Weather Forecast
Sunday: The ridge of high pressure that has dominated the recent weather pattern rebuilds, while lingering moisture from a weak disturbance will bring mid-level cloud. Winds will be very light and little to no significant precipitation is expected.Sunday:Alpine Temps: -5Freezing Level: 1200mPrecip: NilOutlook: Another weak shortwave will bring light precipitation Monday into Monday night. Mainly dry conditions are forecast on Tuesday & Wednesday. Freezing levels look to remain near 1200 m early next week. The models currently show a change in pattern way out in the future, on Day 8, which is Friday Feb. 17th. As many of you know, forecasting anything that far out can only be done with very little confidence.
Avalanche Summary
Last weekend numerous highly destructive persistent deep slab avalanches involving basal facets and depth hoar occurred in the alpine and ran to valley bottoms (check out the Avalanche Image Gallery under the Library tab for some photos).
Snowpack Summary
In Elk Valley North and the Crowsnest, the average snowpack depth at treeline is 150 cm. In Elk Valley S and the Flathead the snowpack depth is closer to 2 m. Surface hoar is continuing to develop on sheltered slopes at all elevations combined with near-surface facets at lower elevations and surface crusts on sun-exposed slopes. A well settled and strong snowpack sits on weak basal facets and depth hoar, which seem to be fairly widespread throughout the region. This deep persistent weakness was activated by warm temperatures last weekend, but cooler temperatures have once again reduced the sensitivity to triggers. Highly unpredictable glide cracks are also opening up, primarily on slopes with smooth ground cover. These full-depth gaping 'crevasses' could release without warning or act as a significant terrain trap.
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.
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.