National Weather Service (NWS) Seattle office forecasters say western Washington can expect a big change in our weather pattern beginning today. A strong upper ridge that brought hot weather over the interior in recent days is moving east and a upper low over the eastern Pacific is heading this way and expected to pass directly across Western Washington on Saturday.
During the transition between the 2 systems, a cool Marine layer will quickly spread across the Puget Sound interior region this evening, with almost complete coverage over the lowlands by midnight tonight.
Saturday could see some thunder and lightning starting at the coast in the morning. The unstable air is expect to then spread into the Puget Sound lowlands in the late morning through Saturday afternoon. Forecasters say while not every western Washington location will get thunder, quite a few will.
“For those with outdoor plans on Saturday, be aware of the considerably cooler and showery weather with the potential for lightning and thunder,” forecasters advise.
Showers may linger Saturday night and into Sunday morning, but Sunday afternoon and evening will be rain-free with skies clearing rapidly areawide. A return to drier weather and near-normal highs is expected starting Sunday afternoon.