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000
FXUS66 KSEW 190333
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
833 PM PDT THU SEP 18 2014

.SYNOPSIS...A WEAK DISTURBANCE WILL MOVE ACROSS THE AREA OVERNIGHT
INTO EARLY FRIDAY MORNING. LOOK FOR HIGH PRESSURE ALOFT TO BEGIN
BUILDING OVER THE REGION ON FRIDAY. STRONG HIGH PRESSURE ALOFT
ALONG WITH LOW LEVEL OFFSHORE FLOW WILL RESULT IN WELL ABOVE
NORMAL DAYTIME TEMPERATURES THIS WEEKEND.

&&

.SHORT TERM...
ZONAL FLOW ALOFT WILL PREVAIL ACROSS THE AREA TONIGHT. A WEAK
SHORT WAVE TROF EMBEDDED IN THIS FLOW WILL BRING PRECIP TO MAINLY
THE NORTHERN PART OF THE CWA OVERNIGHT INTO FRI MORNING. KLGX
DOPPLER RADAR CURRENTLY SHOWED THE LEADING EDGE OF THE RAIN SHIELD
NOT TOO FAR OFF THE NORTH COAST.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION ON FRI FOR
CLEARING SKIES. THE RIDGE WILL AMPLIFY FURTHER THIS WEEKEND. THIS
COMBINED WITH LOW LEVEL OFFSHORE FLOW WILL RESULT IN WELL ABOVE
NORMAL DAYTIME TEMPS ACROSS MUCH OF THE CWA.

.LONG TERM FROM THE PREV DISCUSSION...
THE UPPER RIDGE AXIS WILL MOVE OVER THE INTERMOUNTAIN WEST ON MON
AND THIS WILL ALLOW A WEAKENING OCCLUDED FRONT TO APPROACH THE
COAST. THIS FRONT WILL LIKELY DISSIPATE AS IT MOVES ONSHORE. THE
MAIN IMPACT WILL BE COOLER AND CLOUDIER WEATHER MON AND TUE.

BEYOND TUE...A STRONGER SYSTEM WILL IMPACT THE PACIFIC NORTHWEST
DURING THE LATTER PART OF THE EXTENDED PERIOD...RESULTING IN BELOW
NORMAL DAYTIME TEMPS AND BREEZY CONDITIONS. THIS SYSTEM IS
EXPECTED TO REMAIN OFF THE COAST THRU THU.

&&

.AVIATION...WESTERLY FLOW ALOFT TONIGHT AND FRIDAY. A WEAKENING
FRONT WILL REACH THE COAST FRIDAY MORNING AND DISSIPATE OVER THE
AREA LATER IN THE DAY. WEAK ONSHORE FLOW WILL CONTINUE WITH HIGH
PRESSURE ALONG THE COAST AND LOWER PRESSURE INLAND. AIR MASS MOIST
AND SLIGHTLY UNSTABLE. THERE WILL BE A MIX OF LOW AND MID CLOUDS
ACROSS THE AREA TONIGHT. THE TREND SHOULD BE FOR LOW CLOUDS TO
INCREASE OVERNIGHT.

KSEA...3000-4000 FOOT CEILINGS THIS EVENING SHOULD LOWER TO
1000-2000 FEET TONIGHT. SOUTHERLY WIND 4-8 KNOTS. SCHNEIDER

&&

.MARINE...WEAK HIGH PRESSURE WILL BE OVER THE COAST WITH LOWER
PRESSURE INLAND TONIGHT AND FRIDAY. SMALL CRAFT ADVISORY WEST WINDS
ARE POSSIBLE FOR THE CENTRAL AND EASTERN STRAIT THROUGH THE EARLY
MORNING HOURS FRIDAY BUT THE EVENT LOOKS MARGINAL AT BEST.

A DISSIPATING FRONT WILL MOVE THROUGH THE WATERS ON FRIDAY. OFFSHORE
FLOW WILL QUICKLY DEVELOP FRIDAY NIGHT AND CONTINUE THROUGH SUNDAY
MORNING AS A TROUGH BUILDS NORTH ALONG THE WEST COAST. SMALL CRAFT
ADVISORY EAST WINDS ARE POSSIBLE FOR THE WESTERN STRAIT SUNDAY
MORNING.

A WEAKENING TROUGH WILL REACH THE COASTAL WATERS MONDAY. A STRONGER
FRONTAL SYSTEM WELL OFFSHORE WILL BE APPROACHING FROM THE WEST ON
TUESDAY. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 2 AM FRIDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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000
FXUS66 KSEW 182246
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
346 PM PDT THU SEP 18 2014

.SYNOPSIS...A WEAK DISTURBANCE WILL MOVE ACROSS THE AREA LATER
TONIGHT THROUGH EARLY FRIDAY MORNING. HIGH PRESSURE ALOFT WILL
BEGIN BUILDING OVER THE REGION ON FRIDAY. LOOK FOR HIGH PRESSURE
ALOFT AND LOW LEVEL OFFSHORE FLOW TO PREVAIL THIS WEEKEND FOR WELL
ABOVE NORMAL DAYTIME TEMPERATURES.

&&

.SHORT TERM...
ZONAL FLOW ALOFT WILL PREVAIL ACROSS THE AREA TONIGHT. A WEAK
SHORT WAVE TROF EMBEDDED IN THIS FLOW WILL RESULT IN SOME SHOWERS
ACROSS MAINLY THE NORTHERN PART OF THE CWA. THE SHOWERS WILL
PERSIST INTO FRI MORNING.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION ON FRI. THE
RIDGE WILL AMPLIFY THIS WEEKEND. THIS COMBINED WITH LOW LEVEL
OFFSHORE FLOW WILL RESULT IN WELL ABOVE NORMAL DAYTIME TEMPS.
SOME PLACES COULD END UP TYING OR BREAKING DAILY RECORDS.

