The National Weather Service (NWS) in Portland forecasts scattered showers and a 20-30% chance of thunderstorms across Northwest Oregon and Southwest Washington through Wednesday evening, as a low-pressure system moves through the region. The showers are expected to continue into Thursday, although thunderstorm activity should diminish by late tonight as the system pushes eastward.
Rainfall accumulations are predicted to be light, with totals under 0.10 inches in areas west of the Cascades, while the Cascades themselves could receive up to 0.50 inches. Thunderstorms that do occur may bring locally heavy rainfall, which is expected to minimize concerns about fire starts from lightning strikes.
NWS forecasters noted that if clouds clear this afternoon, the resulting surface heating could increase the likelihood of thunderstorms. However, as the low-pressure system moves out of the area tonight, the chance for storms will decrease. By Thursday, some lingering showers may remain, particularly in higher terrain, but overall precipitation amounts should be minimal.