Storm slabs are expected to remain touchy on Monday. Use a conservative approach to travel and stick to mellow terrain until conditions improve.
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 around 5mm but amounts are expected to vary across the region and localized areas could receive larger amounts. Freezing levels are expected to reach around 1700m and alpine winds are forecast to be light-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 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 or within the storm snow. At lower elevations, these slabs were moist or wet. Human-triggered avalanches remain a major concern for Monday, especially for steep alpine features.
Snowpack Summary
At higher elevations, 40-60cm of dense storm snow sits over the mid-March interface which had included crusts, moist snow, wind affected surfaces, and/or old wind slabs. New snowfall amounts taper off substantially towards the south of the region. In exposed terrain, strong SW winds have redistributed new snow into wind slabs on leeward features. Down 50-80cm is the mid-February facet/crust interface. This interface appears to be well bonded in the South Columbia region but in the North Columbia region it is very reactive and has produced numerous large avalanches. There is still 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. On Saturday, the snow surface was reported to be wet to around 1700m and moist to around 2000m. The snow surface is now expected to be undergoing melt-freeze cycles as freezing levels drop overnight.
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.