Hot Spell Begins

May 14, 2008

Snapshot Snapshot2
I guess the graphics don’t actually say it anywhere, but these are current water temperatures on area rivers…chilly!  In fact I went down to the boat ramp on the Sandy river at Troutdale to measure the temperature today, and was surprised by how cold it was.  Because of the warm and slightly moist weather + cold water temp, you could see a condensation fog hovering over the river…kind of like when we have a flood in winter.  The chilly water is cooling the air right near the river, causing the moisture to condense out to fog.  Pretty cool…

Moving on, I was real happy with today’s weather vs. the forecast.  Nice clearing after about mid-afternoon let temps jump up into the lower 70s.  Funny how it felt a bit humid, but dewpoints were below 60 degrees the whole time, obviously we just are blessed, and spoiled, by dry air usually associating with warm/hot days.

I see the Salem sounding this evening confirmed 500mb heights of 590dm right now.  A strong upper-level ridge HAS formed directly over the top of us and the lower-level atmosphere will respond to that tomorrow.  You can see how the warm frontal clouds just evaporated this afternoon on the IR satellite picture.  By 8-11am, an easterly flow develops through the Gorge, but probably not enough to move past Troutdale even at midday.  More likely we get a breezy north wind in most of the metro area tomorrow as a thermal trough develops to our south.  I’m tempted to drop tomorrow’s high to 88 as a result. 

Then the stronger easterly flow at the surface arrives tomorrow night and Friday A.M..  By then we have several millibars of easterly gradient through the Gorge and the thermal trough is out at the Beaches.  It moves inland again by Friday evening, so Friday is that perfect setup where we get gusty east wind in the morning.  The wind pushes out towards PDX by midday, then dies down, leaving a hot & calm atmosphere by late afternoon.  You couldn’t ask for a more perfect setup any summer day.  850mb temps should be around +22 deg. C.  Assuming all this pans out as forecast, 94 is the bottom range of PDX forecast high.  The upper range is 98 or so.  We may be awfully close to our all-time May high of 100 degrees late Friday afternoon.  If the latest 00z mesoscale models say the same thing (I’m ignoring WRF-GFS sfc. temps, they were wacky with warm weather back in April), I may up the high for Friday by 10pm.

A decent, but shallow marine push later Saturday should cap us near 90 degrees (if not below), then much more significant cooling arrives Sunday for highs closer to 80.

GFS builds ridging back in over us next week, ECMWF does not…Quite a difference in models, but that’s a ways away…Mark Nelsen