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000
FXUS66 KSEW 192153
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT WED JUN 19 2013

.SYNOPSIS...AN UPPER LEVEL LOW IS OVER THE PACIFIC NORTHWEST.
SHOWERS WILL INCREASE...AND RAIN WILL LIKELY DEVELOP IN THE NORTH
CASCADES. WEAK HIGH PRESSURE WILL BUILD INTO THE AREA FRIDAY NIGHT
AND SATURDAY. RAIN IS LIKELY EARLY NEXT WEEK AS WEATHER SYSTEMS
MOVE THROUGH THE REGION.

&&

.SHORT TERM...AN UPPER LOW IS OVER THE PACIFIC NORTHWEST WITH
SCATTERED SHOWERS OVER EASTERN WA. THERE IS STRONGER ONSHORE FLOW
NOW AND THE AIR HAS MORE MOISTURE...EXCEPT FOR ALONG THE COAST WHERE
SKIES WERE SUNNY MUCH OF THE DAY. THE GREATEST AMOUNT OF PRECIP IS
LIKELY TO BE NORTH AND EAST OF SEATTLE THROUGH THURSDAY NIGHT. THE
NORTH CASCADES WILL PROBABLY BE WET...WITH AN INCH OR TWO OF RAIN A
GOOD BET. THE GLOBAL MODELS HAVE BEEN SHOWING RATHER HEAVY RAIN NEAR
THE B.C. ALBERTA BORDER AROUND BANFF AND A GOOD SOAKING RAIN ACROSS
MUCH OF SOUTHERN BRITISH COLUMBIA...SOME OF THAT MOISTURE SEEMS
LIKELY TO WORK SOUTH INTO NW WA. IT MIGHT BE THAT MOISTURE
CIRCULATING ABOUT THE UPPER LOW INTERACTS WITH THE THE STRONGER MORE
NW FLOW IN THE MID LEVELS OVER WESTERN WA ON THU...PLUS THE LOW
LEVEL ONSHORE FLOW...FOR A DECENT OROGRAPHIC RAIN FOR THE NORTH
CASCADES. WEAK HIGH PRESSURE BUILDS IN OVER THE AREA FRIDAY NIGHT
AND SATURDAY FOR DRY WEATHER...CLEARING SKIES...AND WARMER HIGHS SAT.

&&

.LONG TERM...THE 12Z GFS AND ECMWF AGREED THAT ANOTHER SYSTEM WILL
MOVE MAINLY INTO OREGON SUNDAY. THE FORECAST KEEPS A CHANCE OF RAIN
BECAUSE OF THE GREAT DEAL OF FLIP FLOPPING IN THE MODELS FOR THAT
SYSTEM...THE ECMWF YESTERDAY WAS ESPECIALLY WET OVER WRN WA ON
SUNDAY BUT THE TREND FOR THE MOMENT SEEMS TO BE HEADING TOWARD A DRY
WEEKEND. HOWEVER BY SUN NITE THE REMNANTS OF THAT FIRST SYSTEM AND
THEN A NEW FRONTAL SYSTEM MOVE INTO WESTERN WA FOR MORE CERTAIN
RAINFALL MON AND TUE.

&&

.AVIATION...THE UPPER LEVEL LOW WAS MOVING INTO NW OREGON THIS
AFTERNOON AND IS FORECAST TO TRACK ACROSS NORTHERN OREGON TONIGHT
INTO THURSDAY. FLOW ALOFT BECOMING MORE EASTERLY ACROSS WASHINGTON
AS THE LOW MOVES INLAND. AIR MASS UNSTABLE AND BECOMING MORE MOIST
INTO THURSDAY. LOW LEVEL ONSHORE FLOW TO INCREASE THROUGH THURSDAY.

DOPPLER WEATHER RADAR SHOWED SCATTERED SHOWERS ACROSS WESTERN
WASHINGTON THIS AFTERNOON WITH MORE IN CENTRAL PUGET SOUND...THE
NORTH INTERIOR AS WELL AS ACROSS SW WASHINGTON. CEILINGS DID RISE TO
MAINLY VFR. YET WITH AN INCREASE IN SHOWERS AND LOW LEVEL ONSHORE
FLOW TONIGHT...WILL FALL BACK TO MVFR IN MANY AREAS OVERNIGHT AND
INTO THU MORNING.

KSEA...SHOWERS IN THE AREA INTO THIS EVENING. VFR CEILINGS OVERALL
BUT COULD FALL TO MVFR WITH A PASSING SHOWER. CEILINGS SHOULD FALL
TO MVFR BETWEEN 09Z-12Z THU AS LOW LEVEL MOISTURE INCREASES
OVERNIGHT WITH MORE SHOWERS - CONFIDENCE HIGH. SW WINDS 6 TO 10
KNOTS THIS EVENING BECOMING MORE SOUTHERLY AFTER 05Z. BUEHNER

&&

.MARINE...PRESSURES WERE FALLING EAST OF THE CASCADES THIS AFTERNOON
WITH LOW LEVEL ONSHORE FLOW INCREASING ACROSS WESTERN WASHINGTON AS
HIGHER PRES WAS BUILDING OFF THE COAST. THIS PATTERN WILL CONTINUE
INTO THURSDAY.

A GALE WARNING REMAINS IN PLACE FOR THE CENTRAL AND EASTERN STRAIT
OF JUAN DE FUCA TONIGHT WITH A SMALL CRAFT ADVISORY IN EFFECT UNTIL
THEN. IN ADDITION A SMALL CRAFT ADVISORY REMAINS FOR THE NORTHERN
INLAND WATERS AND NOW IN THE WESTERN STRAIT. WINDS SHOULD EASE LATER
THURSDAY AS SURFACE HIGH PRESSURE BUILDS ONSHORE. HIGH PRESSURE OVER
THE WATERS ON FRIDAY INTO SATURDAY. A FRONT WILL APPROACH THE
COASTAL WATERS ON SATURDAY AND MOVE INLAND ON SUNDAY WITH ANOTHER
SYSTEM ARRIVING MONDAY. BUEHNER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT.
     SMALL CRAFT ADVISORY NORTHERN INLAND WATERS AND WESTERN STRAIT.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML