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Avalanche Forecast

Archived

Apr 18th, 2021–Apr 19th, 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.

A quick return to winter on Sunday has made new snow surface instabilities the main concern for the next couple of days.

Weather Forecast

A cold front dropping through Alberta has brought 10-15 cm with moderate NE winds as of Sunday afternoon. Temperatures are expected to drop as low as -15C in the alpine and just below 0C at valley bottom overnight. An unstable atmosphere seems likely Monday that should result in spotty clouds while freezing levels approach 2000m in the afternoon.

Snowpack Summary

Up to 15cm of new snow Sunday tapers with elevation and buries crusts found on solar aspects and up to 2200m on shaded aspects. Persistent layers in the mid and lower snowpack were re-activated in a few instances during the heating over the last week producing avalanches with cornice failures and explosives.

Avalanche Summary

On Friday and Saturday explosive control on the 93 S and in Yoho 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. Cooling Sunday has brought natural activity to a halt

Confidence

Problems

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.

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.