Sharp Marine Inversion

September 13, 2011

A great picture from Scott Withers showed up on our Facebook page (fox12weather…”like” it!) today.  The location is Lookout Mountain is on the east side of Mt. Hood.  You can clearly see the inversion over the lower valleys; cooler nighttime air drains down into the lowest elevations while warm air remains above.  What you see here is not the marine inversion west of the mountains, but just overnight cooling.  Nonetheless, it shows the cooler/denser air down below trapping the smoke.

Check out the westside temps:  70 here in Portland, 61 at 1,100′ or so at Brightwood, but 71 up at Timberline Lodge at 6,000′!  Timberline has dropped less than 10 degrees since Sunday, while down in the valley it’s dropped 26 degrees (Brightwood).  The layer of cool air was about 3,000′ thick today, and will probably thin slightly tomorrow.  The marine inversion goes away Thursday and Friday with much cooler air moving in at the higher elevations.

Speaking of cooler, both the GFS and ECMWF show some sort of “real” rain arriving over the Pacific Northwest Saturday night or Sunday.  If so, it’ll be the first significant rain since late July.  It will have been exactly two months since the big soaking on the 17th of July.

Chief Meteorologist Mark Nelsen