Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 101604
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
903 AM PDT WED SEP 10 2014

.SYNOPSIS...HIGH PRESSURE WILL MAINTAIN A DRY WEATHER PATTERN INTO
EARLY NEXT WEEK. OFFSHORE WINDS WILL BECOME BREEZY IN EXPOSED SPOTS
LATER TODAY THROUGH THURSDAY. ABUNDANT SUNSHINE WILL ACCOMPANY A
VERY GRADUAL WARMING TREND OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...A HIGH AMPLITUDE RIDGE IS OVER THE NE PAC TODAY WITH
NORTHERLY FLOW ALOFT OVER WESTERN WA. AT THE SURFACE...PRESSURE
GRADIENTS ARE OFFSHORE WITH A THERMALLY INDUCED TROUGH OF LOW PRES
ALONG THE COAST AND HIGH PRES CENTERED OVER B.C./ALBERTA. OFFSHORE
FLOW WILL INCREASE THIS MORNING AND AFTERNOON WHICH WILL SCOUR OUT
THE LOW LEVEL MOISTURE...WITH SKIES BECOMING CLEAR ACROSS ALL OF
WESTERN WA. THERE IS ALREADY CLEARING OVER THE STRAIT AND NORTHWEST
INTERIOR. THE SEATTLE METRO SHOULD SEE LOW CLOUDS SCATTERING OUT BY
NOON. EXPECT NORTH WINDS OF 15 TO 25 MPH THROUGH THE INTERIOR TODAY
AND TONIGHT. TEMPS WILL BE CLOSE TO NORMAL WITH HIGHS IN THE MID 60S
TO LOWER 70S.

OFFSHORE FLOW WILL BRING A DRIER AIR MASS INTO WESTERN WA TONIGHT
WITH DEW POINTS DROPPING INTO THE 30S. THIS COMBINED WITH BREEZY
WINDS SHOULD LIMIT FOG DEVELOPMENT. BUT SHELTERED AREAS /LIKE KOLM
AND KUIL/ WILL ALSO SEE A DROP IN TEMPS FOR FAIRLY CHILLY
LOWS...UPPER 30S EXPECTED.

HIGH PRESSURE ALOFT COMBINED WITH LOW LEVEL OFFSHORE FLOW WILL
CONTINUE TO PRODUCE DRY AND STABLE WEATHER THROUGH THE WEEKEND.
TEMPS WILL MODERATE EACH DAY WITH HIGHS ABOVE NORMAL THROUGH THE
PERIOD. THE INTERIOR WILL SEE HIGHS IN THE LOWER 80S BOTH SAT AND
SUN. EVEN THE COAST SHOULD SEE LOWER 80S. THE COOL SPOTS WILL BE THE
STRAIT AND SAN JUANS WITH HIGHS IN THE 70S. LOWS WILL LIKELY RANGE
IN THE 40S TO LOWER/MID 50S. 33

.LONG TERM...PREVIOUS DISCUSSION...DRY WEATHER SHOULD PERSIST
THROUGH NEXT TUESDAY. THE AIR MASS WILL TRANSITION TO A WARMER
OFFSHORE FLOW PATTERN THIS WEEKEND. HIGH PRESSURE ALOFT REMAINS
ANCHORED OFFSHORE...THEN TRAVERSES THE PAC NW MONDAY. MODELS SHOW
850 MB TEMPERATURES WARMING TO 16-18C WITH CONTINUED LOW LEVEL
OFFSHORE FLOW. HIGHS SHOULD RISE TO THE MID/UPPER 70S...AND INTO THE
LOW 80S BY SUNDAY OR MONDAY AROUND PUGET SOUND/SW INTERIOR. AVERAGE
HIGH TEMPERATURES FOR THIS TIME OF YEAR AROUND ARE IN THE LOW 70S.

LONG RANGE MODELS ARE AT ODDS ON A POSSIBLE WEAK UPPER LOW REACHING
THE AREA BY TUESDAY. RIGHT NOW NONE OF THE MODELS REALLY SHOW MUCH
SURFACE REFLECTION. SOME PREVIOUS RUNS WERE SHOWING A WEAK PUSH SO
NO CHANGES WERE MADE TO THE FORECAST GIVEN THE UNCERTAINTY. MERCER

&&

.AVIATION...FLOW ALOFT WILL REMAIN NORTHWESTERLY THROUGH THURSDAY.
LOW LEVEL ONSHORE FLOW WILL BECOME INCREASINGLY NORTHERLY AND
OFFSHORE TODAY. THE AIR MASS IS STABLE AND DRY EXCEPT FOR MARINE
STRATUS AND FOG OVER THE LOWLANDS THIS MORNING.

GENERALLY IFR CEILINGS COVER MOST OF THE LOWLANDS THIS MORNING.
CEILINGS WILL LIFT BY MID MORNING TO MVFR LEVELS AND SCATTER OUT BY
MID DAY OVER THE INTERIOR. THE COAST WILL IMPROVE AT A SLOWER
PACE...CLEARING BY AFTERNOON.

KSEA...IFR CEILINGS WILL LIFT BY MID MORNING AND SCATTER OUT LATE
MORNING. LIGHT WIND WILL BECOME NORTHERLY 4-8 KT 14Z AND STRENGTHEN
TO 10-15 KT DURING THE AFTERNOON. CHB

&&

.MARINE...LOW LEVEL FLOW WILL BECOME INCREASINGLY OFFSHORE AND
NORTHERLY TODAY AS A SURFACE HIGH DROPS SOUTH ACROSS ALBERTA AND A
THERMALLY INDUCED SURFACE TROUGH WORKS NORTH ALONG THE WASHINGTON
COAST. THIS PATTERN WILL PRODUCE SMALL CRAFT ADVISORY NORTHEASTERLY
TO NORTHERLY WINDS OVER MUCH OF THE INTERIOR WATERS AT TIMES TODAY
THROUGH THURSDAY. EAST WINDS ARE ALSO EXPECTED TO REACH SMALL CRAFT
ADVISORY LEVELS IN THE WESTERN STRAIT AND NORTHERN INNER COASTAL
WATERS THIS AFTERNOON AND EVENING...EASING AFTER MIDNIGHT...THEN
INCREASING AGAIN THURSDAY. THE OFFSHORE FLOW PATTERN WILL CONTINUE
THROUGH SATURDAY. CHB

&&

SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY WEST ENTRANCE TO THE STRAIT OF JUAN DE
     FUCA...NORTHERN INNER COASTAL WATERS...NORTHERN INLAND
     WATERS...ADMIRALTY INLET...PUGET SOUND AND HOOD CANAL.

&&

$$

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