Weak atmospheric river brings first round of fall rains to Portland area

PORTLAND, Ore. (KOIN) -- The first round of autumn rains arrives Wednesday as temperatures plummet nearly 30 degrees around Oregon and Washington.

Rain showers aren't expected to start along the Willamette Valley until the late-morning to early afternoon. Scattered showers will help drop temperatures into the upper 60s to low 70s along the valley.

Wednesday's rain showers are technically from a weakening atmospheric river. The bull's eye still remain over British Columbia, but the outskirts of the atmospheric river will produce Oregon and Washington's showers mid-week. The weakening atmospheric river has minimal impacts, but is the first of the autumn season. Rain accumulation totals will only amount to a quarter-inch for most locations. Coastal communities could see closer to a half-inch of rain.

The wet weather will keep temperatures cool Wednesday afternoon. Clearing showers and clouds will help cool early morning lows Thursday to the upper 40s to low 50s. That's where fall-like conditions are expected to last through the end of the week and into the weekend across the Pacific Northwest.

A stray rain shower or two is possible as clouds come and go along the Willamette Valley late in the week. A drier and sunnier end to the weekend and start of next week is likely.