Atmospheric river to bring drenching rain, possible flooding

An anticipated atmospheric river with a firm tap of Pacific moisture will bring more rain to the area starting Thursday afternoon and lasting through Friday morning.

It will also be breezy at times with the rain though high winds aren’t expected. Rainfall through Friday will total around 1 to 2 inches in the Puget Sound region, though the South Sound could get a little more, 3 to 4 inches at the coast, and with high snow levels of 8,000 to 9,000 feet in the mountains, 5 to 8 inches of rain will fall.

Of course, rain like this will cause some urban flooding from clogged storm drains late Thursday through Friday morning before the heavy rain subsides Friday afternoon and evening.

We have a flood watch in effect for all of western Washington as rivers will spike higher and most of our rivers around the area will reach flood stage either Friday or Saturday, depending on proximity to the Cascades. River levels will be notably higher than what we’ve seen so far this fall, with many of our main rivers forecast to reach the “moderate” flood category. River stages and forecasts can be found here.

Heavy rain will increase this afternoon and evening. A Flood Watch will kick in this afternoon. Moderate level flooding is possible on some area rivers. #NickKnows #wawx pic.twitter.com/DNCeIJ8NoI

— Nick Allard (@NickAllardKIRO7) November 11, 2021

Highs will be warm in the upper 50s and it will be a little breezy with the chance of isolated thunderstorms Thursday night into Friday.

The extra moisture in the soil will also produce an increased risk of shallow landslides even after the rain ends late Friday.

Saturday will be mainly dry so it will be a nice break before some light rain arrives Sunday through Tuesday. This later rainfall won’t cause flooding concerns. We could get a bit more dry weather late next week.

By Meteorologist Nick Allard, KIRO 7 News