Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 012251
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
400 PM 900 AM PDT SAT AUG 1 2015

.SYNOPSIS...AN UPPER RIDGE WILL GRADUALLY WEAKEN OVER THE NEXT
COUPLE OF DAYS. ONSHORE FLOW WILL RETURN EARLY NEXT WEEK FOR COOLER
WEATHER. AN UPPER TROUGH WILL BRING A CHANCE OF SHOWERS TO THE
MOUNTAINS LATER IN THE WEEK.

&&

.SHORT TERM...TODAY IS ANOTHER 90+ DEGREE DAY FOR THE INTERIOR FROM
SEATTLE SOUTHWARD. HEIGHTS SUNDAY ARE JUST A TAD LOWER SO HIGH
TEMPERATURES WILL BE QUITE SIMILAR...PERHAPS A DEGREE OR TWO LOWER.
STILL LOOKING AT 90 DEGREES SUNDAY FOR THE SEATTLE AREA. THE HEAT
ADVISORY FOR THE INTERIOR WILL CONTINUE THROUGH SUNDAY EVENING.

MODELS SHOW SOME HIGH BASED CONVECTION IS POSSIBLE IN THE CASCADES
BEGINNING LATE SUNDAY NIGHT AND CONTINUING INTO MONDAY EVENING. HAVE
ADDED A CHANCE OF THUNDERSTORMS TO THE CASCADES THEN. OTHERWISE
MONDAY LOOKS MOSTLY SUNNY BUT COOLER. HEIGHTS FALL INTO THE 570S AS
A DEEP UPPER TROUGH MOVES ONTO THE CENTRAL BRITISH COLUMBIA COAST.
HIGH TEMPERATURES OVER INLAND AREAS WILL BE IN THE LOW TO MID 80S.

ON TUESDAY THE UPPER TROUGH MOVES SLOWLY INTO BRITISH COLUMBIA AND
HEIGHTS FALL FURTHER OVER WESTERN WASHINGTON. SOME MODELS HAVE HAD A
FAIR AMOUNT OF MOISTURE OVER WASHINGTON AS THIS TROUGH MOVES PAST
THE AREA. HOWEVER BOTH THE GFS AND EURO ARE PRETTY DRY NOW. HAVE
REMOVED ANY MENTION OF PRECIPITATION FROM THE FORECAST FOR THE
LOWLANDS. HIGH TEMPERATURES ON TUESDAY WILL BE MOSTLY IN THE 70S
WITH SOME LOW 80S OVER THE SOUTH INTERIOR. BURKE

.LONG TERM...THE UPPER TROUGH IN BRITISH COLUMBIA CONTINUES TO
INFLUENCE THE WEATHER OVER WESTERN WASHINGTON WEDNESDAY AND
THURSDAY. MAINLY IT IS A MATTER OF DEPRESSING THE HEIGHTS AND GIVING
A CHANCE OF SHOWERS TO THE MOUNTAINS. HAVE KEPT THE LOWLANDS DRY
WITH HIGH TEMPERATURES MAINLY IN THE 70S.

THE UPPER TROUGH IS PAST BY FRIDAY AND AN UPPER RIDGE ACTUALLY
BUILDS OVER THE AREA. THIS SHOULD KEEP THE WHOLE AREA INCLUDING THE
MOUNTAINS DRY...WITH SUNNY SKIES AND HIGH TEMPERATURES REBOUNDING
INTO THE LOW TO MID 80S INLAND. ANOTHER TROUGH COULD BRING A CHANCE
OF SHOWERS TO THE MOUNTAINS BY NEXT WEEKEND. BURKE

&&

.CLIMATE...JULY 2015 WAS THE WARMEST MONTH ON RECORD IN SEATTLE WITH
AN AVERAGE TEMPERATURE OF 71.2 DEGREES. THE OLD RECORD WAS 71.1
DEGREES SET IN AUGUST OF 1967. THIS RECORD INCLUDES THE FEDERAL
BUILDING RECORDS WHICH GO BACK TO THE 1890S.

IT WAS THE WARMEST JULY ON RECORD AT BOTH HOQUIAM AND FORKS. AT
HOQUIAM THE AVERAGE TEMPERATURE FOR JULY WAS 63.9 DEGREES BREAKING
THE RECORD OF 63.0 DEGREES SET IN 1958. AT FORKS THE AVERAGE
TEMPERATURE WAS 63.0 DEGREES BREAKING THE RECORD OF 61.4 SET IN
1990. RECORDS BEGAN IN HOQUIAM IN 1953 AND AT FORKS IN 1966.

OTHER LOCATIONS AROUND WESTERN WASHINGTON...AT BELLINGHAM IT WAS THE
2ND WARMEST JULY ON RECORD WITH AN AVERAGE TEMPERATURE OF 67.2. THE
RECORD IS 68.0 DEGREES SET IN 1958. OLYMPIA ALSO HAD THE SECOND
WARMEST JULY ON RECORD WITH AN AVERAGE TEMPERATURE OF 68.0 DEGREES.
THE RECORD IS 69.1 SET ALSO IN 1958. FELTON

&&

.AVIATION...A BROAD UPPER RIDGE WILL REMAIN OVER THE REGION THROUGH
SUNDAY WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS WILL BE STABLE
AND DRY...EXCEPT FOR SHALLOW MARINE MOISTURE MAINLY ALONG THE COAST.