.LONG TERM...
THE UPPER RIDGE AXIS WILL MOVE OVER THE INTERMOUNTAIN WEST ON MON
AND THIS WILL ALLOW A WEAKENING OCCLUDED FRONT TO APPROACH THE
COAST. THIS FRONT WILL LIKELY DISSIPATE AS IT MOVES ONSHORE. THE
MAIN IMPACT WILL BE COOLER AND CLOUDIER WEATHER MON AND TUE.

BEYOND TUE...A STRONGER SYSTEM WILL IMPACT THE PACIFIC NORTHWEST
DURING THE LATTER PART OF THE EXTENDED PERIOD...RESULTING IN BELOW
NORMAL DAYTIME TEMPS AND BREEZY CONDITIONS. THIS SYSTEM IS
EXPECTED TO REMAIN OFF THE COAST THRU THU.

&&

.AVIATION...THE FLOW ALOFT IS WESTERLY AS AN UPPER LEVEL TROUGH
PUSHES INTO EASTERN WA. A WEAK WARM FRONT WILL SPREAD SPOTTY LIGHT
RAIN TO THE AREA TONIGHT. THE AIR MASS IS MOIST AND STABLE. CEILINGS
WILL LOWER TONIGHT WITH MVFR CONDITIONS LIKELY. A COLD FRONT WILL
CROSS THROUGH WESTERN WA FRI MORNING FOR A FEW MORE SHOWERS. 33

KSEA...CIGS LIKELY REMAINING IN MVFR RANGE TONIGHT WITH SPOTTY LIGHT
PRECIP IN THE VICINITY. SURFACE WINDS WILL REMAIN LIGHT SLY. 33

&&

.MARINE...SURFACE WINDS WILL BE MAINLY LIGHT ACROSS THE WATERS
TONIGHT WITH WEAK HIGH PRES ALONG THE COAST. HOWEVER...A WESTERLY
ONSHORE PUSH WILL BRING A FEW HOURS OF SMALL CRAFT ADVISORY WINDS
THROUGH THE CENTRAL AND EAST STRAIT OF JUAN DE FUCA THIS EVENING. A
WEAK COLD FRONT WILL CROSS THROUGH WESTERN WA ON FRIDAY. WINDS WILL
FLIP TO OFFSHORE FRI NIGHT THROUGH SAT AS A THERMALLY INDUCED TROUGH
OF LOW PRES FORMS ALONG THE COAST. THE WINDS WILL THEN TURN
SOUTHERLY ON SUN AS A SURFACE TROUGH DEVELOPS OVER THE OFFSHORE
WATERS. THIS TROUGH WILL CROSS THROUGH THE COASTAL WATERS ON MON. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 2 AM FRIDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
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000
FXUS66 KSEW 182246
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
346 PM PDT THU SEP 18 2014

.SYNOPSIS...A WEAK DISTURBANCE WILL MOVE ACROSS THE AREA LATER
TONIGHT THROUGH EARLY FRIDAY MORNING. HIGH PRESSURE ALOFT WILL
BEGIN BUILDING OVER THE REGION ON FRIDAY. LOOK FOR HIGH PRESSURE
ALOFT AND LOW LEVEL OFFSHORE FLOW TO PREVAIL THIS WEEKEND FOR WELL
ABOVE NORMAL DAYTIME TEMPERATURES.

&&

.SHORT TERM...
ZONAL FLOW ALOFT WILL PREVAIL ACROSS THE AREA TONIGHT. A WEAK
SHORT WAVE TROF EMBEDDED IN THIS FLOW WILL RESULT IN SOME SHOWERS
ACROSS MAINLY THE NORTHERN PART OF THE CWA. THE SHOWERS WILL
PERSIST INTO FRI MORNING.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION ON FRI. THE
RIDGE WILL AMPLIFY THIS WEEKEND. THIS COMBINED WITH LOW LEVEL
OFFSHORE FLOW WILL RESULT IN WELL ABOVE NORMAL DAYTIME TEMPS.
SOME PLACES COULD END UP TYING OR BREAKING DAILY RECORDS.

.LONG TERM...
THE UPPER RIDGE AXIS WILL MOVE OVER THE INTERMOUNTAIN WEST ON MON
AND THIS WILL ALLOW A WEAKENING OCCLUDED FRONT TO APPROACH THE
COAST. THIS FRONT WILL LIKELY DISSIPATE AS IT MOVES ONSHORE. THE
MAIN IMPACT WILL BE COOLER AND CLOUDIER WEATHER MON AND TUE.

BEYOND TUE...A STRONGER SYSTEM WILL IMPACT THE PACIFIC NORTHWEST
DURING THE LATTER PART OF THE EXTENDED PERIOD...RESULTING IN BELOW
NORMAL DAYTIME TEMPS AND BREEZY CONDITIONS. THIS SYSTEM IS
EXPECTED TO REMAIN OFF THE COAST THRU THU.

