FXUS66 KPQR 201009 AFDPQR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PORTLAND OR 308 AM PDT SAT SEP 20 2008 .SYNOPSIS...ISOLATED MOUNTAIN SHOWERS WILL DECREASE EARLY THIS MORNING AS AN UPPER LEVEL TROUGH OVER SOUTHWEST OREGON MOVES TO THE EAST. ANOTHER WEAK UPPER TROUGH FROM THE GULF OF ALASKA WILL BRUSH THE NORTH PART OF THE FORECAST AREA LATER TODAY...THEN A LITTLE STRONGER UPPER TROUGH WILL DIG ACROSS THE REGION ON SUNDAY...BRINGING THE BEST PROSPECT OF SOME MEASURABLE RAIN TO THE FORECAST AREA. A WETTER SYSTEM FROM THE PACIFIC IS EXPECTED TO MOVE INTO THE AREA ON WEDNESDAY. && .SHORT TERM...INFRARED AND WATER VAPOR SATELLITE IMAGERY SHOW THE UPPER TROUGH MOVING SLOWLY E ALONG THE CA/OREGON BORDER...WITH RADAR IMAGES SHOWING SOME SHOWERS CONTINUING OVER THE CASCADES IN SE MID LEVEL FLOW. AS THE UPPER LOW MOVES FURTHER E BY SUNRISE...THE SHOWERS WILL TAPER OFF AS THE FLOW BECOMES MORE WESTERLY. ANOTHER WEAK UPPER LEVEL SHORTWAVE WILL MOVE ACROSS THE FORECAST AREA TODAY WITH LOW CHANCES FOR SHOWERS OVER THE FAR NORTHERN ZONES. A MORE ENERGETIC UPPER LEVEL TROUGH WILL DIG ACROSS THE FORECAST AREA SUN AND SUN NIGHT WITH A BETTER POSSIBILITY OF SHOWERS...WITH THE BEST CHANCES OF MEASURABLE SHOWERS IN THE NORTHERN ZONES ESPECIALLY FAVORED MOUNTAIN AREAS. FLAT RIDGING MOVES INTO THE PAC NW ON MON BUT WEAK ONSHORE FLOW MAY STILL GIVE A SLIGHT CHANCE OF SHOWERS IN THE FAR NORTHERN ZONES AND CASCADES. RW .LONG TERM...LONG RANGE MODELS CONTINUE TO SHOW A LOT OF VARIABILITY IN THE EXTENDED TIME PERIOD. HOWEVER IN THE WED TIME FRAME MODELS AT LEAST TEMPORARILY HAVE CONVERGED ON A FAIRLY STRONG SYSTEM MOVING INTO THE PAC NW. HAVE INCREASED POPS TO CHANCE...WHICH WILL NEED FURTHER ENHANCEMENT IF THE MODELS CAN MAINTAIN CONSISTENT SOLUTIONS. OTHERWISE...HAVE KEPT FORECAST MORE IN LINE WITH PREVIOUS RUNS OF GFS AND ECMWF FOR TIME BEING UNTIL ALL MID RANGE MODELS BEGIN TO SHOW SOME AGREEMENT. SHOULD SEE MODERATE TEMPERATURES AND CLOUDY SKIES THROUGH MUCH OF THE LATTER HALF OF NEXT WEEK. RW/BROWN && .AVIATION...A COMPLICATED PATTERN IS CAUSING A VARIETY OF CONDITIONS THIS MORNING. PATCHY LIFR CONDITIONS ON THE COAST WITH MAINLY VFR ELSEWHERE EXCEPT SOME LOCAL MVFR IN AND AROUND THE COLUMBIA RIVER. MODELS ARE NOT HANDLING THE SITUATION VERY WELL. FEEL COMFORTABLE KEEPING LOWER CEILINGS IN TAFS EVEN THOUGH PROBABILITY IS MORE LOCALIZED THAN WIDESPREAD. BEST CHANCE FOR CEILINGS REMAINS IN THE NORTH VALLEY PRIMARILY AROUND THE COLUMBIA RIVER. COAST SHOULD SEE PERIODS OF LIFR CIGS/VIS. KPDX AND APPROACHES...40 PERCENT CONFIDENT IN MVFR CIGS BETWEEN 13-19Z SAT MORNING...LIFTING TO VFR AFTERWARD. WOLFE && .MARINE...NO CHANGES...PREV DISCUSSION FOLLOWS. WEAK HIGH PRESSURE OVER THE COASTAL WATERS WILL CAUSE LIGHT WINDS/SEAS TO CONTINUE INTO SAT WITH SWELLS AT AROUND 5 FEET. AFTERWARD SEAS SHOULD LOWER TO LESS THAN 5 FT. THIS LIGHT SWELL IS ALLOWING THE COLUMBIA RIVER BAR TO REMAIN FREE OF ADVISORIES DESPITE THE STRONG ASTRONOMICAL EVENING EBB CURRENTS THIS WEEK. INCREASING NW WINDS/SEAS LIKELY LATER SUN NIGHT AND MON AS HIGH PRES BUILDS IN BEHIND A WEAK GULF OF ALASKA COLD FRONT. WS/DALTON/WOLFE && .PQR WATCHES/WARNINGS/ADVISORIES... OR/WA...NONE. && .PRELIMINARY POINT POPS (PROBABILITY OF MEASURABLE PRECIPITATION) AST 22322 PDX 11321 SLE 11221 EUG 11221 $$ MORE WEATHER INFORMATION ONLINE AT... HTTP://WEATHER.GOV/PORTLAND THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY REFERRED TO AS THE FORECAST AREA.