MARINE STRATUS ALONG THE COAST WILL INCREASE TONIGHT AND MOVE INTO
THE LOWER CHEHALIS VALLEY LATE TONIGHT...BRINGING LOCAL IFR
VISIBILITY AND CEILINGS THROUGH SUNDAY MORNING. OTHERWISE SKIES WILL
REMAIN CLEAR ACROSS THE FORECAST AREA.

KSEA...NORTH TO NORTHWEST WIND MOSTLY 4-10 KT.   MCDONNAL

&&

.MARINE...HIGH PRESSURE OFFSHORE AND LOW PRESSURE EAST OF THE
CASCADES WILL RESULT IN STRONGER ONSHORE FLOW THROUGH THE MIDDLE OF
NEXT WEEK. SMALL CRAFT ADVISORY NORTHWEST WINDS ARE LIKELY OVER THE
OUTER COASTAL WATERS THROUGH AT LEAST SUNDAY MORNING...WITH SMALL
CRAFT ADVISORY NORTHWESTERLIES THIS EVENING OVER THE SOUTHERN TWO
INNER COASTAL WATERS ZONES. HIGH END SMALL CRAFT ADVISORY WESTERLIES
ARE LIKELY IN THE CENTRAL STRAIT OF JUAN DE FUCA AND EAST ENTRANCE
STRAIT TONIGHT AND SUNDAY NIGHT...AND GALES ARE NOT OUT OF THE
QUESTION. GALE FORCE WESTERLIES ARE A GOOD BET THERE MONDAY NIGHT.
MCDONNAL

&&

.FIRE WEATHER...THE UPPER LEVEL RIDGE WHICH HAS BEEN RESPONSIBLE FOR
THE VERY DRY AIR MASS IN RECENT DAYS WILL START TO LOOSEN ITS GRIP
ON THE AREA ON SUNDAY. IN FACT...AN UPPER RIDGE AXIS WILL PASS
WESTERN WASHINGTON TONIGHT AND EXIT EAST TO THE NORTHERN ROCKIES BY
SUNDAY EVENING. THIS WILL ALLOW THE AIR MASS TO MOISTEN JUST ENOUGH
TO LET THE RED FLAG WARNINGS EXPIRE THIS EVENING. ONCE THE RED FLAG
WARNING DOES EXPIRE LATE THIS EVENING...IT JUST MEANS THAT WEATHER
WILL BE LESS OF AN AGGRAVATING FACTOR IN THE FIRE ENVIRONMENT.
BACKGROUND FIRE DANGER WILL STILL BE ELEVATED DUE TO DRY FUELS.

THE NEW WRINKLE IN THE FIRE WEATHER FORECAST IS THE INTRODUCTION OF
ISOLATED DRY LIGHTNING TO THE CASCADES FROM LATE SUNDAY NIGHT UNTIL
EARLY MONDAY EVENING. AS THE UPPER RIDGE AXIS MOVES EAST...SOUTHERLY
FLOW ALOFT WILL DEVELOP AND BRING NORTH THE NEEDED MOISTURE AND
INSTABILITY. TODAY`S MODELS CAME AROUND TO SHOWING THE CASCADES AT
THE NORTHWEST EDGE OF A LARGER-SCALE LIGHTNING RISK AREA. THE FIRST
THREAT OVER THE CASCADES WILL BE FROM HIGH-BASED NOCTURNAL
CONVECTION THAT COULD BRING ISOLATED DRY LIGHTNING TO THE CASCADES
FROM MOUNT RAINIER ON SOUTH IN THE HOURS AROUND SUNRISE ON MONDAY.
THE LIGHTNING THREAT WILL REACH THE NORTH CASCADES ON MONDAY
AFTERNOON...THEN END ON MONDAY EVENING. A DRY SUB-CLOUD LAYER AND
THE STEADY FORWARD MOVEMENT OF THE STORMS IS A RECIPE FOR SUB-
WETTING RAINS WITH ANY STORMS.HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES... WA...HEAT ADVISORY REMAINS IN
EFFECT TIL 8 PM SUNDAY FOR PARTS OF THE PUGET SOUND REGION AND
SOUTHWEST INTERIOR.

     RED FLAG WARNING IN EFFECT TIL 10 PM THIS EVENING FOR THE
CASCADES AND OLYMPICS ABOVE 2000 FEET.

PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS AND TWO SOUTHERN
      INNER COASTAL WATERS ZONES...CENTRAL STRAIT OF JUAN DE
FUCA...EAST ENTRANCE STRAIT.

&&

$$

AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION CAN BE SEEN AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML


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