The Day After

July 5, 2010

No, the title doesn’t refer to the nuclear holocaust movie; I’m referring to working the morning after the 4th of July.  The Metro area was just dead at 7am when I drove into work.  Talk about a town sleeping in.  In the weather center we are working strange shifts today due to vacation schedules and the holiday, so I did part of the morning show and then our Midday Oregon 11am show.  Just took a bike ride through the West Hills, a bit nippy, felt more like early May…but not for long!

As expected, not much change in the marine layer this morning, wind from the surface to around 5,000′ doesn’t go northerly until this evening and overnight, so there’s nothing to push the moist clouds out of here.  Sure, the edges are fraying from all sides on the visible imagery, but the east side of the metro area is still totally socked in at 2pm where the moisture is running into  the elevated terrain of the Cascades and foothills.  I noticed a few sunbreaks out here on the westside ( that’s why I chose to ride here instead of in the gloom/cold at home) but we won’t get much more until evening.

Cross-sections show the flow going offshore at all levels overnight tonight; probably a situation where whatever low-mid clouds are left this evening dissipate with no lower level clouds redeveloping.  We should wake up to sun in the morning…finally!  Weak offshore flow tomorrow along with an atmosphere that won’t be hot overhead means highs in the mid-80s at best.  Totally different story Wednesday and Thursday with several millibars easterly gradient across the Cascades and through the Gorge.  East wind both days will probably make it to PDX; it may even surface all over the Metro area Wednesday since the thermal trough is on the Coast all day.  Of course that means 90 degrees is a good bet for just one day out at the Beaches! 

The big picture for the general public is no problem…hot and dry through the foreseeable future.  The temperature details are a bit tricky.  A +20 to +22 deg. C. 850mb temp (@ SLE) Wednesday and Thursday afternoons gives a PDX high between 92 and 101 degrees on my chart based on past cases.  Due to that I raised Wednesday up to 95 and 98 on Thursday…assuming that’s the day the thermal trough comes inland (but still west of Cascades) and the easterly wind dies down at PDX in the afternoon.  This is going to be an unsually sharp change for us considering we haven’t even been close to 90 even once this year!

Beyond Thursday I took a middle road approach.  The GFS seems overly strong on ridging, but the ECMWF plunges a sharp upper-level trough right down over us…seems unlikely, and NCEP thinks so too.  I went for a weak push (end to offshore flow) Friday-Sunday, but still high heights and summertime temps.

The main weather message is:  Summer is going to blast into the region the next few days…and it’s going to stick around.  Oh, and it’s not “cancelled” either (had to get that one in).

For the weather geeks:  Apparently it’s not going to be a repeat of the Summer of  ’54?

Chief Meteorologist Mark Nelsen