000 
FXUS66 KPQR 090957
AFDPQR

NORTHWEST OREGON AND SOUTHWEST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 AM PDT TUE SEP 9 2003

.SYNOPSIS...A LOW PRESSURE SYSTEM WITH A COLD FRONT WILL MOVE ACROSS
THE FORECAST AREA TODAY...AND E OF THE CASCADES BY THE END OF THE
DAY.  A COUPLE OF ADDITIONAL FRONTAL SYSTEMS WILL MOVE ACROSS WA WED
THROUGH THU NIGHT BRUSHING THE NORTHERN PART OF THE FORECAST AREA.
LATE IN THE WEEK AN UPPER LEVEL RIDGE WILL BUILD OVER THE E PACIFIC
LEAVING THE REGION UNDER DRIER NORTHWEST FLOW.

.DISCUSSION...
.SHORT TERM...WET LOW PRESSURE AND COLD FRONT PUSHING THROUGH
FORECAST EARLY THIS MORNING...JUDGING BY SATELLITE AND RADAR SHOULD
BE ABLE TO CONTINUE WITH CATEGORICAL POPS AT LEAST EARLY THIS
MORNING. UPPER LOW TO MOVE ACROSS LATER TODAY...THEN A MOIST AIR MASS
REMAINS IN PLACE TONIGHT WHEN SOME WEAK WARM AIR ADVECTION KICKS IN
AS UPPER TROUGH PULLS OUT...SO WILL LEAVE IN A CHANCE FOR SHOWERS
EVERYWHERE. WED THE UPPER HEIGHTS REBUILD QUITE A BIT...BUT TAIL END
OF A WARM FRONT BRUSHES NORTHERN AREA...AND GIVEN THE BROAD AREA OF
RESIDUAL LIGHT RAIN DEPICTED BY THE GFS...WILL LEAVE IN A SMALL
CHANCE FOR LIGHT RAIN.  THU AREA REMAINS UNDER HIGH UPPER HEIGHTS
WITH A STRONG NEARLY ZONAL FLOW TO THE N.  MODELS TRY TO WAVER A
FRONT DOWN INTO THE FORECAST AREA WITH A PASSING WAVE...BUT TEND TO
BELIEVE GFS PRECIPITATION IS A BIT OVERDONE. SOME OF THE MOISTURE
LATE IN THE DAY ALSO APPEARS TO HAVE A TROPICAL ORIGIN...MAKING IT
DIFFICULT TO COMPLETELY DISCOUNT CHANCES FOR RAINFALL DESPITE THE
HIGH UPPER HEIGHTS...SO WILL HANG ONTO SOME LOW POPS ACROSS THE FAR
NORTHERN PART OF FORECAST AREA.

.LONG TERM...ALTHOUGH TIMING DIFFERS...BOTH GFS AND ECMWF TEND TO
AGREE ON BUILDING A FAIRLY STRONG RIDGE JUST OFFSHORE FOR THE
WEEKEND...ALTHOUGH THERE ARE HINTS OF A WEAK FRONT DROPPING S IN THE
NW FLOW FRI.  ANOTHER MORE SIGNIFICANT SHORTWAVE AND FRONT DROPS S
MON CUTTING INTO THE E SIDE OF THE RIDGE.  WILL GO AHEAD AND ADD IN
SOME LOW POPS IN THE N FOR MON...OTHERWISE CONTINUE WITH A DRY
EXTENDED FORECAST.

AST 84442  PDX +5321  SLE +5211  EUG +5211

.PQR...GALE WARNING CAPE SHOALWATER TO FLORENCE.
$$