The cooler weather of Memorial Day is replaced by much warmer weather for all of Washington as we head into Thursday. While we’ll have sunshine and highs in the 70s and low 80s in much of Western Washington, the temperatures will be even hotter east of the Cascades, with 80s and 90s common.
Meanwhile, the upper-level low-pressure system that brought that Memorial Day rain around some of the area will send one round of thunderstorms toward Washington late in the day Thursday before it exits the western part of the U.S.
As of Wednesday night’s forecasts, it looks like the threat for thunderstorms Thursday and Thursday night is greatest from the Cascades eastward across central and eastern Washington. In fact, the Storm Prediction Center has much of the central and eastern part of Washington in a “slight” risk for severe thunderstorms on Thursday and Thursday night. This can be considered a “2” on a scale of one to five. While “slight risk” doesn’t sound significant and is the lowest threat of severe thunderstorms on the SPC risk scale, that level of severe threat is unusual for Washington!
(A thunderstorm is deemed “severe” if it produces winds of 58mph or greater, hail of one inch diameter or larger, or a tornado.)
I expect a few isolated thunderstorms in the central and south Cascades late Thursday afternoon, but as we head later in the evening, a band of strong to severe thunderstorms will move from southeast to northwest across much of central and eastern Washington. These storms will weaken after midnight as they move toward the Canadian border.
The greatest severe weather risk appears to be from damaging wind gusts, with isolated large hail possible too. The tornado risk in Washington appears relatively low, with a slightly better chance earlier in the day down in central and eastern Oregon.
West of the Cascades, the threat of thunderstorms is far lower, though we could see some lightning strikes on the eastern horizon after dark as the storm chances along and east of the crest will continue into Thursday night. But for the Western Washington lowlands, we’ll just watch for a few rain showers Thursday night and Friday with sharply cooler temperatures topping out only in the 50s to low 60s Friday.
We’ll certainly update this threat for storms through Thursday on KIRO 7. Be sure to download the KIRO 7 Pinpoint Weather app for the latest forecast updates and Pinpoint Stormtracker radar.