Could It Hit 100 This Weekend?

June 1, 2016

The short answer is YES, it’s possible we hit 100.  But at this point it appears we’ll end up a few degrees short and right now our forecast doesn’t have a triple digit number in it.  Regardless, get ready for a record-breaking hot (and possibly historic) first weekend of June!

Highlights:

  • Get ready for a little RAIN overnight. Anyone north of Salem could see a shower/sprinkles by daybreak.  Cover up anything that shouldn’t get wet!  Not much rain, but a little is possible west of the Cascades.
  • Friday will be much warmer, back up into the mid 80s
  • Saturday & Sunday High temperatures will be somewhere between 94-98 degrees in the Willamette Valley and lowest elevations of SW Washington both days.  This is scorching hot anytime in the summer but especially so this early in the season
  • Oregon Coast This is NOT a pattern for hot weather at the coast.  Likely in the 70s both days out there.
  • Just a two-day heat event Strong onshore flow Monday means highs drop at least 10 degrees, back into the reasonable 80s.  Cooler yet Tuesday and beyond.

 

Let’s talk about how hot it COULD get this time of year:

Only once in Portland airport’s recorded weather history has the high temperature gone above 98 before the 3rd week of June.  Got that?  At the airport we hit 100 in late May 1983.  There were early season heatwaves in June 2003 and June 1970.  In that 2nd event downtown hit 100 degrees for one day.  You can see that EVERYTHING HAS TO BE JUST “PERFECT” IN THE METEOROLOGICAL WORLD TO GET PORTLAND TO 100 DEGREES BEFORE LATE JUNE.  It’s a tough number to get this early in the season.  For that matter we often go a summer or two without seeing 100 degrees.  We’ve only hit it 4 times in 6 years!

MarkHot_HeatWave_HottestSoFar

What was similar in those previous events compared to what models are showing for this weekend?  850mb temps (temperature in celsius around 5,000′) were in the low to mid 20s and 500mb heights were around 590dm.  The May 1983 event was crazy with a +26.6 degree reading on the Salem balloon sounding that afternoon.  The long-lived (4 days!) 2003 event peaked at +21.8 degrees.  1970 was 22.4 degrees.  Models have been consistently forecasting +21 to +24 for both days this coming weekend as you can see in the peak of both the GFS and ECMWF 850mb ensemble charts:

Note the ECMWF operational run is just slightly warmer than the average of all its members.  Seems like 100 is a possibility if you consider just this.

But I went back and checked out surface observations with the 1983, 2003, & 1970 events and noticed one big difference.  Each of those produced at least one day, or several in 2003’s case, of stronger offshore flow than what we’re expecting.  East wind made it to PDX each time.  That definitely won’t be happening this time.  The thermal trough will just barely form west of the Cascades, due the upper level ridge being centered to our east.  In fact we’ll be lucky to get any easterly wind even to Troutdale.  Offshore flow looks quite weak this coming weekend.  Here’s the WRF-GFS cross section through Saturday 5pm; Saturday is highlighted in yellow:

Capture

That’s a key component with heatwaves here, and even more important in early June.  So I think 98 is about the warmest we’ll see at PDX.

Now it may seem ridiculous to think June 4th or June 5th will see the hottest day of Summer 2016?  Well, let’s assume we hit 98 degrees.  Some years we don’t get above that number and once every few years the hottest day of summer is in June.  So it’s POSSIBLE Saturday or Sunday could be the warmest day of the summer…we can only hope!

Chief Meteorologist Mark Nelsen