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Avalanche Forecast

Archived

Apr 30th, 2017–May 1st, 2017

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

Little Yoho.

Pay attention to freezing levels this week. The first really big warmup is forecasted for Wednesday when freezing levels are expected to rise to 3000m.

Weather Forecast

Mixed sun and cloud with some convective flurries are forecast for Monday. Freezing levels will be around 2000 m on Monday and rising significantly to 3000m by Wednesday as an upper ridge moves into the region from the west.

Snowpack Summary

15 cm of overnight snow and 40-60cm of storm snow from this past week. There is moist surface snow and variety of melt freeze crusts in the upper snow pack in all areas except for due north above 2300 m. A basal weakness remains at the bottom of the snow pack. It is currently only reactive to large triggers but may wake up with solar warming.

Avalanche Summary

Several fresh wind slab avalanches (up to size 2) were observed in the alpine on north aspects in the Field and Lake Louise area on Sunday. Loose wet avalanches and several slab avalanches (associated with day time heating) were also observed on Sunday.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

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.