Our First Heatwave? Possible Early Next Week

June has been about as “normal” as it gets.  Temperatures here in Portland are running just slightly warmer and slightly drier than average.  We have two more cloudy and cool days ahead with showers at times; we could still end up above average for the month I suppose.

Beyond Wednesday?  Models have been advertising (for many days) strong upper-level high pressure developing over the Western USA.

Here are the key points:

• The end of this week MAY be the “turning of the summer switch”.  We often start our real summer (abundant sunshine and dry weather) suddenly.  Not always, but more often than not it happens that way.  That may be about to happen.
• 80+ temps arrive Friday and continue through at least the middle of next week…high confidence in this.
• 90+ temps are possible Monday-Wednesday of next week…somewhat good confidence with this.
• Near or above 100 degrees?  It’s looking likely most areas east of the Cascades below 2,000′ this weekend through early next week.  Some models are showing it nearly that hot here in the western Valleys the middle of next week too, very low confidence on this for now.

 

Here is the 12z ECMWF and 00z GFS 500mb chart for next Tuesday morning.  That is a hot ridge!

Of course there have been variations on the strength of the ridge and location.  The closer to us it ends up the warmer we get.   The 12z ECMWF above was particularly hot with 850 mb temps around +27 for the 2nd of July (next Tuesday).  If so, the weak offshore flow shown (under 595+ heights!) could easily put us over 100 degrees.  Luckily the ensemble chart 

shows it was at the high-end, with the average more like the 12z GFS’s +22-23.  That’s still would put us well into the 90s Tuesday/Wednesday next week.  Here is the new 00z GFS ensemble chart:

A little warmer than earlier runs, but the hot operational model is still warmer than its ensemble members.  Quite a bit of uncertainty on how far west the upper-level ridge builds.

One thing sticks out on all the model runs…we are headed into a warmer and most likely dry weather pattern as June ends and July begins.

Chief Meteorologist Mark Nelsen

ECMWF Monthly Maps

Last night’s run of the ECWMF out to one month…looks real hot next week and then above average beyond that.  This weekend MIGHT be the start of Pacific Northwest summer.