Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 010337
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT THU JUL 31 2014

.SYNOPSIS...A STRONG RIDGE OF HIGH PRESSURE OVER THE PACIFIC
NORTHWEST WILL BRING MAINLY SUNNY AND WARM WEATHER TO WESTERN
WASHINGTON INTO NEXT WEEK. LIGHT ONSHORE FLOW WILL RESULT IN SOME
NIGHT AND MORNING LOW CLOUDS...ESPECIALLY AT THE COAST. WEAK
INSTABILITY ALOFT COULD PRODUCE ISOLATED THUNDERSTORMS FRIDAY
THROUGH SUNDAY...MAINLY OVER THE MOUNTAINS.

&&

.SHORT TERM...THE LARGE-SCALE PATTERN REMAINS THE SAME AS IT HAS FOR
SEVERAL DAYS NOW...WITH A LARGE UPPER LEVEL RIDGE COVERING THE
WESTERN UNITED STATES. MONSOONAL MOISTURE MOVING NORTHWARD ALONG THE
WEST SIDE OF THE RIDGE IS PRODUCING THUNDERSTORMS ALONG THE OREGON
CASCADES AND ACROSS EASTERN WASHINGTON...WITH A SINGLE STRIKE OVER
YAKIMA COUNTY EARLIER THIS EVENING. ASIDE FROM A FEW HIGH DEBRIS
CLOUDS...THE SKIES OVER THE FORECAST AREA ARE VIRTUALLY CLEAR --
INCLUDING AN ABSENCE OF MARINE STRATUS OVER THE COAST OR COASTAL
WATERS.

THERE WILL BE LITTLE CHANGE IN THE SYNOPTIC PATTERN TONIGHT OR
FRIDAY. ASIDE FROM THE DIURNAL SEABREEZE -- SHOWING UP MAINLY AS
GALE WESTERLIES IN THE STRAIT OF JUAN DE FUCA AGAIN THIS EVENING --
THE LOW LEVEL FLOW IS WEAKLY OFFSHORE...AND IT WILL TURN ONLY WEAKLY
ONSHORE LATE TONIGHT. THERE COULD BE A LITTLE COASTAL STRATUS BUT
LITTLE TO ANY INLAND TONIGHT OR FRIDAY MORNING.

THERE IS A MINOR UPPER LOW OVER THE CENTRAL OREGON WATERS THIS
EVENING...AND IT WILL MOVE NORTHWARD THROUGH THE WASHINGTON COASTAL
WATERS LATER TONIGHT AND FRIDAY. THIS FEATURE COULD DRAW THE
CONVECTIVE ACTIVITY OVER THE OREGON CASCADES NORTH OR NORTHWEST INTO
OUR FORECAST AREA. SO THERE IS A POSSIBILITY OF ISOLATED
THUNDERSTORMS OVER PARTS OF THE WESTERN WASHINGTON LOWLANDS LATE
TONIGHT THROUGH FRIDAY EVENING...AS WELL AS THE MOUNTAINS. THE
FORECAST FOR ONLY PARTLY SUNNY SKIES FRIDAY IS DUE TO THE CLOUDS
ASSOCIATED WITH THAT ACTIVITY...BUT CERTAINLY WE COULD END UP WITH
MOSTLY SUNNY SKIES.

THE FAMILIAR PATTERN OF THE UPPER RIDGE AND LIGHT ONSHORE LOW LEVEL
FLOW WILL CONTINUE SATURDAY AND SUNDAY. COASTAL STRATUS WILL
PROBABLY BE PRESENT AND MOVE INLAND A BIT EACH NIGHT. DAY BREAK
STRATUS OVER THE WESTERN WASHINGTON INTERIOR WILL GIVE WAY QUICKLY
TO SUNSHINE. ISOLATED THUNDERSTORMS ARE POSSIBLE OVER THE
MOUNTAINS...ESPECIALLY ALONG THE CASCADES CREST SATURDAY.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- A RIDGE WILL STRENGTHEN OVER THE PAC NW EARLY
NEXT WEEK. THIS WILL BRING A RETURN TO WARMER TEMPERATURES AND LESS
MORNING CLOUD COVER OVER THE INTERIOR. HIGHS MONDAY THROUGH MID WEEK
WILL GENERALLY BE IN THE 80S AROUND PUGET SOUND. BY THURSDAY SOME
LONG RANGE MODELS TRY TO DEVELOP WESTERLIES OVER THE NE PACIFIC.
THIS COULD RESULT IN STRONGER ONSHORE FLOW AND COOLER DAYTIME
TEMPERATURES. THERE ARE NO WELL DEFINED FRONTS APPROACHING THE AREA
SO IT LOOKS TO STAY DRY THROUGH NEXT WEEK. MERCER

