Cooler Thursday, Then A Hot Weekend!

July 15, 2015

9pm Wednesday…

That was a windy bike ride that I just took between shows!  Obviously not a stormy-type of wind, but gusts 25-30 mph coming in from the northwest.  Quite a chill in the air (for July) too.  We are getting a strong push of cool marine air as an upper-level disturbance passes by.  The breezes and cool temps are refreshing after an 83 degree day here in Portland.

The result will be most noticeable tomorrow morning in the form of low clouds in the northwest part of Oregon and southwest Washington.  These “northwesterly pushes” don’t tend to have the extensive thick low cloud cover in the mornings that southwest pushes do, so temperatures won’t be dramatically cooler tomorrow, just down about 5 degrees.  You can see our RPM model forecast of cloud cover…

RPM_Cloud_Rain_Fcst

After that it’s on to sunshine again in the afternoon.

I’ve upped forecast temperatures for this weekend a few more notches today.  It’s looking pretty obvious that our current onshore flow will go flat or even slightly offshore.  850mb temps jump from +9 tomorrow morning to +20 (celsius) Saturday afternoon.  It’s going to get hot!  According to my July “magic chart”, that should get us to at least 90.  Easterly wind flow situations have been as warm as 98 in these conditions.  We should be closer to 90 than 98 both Saturday and Sunday.  Either way we’re likely going to add two more 90 degree days to our summer total.

MarkHeatwaveStudio_90DegreeTemps

That’ll make 18, just 7 away from breaking the all-time record.  If we have typical summer weather through early September, there’s a chance we’ll break that record of 24 days set in 2009

It looks unlikely that we’ll hit 90 after that for at least a week.  Take a look at the ECMWF ensemble chart

tseries_850t_000-360_Portland

you see the big rise this weekend and then a big fall as an upper-level trough tries to set up over us later next week.

It is interesting to note one week ago it appeared we would have a cool a showery weekend; now that weekend will be in the 90s.  In this case it was because models were too far west with the trough dropping over us.  Instead of coming over us, it’s dropping into the Intermountain region Friday and Saturday.

Enjoy the cooler temps tomorrow!

Chief Meteorologist Mark Nelsen