Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 162129
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 PM PDT TUE SEP 16 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING A CHANCE OF SHOWERS TO
THE AREA WEDNESDAY THROUGH FRIDAY NIGHT...WITH SHOWERS MOST LIKELY
ON THURSDAY. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
WEEKEND FOR WARMER AND DRY WEATHER.

&&

.SHORT TERM...MID AND HIGH CLOUDS FROM AN UPPER LOW OFF NORTHERN
CALIFORNIA HAVE BEEN STREAMING INTO WASHINGTON FROM THE SOUTHWEST.
THIS TREND WILL CONTINUE TONIGHT AND WEDNESDAY. SURFACE FLOW IS
ONSHORE WHICH WILL ALLOW MARINE STRATUS INLAND OVERNIGHT. THE UPSHOT
IS A FORECAST FOR INCREASING CLOUDS TONIGHT AND MOSTLY CLOUDY SKIES
WEDNESDAY. MODELS ALSO BEGIN BRINGING SOME MOISTURE INTO THE AREA
TOMORROW...ENOUGH FOR A CHANCE OF SHOWERS IN THE AFTERNOON. THE
CLOUDS WILL KEEP HIGH TEMPERATURES IN THE LOW TO MID 70S INLAND WITH
MAINLY 60S ON THE COAST.

A STRONGER IMPULSE ARRIVES WEDNESDAY NIGHT AND THURSDAY. SHOWERS ARE
LIKELY OVER WESTERN SECTIONS WEDNESDAY NIGHT AND ARE LIKELY
EVERYWHERE THURSDAY. TEMPERATURES WILL TAKE ANOTHER DIP WITH HIGHS
MOSTLY IN THE 60S AND LOW 70S THURSDAY. RAINFALL AMOUNTS WILL BE
LIGHT BUT COULD SUM TO A COUPLE OF TENTHS OF AN INCH BY THURSDAY
NIGHT OR SO. A PUGET SOUND CONVERGENCE ZONE PATTERN IS EVIDENT IN
MESOSCALE MODELS THURSDAY NIGHT.

FLOW ALOFT REMAINS WESTERLY FRIDAY...ALLOWING ANOTHER IMPULSE TO
REACH THE AREA AND KEEPING A CHANCE OF SHOWERS IN THE FORECAST.
THERE SHOULD BE LESS CLOUD COVER OVERALL AND HIGH TEMPERATURES WILL
REBOUND A BIT INTO MOSTLY 70S. BY FRIDAY NIGHT MODELS BUILD A STRONG
UPPER RIDGE THAT SHOULD GIVE A CLEARING AND DRYING TREND. BURKE

.LONG TERM...THE WEEKEND WILL SEE A STRONG UPPER RIDGE WITH OFFSHORE
SURFACE FLOW. MODEL HEIGHTS ARE IN THE MID 580S. THIS IS A SUNNY AND
WARM PATTERN. FOR NOW HAVE BOOSTED TEMPS INTO THE 70S AND LOW 80S
FOR SATURDAY. FOR SUNDAY THE FORECAST CALLS FOR MORE WIDESPREAD 80S.
ON MONDAY SURFACE FLOW TURNS WEAKLY ONSHORE AND HEIGHTS FALL IN
RESPONSE TO AN APPROACHING SYSTEM. MONDAY IS LIKELY TO REMAIN DRY
BUT CLOUDS WILL INCREASE MONDAY NIGHT AND A CHANCE OF SHOWERS
APPEARS IN THE TUESDAY FORECAST. BURKE

&&

.AVIATION...HIGH PRESSURE ALOFT OVER THE PAC NW WILL SHIFT INLAND ON
WED AS A BROAD UPPER TROUGH APPROACHES THE REGION. LIGHT TO
MODERATE SW FLOW ALOFT. MOISTURE WILL INCREASE IN THE MID/UPPER
LEVELS AGAIN LATER TONIGHT AND WED AHEAD OF THE SYSTEM. THE LOW
LEVELS WILL REMAIN MOIST WITH PATCHY MVFR STRATUS POSSIBLE IN THE
MORNING AT ANY OF THE TAF SITES. KHQM AND KCLM WILL HAVE MORE
EXTENSIVE MVFR STRATUS OVERNIGHT INTO WED MORNING DUE TO WLY ONSHORE
FLOW.

KSEA...ANOTHER SURGE OF MID/HIGH CLOUDS WILL ARRIVE LATE TONIGHT AND
WED. PATCHY MVFR STRATUS COULD ALSO FORM AT OR NEAR THE TERMINAL FOR
A FEW HOURS WED MORNING. ONSHORE FLOW WITH S TO SW WIND LESS THAN 10
KT...BECOMING LIGHT BY WED MORNING...THEN SWITCHING THE N-NWLY LATE
IN THE AFTERNOON. DTM

&&

.MARINE...SMALL CRAFT WINDS TO 25 KT WILL CONTINUE THROUGH ABOUT
MIDNIGHT BEFORE DECREASING. AFTER THE MARINE PUSH THIS EVENING...
THE ONSHORE FLOW WILL BE FAIRLY LIGHT AS WEATHER SYSTEMS MOVING
THROUGH THE AREA ARE EXPECTED TO BE RATHER WEAK. OFFSHORE FLOW
DEVELOPS SAT AND SUN WITH BREEZY CONDITIONS AT THE W ENTRANCE TO THE
STRAIT. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
     THROUGH MIDNIGHT TONIGHT.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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