Warm Weekend Ahead

May 2, 2013

Summer is arriving early, or at least a preview of summer is.  We made it to 79 in Portland today:

PLOT_Highs_Metro

Troutdale was the warm spot in the metro area with a gusty morning east wind that went calm during the warmest part of the day; that’s always a perfect setup to maximize your high temperature here in the metro area.

The Weekend Highlights:

  • The Ocean Beaches will be in the 75-85 degree range Saturday, possibly Sunday too…Summer!
  • Friday-Sunday = Summer weather inland…Highs 78-85 and sunny
  • Gusty northeast wind for the entire metro area Saturday, possibly Sunday too.
  • Cooling next week, but still above average for early May.
  • No sign of rain or at least a dousing rain for at least another week.

 

More of the same is on the way for the next 3-4 days as an upper level ridge builds just to our west and then north.  This isn’t quite the usual setup where a large ridge settles in over the West Coast.  Instead we get more of what we call a “Rex Block” with an upper level high pinched off by a developing upper level low off the northern California coast.  Here’s the 500mb chart for Sunday morning:

500vor.72.0000

This is often a stable pattern (for several days at least).  In our case we will be in the strong easterly flow between the two. Take a look at the cross-section over Portland from the WRF-GFS model:

kpdx.th

You can see strong easterly wind developing Saturday and Sunday with wind speeds 40-50 kts between 3,000-5,000′ later Saturday and early Sunday.  That’s unusually strong for early May.  That’s a strong downsloping wind that should give the entire metro area a windy day Saturday and probably Sunday too (maybe a bit less that day).  Due to that strong wind, I lowered Saturday’s high temp to 80.

Temperatures will be warmest Sunday as the wind backs off a bit and the atmosphere warms.  Models seem to have settled on a +14 or +15 temp at 850mb that afternoon.  Obviously we have perfect conditions with a well-mixed atmosphere with the east wind, so my chart says 84-87 is likely that day.  I’ll stay with the 85 we’ve been forecasting for a few days.

Beyond Sunday, that upper level low appears to either wander around off the California coast or gradually move closer to us…very uncertain and a real pain to forecast.  Models still show well above average temperatures, but with some sort of onshore flow.  Ahh, the “partly cloudy and 70 degrees” early May forecast.  Seems to be a safe bet for the 2nd part of the 7 Day forecast.  If the low were to move closer to us we could possibly get into a “thunderstormy” pattern, but I don’t see that…for now.

Here are the latest two (18z GFS & 12z ECMWF) ensemble forecast charts:

tseries_850t_000-384_Portland

tseries_850t_000-360_Portland

Both show above average temps through mid May…that cold and showery weather must be waiting in the wings for Rose Festival time???

Speaking of that, here is the monthly run of the ECMWF, separated into weekly maps.  Appears to be some troughing near the end of the month?

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA
I’m off for a day tomorrow so no posts (probably) until Monday afternoon/evening.  Enjoy the early taste of summer!

Chief Meteorologist Mark Nelsen