&&

.AVIATION...THE FLOW ALOFT IS WESTERLY AS AN UPPER LEVEL TROUGH
PUSHES INTO EASTERN WA. A WEAK WARM FRONT WILL SPREAD SPOTTY LIGHT
RAIN TO THE AREA TONIGHT. THE AIR MASS IS MOIST AND STABLE. CEILINGS
WILL LOWER TONIGHT WITH MVFR CONDITIONS LIKELY. A COLD FRONT WILL
CROSS THROUGH WESTERN WA FRI MORNING FOR A FEW MORE SHOWERS. 33

KSEA...CIGS LIKELY REMAINING IN MVFR RANGE TONIGHT WITH SPOTTY LIGHT
PRECIP IN THE VICINITY. SURFACE WINDS WILL REMAIN LIGHT SLY. 33

&&

.MARINE...SURFACE WINDS WILL BE MAINLY LIGHT ACROSS THE WATERS
TONIGHT WITH WEAK HIGH PRES ALONG THE COAST. HOWEVER...A WESTERLY
ONSHORE PUSH WILL BRING A FEW HOURS OF SMALL CRAFT ADVISORY WINDS
THROUGH THE CENTRAL AND EAST STRAIT OF JUAN DE FUCA THIS EVENING. A
WEAK COLD FRONT WILL CROSS THROUGH WESTERN WA ON FRIDAY. WINDS WILL
FLIP TO OFFSHORE FRI NIGHT THROUGH SAT AS A THERMALLY INDUCED TROUGH
OF LOW PRES FORMS ALONG THE COAST. THE WINDS WILL THEN TURN
SOUTHERLY ON SUN AS A SURFACE TROUGH DEVELOPS OVER THE OFFSHORE
WATERS. THIS TROUGH WILL CROSS THROUGH THE COASTAL WATERS ON MON. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 2 AM FRIDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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000
FXUS66 KSEW 181622
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
923 AM PDT THU SEP 18 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL CROSS WESTERN WASHINGTON
TODAY BRINGING MOSTLY CLOUDY SKIES AND SCATTERED SHOWERS. A SECOND
WEAKER UPPER LEVEL TROUGH WILL FOLLOW TONIGHT...PROLONGING THE
CHANCE OF SHOWERS THROUGH FRIDAY. A STRONG UPPER LEVEL RIDGE WILL
BUILD OVER THE REGION FRIDAY NIGHT AND SATURDAY...THEN SHIFT EAST ON
SUNDAY. THE RIDGE AND LOW LEVEL OFFSHORE FLOW WILL BRING SUNNY SKIES
AND HIGH TEMPERATURES IN THE 70S TO MID 80S. A SERIES OF UPPER LEVEL
TROUGHS WILL BRING A CHANCE OF RAIN AND COOLER WEATHER NEXT WEEK.

&&

.SHORT TERM...A WEAK UPPER LEVEL TROUGH AXIS WAS OVER WRN WA THIS
MORNING. THE TROUGH AXIS WILL MOVE EAST TO WRN MONTANA BY LATE THIS
EVNG. LARGE-SCALE LIFT IS FAIRLY WEAK...BUT THE AIR MASS IS VERY
MOIST. THE 12Z KUIL SOUNDING SHOWED PRECIPITABLE WATER OF 1.28
INCHES AND A MOIST LAYER ALL THE WAY UP TO NEAR 15 THOUSAND FT MSL.
SFC OBS ACROSS THE AREA SHOW DEWPOINTS IN THE UPPER 50S. WITH THIS
KIND OF MOISTURE...EVEN MINOR LIFT WILL CAUSE AT LEAST SOME SHOWERS
OR LIGHT RAIN. ONCE THE TROUGH AXIS PASSES EAST THIS AFTN...LIGHT
ONSHORE FLOW WILL CONTINUE TO PROVIDE THE MINOR LIFT NEEDED FOR SOME
SHOWERS THIS AFTN AND EVNG...BUT SHOWER ACTIVITY WILL BECOME MORE
FOCUSED ON TERRAIN AND IN AN ILL-DEFINED PUGET SOUND CONVERGENCE
ZONE THIS AFTN.

LATE TONIGHT...THE TAIL END OF A SHORTWAVE SCOOTING ACROSS NRN B.C.
WILL MAINTAIN ENOUGH WARM ADVECTION LIFT...DEEP MOISTURE AND ONSHORE
FLOW TO KEEP SHOWERS AND LIGHT RAIN GOING WELL INTO FRI MRNG.

BY FRI AFTN...UPPER HEIGHTS RISE QUICKLY AND CONSIDERABLY IN
RESPONSE TO A BUILDING UPPER RIDGE AXIS BETWEEN THE COAST AND 130W.
AS SUBSIDENCE ALOFT KICKS IN...THE SURFACE-BASED MOIST LAYER WILL
QUICKLY BECOME MORE SHALLOW OVER THE COURSE OF FRI AFTN AND FRI NGT.
WITH CLEARING SKIES ON FRI NGT...AND A SHIFT TO LIGHT N-NE SFC
WIND...AND LEFTOVER SFC MOISTURE...EXPECTING QUITE A BIT OF FOG
DEVELOPMENT OVER THE LOWLANDS DURING THE PRE-DAWN HOURS ON SAT MRNG.
AS NORTHERLY AND EASTERLY GRADIENTS INCRS ON SAT...LOW CLOUDS AND
MORNING FOG WILL READILY BURN OFF BY MID-DAY WITH AN OUTSTANDINGLY
SUNNY AND WARM AFTERNOON. THE LOW-LEVEL AIR MASS WILL ALSO DRY
OUT...WITH LOWLAND DEWPOINTS FALLING TO LESS MUGGY VALUES IN THE
UPPER 40S AND LOW 50S.       HANER

