A Cool July?

July 13, 2010

It’s looking likely that July will either be near or below average temperature-wise.  Sure, we’re just barely halfway through, but all long range models agree that a trough (dip in the upper-level flow) will develop near the West Coast later this weekend and linger at least through next week.  In fact 850mb temps down in the single digits are likely at some point…more like early June than the latter half of the hot month of July.  Here’s a CPC 8-14 day outlook:  It’s a bit blurry, but if you click on the image you’ll see the effect of a hot ridge in the middle of the country and that upper-level trough off the West Coast.

Of course in the short term we have a brief warm up.  The strong onshore flow has really decreased; the PDX-GEG gradient has dropped from around 16 millibars yesterday evening to 3-4 this evening.  Gorge gradient has decreased as well.  By morning it should be just about flat.  Combine that with 850mb temps that go from +2 this morning to +12 tomorrow AM to +16 Thursday spell a signficant warming in mid-July.  Probably no low clouds in the morning west of the Cascades, or at least very minimal coverage.

The onshore flow returns Friday, but isn’t very strong until Sunday night since upper-level heights will remain high.  I have next week off…getting concerned that I may need to head east of the Cascades for a sun fix!

Chief Meteorologist Mark Nelsen