Today, some of the media are forecasting general showers over western Washington, but the reality will be very different between north and south. A tight upper level low is moving SE into Oregon (see graphic above) and a band of clouds and precipitation are wrapping around it (see image).
Try this animation of the visible satellite imagery:
http://sat.wrh.noaa.gov/satellite/loopsat.php?wfo=sew&area=west&type=vis&size=1
The current radar picture shows that showers are limited to the south Sound area...so north of Seattle it might be completely dry. This kind of pattern brings precipitation into eastern Washington and of course the Cascades. In fact, with easterly flow approaching the Cascades, normally dry locations could get hit by heavy showers. The air will be somewhat unstable after the surface heats, so thunderstorms are possible over eastern WA and over the mountains. As the low moves SE the showers should follow.
If you dig down on the Seattle National Weather Service web site you can see their graphical forecasts (http://www.weather.gov/forecasts/wfo/sectors/sew.php)...here is their prediction today for 12-h precipitation ending 5 PM--the probability of rain varies from 83% in Olympia to 32% in Bellingham.So advice for today....want dry condition...go north.
