Highway 93 from Athabasca Falls to the Saskatchewan River Crossing is now closed (as of 14:00 Thursday March 29) for the anticipated completion of avalanche control work Friday March 30 and Saturday March 31. Please plan accordingly
Weather Forecast
Snow is forecast to begin falling over the region Thursday evening as a strong pacifc flow collides with an arctic front almost directly overhead. 15 to 20cm are expected through Friday afternoon. Watch for winds to shift from SW to E Friday morning and temperatures to drop as the cold air pushes back. Skies will clear Saturday under the arctic air
Snowpack Summary
Wind slabs up to 50cm thick sit on a sun-crust on solar aspects and facets on polar aspects. Heating in early March created some strength in the upper snowpack (mainly BTL and on solar aspects) however some deep slabs resulting from recent loading on N and E aspects in the lower alpine indicate that weakness in the mid and lower snowpack persist.
Avalanche Summary
A morning patrol of the 93N revealed several slabs on the west side of the highway. A few slabs up to 40cm thick were seen on solar slopes. Several slabs were seen on N and E slopes from 2300m to 2600m. Most of these were 20 to 60cm deep however two sz 3 slabs were seen where cornices had likely failed taking slabs 300m wide and 80cm to 100cm deep.
Confidence
Intensity of incoming weather systems is uncertain on Thursday
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.