First Marine Layer Forecast Miss Today

May 8, 2013

9:45pm Wednesday…

It will happen a bunch of times between now and September, we’ll forecast morning clouds and then they will stick around most of the day instead of disappearing.  Our high temperature will be 5-10 degrees cooler than we expected.  A classic (minor) forecast bust in the warm season.  We ended up at 70 instead of 75 at PDX today.  You can see the solid low clouds on the satellite picture below about 3,000′ west of the Cascades this morning:

MarkSat_Tease

Note that even though it was “cool” today, the high was still 3 degrees above average!  By 3pm the clouds were all gone.

If you are looking for more sunshine and warmer temps, tomorrow should be the day.  Temperatures are running several degrees warmer than last night at this time in Corvallis, McMinnville, & Kelso.  Those are the spots the marine air hit first as it poured into the Valley last night.  This weaker evening surge plus warming temperatures in the atmosphere above plus strong subsidence (sinking motions) from a strengthening upper level high directly overhead will squash the marine layer.  Thus what low clouds we get tomorrow should evaporate quickly.  Our 80 degrees forecast might be a couple notches too high, but I’m feeling lucky tonight.

Still looking for a very warm day Friday with mostly sunny skies, 850mb temps around +16 to +17 and no onshore flow.  That should get us up into the mid 80s.

Saturday is a bit of a question mark tempwise due to cloud cover.  I doubt we get low clouds, but probably hazy sunshine from high clouds.  Although morning temps should start in the upper 50s too.

Altogether, we’ll see at least one and possibly 3 more 80 degree days.  So far we’ve seen 3 this month:

MarkHeatwaveStudio_80DegreeTemps_May

What a change from 2010 and 2011 eh?

Some much-needed rain is still on the way for Saturday night through Monday.  We could see more than .50″ even in the driest parts of the metro area.  We’ve seen very little in the past 2+ weeks so it’s time.

Interesting disagreement in the longer range.  The ECMWF & GEM models are both flatter with more westerly flow over us through the middle of next week.  They show real seasonal weather with plenty of cloud cover but more dry than wet after Monday.   The 12z ECMWF 850mb temp ensemble forecast shows temps near average, or just slightly above most of next week:

tseries_850t_000-360_Portland

 

But the 12z/18z GFS had shown a quick rebound to well above average temps:

tseries_850t_000-384_Portland

However, the brand new 00z GFS looks more like the ECMWF/GEM (flatter zonal flow), so I’m going with a slower warmup and just average temps for the first part of next week.

I suppose the good news is that no models are showing a cold upper level low or long-term wet/cold pattern that we often see in late spring.  Just back to normal, which isn’t so bad in mid May!

Chief Meteorologist Mark Nelsen