Regions
Banff Yoho Kootenay.
A beautiful day in the mountains, and strong winds aloft kept the snow surface mostly cool except in sheltered, south facing areas. Next few days - classic SPRING conditions. Start early and finish early as we transition into melt/freeze conditions.
Weather Forecast
A strong ridge of high pressure is settling into the region and the next 5 days look to be sunny and warm. Spring is here! Expect highs over the next few days between 5 and 10 degrees, and freezing levels will hit 2300m on Friday. Winds will generally be light at treeline, but will continue to smoke along between 35-60 km/hr at high elevations.
Snowpack Summary
Last 5 days of storm snow totalled 35cm at Bow Summit, 49 cm at Lake Louise and 32cm at Sunshine. Strong winds have blown this snow into windslabs at treeline and above, and now the solar influence will weaken the snowpack structure in the afternoon. Cornices are a major concern (see avalanche activity) and seem to be waking up the deep facets.
Avalanche Summary
A large (size 3) slab avalanche triggered by a cornice fall was observed on the Simpson Ridge, beyond the Sunshine backcountry. Also, a pair of skiers triggered a size 2 avalanche on the obviously windloaded roll to the north of Quartz Ridge - this one could have been predicted as that is a fat, convex roll. Generally the wind kept the snow cool.
Problems
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.