Purcells

Fair - Forecast snowfall amounts are uncertain on Thursday

The storm on Wednesday was a little bit slower and a little further west than originally forecast. Heavy precipitation is forecast for Wednesday evening and overnight into Thursday morning, bringing about 20 mm of precipitation. The wind is forecast to be about 70km/Hr out of the south-southeast tonight at ridgetops. As the freezing level drops tonight, the precipitation could become up to about 30 cm of snow at higher elevations. The storm is expected to move east into Alberta by Thursday noon. A ridge of high pressure is expected to move into the region by Friday bringing clear skies and light winds with freezing levels rising to about 1400 metres during the day.

Explosive control on north-northeast aspects on Tuesday caused size 2.5 avalanches that failed down about 60 cm most of the time, but failed down 200 cm on one slope. There were some explosive controlled avalanches up to size 3.0 that released in the storm snow down about 70 cm on various aspects on Monday. Avalanches releasing on the deeply buried mid-February surface hoar are becoming less likely. Avalanches may step down to the weak layer of facets or depth hoar on a crust that was buried in October. There was another report of a skier who propagated a size 3.0 avalanche on the weekend near Golden; the skier was fully buried and quickly rescued by their companions (the incident is attached to this bulletin).

The new storm has started to develop new windslabs on northerly aspects. The recent storms have added up to about a metre of snow in the region. High freezing levels have consolidated the storm snow into a cohesive slab that may be propagated remotely. The storm snow slab is sitting on top of a sun crust that was buried on March 27th on southerly aspects, and above wind affected surfaces that may be facetted on northerly aspects. Operators are reporting moderate shears on the storm snow interface. Forecast new snow will add another load that may cause another cycle of natural avalanches or easily triggered avalanches. Cornices are reported to be very large in the region, and new cornice growth is expected with forecast new snow and strong southerly winds. The mid snowpack is well settled and strong. There is a weak layer of facets or depth hoar in shallower snowpack areas that may fail with initial warming of the snowpack. There is also a weak layer of of facets or depth hoar above a crust at higher elevations where there was already snow in October.