Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

803
FXUS66 KSEW 271052 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED SYNOPSIS
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT WED APR 27 2016

.SYNOPSIS...A WEAK UPPER TROUGH WILL MOVE ACROSS WESTERN
WASHINGTON TODAY FOR MAINLY CLOUDY SKIES AND A CHANCE OF LIGHT
SHOWERS FOR THE COAST...MOUNTAINS...AND SOUTH PART. AN UPPER RIDGE
WILL BRING MOSTLY SUNNY WEATHER THURSDAY...FOLLOWED BY AN UPPER
TROUGH AND SCATTERED SHOWERS FRIDAY. A STRONG UPPER RIDGE WILL BRING
DRY WEATHER AND A WARMING TREND SATURDAY THROUGH MONDAY.

&&

.SHORT TERM...A WEAK FRONTAL SYSTEM IS SPLITTING AS IT MOVES INTO
THE PACIFIC NORTHWEST EARLY THIS MORNING...WITH THE CORE OF THE
SYSTEM MOVING SOUTHEAST ACROSS OREGON. THIS FEATURE BROUGHT SPOTTY
LIGHT PRECIPITATION -- UP TO 0.10 INCH -- TO THE OLYMPICS AND
CASCADES FROM AROUND MOUNT RAINIER SOUTH. OTHERWISE WESTERN
WASHINGTON HAS HAD CLOUDY SKIES OVERNIGHT WITH 3 AM TEMPERATURES
IN THE MID 40S TO LOWER 50S.

A WEAK UPPER TROUGH WILL MOVE ACROSS THE REGION TODAY...KEEPING
SKIES GENERALLY CLOUDY. THE PUGET SOUND REGION AND NORTH INTERIOR
SHOULD REMAIN GENERALLY DRY. THERE IS A CHANCE OF SHOWERS AT THE
COAST...IN THE MOUNTAINS...AND IN THE SOUTH INTERIOR. WHERE RAIN
FALLS IN THE LOWLANDS IT SHOULD AMOUNT TO ONLY A FEW HUNDREDTHS
OF AN INCH...WITH UP TO 0.10 INCH PRECIPITATION IN THE MOUNTAINS.
HIGHS TODAY WILL BE IN THE UPPER 50S TO MID 60S.

THE UPPER TROUGH WILL MOVE EAST TONIGHT...AND ANY LINGERING
SHOWERS SHOULD END THIS EVENING. AN UPPER RIDGE WILL MOVE INTO THE
WASHINGTON OFFSHORE WATERS LATE TONIGHT AND THEN INTO WESTERN
WASHINGTON THURSDAY. FOR MOST OF THE FORECAST AREA IT WILL BE A
MOSTLY SUNNY AND SLIGHTLY WARMER DAY...WITH HIGHS IN THE UPPER 50S
TO 60S. SOME LOW LEVEL MOISTURE AND WEAK INSTABILITY SHOULD LEAD
TO SOME AFTERNOON CLOUD BUILDUPS AND ISOLATED SHOWERS OVER THE
MOUNTAINS.

THE UPPER RIDGE WILL MOVE EAST OF THE CASCADES THURSDAY NIGHT. AN
UPPER TROUGH AND POSSIBLY A WEAK COLD FRONT WILL MOVE INTO THE
COASTAL WATERS LATE THURSDAY NIGHT AND INTO WESTERN WASHINGTON ON
FRIDAY...FOLLOWED BY FAIRLY STRONG ONSHORE FLOW IN THE AFTERNOON.
THIS SYSTEM SHOULD BRING AT LEAST SCATTERED SHOWERS -- AND MAYBE
MORE WIDESPREAD SHOWERS -- TO THE FORECAST AREA. THE INTERIOR
LOWLANDS SHOULD MAINLY RECEIVE 0.10 INCH OR LESS...EXCEPT MAYBE A
BIT MORE WILL FALL IN THE PUGET SOUND CONVERGENCE ZONE. UP TO
0.25 INCH IS LIKELY AT THE COAST AND IN THE MOUNTAINS. THE SNOW
LEVEL WILL BE AROUND 4500 FT. MCDONNAL

.LONG TERM...THE MODELS REMAIN IN FAIRLY GOOD AGREEMENT THAT AN
UPPER RIDGE WILL BUILD OFFSHORE ALONG 130W ON SATURDAY...SHIFT
SLOWLY TO THE COAST ON SUNDAY AND MONDAY. THIS SHOULD BE A PERIOD
OF MOSTLY SUNNY WEATHER WITH A WARMING TREND. THE UPPER RIDGE WILL
PROBABLY MOVE EAST OF THE AREA ON TUESDAY...AND SOUTHERLY FLOW
ALOFT WITH HIGH LEVEL MOISTURE AND WEAK INSTABILITY COULD PRODUCE
SOME SHOWERS. MCDONNAL

&&

.AVIATION...A WEAK UPPER LEVEL TROF WILL REMAIN OVER THE AREA
TODAY. THE FLOW ALOFT WILL BE LIGHT AND VARIABLE. LOW LEVEL
ONSHORE FLOW WILL STRENGTHEN THIS AFTERNOON. THERE WERE AREAS OF
MVFR CIGS OVER THE COAST EARLY THIS MORNING WITH LOCALIZED MVFR
CIGS OVER THE PUGET SOUND REGION. VFR CONDITIONS ARE ANTICIPATED
OVER THE ENTIRE AREA BY 1900 UTC.

KSEA...LOCALIZED MVFR CIGS OVER THE PUGET SOUND REGION EARLY THIS
MORNING HAPPENED TO BE RIGHT OVER THE TERMINAL. EXPECT VFR
CONDITIONS TO RETURN BY 1800 UTC. LIGHT AND VARIABLE WINDS WILL
BECOME NLY THIS AFTERNOON.

&&

.MARINE...
A 1013 MB LOW OVER THE OREGON COASTAL WATERS WILL DISSIPATE THIS
MORNING. HIGH PRES WILL THEN BUILD OVER THE OFFSHORE WATERS. THIS
COMBINED WITH LOWER PRES E OF THE CASCADES WILL RESULT IN ONSHORE
OR WESTERLY FLOW THROUGH THU.

STRONG ONSHORE FLOW WILL DEVELOP ON FRI IN THE WAKE OF A COLD
FRONT. THIS WILL LEAD TO GALE FORCE WESTERLIES OVER THE CENTRAL
AND EASTERN STRAIT OF JUAN DE FUCA...AND THE POSSIBILITY GALE
FORCE NORTHWESTERLIES OVER PARTS OF THE COASTAL WATERS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 AM PDT
     THURSDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
     EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO MIDNIGHT PDT
     TONIGHT FOR ADMIRALTY INLET.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.