Weather Synopsis for Thursday night through Saturday

430pm update: Adjusted sky cover for Friday. 

A deep low pressure center stalled off the Washington coast continues to spin showers over the area in SSW flow aloft. Showers will be the heaviest and most persistent over the Olympic peninsula (especially the southern slopes of the Olympics) today and tonight closer to the low. Further inland, showers are becoming more intense this afternoon with daytime heating and there have been a few lightning strikes over the western WA lowlands. We have a cool, unstable air mass overhead and convective showers may be heavy at times through midnight, contain graupel, along with the chance of thunderstorms mainly over the foothills. Snow levels will plummet to around 3000-3500' during showers. Shower activity and moderate to locally strong ridgeline winds will continue through this evening and begin to ease overnight. 

The low pressure system will pull away from the Pacific Northwest and drop south along the coastline Thursday night and Friday. There should be plenty of leftover cloud cover tonight from the showers that sticks around on Friday. With a weak upper level trough overhead, we'll see a renewed threat of afternoon mountain showers. With the flow aloft becoming light out of the north, showers are more likely to fire up over the north Cascades and along the east slopes of the Cascades and slowly drift S-SW. Shower coverage and intensity will be less compared to Thursday. Freezing/snow levels will be a bit warmer on Friday as well.

The upper level ridge will build further into British Columbia on Saturday with continued northerly flow aloft over the PNW.  We can expect dry conditions with freezing levels topping out around 6000' and mid-mountain temperatures in the mid 30s to low 40s.