A complex and unpredictable snowpack exists. Continued warm temperatures, rain, and periods of sunshine will create the perfect recipe for avalanches. Avalanche Canada has released a Special Avalanche Warning for this region.
Summary
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
An unsettled, winter-like weather pattern will continue through the forecast period. A weaker storm will make way to the Interior tonight and freezing levels will drop significantly in the wake of the cold front. As the front sweeps through, light-moderate precipitation will fall and ridgetop winds will be moderate from the west. On Saturday and Sunday, accumulated precipitation 5-20 mm with ridgetop winds blowing strong from the west and freezing levels steady around 1900 m. The general weather pattern is expected to bring multiple systems but the confidence in the exact timing, track, and strength of each system is poor.
Avalanche Summary
Warm, wet and windy weather on Thursday was responsible for a widespread natural avalanche cycle which occurred on all aspects above 1900 m up to size 2.5. Numerous human triggered slab avalanches up to size 1.5 and loose wet avalanches up to size 1.5 were also reported. I suspect natural avalanche activity will likely continue with warm temperatures, strong winds and periods of sun and rain. Avalanches failing on the mid-March persistent interface will be large and destructive.
Snowpack Summary
A rain soaked upper snowpack exists to 2300 m. Above that elevation, new, dense storm snow (25 cm) has added load over the mid-March interface 40-60 cm down. This interface is comprised of a series of crusts, wind affected surfaces, and old wind slabs which has recently come alive and has been reactive, especially in the North (Revelstoke and surrounding area). Snow-pit testing varies regionally, with this interface generally showing moderate to hard results with a resistant-sudden planar fracture characteristic. Recent snowfall amounts taper off towards the south of the region. Strong SW winds had redistributed the new snow into wind slabs on leeward features. Digging deeper, 50-80 cm is the mid-February facet/crust interface which has also been reactive with larger loads like smaller avalanches stepping down to this interface. Regardless, both layers seem to have very similar sensitivity to triggers and large and destructive avalanches are resulting.
swerner,
Avalanche Canada
