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Forecast Discussion:NW Oregon - SW Washington
248 PM PST SAT NOV 7 2009SYNOPSIS
A COOL SHOWERY AIR MASS WILL CONTINUE TO SPREAD INTO THE PACIFIC NORTHWEST EARLY TONIGHT. THE AIR MASS WILL ALSO CONTINUE TO BE RATHER UNSTABLE FOR A THREAT OF THUNDERSTORMS NEAR THE COAST. THE SHOWERS ARE EXPECTED TO TAPER OFF ON SUNDAY IN THE SOUTH...WHILE A WARM FRONT SHOULD MOVE THROUGH THE NORTHERN AREAS FOR ADDITIONAL RAIN. A RATHER STRONG COLD FRONT WILL MOVE THROUGH MONDAY AFTERNOON AND EVENING WITH MORE RAIN...MOUNTAIN SNOW AND BRISK WINDS. &&
SHORT TERM
A COOL UNSTABLE WESTERLY FLOW ALOFT WILL CONTINUE TO MOVE INTO THE REGION THROUGH THIS EVENING...WITH EMBEDDED CONVECTION FOR TSTMS NEAR THE COAST. LOCAL HEAVY RAIN INLAND AREAS SHOULD PUSH INTO THE CASCADES THIS EVENING...AND THE URBAN AND SMALL STREAM FLOOD ADVISORY IN THE N WILL LIKELY END. THE WINTER WEATHER ADVISORY FOR THE CASCADES CONTINUES TO LOOK GOOD THROUGH THE 10 PM TERMINATION TIME AS THE SLUG OF PRECIP MOVES THROUGH. SNOW LEVELS WILL BE MAINLY AROUND 3500 TONIGHT. THE UPPER FLOW BEGINS TO SLOWLY BUCKLE SUN AND MON AS THE NEXT FRONTAL SYSTEM DEVELOPS OFF THE COAST. THE MODELS SAY SOME SORT OF WARM ADVECTION PRECIP MAY WILL SPREAD ACROSS THE NW HALF OF OUR AREA SUN...WITH LOCAL MODERATE RAINFALL AMOUNTS AROUND ONE HALF INCH INDICATED IN THE GFS AND NAM. THIS COULD REQUIRE ANOTHER WINTER WEATHER ADVISORY IN THE S WA CASCADES SUN. CONDITIONS APPEAR TO DRY OUT SUN NIGHT INTO MON MORNING IN THE SLIGHTLY WARMER SECTOR...THEN THE ASSOCIATED STRONG COLD FRONT WILL MOVE IN MON AFTERNOON AND MOVE E MON NIGHT. THIS FRONT SHOULD PRODUCE GUSTY WINDS ALONG THE COASTAL STRIP...AND BREEZY CONDITIONS INLAND. SNOW LEVELS LIFT SOME AHEAD OF THIS FRONT...SO WE WILL HAVE TO SEE IF THEY LOWER SOON ENOUGH TO GET ENOUGH SNOW FOR ANOTHER WINTER WEATHER ADVISORY IN THE CASCADES. RIGHT NOW IT IS LOOKING RATHER IFFY. GFS SHOWS DRYING AGAIN ON TUE AHEAD OF THE NEXT SYSTEM...ALTHOUGH THE ECMWF HAS FASTER TIMING WITH A MINIMAL PERIOD OF DRY WEATHER. RW
LONG TERM
MODELS IN FAIRLY GOOD AGREEMENT SHOWING A COOL UPPER TROUGH DROPPING SE THROUGH THE REGION WED AND THU. THIS SHOULD BRING SHOWERY WEATHER WITH SNOW LEVELS BETWEEN 3000 AND 4000 FT. EXTENDED MODELS ARE STILL SHOWING A POTENTIAL BREAK IN THE WEATHER FROM LATE THU INTO AT LEAST FRI MORNING AS A WEAK UPPER RIDGE MOVES THROUGH. ANOTHER PAC SYSTEM LOOKS LIKELY FRI NIGHT AND SAT. RW &&
