AVOID ALL AVALANCHE TERRAIN. The storm will reach its apex tomorrow morning with a confluence of rising freezing levels, heavy precipitation and strong winds.
Heavy snowfall, strong winds and rising freezing levels will contribute to the new snow rapidly forming slabs at higher elevations that will increase in both reactivity and destructive potential. Below treeline hazard reflects the potential for large avalanches to initiate at upper elevation bands and run to valley bottom.
The interior ranges will continue to see the effects of the atmospheric river that arrived on Tuesday. Precipitation will initially fall as snow at upper elevations and rain lower. Strong to extreme winds will accompany this precipitation with freezing levels rising to 2400m by Wednesday morning.
Tuesday night: 25-35mm of mixed precipitation is expected overnight accompanied by strong to extreme southwest winds. Freezing levels will start at 1500m climbing to 2400m by early morning.
Wednesday: 10-20mm of mixed precipitation is expected, heaviest in the morning. 2400m freezing levels will drop slightly reaching 1500m by end of day. Mountaintop winds will be strong to extreme from the southwest. Another 5-15mm can be expected late afternoon and overnight, with winds tapering into the moderate to strong range.
Thursday: The system will gradually pass. Flurries tapering, up to 5cm in the morning. Freezing levels lowering to 500m throughout the day. Light westerly winds.
Friday: Mainly clear skies and no new precipitation. Freezing levels at valley bottom. Light winds from the northwest.
There has been very few reports in the past 24 hours, with most folks staying out of the backcountry during this atmospheric onslaught. I suspect a widespread natural avalanche cycle will occur, with the potential for large avalanches to run full-path into valley bottom. Strong winds and rapidly rising freezing levels will only increase the reactivity and destructive potential of storm slabs.
On Sunday, following the last major storm event, a widespread natural storm slab avalanche cycle was observed up to size 3 and running to valley bottom along the Highway 1 corridor near Revelstoke. Explosive control work at alpine and treeline elevations produced storm slabs up to size 2.5, accumulating loose wet in the track and running full path.
Significant new load has been added to the snowpack, with over a meter of moist new snow accumulating at higher elevations. At lower elevations, a mix of rain and snow has promoted a wet and saturated upper snowpack.
The mid-November crust is up to 5cm thick and found down 70-150cm with faceting below the crust. The lower snowpack contains several early season crusts which appear well bonded.
Snowpack depths exceed 300cm at treeline and alpine elevations, while below 1600m the snowpack decreases rapidly with elevation.
