Storm slabs are expected to remain touchy on Monday. A deep weak layer has also been reactive and has resulted in very large avalanches. Use a conservative approach to travel and stick to mellow terrain until conditions improve.
Summary
Confidence
Fair - Due to the number of field observations
Weather Forecast
A cold front should bring light snowfall to the region on Monday morning and convective flurries are expected in the afternoon. Models are currently showing 5-10mm but amounts are expected to vary across the region and localized areas could receive larger amounts. Freezing levels are expected to reach around 1500m and alpine winds are forecast to be moderate from the SW switching to NW in the afternoon. Good overnight recovery is expected through the forecast period with freezing levels falling to valley bottom each night. Unsettled conditions with convective flurries are expected for Tuesday. Freezing levels should again reach around 1500m in the afternoon and alpine winds should be light. A weak ridge of high pressure is expected for Wednesday bringing a mix of sun and cloud.
Avalanche Summary
A widespread natural avalanche cycle occurred on Saturday with storm slabs up to size 3 being reported. These avalanches were failing on a crust layer from mid-March and also stepping down to a deeper crust/facet layer from mid-February. At lower elevations, these slabs were moist or wet. In the N Columbia region, many remotely triggered avalanches were reported from up to 100m away. Unfortunately, a fatality occurred in the Cariboo region from a very large avalanche that released on the mid-February layer. This layer is expected to remain touchy for longer than normal and human-triggered avalanches remain a major concern for Monday, especially for steep alpine features.
Snowpack Summary
At higher elevations, 40-50cm of dense storm snow sits over the mid-March interface which had included crusts, moist snow, wind affected surfaces, and/or old wind slabs. Anywhere from 70-100cm now sits over the mid-February persistent weak interface. This interface has recently been very reactive and has produced very large avalanches. In exposed terrain, strong SW winds have redistributed new snow into wind slabs on leeward features. On Saturday, the snow surface was reported to be wet to around 1600m and moist to around 1900m. The snow surface is now expected to be undergoing melt-freeze cycles as freezing levels drop overnight.
rbuhler,
Avalanche Canada