.LONG TERM...FROM PREVIOUS DISCUSSION...MODELS HAVE BEEN QUITE
CONSISTENT WITH THE UPPER LEVEL RIDGE AND THE THERMALLY INDUCED
SURFACE TROUGH. E-NE LOW LEVEL FLOW SATURDAY NIGHT WILL BRING THE
SURFACE TROUGH UP ALONG THE WA COAST ON SUNDAY. THIS WILL BE THE
WARMEST DAY WITH MAX TEMPS IN THE MID 70S TO MID 80S. MOS GUIDANCE
MAX TEMPS SEEM TO BE OVERLY COLD BUT MAY GET CLOSER TO THE EXPECTED
MID 80S MAXES AS SUNDAY DRAWS CLOSER. ALONG THE COAST THE E FLOW
WILL CONTINUE INTO SUNDAY AFTERNOON...SO EVEN THERE MAX TEMPS WILL
BE IN THE 70S TO LOWER 80S.

MODELS HAVE ALSO BEEN FAIRLY CONSISTENT IN BRINGING A WEAKENING
FRONT AND UPPER LEVEL TROUGH TO THE COAST LATE MONDAY OR TUESDAY.
TIMING IS STILL IN QUESTION...SO IT IS STILL UNCERTAIN JUST HOW MUCH
OF MONDAY WILL STAY MOSTLY SUNNY. THIS IS AN INTERESTING LITTLE
SYSTEM WITH AN 80-100 KT JET STREAK AND 500 MB VORTICITY LOBE
VERTICALLY STACKED OVER THE SURFACE FRONT. BOTH ECMWF AND GFS SHOW
THE SYSTEM WEAKENING RAPIDLY MONDAY EVENING AS IT NEARS THE COAST.
THE UPPER LEVEL TROUGH AND 500 MB VORTICITY LOBE SHEAR OFF FROM THE
SURFACE FRONT...PROBABLY BRINGING SOME SHOWERS TO THE CASCADES AND E
WA MONDAY NIGHT. 1000-850 MB RH PROGS SHOW THE SURFACE FRONT
STALLING ALONG THE COAST MONDAY NIGHT...BUT THE MOISTURE WILL
EVENTUALLY BE SHOVED INLAND BY LATE TUESDAY AS ANOTHER TROUGH
APPROACHES. KAM

&&

.AVIATION...AN UPPER LEVEL TROUGH IS OVER WESTERN WA THIS MORNING
AND WILL SHIFT EAST OF THE CASCADES THIS AFTERNOON. THE FLOW ALOFT
IS WESTERLY. THE AIR MASS IS MOIST WITH LIGHT RAIN MAINLY OVER THE
INTERIOR THIS MORNING. THERE ARE SEVERAL BROKEN LAYERS THIS MORNING
FROM IFR TO VFR. BUT IN GENERAL IT LOOKS LIKE CIGS WILL HOVER NEAR
3000 FT THIS AFTERNOON. CIGS WILL LOWER BACK INTO MVFR TO IFR RANGE
TONIGHT AS A WEAK WARM FRONT STALLS OVER THE REGION. THE COLD FRONT
WILL CROSS THROUGH WESTERN WA FRI MORNING FOR A FEW SHOWERS. 33

KSEA...CIGS NEAR 3000 FT TODAY. MODELS SHOW SPOTTY LIGHT SHOWERS IN
THE VICINITY THROUGH MUCH OF THE DAY. CIGS WILL LOWER BACK TO MVFR
RANGE OVERNIGHT. SURFACE WINDS WILL REMAIN LIGHT SLY. 33

&&

.MARINE...SURFACE WINDS WILL BE MAINLY LIGHT ACROSS THE WATERS TODAY
WITH WEAK HIGH PRES ALONG THE COAST. A WESTERLY ONSHORE PUSH WILL
BRING A FEW HOURS OF SMALL CRAFT ADVISORY WINDS THROUGH THE CENTRAL
AND EAST STRAIT OF JUAN DE FUCA THIS EVENING. A WEAK COLD FRONT WILL
CROSS THROUGH WESTERN WA ON FRIDAY. WINDS WILL FLIP TO OFFSHORE FRI
NIGHT THROUGH SAT AS A THERMALLY INDUCED TROUGH OF LOW PRES FORMS
ALONG THE COAST. THE WINDS WILL THEN TURN SOUTHERLY ON SUN AS A
SURFACE TROUGH DEVELOPS OVER THE OFFSHORE WATERS. THIS TROUGH WILL
CROSS THROUGH THE COASTAL WATERS ON MON. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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









000
FXUS66 KSEW 180950
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
250 AM PDT THU SEP 18 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL CROSS WESTERN WASHINGTON
TODAY BRINGING MOSTLY CLOUDY SKIES AND SCATTERED SHOWERS. A SECOND
WEAKER UPPER LEVEL TROUGH WILL FOLLOW...PROLONGING THE CHANCE OF
SHOWERS THROUGH FRIDAY. A STRONG UPPER LEVEL RIDGE WILL BUILD OVER
THE REGION FRIDAY NIGHT AND SATURDAY...THEN SHIFT EAST ON SUNDAY.
THE RIDGE AND LOW LEVEL OFFSHORE FLOW WILL BRING SUNNY SKIES AND
HIGH TEMPERATURES IN THE 70S TO MID 80S. A SERIES OF UPPER LEVEL
TROUGHS WILL BRING A CHANCE OF RAIN AND COOLER WEATHER NEXT WEEK.

