Hazard ratings reflect conditions in the north and west parts of the region that received the most storm snow. Storm and/or wind slabs are expected to remain reactive to human-triggering. Use a conservative approach to travel.
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. 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 system on the coast spills into the interior bringing light precipitation in the afternoon. Models are currently showing 3-6mm between Wednesday afternoon and Thursday afternoon. On Wednesday, freezing levels are expected to reach around 1800m and alpine winds are expected to become moderate from the SW to NW. On Thursday, freezing levels are forecast to reach around 2500m by the end of the day.
Avalanche Summary
On Saturday in the deeper snowfall areas, a natural avalanche cycle to size 2.5 was reported. These were storm slabs were typically 40-60cm thick but were up to 1m deep in wind loaded areas. On Sunday, explosives triggered numerous more storm slab avalanches. On a glacier feature, one of these explosive triggered avalanches stepped down 250cm to the glacial ice. Human-triggered avalanches were also reported including a remotely triggered avalanche from 35m away. In the Dogtooth, touchy size 1 wind slabs were being skier triggered and explosives produced a size 2 with slab depth of 20-50cm. On Tuesday, human-triggered storm slabs remain a concern for the deeper snowfall areas while wind slabs are a concern for the rest of the region.
Snowpack Summary
Recent snowfall amounts vary greatly across the region. The NW part of the region received up to 60cm while the Dogtooth received around 30cm and the far south received close to zero. At higher elevations, this dense storm snow sits over the mid-March interface which had included crusts, moist snow, wind affected surfaces, and/or old wind slabs. In exposed terrain, strong SW winds had redistributed new snow into wind slabs on leeward features. On Sunday, the snow surface was reported to be wet to around 1800m and moist to around 2200m. The snow surface is now expected to undergo melt-freeze cycles as freezing levels fluctuate overnight. 20-50 cm below the surface is the mid-February facet/crust interface. This interface has not been reactive in the Purcells but has been very reactive in the neighboring North Columbia region. With additional loading, this layer could become a concern. Deeper persistent weak layers in the snowpack that have been dormant for several weeks are not currently a problem but still have the potential to wake-up with major warming or heavy loading.
rbuhler,
Avalanche Canada
