Regions
Banff Yoho Kootenay.
Weaker midpack layers and the potential for sudden dramatic warming Sunday indicate the need to have options if the sun pops out where you are. In general it is getting better but avoid center punching the steep open slopes for a while still.
Weather Forecast
Rising freezing levels (up to 2000m) with moderate West winds and small amounts of precipitation are forecast for Sunday. Watch for sunny periods that will greatly increase warming.
Snowpack Summary
Valley bottoms have begun to melt out. Warm days and cool nights are bringing us to the edge of spring conditions below treeline. At treeline and above there are suncrusts, windslabs near ridgecrests, and rotten weak pockets in shallower areas. In most areas it is still possible to find a layer of rotten facets in the midpack underlying a slab.
Avalanche Summary
Poor visibility limited observations, but no new avalanches were seen today.
Confidence
Freezing levels are uncertain
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.
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.