&&

.SHORT TERM...THE MOIST UPPER LEVEL TROUGH ALONG THE COAST THIS
MORNING WILL MOVE OVER THE CASCADES BY 18Z/11 AM AND TO THE ID
BORDER BY 00Z/5 PM THIS AFTERNOON. RADAR IMAGERY INDICATES THE MAIN
SHOWER ACTIVITY HAS SHIFTED OVER THE N INTERIOR AHEAD OF THE TROUGH
AXIS...WITH DIMINISHING SHOWERS ALONG THE COAST. ALTHOUGH THE TROUGH
WILL BE EAST OF THE AREA THIS AFTERNOON...THE LOWER AIR MASS WILL
BECOME UNSTABLE UP TO ABOUT 700 MB/10000 FEET THIS AFTERNOON...SO A
CHANCE OF SHOWERS WILL CONTINUE.

THIS EVENING SHOULD QUALIFY AS A MINOR LULL WITH W FLOW ALOFT
MAINTAINING A CHANCE OF MOUNTAIN SHOWERS...BUT ONLY ABOUT A 20
PERCENT CHANCE OF SHOWERS OVER THE LOWLANDS.

W FLOW ALOFT OVER THE NE PACIFIC WILL DRIVE THE NEXT UPPER LEVEL
SHORTWAVE TROUGH OVER THE REGION LATER TONIGHT AND ON FRIDAY. THIS
IS THE SYSTEM AROUND 50N AND BETWEEN 130W AND 135W AT 09Z/2 AM. THIS
SYSTEM WILL BRING SHOWERS TO PRIMARILY THE COAST AND N INTERIOR
THROUGH FRIDAY MORNING...WITH SHOWER ACTIVITY DIMINISHING FRIDAY
AFTERNOON AS THE BUILDING RIDGE OFFSHORE WEAKENS THE SYSTEM. MODELS
HAVE BEEN PRETTY DRY FOR FRIDAY NIGHT SO THE CHANCE OF SHOWERS WAS
DROPPED. CLOUDS WILL DECREASE OVERNIGHT...SO WITH IMPROVING
RADIATIONAL COOLING CONDITIONS PATCHY FOG WAS ADDED TO THE FORECAST
FOR SATURDAY MORNING.

THE MODELS REMAIN ON COURSE IN BUILDING A STRONG UPPER LEVEL RIDGE
OFFSHORE FRIDAY NIGHT THEN MOVING IT OVER W WA ON SATURDAY. THE AIR
MASS WILL DRY RAPIDLY FOR SUNNY SKIES ON SATURDAY. E-NE LOW LEVEL
OFFSHORE FLOW WILL CAUSE A THERMALLY INDUCED SURFACE TROUGH TO FORM
ALONG THE OREGON COAST. THE SURFACE TROUGH WILL INCREASE THE LOW
LEVEL N-NE FLOW THROUGH PUGET SOUND SATURDAY AFTERNOON. THIS SHOULD
CAP MAX TEMPS IN THE 70S AROUND PUGET SOUND. KAM

.LONG TERM...MODELS HAVE BEEN QUITE CONSISTENT WITH THE UPPER LEVEL
RIDGE AND THE THERMALLY INDUCED SURFACE TROUGH. E-NE LOW LEVEL FLOW
SATURDAY NIGHT WILL BRING THE SURFACE TROUGH UP ALONG THE WA COAST
ON SUNDAY. THIS WILL BE THE WARMEST DAY WITH MAX TEMPS IN THE MID
70S TO MID 80S. MOS GUIDANCE MAX TEMPS SEEM TO BE OVERLY COLD BUT
MAY GET CLOSER TO THE EXPECTED MID 80S MAXES AS SUNDAY DRAWS CLOSER.
ALONG THE COAST THE E FLOW WILL CONTINUE INTO SUNDAY AFTERNOON...SO
EVEN THERE MAX TEMPS WILL BE IN THE 70S TO LOWER 80S.

MODELS HAVE ALSO BEEN FAIRLY CONSISTENT IN BRINGING A WEAKENING
FRONT AND UPPER LEVEL TROUGH TO THE COAST LATE MONDAY OR TUESDAY.
TIMING IS STILL IN QUESTION...SO IT IS STILL UNCERTAIN JUST HOW MUCH
OF MONDAY WILL STAY MOSTLY SUNNY. THIS IS AN INTERESTING LITTLE
SYSTEM WITH AN 80-100 KT JET STREAK AND 500 MB VORTICITY LOBE
VERTICALLY STACKED OVER THE SURFACE FRONT. BOTH ECMWF AND GFS SHOW
THE SYSTEM WEAKENING RAPIDLY MONDAY EVENING AS IT NEARS THE COAST.
THE UPPER LEVEL TROUGH AND 500 MB VORTICITY LOBE SHEAR OFF FROM THE
SURFACE FRONT...PROBABLY BRINGING SOME SHOWERS TO THE CASCADES AND E
WA MONDAY NIGHT. 1000-850 MB RH PROGS SHOW THE SURFACE FRONT
STALLING ALONG THE COAST MONDAY NIGHT...BUT THE MOISTURE WILL
EVENTUALLY BE SHOVED INLAND BY LATE TUESDAY AS ANOTHER TROUGH
APPROACHES. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH WILL MOVE THROUGH THE AREA
TODAY WITH INCREASING WESTERLY FLOW ALOFT TONIGHT. AT THE SURFACE...
HIGH PRESSURE WILL BE OVER THE COAST WITH LOWER PRESSURE INLAND. AIR
MASS MOIST AND UNSTABLE.

