MOUNTAIN WEATHER FORECAST

Time and Day: 0700 Wednesday

The Snapshot: 4" overnight, showers tapering this morning. The precipitation should start as snow this afternoon and then is expected to turn to rain overnight and then back to snow Thursday morning.

The Science: The convergence showers that fell overnight are ending this morning with as the leading edge of a large atmospheric river takes aim from Hawaii. Overriding warm air and heavy precipitation will be associated with this feature. Easterly winds at pass levels are expected with this event.  However, there is cold air in place on the east side of the crest, with some luck Stevens Pass may get through or even avoid the short-lived warm up. A deep (966mb) surface low tracking up the coast towards British Columbia brings a cold front across Western Washington early tomorrow morning.  Temperatures fall back down but also rapidly tapering precipitation. Another front will cross Stevens Pass Thursday night for light-moderate snow.

The Long Range: The rain vs. snow game is back for Friday night/Saturday morning. Light snow showers Saturday and Sunday.  

Precipitation Ending at 4 am: Today 24hr water = 1.0 Snow = 7-10” Tomorrow’s 24hr water = .25 snow = 1-3” Trend and Timing: Heavy snow is beginning this afternoon, increasing in the evening hours, potentially switching to rain between 10 pm and 1 am,  then back to snow by daybreak.

24hr temperature ending at 4 am tomorrow: Low: 26 High: 34 Freezing level: 3500-6000’- 4000.' Trend and Timing: Free air freezing levels will rise throughout the day until around midnight, then cool back down.

24hr Winds (mph) ending at 4 am tomorrow: Base: 10-15 E, then 10-15 WSW (?) Ridge Top: 15-20 SE, then 15-25 SW Trend and Timing: Easterly winds will strengthen today. The big question will be whether they shift westerly overnight.

DV