Confidence
Fair - Intensity of incoming weather is uncertain on Monday
Weather Forecast
The strong ridge of high pressure is expected to chew up a weak system that attempts to enter the region Sunday. On Monday, we'll see some mid & high level cloud as said system limps across the province. Winds are expected to be light out of the NW for most of the day before switching to the NE in the evening as what's left of the system exits to the east. The region will likely see a little bit of upslope conditions which could result in a bit of snow, at the moment the forecast calls for 6 - 8 cm, but it should be noted that this type of activity is hard to forecast. Skies clear overnight Monday. Tuesday starts off cool and cloudy. We may even see the occasional flurry as a weak trough passes over the region. High pressure steps back in around lunch time and should remain in place through Wednesday.Monday:Alpine Wind: NW20Alpine Temp: -8Precip: 6-8 cm in the evening.Freezing Level: 1100mTuesday:Alpine Wind: W-NW 10 - 30Alpine Temp: -4Precip: NilFreezing Level: 950m
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.