The ECMWF actually shows a high of 69 that day in both Charleston and at SEA but 69 at SEA means 73-75 in North Bend on a sunny day. Again... its a little annoying if it is actually that cool in Charleston but more annoying that we would miss a sunny day in the 70s here. Hope it changes!
Charleston would likely still be as warm or warmer than North Bend in that setup. The solar heating of the boundary layer is very intense out here in May, usually underestimated by guidance when there is cold air aloft+offshore winds.
We just got hit here in Ballard by the core of that midlevel shower passing over Seattle. Large raindrops, hence the higher reflectivity on radar, but oddly no cloudcover, or even much of any clouds at all. Mainly just large raindrops amidst sunny skies with some disorganized accas. Maybe the clouds that formed those drops dissipated rapidly?