A complex and unpredictable snowpack exists, especially in the northern half of this region. Avalanche danger will rise with rapid warming, precipitation and strong winds.
Summary
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A Pacific frontal system reaches the coast today and affects the Interior regions tonight through the forecast period. Warm air aloft will invade the region until Friday night with associated freezing levels near 2800 m. A trailing cold front will bring light precipitations and strong ridgetop winds. On Thursday, light precipitation amounts up to 3-10 mm is expected, ridgetop winds strong from the SW and freezing levels rising to 2700 m. On Friday, solar radiation may come into play with a mix of sun, cloud and freezing levels steady at 2800 m. Unsettled conditions on Saturday will bring light precipitation amounts 2-10 mm, ridgetop winds moderate from the NW and freezing levels dropping to 1500 m.
Avalanche Summary
On Tuesday, numerous natural solar induced slab avalanches were reported, with the majority being size 1. We also received numerous reports of human triggered slab avalanches up to size 2, mostly running on N-NE aspects and above 2000 m. Explosive controlled avalanches were also initiated up to size 3. Most of these avalanches from Tuesday failed within the recent storm interface and on the mid-March persistent interface. With a warm, wet and windy storm in the forecast natural and human triggered avalanche activity will likely continue. Avalanches that fail on the deeper weak interfaces will be large and destructive.
Snowpack Summary
At higher elevations, 40-60 cm of dense storm snow sits over the mid-March interface which included crusts, wind affected surfaces, and/or old wind slabs. This interface 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 resistent-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. There is some concern for this layer to wake-up in the South Columbia region and storm slab avalanches have the potential to step down to it. Snow surfaces are wet to around 1700 m and moist to around 2200 m.
swerner,
Avalanche Canada
