Big Change In The Forecast: Gray and Cool Friday

October 24, 2013

Friday (and maybe Saturday) will be MUCH different from the past few days.  Expect a gray and cool day with high temps only in the 50s instead of sunshine and 70-75 degree temps.

Take a look at this great chart, created by Brian Schmit.  It shows what has been going on the past week or so:

photo_brian

  • Elevations above 1,000′ or so have been above all fog and low clouds, with the warmest temps in our area between 1,000′ and 3,000′.  Larch Mtn. Washington is around 1,100′ east of Battle Ground.
  • In the lowest elevations (where most of us live) in NW Oregon and SW Washington we’ve had just enough offshore flow, with its breezes and drier air, to keep the fog/low clouds to a minimum.
  • Farther north, in Puget Sound, there hasn’t been enough drier air mixing down to the surface to break up the fog and clouds.
  • As a result, it’s been a miserable gray and cold period up there, pretty nice here in our area, and similar to late summer in the foothills and mountains.

That setup is changing quickly this evening.

I have been expecting the offshore flow to weaken the next few days, and that has happened the past few hours;  the east wind blowing through the Gorge has disappeared.  It’s calm at Crown Point at 9pm.  But what I didn’t expect is the stratus/fog that’s been on the coastline the past few days is suddenly lifting a bit and coming up the Columbia River and over the Coast Range.  Tidewater RAWS at 2,000′ just SE of Astoria dropped from 68 to 50 degrees from 2-4pm.  So it’s safe to say that marine layer thickened rapidly at that location in the middle of the “peak heating” of the day.  This satellite loop shows the surge of moisture (clouds/fog) pretty well too after dark:  http://sat.wrh.noaa.gov/satellite/alternative.php?wfo=pqr&area=west&type=fog&size=2

Models now show solid low clouds/fog west of the Cascades tomorrow morning, note our RPM model at 9am.  It’s visibility, but you get the idea:

rpm_9am

In the last week of October, when you get low clouds/fog in the morning with warmer air above (an inversion) and no offshore flow, they sure aren’t going anywhere in the afternoon!  The screaming message is that we’re going to be like Puget Sound tomorrow.  I cringed this afternoon on the way to work when I heard a DJ on a local radio station say “SUNNY EVERY DAY THROUGH THE MIDDLE OF NEXT WEEK”.  Ughhh!  Now everyone that heard that will wonder how the forecasters “screwed up the forecast” so badly.  We all get lumped together in the public’s mind.

No other changes to yesterday’s thinking for the cold trough early next week.  It sure moves out of here quickly.  In fact both the ECMWF and GFS both have cloud cover moving in already next Wednesday.  As a result there may only be one real chilly night (Monday night) before high clouds keep us milder Tuesday night.  I raised the low temp forecast to 32 for PDX at that time as a result.  AND, for the average John Q. Citizen, the clouds and 50s for tomorrow is going to feel cooler than the sunny and 50s for Monday/Tuesday, so I took the COOLER wording off the 7 Day Forecast.

Chief Meteorologist Mark Nelsen

 


For the Geeks: ECMWF Weekly Maps

October 24, 2013

Last night’s monthly run of the ECMWF model.  500mb height anomaly forecasts for each of the next 4 weeks.  Looks like the upper level high wants to hang nearby for awhile longer…Sure looks like last January/February:

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA