Back to wet, cool and possibly a winter similar to the last

Sep 16, 2011

That's it – nine days of summer. The nine days of over 80 degree temperatures in September look like the best we'll get this year.

“Looking at the maps, the large scale maps over the hemisphere, things have really changed. We’ve gone from a summer-type pattern to a much more winter-like pattern," Cliff Mass told KPLU's Keith Seinfeld in this morning's weather report. "The Jet stream is really strengthening and the storm systems are moving south. “

Today's weather will be partly cloudy with not much rain and even some sun breaks with temperatures in the 60s (which is the return of our normal fall- and winter-like temperatures), predicts Mass, University of Washington Professor of Atmospheric Sciences.

Tomorrow a weak front comes in and there could be considerable clouds on the whole western side of Washington and Oregon with temperatures getting up into the mid 60s andn even some scattered showers.

"Not a terrible day but not a great day," he said.

The "real weather" comes in on Sunday

Probably in the morning, said Mass, we'll see the strongest weather system we’ve had in a while. 

“Light to moderate rain over the whole region. Clouds. So it will be like a winter-type storm with extensive precipitation and clouds,” Mass said.

Monday and Tuesday are slightly nicer, but then more storms by Wednesday or Thursday.

This is a hint of what the National Weather Service is modeling for the winter: another La Nina. That means colder, wetter and more snow ... like last year.

You can get the full rundown on the La Nina predictions on Mass's blog.

The general consensus is this coming year's La Nina pattern will be weaker than last year but wet and cool all the same.  (That's in contrast to the El Nino pattern of warmer weather.)

The weekly KPLU feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and repeats twice on Friday afternoons during All Things Considered. The feature is hosted by KPLU’s Health and Science reporter Keith Seinfeld. Cliff Mass is a University of Washington Professor of Atmospheric Sciences and renowned Seattle weather prognosticator.