AVIATION
TWO ORGANIZED BANDS OF HEAVY SHOWERS AND ISOLATED THUNDERSTORMS ARE MOVING THROUGH THE AREA THIS AFTERNOON. THE FIRST LINE IS CREATING FAIRLY WIDESPREAD MVFR CIGS/VSBYS ACROSS THE NORTHERN HALF OF THE WILLAMETTE VALLEY...WITH LOCAL IFR EMBEDDED IN THE HEAVIER AREAS OF RAIN. A SECOND LINE OF STORMS...CURRENTLY WEAKER THAN THE FIRST...IS MOVING ONSHORE NEAR ASTORIA. THIS LINE WILL LIKELY SPREAD MORE SHOWERS ONSHORE THROUGH THE EVENING...BUT OVERALL ACTIVITY IS EXPECTED TO GRADUALLY DECREASE AS THE NIGHT GOES ON. YET ANOTHER AREA OF SHOWERS IS EXPECTED TO MOVE ONSHORE EARLY SUNDAY MORNING. SMALL HAIL IS POSSIBLE WITH ANY OF THE HEAVIER SHOWERS. OUTSIDE OF SHOWERS...MAINLY VFR CONDITIONS ARE EXPECTED THROUGH SUN MORNING. KPDX AND APPROACHES...MAINLY VFR...BRIEF MVFR CIGS/VSBYS AND GUSTY WINDS UP TO 35 KT POSSIBLE IN SHOWERS/ISOLATED THUNDERSTORMS THROUGH THIS EVENING. BRIEF SMALL HAIL IS ALSO POSSIBLE WITH THE HEAVIER CELLS. SHOWERS TAPER OFF OVERNIGHT...BUT AREAS OF MVFR CIGS MAY LINGER THROUGH THE NIGHT. MORE RAIN EXPECTED SUN MORNING...POSSIBLY BRINGING MORE WIDESPREAD MVFR.WEAGLE &&
MARINE
COASTAL BUOYS CONTINUE TO REPORT 20-22 FT SEAS...SLIGHTLY DOWN FROM THE EARLIER PEAK AROUND 23-27 FT. SLOW DOWNWARD TREND IN SEAS WILL CONTINUE THROUGH TONIGHT AND SUNDAY...THEREFORE WILL REPLACE THE HIGH SURF WARNING WITH AN ADVISORY. ONE MORE ORGANIZED ROUND OF SHOWERS MAY BRING SOME LIGHTNING AND GUSTS APPROACHING GALE FORCE...BUT MOST OF THE GALES ARE DONE FOR NOW...PUSHED SOUTH OF FLORENCE ALONG WITH THE COLD FRONT. ANOTHER GOOD CHANCE FOR GALES WITH A STRONGER FRONT ANTICIPATED EARLY MONDAY AS ANOTHER STRONG FRONT MOVES ACROSS THE COASTAL WATERS...AND LONG RANGE MODELS ARE SUGGESTING THIS UNSETTLED WEATHER PATTERN WILL CONTINUE WELL INTO THE UPCOMING WEEK. WEAGLE &&
PQR WATCHES/WARNINGS/ADVISORIES
WA/OR...SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE OUT 60 NM THROUGH SUNDAY AFTERNOON. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER TO FLORENCE OUT 60 NM THROUGH MONDAY AFTERNOON. SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR THROUGH SUNDAY NIGHT. HIGH SURF ADVISORY SOUTH WASHINGTON...NORTH AND CENTRAL OREGON COAST THROUGH SUNDAY AFTERNOON. WINTER WEATHER ADVISORY FOR SNOW FOR THE SOUTH WASHINGTON AND THE NORTH AND CENTRAL OREGON CASCADES CONTINUES THROUGH 10 PM TONIGHT. && $$ 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.