Storm slabs remain sensitive to human-triggering. 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 - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Unsettled spring conditions are expected on Tuesday. A mix of sun and cloud is forecast with localized convective snow flurries possible. Freezing levels are expected to reach around 1700m with light alpine winds. Good overnight recovery is expected with freezing levels falling to near valley bottom Tuesday overnight. On Wednesday, a warm storm on the coast spills into the interior bringing light precipitation. Models are currently showing 5-15mm between Wednesday afternoon and Thursday afternoon. On Wednesday, freezing levels are expected to reach around 1700m and alpine winds are expected to become moderate from the SW. On Thursday, freezing levels are forecast to reach 2500m by the end of the day.
Avalanche Summary
A widespread natural avalanche cycle occurred on Saturday with storm slabs up to size 3 being reported. On Sunday, natural avalanches tapered off but were still occurring on sun-exposed slopes. Many explosive and human-triggered storm slab avalanches were reported on Sunday. 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. Many remotely triggered avalanches were reported from up to 100m away. On Tuesday, human-triggered storm slabs and persistent slabs remain a serious concern, especially in steep alpine terrain. If an avalanche steps down to the persistent weak layer, very large and destructive avalanches are possible.
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. Anywhere from 80-120cm 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 had redistributed the new snow into wind slabs on leeward features. On Sunday, the snow surface was reported to be moist below around 1800m. The snow surface is now expected to be undergoing melt-freeze cycles as freezing levels drop overnight.
rbuhler,
Avalanche Canada
