Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 250354
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
855 PM PDT THU JUL 24 2014

.SYNOPSIS...MOIST ONSHORE FLOW WILL CONTINUE TONIGHT AND FRIDAY AS A
WEAK WEATHER SYSTEM MOVES TO THE BRITISH COLUMBIA COAST. THERE COULD
BE SOME LIGHT SHOWERS...ESPECIALLY AT THE COAST...BUT THE WESTERN
WASHINGTON INTERIOR SHOULD BE MOSTLY SUNNY FRIDAY AFTERNOON. HIGH
PRESSURE ALOFT WILL BUILD OVER THE REGION THIS WEEKEND...BRINGING
SUNNY WARM WEATHER THAT SHOULD CONTINUE NEXT WEEK.

&&

.SHORT TERM...MOIST ONSHORE FLOW WILL CONTINUE TONIGHT. RADAR SHOWS
THE PUGET SOUND CONVERGENCE ZONE FROM EARLIER TODAY HAS PRETTY MUCH
ENDED AND SHOWERS LOOK THEY WILL BE CONFINED TO THE CASCADES FOR THE
REMAINDER OF TONIGHT...WITH MAYBE A FEW ALSO NEAR THE COAST AS A
VERY WEAK SYSTEM APPROACHES FROM THE WEST. CLOUDS HAVE CLEARED A BIT
THIS EVENING...ESPECIALLY OVER THE NORTHWEST AND SOUTHWEST INTERIOR
BUT THEY SHOULD FILL BACK IN WITH CONTINUED ONSHORE FLOW.

A VERY WEAK UPPER LEVEL DISTURBANCE WILL REACH THE AREA FRIDAY. THE
LATEST NAM AND ECMWF WASH THIS FEATURE OUT COMPLETELY WHILE THE GFS
HAS SOME DRIPS AND DRABS NEAR THE COAST AND OVER THE NORTH CASCADES.
THE LOW LEVELS WILL BE DRYING BY AFTERNOON WHICH SHOULD RESULT IN
SOME MID TO LATE AFTERNOON SUNSHINE. HIGHS WILL WARM SEVERAL DEGREES
MOST AREAS. UPPER HEIGHTS WILL CONTINUE TO RISE ACROSS THE REGION
THIS WEEKEND...GIVING MOSTLY SUNNY AND WARMER WEATHER. SCHNEIDER

.LONG TERM...THE UPPER RIDGE WILL BE ALONG THE ROCKY MOUNTAINS ON
MONDAY AND IT SHOULD KEEP WESTERN WASHINGTON DRY THROUGH AT LEAST
THURSDAY. SOME RECENT RUNS OF THE LONGER RANGE MODELS -- ESPECIALLY
OF THE ECMWF -- SHOW THE UPPER RIDGE SHIFTING WESTWARDS TOWARD OUR
AREA DURING THE MIDDLE OF THE WEEK...WHICH WOULD RESULT IN WARMER
WEATHER YET. FOR NOW WE CAN EXPECT LIGHT ONSHORE FLOW TO KEEP THE
COAST IN THE UPPER 60S TO 70S...WITH TEMPERATURES IN THE 80S TO
LOWER 90S INLAND.   MCDONNAL

&&

.AVIATION...WEAK UPPER LEVEL RIDGING AND MODERATE WESTERLY FLOW
ALOFT WILL SETTLE OVER THE REGION TONIGHT AND FRIDAY. THE MODERATE
ONSHORE LOW LEVEL ONSHORE FLOW THAT ESTABLISHED ITSELF THIS
AFTERNOON WILL WEAKEN AFTER MIDNIGHT.

THE AIR MASS STILL REMAINS SOMEWHAT UNSTABLE THIS EVENING...THOUGH
THE PUGET SOUND CONVERGENCE ZONE THAT FORMED THIS AFTERNOON HAS
DISSIPATED...LEAVING ONLY A FEW ISOLATED SHOWERS MAINLY OVER THE
CASCADES AND THE COASTAL WATERS. EXPECT THE AIR MASS TO CONTINUE TO
DRY AND BECOME MORE STABLE OVERNIGHT...THE EXCEPTION IS THE COAST
AND OLYMPICS WHERE A WEAK UPPER LEVEL SYSTEM MOVING INTO BRITISH
COLUMBIA COULD BRING A LITTLE RAIN OR DRIZZLE LATE TONIGHT INTO
FRIDAY MORNING.

CONDITIONS WILL REMAIN GENERALLY VFR TONIGHT WITH CEILINGS 4-6K
FT...FALLING TO MVFR LEVELS LATE TONIGHT AND FRIDAY MORNING. RAIN OR
DRIZZLE THAT MAY DEVELOP ALONG THE COAST WILL ALSO HELP LOWER
CONDITIONS. MORNING CLOUDS WILL LIFT TO VFR LEVELS BY MIDDAY...WITH
CLEARING OVER MUCH OF THE INTERIOR DURING THE AFTERNOON.

KSEA...VFR CONDITIONS...WITH CEILINGS 4-6K FT WILL PERSIST THIS
EVENING BEFORE LOWERING AROUND DAY BREAK TO MVFR LEVELS NEAR 1.5K
FT. LIGHT NORTHEAST WINDS 4 TO 6 KT WILL BECOME SOUTHWESTERLY BY
LATE MORNING.

&&

.MARINE...MODERATE ONSHORE FLOW HAS WEAKENED SOMEWHAT THIS
EVENING...KUIL TO KBLI GRADIENTS DOWN TO 1.3 MB AS OF 03Z. EXPECT
GRADIENTS TO CONTINUE TO WEAKEN WITH WINDS THROUGH THE STRAIT
DROPPING BELOW THE ADVISORY LEVEL OVER THE NEXT FEW HOURS.

EXPECT  A TYPICAL ONSHORE FLOW PATTERN THROUGH THE WEEKEND WITH HIGH
PRESSURE OVER THE COASTAL WATERS AND ONSHORE FLOW DRIVING WESTERLIES
THROUGH THE STRAIT...WITH SMALL CRAFT ADVISORY LEVEL WINDS POSSIBLE
AT TIMES DURING THE AFTERNOON AND EVENING HOURS. EXPECT 10 TO 20 KT
WINDS FRIDAY AFTERNOON AND SMALL CRAFT ADVISORY WINDS SATURDAY AND
SUNDAY EVENINGS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EAST STRAIT.

&&

$$

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







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