Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 102159
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM 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...AN UPPER LEVEL RIDGE IS OVER THE NE PAC WITH NORTHERLY
FLOW ALOFT OVER WESTERN WA. AT THE SURFACE...PRESSURE GRADIENTS ARE
OFFSHORE WITH A THERMALLY INDUCED TROUGH ALONG THE COAST AND HIGH
PRES CENTERED OVER ALBERTA. DRY OFFSHORE WINDS SCOURED OUT THE LOW
LEVEL MOISTURE THAT WAS OVER THE LOWLANDS THIS MORNING. DEWPOINTS
ARE DOWN IN THE 20S OVER THE NORTH INTERIOR WITH GUSTY NE WINDS TO
25 KT. THIS DRY AIR WILL CONTINUE WORKING ITS WAY SOUTH TONIGHT.
THE DRY AIR COMBINED WITH BREEZY NORTH WINDS SHOULD LIMIT FOG
DEVELOPMENT FOR CLEAR SKIES OVERNIGHT. BUT SHELTERED AREAS /LIKE
KOLM...KSHN AND KUIL/ WILL SEE FAIRLY CHILLY LOWS...TEMPS IN THE MID
TO UPPER 30S EXPECTED. AS MENTIONED ABOVE...EXPECT GUSTY N/NE WINDS
TONIGHT THROUGH THURSDAY. SUSTAINED WIND SPEEDS OF 10 TO 20 MPH WILL
BE COMMON THROUGH THE INTERIOR...WITH EAST WINDS 20 TO 30 MPH IN THE
CASCADE FOOTHILLS.

HIGH PRESSURE ALOFT COMBINED WITH LOW LEVEL OFFSHORE FLOW WILL
CONTINUE TO PRODUCE DRY AND STABLE WEATHER FRI 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...THE THERMALLY INDUCED TROUGH OF LOW PRES OVER THE COAST
WILL WEAKEN AND SHIFT INLAND ON MON. THIS WILL BRING SLIGHTLY COOLER
WEATHER TO THE COAST AS THE WINDS SWITCH BACK TO WESTERLY. THE UPPER
LEVEL RIDGE IS STILL OVERHEAD AT THIS POINT FOR ANOTHER ROUND OF
WARM AND DRY WEATHER IN THE INTERIOR.

AN UPPER LEVEL SHORT WAVE TROUGH WILL KICK THE RIDGE FARTHER INLAND
ON TUE AS IT TRACKS NORTH THROUGH WESTERN WA. THERE IS LITTLE
MOISTURE TAP WITH THIS FEATURE SO WILL STICK WITH A DRY FORECAST FOR
NOW. MODELS DO SHOW MARINE CLOUDS SURGING NORTH OVER THE COASTAL
WATERS TUE AFTERNOON AND EVENING WHICH MAY PUSH INLAND TUE
NIGHT...MAINLY OVER THE COAST. THE RIDGE WILL FINALLY EXIT ON WED AS
A COLD FRONT ARRIVES. LATEST MODELS ARE A LITTLE SLOWER...NOW
DELAYING THE FRONT UNTIL WED EVENING. BUT IN GENERAL WE SHOULD SEE
COOLER WEATHER WITH INCREASING CLOUDS ON WED...THEN RAIN POSSIBLE
WED NIGHT. 33

&&

.FIRE WEATHER...WITH FRASER OUTFLOW ALREADY OCCURRING RIGHT NOW NEAR
BELLINGHAM...CONFIDENCE IS HIGH THAT A COLD AIR MASS WILL SPREAD
DOWN EAST OF THE CASCADES TODAY. NORTHEAST-EAST PRESSURE GRADIENTS
WILL BECOME TIGHTLY PACKED ACROSS THE AREA TONIGHT...INDUCING ENOUGH
E-NE WIND AND LOW HUMIDITY ON THURSDAY AND POSSIBLY FRIDAY TO EASILY
EXCEED RED FLAG WIND AND HUMIDITY CRITERIA. IN GENERAL...FUELS ARE
TOO MOIST OVER THE NORTH INTERIOR AND THE NORTH CASCADES TO WARRANT
A RFW...BUT FUELS ARE DRY ENOUGH TO REACH CRITERIA WITH A COUPLE
DAYS OF WARM AND DRY WEATHER SOUTH OF A LINE FROM SILVERDALE TO
ENUMCLAW TO STAMPEDE PASS...AND OVER THE OLYMPIC PENINSULA. OF
COURSE...LIGHT FUELS WILL BE THE QUICKEST TO DRY OUT. THE
COMBINATION OF WIND AND LOW HUMIDITY ON THURSDAY AND FRIDAY WILL
CAUSE RAPID RATES OF SPREAD ON ANY FIRES THAT GET STARTED...
ESPECIALLY IN LIGHT FUELS SUCH AS TALL BROWN GRASS.

ON A DAY-TO-DAY SCALE...EAST WINDS WILL GRADUALLY EASE OVER THE
WEEKEND...BUT A WARM AND DRY AIR MASS WILL REMAIN IN PLACE. POOR
NIGHTTIME HUMIDITY RECOVERY WILL CONTINUE THROUGH MONDAY NIGHT ON
ELEVATED TERRAIN ABOVE RADIATION INVERSIONS. MID-LEVEL HAINES 5-6
CONDITIONS WILL BE PREVALENT ON SUNDAY AND MONDAY...INDICATING VERY
DRY AND SOMEWHAT UNSTABLE CONDITIONS IN THE 850-700 MB LAYER. THOSE
ATMOSPHERIC CONDITIONS SUPPORT AN ACTIVE BURNING ENVIRONMENT.
HANER

&&

.AVIATION...FLOW ALOFT WILL REMAIN NORTHWESTERLY THROUGH THURSDAY.
NORTHERLY AND OFFSHORE LOW LEVEL FLOW WILL CONTINUE THROUGH
THURSDAY. THE AIR MASS IS STABLE AND DRY. SKIES HAVE CLEARED NICELY
AND WILL REMAIN CLEAR TONIGHT AND THURSDAY.

KSEA...CLEAR SKIES. NORTHERLY WIND 4-8 KT WILL STRENGTHEN TO 10-15
KT DURING THE LATE AFTERNOON AND EVENING HOURS. GRADIENTS WILL TURN
EASTERLY THURSDAY AND SOME LLWS IS POSSIBLE. SURFACE WINDS WILL
REMAIN NORTHERLY WITH STRONG EAST WINDS 1K FT ABOVE THE SURFACE. CHB

&&

.MARINE...LOW LEVEL FLOW WILL REMAIN OFFSHORE AND NORTHERLY THROUGH
THE END OF THE WEEK AT LEAST. THIS PATTERN WILL PRODUCE SMALL CRAFT
ADVISORY NORTHEASTERLY WINDS OVER THE NORTH INTERIOR WATERS AND AT
THE WEST ENTRANCE AT TIMES TONIGHT AND THURSDAY. LATEST MODELS DO
NOT HAVE WIND OVER 20 KT ANYWHERE ELSE SO HAVE ENDED THE OTHER
ADVISORIES. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...RED FLAG WARNING FOR WIND AND LOW HUMIDITY ON THURSDAY AND
     FRIDAY IN FIRE WEATHER ZONES 649...650...651...654...655...
     657...659 AND 661.

PZ...SMALL CRAFT ADVISORY WEST ENTRANCE TO THE STRAIT OF JUAN DE
     FUCA...NORTHERN INNER COASTAL WATERS...AND NORTHERN INLAND
     WATERS.

&&

$$

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