CEILINGS WILL GRADUALLY LOWER EARLY THIS MORNING AS A BATCH OF
SHOWERS MOVING NORTH THROUGH THE AREA MOISTENS THE MID AND LOW
LEVELS. LOW CLOUDS ARE EXPECTED TO BE FAIRLY WIDESPREAD ACROSS THE
AREA FOR MUCH OF THE DAY WITH SOME IMPROVEMENT IN THE AFTERNOON.

KSEA...MID CLOUDS EARLY THIS MORNING WITH A BATCH OF SHOWERS PUSHING
NORTH THROUGH THE AREA. LOW CLOUDS ARE EXPECTED TO DEVELOP BY
DAYBREAK AND PERSIST THROUGH THE MORNING...LIFTING A BIT IN THE
AFTERNOON. SOUTHERLY WIND 4-8 KNOTS. SCHNEIDER

&&

.MARINE...WEAK HIGH PRESSURE WILL BE OVER THE COAST THROUGH TONIGHT.
THERE COULD BE A FEW HOURS OF SMALL CRAFT ADVISORY WEST WINDS IN THE
CENTRAL AND EAST STRAIT THIS EVENING AS ONSHORE FLOW INCREASES A BIT
BUT THIS LOOKS PRETTY MARGINAL.

A WEAK FRONT WILL CROSS THE WATERS FRIDAY. OFFSHORE FLOW WILL
DEVELOP FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY NIGHT WITH A
TROUGH JUST OFFSHORE. SOUTHERLY WINDS WILL DEVELOP SUNDAY AND
CONTINUE INTO MONDAY AS A TROUGH APPROACHES FROM THE WEST. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTER STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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








000
FXUS66 KSEW 180950
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
250 AM PDT THU SEP 18 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL CROSS WESTERN WASHINGTON
TODAY BRINGING MOSTLY CLOUDY SKIES AND SCATTERED SHOWERS. A SECOND
WEAKER UPPER LEVEL TROUGH WILL FOLLOW...PROLONGING THE CHANCE OF
SHOWERS THROUGH FRIDAY. A STRONG UPPER LEVEL RIDGE WILL BUILD OVER
THE REGION FRIDAY NIGHT AND SATURDAY...THEN SHIFT EAST ON SUNDAY.
THE RIDGE AND LOW LEVEL OFFSHORE FLOW WILL BRING SUNNY SKIES AND
HIGH TEMPERATURES IN THE 70S TO MID 80S. A SERIES OF UPPER LEVEL
TROUGHS WILL BRING A CHANCE OF RAIN AND COOLER WEATHER NEXT WEEK.

&&

.SHORT TERM...THE MOIST UPPER LEVEL TROUGH ALONG THE COAST THIS
MORNING WILL MOVE OVER THE CASCADES BY 18Z/11 AM AND TO THE ID
BORDER BY 00Z/5 PM THIS AFTERNOON. RADAR IMAGERY INDICATES THE MAIN
SHOWER ACTIVITY HAS SHIFTED OVER THE N INTERIOR AHEAD OF THE TROUGH
AXIS...WITH DIMINISHING SHOWERS ALONG THE COAST. ALTHOUGH THE TROUGH
WILL BE EAST OF THE AREA THIS AFTERNOON...THE LOWER AIR MASS WILL
BECOME UNSTABLE UP TO ABOUT 700 MB/10000 FEET THIS AFTERNOON...SO A
CHANCE OF SHOWERS WILL CONTINUE.

THIS EVENING SHOULD QUALIFY AS A MINOR LULL WITH W FLOW ALOFT
MAINTAINING A CHANCE OF MOUNTAIN SHOWERS...BUT ONLY ABOUT A 20
PERCENT CHANCE OF SHOWERS OVER THE LOWLANDS.

W FLOW ALOFT OVER THE NE PACIFIC WILL DRIVE THE NEXT UPPER LEVEL
SHORTWAVE TROUGH OVER THE REGION LATER TONIGHT AND ON FRIDAY. THIS
IS THE SYSTEM AROUND 50N AND BETWEEN 130W AND 135W AT 09Z/2 AM. THIS
SYSTEM WILL BRING SHOWERS TO PRIMARILY THE COAST AND N INTERIOR
THROUGH FRIDAY MORNING...WITH SHOWER ACTIVITY DIMINISHING FRIDAY
AFTERNOON AS THE BUILDING RIDGE OFFSHORE WEAKENS THE SYSTEM. MODELS
HAVE BEEN PRETTY DRY FOR FRIDAY NIGHT SO THE CHANCE OF SHOWERS WAS
DROPPED. CLOUDS WILL DECREASE OVERNIGHT...SO WITH IMPROVING
RADIATIONAL COOLING CONDITIONS PATCHY FOG WAS ADDED TO THE FORECAST
FOR SATURDAY MORNING.

