Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 080402
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
802 PM PST SUN FEB 7 2016

.SYNOPSIS...A STRONG UPPER LEVEL RIDGE AND LOW LEVEL OFFSHORE FLOW
WILL BRING SUNNY AND WARMER WEATHER TO WESTERN WASHINGTON MONDAY AND
TUESDAY. A WEAK UPPER LEVEL TROUGH WILL BRING PARTLY CLOUDY SKIES
AND A CHANCE OF RAIN TO THE COAST ON WEDNESDAY. STARTING WEDNESDAY
NIGHT...MOIST SOUTHWEST FLOW ALOFT WILL BRING A WETTER WEATHER
PATTERN THROUGH SATURDAY AS A SERIES OF UPPER LEVEL TROUGHS CROSS
THE AREA.

&&

.SHORT TERM...A MODERATE AMPLITUDE UPPER LEVEL RIDGE IS ALREADY
CENTERED OVER W WA THIS EVENING WITH A SURFACE RIDGE OVER INTERIOR
B.C. EXTENDING ACROSS THE ID PANHANDLE. EASTERLY OFFSHORE FLOW WILL
CONTINUE THROUGH MONDAY NIGHT THEN TURN SOUTHERLY ON TUESDAY WHILE
THE UPPER LEVEL RIDGE BUILDS AND DRIFTS SLOWLY E OVER OVER E WA. A
COUPLE OF CLOUD LAYERS BKN-OVC045-080 FROM PUGET SOUND OVER THE N
INTERIOR...LEFTOVER FROM A WEAK WARM FRONT EARLIER TODAY...WILL
DRIFT N AND DISSIPATE OVERNIGHT. SKIES ARE ALREADY CLEAR OVER THE SW
INTERIOR.

THE OFFSHORE FLOW COMBINED WITH WARMING FROM THE UPPER LEVEL RIDGE
WILL BE STRONG ENOUGH TO PUSH HIGH TEMPERATURES INTO THE UPPER 50S
TO NEAR 60 MONDAY AND TUESDAY...WHICH WOULD BE ALMOST 10 DEGREES
ABOVE NORMAL. OVERNIGHT TEMPERATURES WILL BE COOL WITH LOWS IN THE
MID 30S TO LOWER 40S. DEWPOINTS THIS EVENING ARE HIGH ENOUGH SO THAT
AREAS OF MORNING FOG CAN BE EXPECTED BOTH MONDAY AND TUESDAY
MORNING...PRIMARILY OVER THE SOUTH PUGET SOUND AND SOUTHWEST
INTERIOR.

THE UPPER LEVEL RIDGE AXIS WILL MOVE OVER THE ID BORDER TUESDAY
AFTERNOON...WHICH WILL OPEN UP W WA TO MOIST SW FLOW ALOFT COMING
OFF THE NE PACIFIC. A STRING OF UPPER LEVEL SHORTWAVE TROUGHS
EMBEDDED IN THE FLOW WILL REACH W WA INTO THE WEEKEND. MODELS ARE IN
PRETTY GOOD AGREEMENT THAT THE FIRST WEAK UPPER LEVEL SHORTWAVE
TROUGH WILL REACH W WA TUESDAY NIGHT. THE GFS SHOWS ANOTHER WEAK BUT
WETTER SHORTWAVE RIGHT BEHIND IT ON WEDNESDAY. THE ECWMF AND
CANADIAN ARE BOTH DRIER AND HOLD PRECIP OFF UNTIL WEDNESDAY NIGHT OR
THURSDAY. AT THIS POINT THE COMPROMISE FORECAST IS FOR PARTLY CLOUDY
SKIES WEDNESDAY...SLIGHTLY COOLER TEMPERATURES AND A CHANCE OF RAIN
ON THE COAST. KAM

.LONG TERM...A WARM FRONT WILL LIFT NORTH THROUGH WESTERN WA ON
THURSDAY FOR AN INCREASE IN CLOUDS AND A CHANCE OF RAIN ACROSS THE
REGION. HOWEVER MODELS HAVE BEEN BACKING OFF ON THIS SYSTEM AND MAY
NOT SEE MUCH RAIN IN THE INTERIOR. FRIDAY IS LOOKING WETTER AS AN
UPPER LEVEL TROUGH DIGS OFF THE COAST AND MOVES INLAND. THERE IS A
CHANCE OF SHOWERS ON SATURDAY WITH ONSHORE FLOW AND A WEAK
DISTURBANCE ALOFT. WE MAY SEE A BREAK IN THE WEATHER ON
SUNDAY...THEN A WETTER PAC SYSTEM ARRIVES SUNDAY NIGHT INTO MONDAY.
33

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED IN THE NEXT 7 DAYS.

&&

.AVIATION...AN UPPER LEVEL RIDGE OVER THE REGION WILL STRENGTHEN
OVERNIGHT. CONTD WLY FLOW ALOFT WITH LOW LEVEL FLOW REMAINING
OFFSHORE. CIGS GENERALLY REMAINING VFR TONIGHT...ALTHOUGH FOG PRONE
AREAS WILL SEE FOG AND ASSOCIATED DIMINISHED VISIBILITIES DEVELOPING
AFTER 06Z AND CONTINUING INTO LATE MONDAY MORNING BEFORE BURNING
OFF. SMR

KSEA...NLY WINDS TURNING NE TONIGHT REMAINING GENERALLY LIGHT AT
AROUND 5 KTS. TERMINAL KIND OF ON THE BORDER AS TO WHERE FOG IS
EXPECTED TO DEVELOP. WHILE REDUCTIONS IN VISIBILITY ARE IN CURRENT
TAFS...WILL REVISIT THIS FORECAST ISSUE FOR 06Z TAF ISSUANCE AS A
LAYER OF CIRRUS MAY INHIBIT FOG DEVELOPMENT LATER
TONIGHT...KEEPING CONFIDENCE IN ANY FOG FORECAST LOW. SMR
.

&&

.MARINE...LOWER PRES OVER THE OFFSHORE WATERS WITH HIGH PRESSURE E
OF THE CASCADES WILL KEEP THE FLOW EASTERLY THROUGH
MIDWEEK...ALTHOUGH THE SURFACE HIGH WILL WEAKEN WITH TIME. A WEAK
WARM FRONT MAY CLIP THE AREA ON WED. NC/SMR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT TIL 6 AM MONDAY FOR THE COASTAL
     WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT TO 10 NM AND THE
     WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.

&&

$$

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