&&

.AVIATION...A RIDGE IS OVER THE WRN U.S. WITH SSW FLOW ALOFT OVER
WA. AT THE SURFACE THERE IS HIGH PRESSURE OFFSHORE WITH THERMAL LOW
PRESSURE INLAND. A DISTURBANCE OVER OREGON WILL MOVE NORTH AND SOME
MOISTURE AND INSTABILITY WILL REACH WRN WA LATER TONIGHT AND FRIDAY.
THERE WILL BE SOME MID AND HIGH CLOUDS AND PERHAPS ACCAS WITH A
CHANCE OF TSTMS FRI. PATCHY FOG WILL BE CONFINED TO THE COAST AND
THERE IS NO FOG OR LOW CLOUDS OVER THE COASTAL WATERS THIS EVENING
WHICH IS A BIT OF A SURPRISE. AT 8PM THERE WERE A THUNDERSTORM NEAR
NEWPORT OREGON SO IT WILL BE WORTH CHECKING THE RADAR LATER TONIGHT
AND FRIDAY.

KSEA...MID LEVEL CLOUDS AND MAYBE SOME ACCAS WITH A SLIGHT CHANCE OF
A HIGH BASED THUNDERSTORM WILL REACH THE PUGET SOUND AREA LATER
TONIGHT AND FRIDAY. THE CHANCE OF A STORM OVER SEATTLE IS PRETTY LOW
BUT IT WILL BE WORTH WATCHING THE RADAR LATER TONIGHT THROUGH FRIDAY.

&&

.MARINE...HIGH PRESSURE IS OVER THE OFFSHORE WATERS WITH THERMAL LOW
PRESSURE EAST OF THE CASCADES...AND THAT HASN`T CHANGED OVER THE
PAST FEW DAYS. WHAT IS DIFFERENT IS THAT THERE IS A WEATHER
DISTURBANCE OVER OREGON MOVING NORTH AND A THUNDERSTORM NEAR NEWPORT
OREGON AT 8PM. WE MAY SEE A COUPLE OF STORMS OVER WRN WA LATE
TONIGHT AND FRIDAY. OTHERWISE...THE FAIRLY STRONG SUMMERTIME
WESTERLY SEA BREEZE FLOW IN THE STRAIT OF JUAN DE FUCA WITH A PRETTY
GOOD NW BREEZE OVER THE COASTAL WATERS CONTINUES. AT 8PM RACE ROCKS
HAD WEST 35 KNOTS...SO A GALE WARNING WILL BE UP FOR A FEW HOURS FOR
THE CENTRAL STRAIT.

&&

.FIRE WEATHER...ELEVATED THUNDERSTORMS COULD MOVE UP INTO INTERIOR
OF WESTERN WASHINGTON ON FRIDAY MORNING. HARD TO PIN DOWN EXACTLY
WHICH ZONES WILL BE AFFECTED...BUT CONFIDENCE HIGH ENOUGH TO ADD
THUNDERSTORMS TO THE FORECAST FOR ALL BUT THE COAST AND WESTERN
OLYMPIC MOUNTAINS. IN THE AFTERNOON...SURFACE-BASED THUNDERSTORMS
MAY DEVELOP OVER THE HIGHEST MOUNTAIN PEAKS...WITH STORM MOTION FROM
SOUTH TO NORTH.

SINCE THE HEAVY RAINS LAST WEEK...FUELS HAVE DRIED TO PRE-REQUISITE
DRYNESS NEEDED TO CONSIDER RED FLAG WARNINGS IN LOWLANDS ZONES FROM
SEATTLE ON SOUTH...OVER THE EASTERN OLYMPIC MOUNTAINS...AND IN THE
STEHEKIN AREA. FUELS REMAIN TOO MOIST IN OTHER LOCATIONS SUCH AS THE
NORTH INTERIOR...WESTERN OLYMPIC PENINSULA AND WEST SLOPES OF THE
CASCADES. HAVE ISSUED A FIRE WEATHER WATCH FOR THE EAST SIDE OF
NORTH CASCADES NATIONAL PARK (STEHEKIN AREA)...WHICH IS THE ONLY
ZONE WHERE FUELS ARE DRY ENOUGH AND THE CONFIDENCE FOR SCATTERED
LIGHTNING ON FRIDAY IS HIGH ENOUGH FOR SUCH AN ISSUANCE. OF
COURSE...A FIRE WEATHER WATCH OFTEN PRECEDES A RED FLAG WARNING.
OVER THE INTERIOR LOWLANDS OF WESTERN WASHINGTON...MERELY CALLING
FOR ISOLATED LIGHTNING...WHICH IS NOT WIDESPREAD ENOUGH TO WARRANT
A RFW.    HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL STRAIT OF JUAN DE FUCA.
     SMALL CRAFT ADVISORY EAST ENTRANCE TO THE STRAIT OF JUAN DE
       FUCA...COASTAL WATERS FROM JAMES ISLAND TO CAPE SHOALWATER OUT
       TO 10 NM.
     GALE WATCH LATE FRIDAY AFTERNOON AND FRIDAY NIGHT FOR THE
       CENTRAL STRAIT OF JUAN DE FUCA AND EAST ENTRANCE STRAIT.

&&

$$

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




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