dry snow. Several persistent layers exist in the mid to lower snowpack from earlier in the winter that may become active layers again over the next 48 hr as things heat up.

Avalanche Summary

On Friday explosive control on the 93 S produced good results up to size 3 with small slabs at treeline gouging into deeper layers at lower elevations and running full path. Widespread natural loose wet avalanche activity up to size 2 was also observed at all elevations. We expect avalanche activity to increase on Saturday. 

Confidence

Problems

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.