THE MODELS REMAIN ON COURSE IN BUILDING A STRONG UPPER LEVEL RIDGE
OFFSHORE FRIDAY NIGHT THEN MOVING IT OVER W WA ON SATURDAY. THE AIR
MASS WILL DRY RAPIDLY FOR SUNNY SKIES ON SATURDAY. E-NE LOW LEVEL
OFFSHORE FLOW WILL CAUSE A THERMALLY INDUCED SURFACE TROUGH TO FORM
ALONG THE OREGON COAST. THE SURFACE TROUGH WILL INCREASE THE LOW
LEVEL N-NE FLOW THROUGH PUGET SOUND SATURDAY AFTERNOON. THIS SHOULD
CAP MAX TEMPS IN THE 70S AROUND PUGET SOUND. KAM

.LONG TERM...MODELS HAVE BEEN QUITE CONSISTENT WITH THE UPPER LEVEL
RIDGE AND THE THERMALLY INDUCED SURFACE TROUGH. E-NE LOW LEVEL FLOW
SATURDAY NIGHT WILL BRING THE SURFACE TROUGH UP ALONG THE WA COAST
ON SUNDAY. THIS WILL BE THE WARMEST DAY WITH MAX TEMPS IN THE MID
70S TO MID 80S. MOS GUIDANCE MAX TEMPS SEEM TO BE OVERLY COLD BUT
MAY GET CLOSER TO THE EXPECTED MID 80S MAXES AS SUNDAY DRAWS CLOSER.
ALONG THE COAST THE E FLOW WILL CONTINUE INTO SUNDAY AFTERNOON...SO
EVEN THERE MAX TEMPS WILL BE IN THE 70S TO LOWER 80S.

MODELS HAVE ALSO BEEN FAIRLY CONSISTENT IN BRINGING A WEAKENING
FRONT AND UPPER LEVEL TROUGH TO THE COAST LATE MONDAY OR TUESDAY.
TIMING IS STILL IN QUESTION...SO IT IS STILL UNCERTAIN JUST HOW MUCH
OF MONDAY WILL STAY MOSTLY SUNNY. THIS IS AN INTERESTING LITTLE
SYSTEM WITH AN 80-100 KT JET STREAK AND 500 MB VORTICITY LOBE
VERTICALLY STACKED OVER THE SURFACE FRONT. BOTH ECMWF AND GFS SHOW
THE SYSTEM WEAKENING RAPIDLY MONDAY EVENING AS IT NEARS THE COAST.
THE UPPER LEVEL TROUGH AND 500 MB VORTICITY LOBE SHEAR OFF FROM THE
SURFACE FRONT...PROBABLY BRINGING SOME SHOWERS TO THE CASCADES AND E
WA MONDAY NIGHT. 1000-850 MB RH PROGS SHOW THE SURFACE FRONT
STALLING ALONG THE COAST MONDAY NIGHT...BUT THE MOISTURE WILL
EVENTUALLY BE SHOVED INLAND BY LATE TUESDAY AS ANOTHER TROUGH
APPROACHES. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH WILL MOVE THROUGH THE AREA
TODAY WITH INCREASING WESTERLY FLOW ALOFT TONIGHT. AT THE SURFACE...
HIGH PRESSURE WILL BE OVER THE COAST WITH LOWER PRESSURE INLAND. AIR
MASS MOIST AND UNSTABLE.

CEILINGS WILL GRADUALLY LOWER EARLY THIS MORNING AS A BATCH OF
SHOWERS MOVING NORTH THROUGH THE AREA MOISTENS THE MID AND LOW
LEVELS. LOW CLOUDS ARE EXPECTED TO BE FAIRLY WIDESPREAD ACROSS THE
AREA FOR MUCH OF THE DAY WITH SOME IMPROVEMENT IN THE AFTERNOON.

KSEA...MID CLOUDS EARLY THIS MORNING WITH A BATCH OF SHOWERS PUSHING
NORTH THROUGH THE AREA. LOW CLOUDS ARE EXPECTED TO DEVELOP BY
DAYBREAK AND PERSIST THROUGH THE MORNING...LIFTING A BIT IN THE
AFTERNOON. SOUTHERLY WIND 4-8 KNOTS. SCHNEIDER

&&

.MARINE...WEAK HIGH PRESSURE WILL BE OVER THE COAST THROUGH TONIGHT.
THERE COULD BE A FEW HOURS OF SMALL CRAFT ADVISORY WEST WINDS IN THE
CENTRAL AND EAST STRAIT THIS EVENING AS ONSHORE FLOW INCREASES A BIT
BUT THIS LOOKS PRETTY MARGINAL.

A WEAK FRONT WILL CROSS THE WATERS FRIDAY. OFFSHORE FLOW WILL
DEVELOP FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY NIGHT WITH A
TROUGH JUST OFFSHORE. SOUTHERLY WINDS WILL DEVELOP SUNDAY AND
CONTINUE INTO MONDAY AS A TROUGH APPROACHES FROM THE WEST. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTER STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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000
FXUS66 KSEW 180408
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
908 PM PDT WED SEP 17 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM OFF THE COAST WILL MOVE ACROSS
THE AREA ON THURSDAY. EXPECT A WEAK DISTURBANCE ALOFT TO KEEP
CONDITIONS SOMEWHAT UNSETTLED THURSDAY NIGHT INTO FRIDAY MORNING.
HIGH PRESSURE ALOFT WILL BUILD OVER THE REGION THIS WEEKEND FOR
DRY WEATHER AND ABOVE NORMAL DAYTIME TEMPERATURES.

&&

.SHORT TERM...
AN UPPER TROF OFF THE COAST WILL MOVE ONSHORE OVERNIGHT AND ACROSS
THE CWA DURING THE DAY THU. OVERALL...PRECIP AMOUNTS WILL BE
LIGHT WITH THIS SYSTEM. NEARLY ZONAL FLOW ALOFT WILL BECOME
ESTABLISHED OVER THE AREA THU NIGHT BUT A WEAK DISTURBANCE IN THE
FLOW WILL KEEP CONDITIONS SOMEWHAT UNSETTLED THRU FRI MORNING.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION FRI AFTERNOON.
THE RIDGE WILL AMPLIFY FURTHER FRI NIGHT AND SATURDAY. THIS
COMBINED WITH THE DEVELOPMENT OF LOW LEVEL OFFSHORE FLOW WILL
RESULT IN ABOVE NORMAL DAYTIME TEMPS ON SATURDAY.

