Regions
Banff Yoho Kootenay.
Avalanche control is planned for the Sunshine road on Tuesday, so the ice climbing routes are closed. We are right on the edge of the big storm in the east, but did not get the same huge dump as they did in K-Country. Expect a big cycle this weekend.
Weather Forecast
This storm is ending on Monday night. Tuesday will remain cold with mostly light NE winds except at higher elevations where the winds will be stronger (brrr). Temperatures will remain in the -20 range for Tuesday. The upper level flow shifts back to SW later this week, and Thursday we will see the start of warming, winds and more precipitation.
Snowpack Summary
The past 3-day storm has deposited 25cm at SSV, 16cm at Lake Louise, 12cm at Mt. Stanley and 35cm in Kootenay Park. Wind effects have generally been light, but we expect soft slab formation in alpine areas where N winds have created reverse loading. All of this sits on a very weak snowpack structure. We are on the cusp of a major avalanche cycle.
Avalanche Summary
Small, explosive triggered slab avalanches reported below treeline at Sunshine Village. Road patrol down Kootenay Park showed no new avalanche activity.
Confidence
Due to the number of field observations
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.
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.