Steady inputs of snow and strong wind will maintain dangerous avalanche conditions in the region - especially on Wednesday, when snowfall rates, winds, and temperatures all rise together. This will be a time to avoid avalanche terrain.
Heavy snowfall followed by strong wind has formed a widespread new storm slab problem. Continuing stormy conditions are likely to increase the size and reactivity of slabs. Another strong storm pulse arrives Tuesday night.
Monday night: Cloudy with continuing scattered flurries bringing about 5 cm of new snow. Moderate to strong southwest winds.
Tuesday: Mainly cloudy with continuing light flurries bringing about 5 cm of new snow, continuing overnight. Moderate to strong southwest winds, easing over the day. Alpine high temperatures around -12, warming overnight.
Wednesday: Cloudy with increasing snowfall bringing 15-30 cm of new snow over the day, easing overnight. Moderate to strong south winds. Alpine high temperatures around -8, cooling overnight.
Thursday: Cloudy with continuing scattered flurries bringing 5-10 cm of new snow. Light variable winds. Alpine high temperatures around -12.
We don't yet have reports of avalanche activity from the weekend storm, but it's safe to assume that a natural avalanche cycle occurred during periods of heavy precipitation over the weekend and potentially again on a more limited scale during Monday's wind event.
Looking forward, it will take some time for the new snow to stabilize and bond, but forecast weather inputs are likely to stall this process. As a result, slabs are likely to remain sensitive to human triggering on Tuesday before increasing again in distribution, reactivity and destructive potential on Wednesday.
About 30 cm of new snow accumulated in the region during the storm on Saturday night and Sunday, with snow totals from Thursday to Sunday closer to 60-70 cm. A dramatic uptick in south winds on Monday morning likely led to much of this snow forming storm slabs (or wind slabs) at all elevations and aspects.
This widespread new storm slab overlies multiple layers of overlapping recent wind slab and old hard wind slab formations that existed previously in all but the most sheltered areas.
Snow depths at White Pass average around 150 cm; deeper locations (higher terrain west of the highway) have as much as 200 cm. It's reasonable to expect a thin snowpack composed mainly of sugary facets in the Wheaton Valley, although we don't yet have observations to confirm this.
