Seattle weather: Increasing sun Wednesday, heavy rain Thursday evening and Friday

Wednesday afternoon will be dry, sunny, and cool ahead of an atmospheric river of rain set to hit Thursday evening.

After some early showers, high temperatures Thursday will be in the mid to upper 40s with increasing sunshine. 

Thursday will start off dry and cloudy, but that will change Thursday afternoon and evening as a very wet system pushes into the Pacific Northwest. An atmospheric river will bring heavy rain Thursday evening through Friday to Western Washington and the Cascades. This precipitation will start off as snow on the Cascade passes Thursday evening, but will change to heavy rain overnight.

As of now, 1-2" of rain is expected from Thursday evening to Friday evening for the north and south Puget Sound areas. Rainfall totals in the mountains could hit 3-6" in parts of the Olympics and Cascades. This is concerning for the burn scar areas. Parts of the central sound may be in the rain shadow and only see .50-1" of rain. The picture below gives a nice look at that potential rain shadow.

Winds will be gusty at times, in the 35-45 mph range Friday afternoon and early evening. We might get an isolated 50 mph gust in some of the more usual areas of the NW interior/San Juans. Saturated ground and gusty winds could cause some scattered power outages Friday.

A Flood Watch is in effect for Mason County in the usual areas of the Skokomish River. Moderate flood stage is expected there (but that could change). If we want to send someone Friday afternoon, I bet we’ll be able to get the usual shots of the salmon swimming over the road. I wouldn’t be surprised to see more Flood Watches issued in other counties as we get closer to the event.

This is a great resource to check on river levels and forecasts near you:

After this storm, we will be tracking cooler temperatures and the possibility for more pass level snow in the Cascades. In the lowlands, temps stay chilly next week with overnight lows well into the 30s.