Cold Nights & Warm Forecast

May 9, 2006

Another cold one last night, but Portland Airport (KPDX) only dropped to 41 degrees, the warmest spot west of the Cascades.  But Scappoose, Hillsboro, & McMinnville all dropped to 32.  Battleground hit 29!

The cold nights this first week and a half of May have kept the average low below normal, but daytimes have been above average for this time of year.  Another chilly one tonight with clear skies overhead, but not quite as cold.

2 significant changes to the 7 Day forecast this evening.  First is the rain, or lack of rain.  2 troughs swing through Thursday & Friday, but models keep us very dry with both.  Just a much cooler airmass which keeps highs down close to 60.

Then the big change in the forecast is for the weekend.  Last night I mentioned that models are all over the place for the weekend.  They seem to have come together into much better agreement.  The flow over the East Pacific and Western U.S. will suddenly amplify or buckle quite a bit Saturday and Sunday.  A big trough develops well offshore and a large ridge builds over the entire West.  We will be on the western edge of this ridge with a much warmer atmosphere Saturday-Sunday.  850 mb. temps Sunday afternoon are around +12 C on the GFS & ECMWF, and reach +16 to +18 C Monday-Tuesday afternoons.  According the Mark Nelsen/Jim Little magic 850mb chart for May, a +16 would give us 85 with no east wind, and 90 with east wind.  So it should be quite easy to get in the 85-90 degree range Monday and Tuesday IF the models don’t suddenly weaken the upcoming ridging.  Looks like some early summer on the way…Mark