Heating Up

July 24, 2009

Most 100 Degree Days Happen in July Here in Portland

Most 100 Degree Days Happen in July Here in Portland

For those of you that have been living here quite a long time, the numbers in the image probably are no surprise.  We don’t tend to have all that many 100 degree days in August, especially after the first week or so.  Mainly because it gets tougher to overcome the longer nights and their associated cooling by mid-August.  By the way, two of those August 100 degree days were from last year.

So what’s new tonight?  Not a whole lot, except it’s obvious that we get no significant offshore flow until Tuesday AM at the earliest.  That’s why I lowered the numbers in the 7 Day forecast for Sunday and Monday.  The heat wave is most definitely still on the way, but it starts a bit more slowly and may not be a historic one.  I’m still real confident that we’ll see 5-7 days at/above 90 degrees.  As for whether we get to/above 100 degrees, we’re going to need at least SOME light offshore flow.

A new twist to our little heat wave is the dewpoints/humidity.  With the upper-level low closer to us tomorrow and Sunday, we add some moisture to the airmass.  Plus with no decent onshore OR offshore flow through at least Monday, we’re not going to get much mixing.  Overnight lows are headed up between 65-70 degrees and dewpoints should jump up into at least the lower 60s.  Looks a bit sweaty Sunday and Monday at least.

Try to stay cool over the weekend!

Chief Meteorologist – Mark Nelsen