A vigourous storm system is forecast to bring heavy amounts of snow and moderate to strong winds to the region Wednesday night through Thursday. Highest amounts of precipitation are expected in the north of the region.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Thursday
Weather Forecast
WEDNESDAY NIGHT: Snow, accumulation 15-25 cm / Moderate southwest wind / Alpine temperature -7 C THURSDAY: Snow, accumulation 20-30 cm / Moderate to strong southwest wind / Alpine temperature -3 C / Freezing level 1200 mFRIDAY: Snow, accumulation 10-15 cm / Moderate to strong south wind / Alpine temperature -7 C SATURDAY: Scattered flurries / Light to moderate west wind / Alpine temperature -6
Avalanche Summary
Expect to see widespread avalanche activity on Thursday as a vigorous storm passes through the region Wednesday night through Thursday.One notable recent avalanche occurring just north of the region, was a large (size 2.5) persistent slab release that was skier triggered below a ridgecrest on a southwest aspect in the Connaught Creek area in Glacier National Park.
Snowpack Summary
20-30 cm of new snow falling Wednesday through the day and night will add to the 30-40 cm of snow that fell last weekend. Moderate to strong southwest winds along with a rise in freezing level associated with the latest weather system is expected to promote storm slab development at all elevations.An aspect-dependant mix of facets, surface hoar, and sun crust buried mid-December now 80-140 cm deep, is reported to be less reactive in snowpack tests and showing signs of strengthening. A heavy trigger might still coax reactivity out of steep north and east facing slopes between 1900-2300 m or a steep south-facing slope in the alpine.The lower snowpack is generally strong and settled, with a crust that formed in late October near the bottom of the snowpack.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.