Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 312242
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PDT FRI JUL 31 2015

.SYNOPSIS...A STRONG UPPER LEVEL RIDGE BRINGING HOT TEMPERATURES
WILL REMAIN OVER THE PACIFIC NORTHWEST THROUGH LATE SUNDAY...WHEN IT
WILL WEAKEN AND SHIFT EASTWARD. AN UPPER LEVEL TROUGH WILL NEAR THE
AREA BY THE MIDDLE OF NEXT WEEK. TEMPERATURES WILL MODERATE TO NEAR
NORMAL WITH A CHANCE OF A FEW SHOWERS WEDNESDAY THROUGH THE END OF
NEXT WEEK.

&&

.SHORT TERM...A STRONG UPPER LEVEL RIDGE IS CURRENTLY SITUATED OVER
THE AREA. GRADIENTS NEAR THE SURFACE ARE NWLY AND THE FLOW IS LIGHT
TO MODERATE NLY AND ONSHORE. HIGHS MAY COOL OFF SLIGHTLY SATURDAY
AND SUNDAY...THANKS TO UPPER LEVEL HEIGHTS DECREASING BY A FEW
DMS...BUT CONFIDENCE IS HIGH THAT TEMPERATURES WILL REMAIN VERY WARM
THROUGH SUNDAY. EXPECT LOWS OVERNIGHT TONIGHT AS WELL AS SATURDAY
NIGHT TO REMAIN AS HIGH AS THE MID 60S IN THE PUGET SOUND AREA.

LATER SUNDAY AND INTO MONDAY MORNING...EXPECT A WEAK MARINE PUSH TO
MOVE THROUGH THE AREA AS SURFACE GRADIENTS SWITCH TO MORE WLY OR
SWLY AND THE UPPER LEVEL RIDGE WEAKENS AND SHIFTS FURTHER EASTWARD.
THIS SHOULD MODERATE TEMPERATURES QUITE A BIT...DROPPING HIGHS INTO
THE 70S AND LOWER 80S ON MONDAY...AND POSSIBLY BRINGING AREAS OF
MORNING CLOUDS. JSMITH

.LONG TERM...ON TUESDAY MODELS HAVE BEEN FAIRLY CONSISTENT IN
SHOWING A SHORTWAVE TROUGH APPROACHING THE AREA. EXPECT CONDITIONS
SIMILAR TO MONDAY...BUT PERHAPS A FEW DEGREES COOLER.

WEDNESDAY THROUGH FRIDAY THE MODELS DIVERGE...WITH THE ECMWF AND
CANADIAN MODELS SHOWING AN UPPER LEVEL CLOSED LOW DROPPING DOWN
ALONG THE COAST FROM HAIDA GWAII AND MOVING DIRECTLY OVER WESTERN
WASHINGTON ON THURSDAY. IN THIS CASE...THE WHOLE AREA COULD SEE
SHOWERS ON THURSDAY AND HIGHS COULD FALL SLIGHTLY BELOW NORMAL. THE
TWO MOST RECENT GFS RUNS HAVE BEEN OUTLIERS...BRINGING THE LOW WELL
TO THE NORTH OF US ACROSS NORTHERN BC. IN THIS CASE...THE AREA WOULD
NOT SEE ANY SHOWERS AT ALL AND SEE NORMAL TO SLIGHTLY ABOVE NORMAL
TEMPERATURES. AS WE GET INTO NEXT WEEK...HOPEFULLY THE MODELS WILL
BEGIN TO CONVERGE ON A SINGLE SOLUTION. JSMITH

&&

.AVIATION...A BROAD UPPER RIDGE WILL REMAIN OVER THE REGION
THROUGH SATURDAY WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS
WILL BE DRY AND STABLE.

STRATUS WILL PROBABLY FORM ALONG THE WASHINGTON COAST AND IN THE
WESTERN STRAIT OF JUAN DE FUCA TONIGHT...BRINGING LOCAL IFR
CONDITIONS TO ADJACENT LAND AREAS. THE STRATUS WILL BURN OFF AGAIN
SATURDAY MORNING. OTHERWISE CLEAR SKIES WILL CONTINUE ACROSS THE
FORECAST AREA.

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

&&

.MARINE...PERSISTENT HIGH PRESSURE OFFSHORE AND LOWER PRESSURE EAST
OF THE CASCADES WILL MAINTAIN LIGHT NORTHWEST PRESSURE GRADIENTS
ACROSS THE FORECAST AREA THROUGH TONIGHT. ONSHORE FLOW WILL
INCREASE THIS WEEKEND. SMALL CRAFT ADVISORY NORTHWEST WINDS ARE
LIKELY OVER THE OUTER COASTAL WATERS TONIGHT THROUGH AT LEAST
SATURDAY NIGHT...WITH SMALL CRAFT ADVISORY NORTHWESTERLIES DURING
THE EVENING HOURS OVER THE SOUTHERN TWO COASTAL INNER COASTAL WATERS
ZONES. SMALL CRAFT ADVISORY WESTERLIES ARE LIKELY IN THE CENTRAL
STRAIT OF JUAN DE FUCA AND EAST ENTRANCE STRAIT TONIGHT...WITH GALE
FORCE WESTERLIES POSSIBLE THERE SATURDAY NIGHT AND SUNDAY NIGHT. A
GALE WATCH IS BEING ISSUED WITH THE AFTERNOON FORECAST PACKAGE.
SOMEWHAT WEAKER ONSHORE FLOW SHOULD PREVAIL NEXT WEEK.

&&

.FIRE WEATHER...A CRITICAL PERIOD FOR FIRE WEATHER CONTINUES OVER
ALL OF WESTERN WASHINGTON...WITH A VERY DRY AIR MASS IN PLACE. THE
IMMEDIATE COAST IS SEEING SOME RELIEF THIS AFTERNOON FROM SEA BREEZES
WHICH HAVE RAISED DEWPOINTS INTO THE UPPER 50S AT HOQUIAM AND
QUILLAYUTE. ELSEWHERE ACROSS WESTERN WASHINGTON...DRY AIR PERSISTS.

IN ADDITION...ELEVATED MOUNTAIN LOCATIONS ARE FEELING THE ADDED
EFFECT OF SOMEWHAT UNSTABLE MID-LEVEL AIR...WITH BOTH MID-LEVEL AND
HIGH-LEVEL HAINES 5 CONDITIONS CONTINUING THROUGH SATURDAY EVENING.
VISIBLE SATELLITE IMAGERY SHOWS A BURST OF SMOKE THIS AFTERNOON
COMING FROM THE PARADISE FIRE...SO IT APPEARS THE FIRE IS FEELING
THE EFFECTS OF THE DRY AND UNSTABLE AIR MASS. WILL KEEP THE RED FLAG
WARNING GOING FOR ELEVATIONS ABOVE 2000 FEET UNTIL SATURDAY EVENING
FOR THE DRY AND UNSTABLE AIR MAS. LARGE FIRE GROWTH IN WESTERN
WASHINGTON HISTORICALLY TAKES PLACE UNDER SUCH CONDITIONS.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 SATURDAY NIGHT FOR THE
 CASCADES AND OLYMPICS ABOVE 2000 FEET.

PZ...SMALL CRAFT ADVISORY COASTAL WATERS EXCEPT ZONE 150...CENTRAL
     STRAIT OF JUAN DE FUCA...EAST ENTRANCE STRAIT.
     GALE WATCH CENTRAL STRAIT OF JUAN DE FUCA...EAST ENTRANCE
     STRAIT FOR SATURDAY NIGHT.

&&

$$

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


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