The danger ratings are based on areas that will receive larger snowfall amounts. Areas that receive less snow will have lower danger ratings than posted.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Tonight and Thursday: Cloudy with precipitation starting overnight and carrying into the day, most accumulations will be along the western slopes of the Rockies. Between 2-10cm expected across the region. Freezing levels between 1300-1500m. Highs around -3 in the alpine. Strong to extreme south west winds at ridgetop.Friday: Moderate amounts of precipitation are forecasted, in the 10-15 cm range with moderate south west winds. Freezing levels rising to 1200m.Saturday: A brief break between systems, mostly cloudy with precipitation starting again in the evening. Mild temperatures with light to moderate northerly winds.
Avalanche Summary
Several natural, snowmobile and skier triggered avalanches up to size 2 running in the the recent storm snow were reported yesterday and today.
Snowpack Summary
Precipitation amounts will vary across the region. Expect between 2-10 cm to fall on Thursday, with possibly more (up to 15cm) near Fernie and the Flathead adding to the 20-30cm of recent storm snow. This new storm snow has formed a slab due to warming temperatures and variable strong to extreme winds. This slab is likely to have poor bonds with underlying hard slabs in the alpine and facets or surface hoar in sheltered areas at treeline and below. At treeline, approximately 40 - 60 cm below the surface exists another surface hoar and/or sun crust layer, that was buried late in January which could become active. The mid snowpack is strong and supportive. Deeper persistent layers have been dormant, however they could wake-up with a heavy load such as a cornice drop or large slab avalanche. The recent avalanche activity is a sign of the unstable snowpack conditions. With more load from forecasted precipitation and wind, expect avalanche sizes and occurrences to increase.
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.