.LONG TERM FROM THE PREV DISCUSSION...
THE WARMING TREND WILL CONTINUE INTO SUNDAY WITH THE RIDGE AND
OFFSHORE FLOW STILL IN PLACE. MOS GUIDANCE SEEMED TOO COOL IN THIS
PATTERN AND MAY BE HEAVILY INFLUENCED BY CLIMATOLOGY. BUILDING
UPPER HEIGHTS AND STRONGER OFFSHORE FLOW SHOULD RESULT IN AT LEAST
A FEW DEGREES WARMING. HIGH TEMPERATURES WERE TRENDED ABOVE MOS...
WITH WIDESPREAD MID 80S OVER THE INTERIOR.

HIGH PRESSURE ALOFT WILL BEGIN TO SHIFT INLAND SUNDAY NIGHT AND
MONDAY. THERMALLY INDUCED LOW PRESSURE OVER THE INTERIOR OF WRN WA
WILL SHIFT EWD...USHERING IN ONSHORE FLOW MONDAY. TEMPERATURES
WILL TREND COOLER ON MONDAY AND MORE SO ON TUESDAY AS A WEAK
SYSTEM ARRIVES. THIS INITIAL TROUGH WILL FALL APART AS IT
ENCOUNTERS THE RIDGE BUT THERE MAY BE ENOUGH MOISTURE FOR SOME
SHOWERS.

LONG RANGE MODELS WERE IN SURPRISINGLY GOOD AGREEMENT ON THE
WESTERLIES ARRIVING BY MID WEEK. THIS PATTERN CHANGE SHOULD USHER
IN WETTER AND COOL CONDITIONS JUST IN TIME FOR THE FIRST WEEK OF
FALL. SOME MODELS INDICATED IT COULD BE RATHER BREEZY AS WELL.
MERCER

&&

.AVIATION...AN UPPER LEVEL TROUGH OVER THE NORTHEAST PACIFIC WILL
MOVE OVER WESTERN WASHINGTON THURSDAY WITH SOUTHERLY FLOW ALOFT
BECOMING WESTERLY. AT THE SURFACE...WEAK HIGH PRESSURE WILL BE OVER
THE COAST WITH LOWER PRESSURE INLAND. AIR MASS UNSTABLE WITH MID AND
HIGH LEVEL MOISTURE...BECOMING MOIST AT THE LOW LEVELS THURSDAY
MORNING.

KSEA...MOSTLY HIGH CLOUDS THIS EVENING WITH SOME MID LEVEL CEILINGS
IN SHOWERS. CEILING WILL GRADUALLY LOWER OVERNIGHT WITH LOW CLOUDS
THURSDAY MORNING. NORTH WIND 4-8 KNOTS BECOMING SOUTH AFTER
MIDNIGHT. SCHNEIDER

&&

.MARINE...WEAK HIGH PRESSURE WILL BE OVER THE COAST THROUGH THURSDAY
NIGHT. THERE COULD BE A FEW HOURS OF SMALL CRAFT ADVISORY WEST WINDS
IN THE CENTRAL AND EAST STRAIT THURSDAY EVENING AS ONSHORE FLOW
INCREASES A BIT BUT THIS LOOKS PRETTY MARGINAL.

A WEAK FRONT WILL CROSS THE WATERS FRIDAY. OFFSHORE FLOW WILL
DEVELOP FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY NIGHT WITH A
TROUGH JUST OFFSHORE. SOUTHERLY WINDS WILL DEVELOP SUNDAY AND
CONTINUE INTO MONDAY AS A TROUGH APPROACHES FROM THE WEST. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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





000
FXUS66 KSEW 180408
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
908 PM PDT WED SEP 17 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM OFF THE COAST WILL MOVE ACROSS
THE AREA ON THURSDAY. EXPECT A WEAK DISTURBANCE ALOFT TO KEEP
CONDITIONS SOMEWHAT UNSETTLED THURSDAY NIGHT INTO FRIDAY MORNING.
HIGH PRESSURE ALOFT WILL BUILD OVER THE REGION THIS WEEKEND FOR
DRY WEATHER AND ABOVE NORMAL DAYTIME TEMPERATURES.

&&

.SHORT TERM...
AN UPPER TROF OFF THE COAST WILL MOVE ONSHORE OVERNIGHT AND ACROSS
THE CWA DURING THE DAY THU. OVERALL...PRECIP AMOUNTS WILL BE
LIGHT WITH THIS SYSTEM. NEARLY ZONAL FLOW ALOFT WILL BECOME
ESTABLISHED OVER THE AREA THU NIGHT BUT A WEAK DISTURBANCE IN THE
FLOW WILL KEEP CONDITIONS SOMEWHAT UNSETTLED THRU FRI MORNING.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION FRI AFTERNOON.
THE RIDGE WILL AMPLIFY FURTHER FRI NIGHT AND SATURDAY. THIS
COMBINED WITH THE DEVELOPMENT OF LOW LEVEL OFFSHORE FLOW WILL
RESULT IN ABOVE NORMAL DAYTIME TEMPS ON SATURDAY.

.LONG TERM FROM THE PREV DISCUSSION...
THE WARMING TREND WILL CONTINUE INTO SUNDAY WITH THE RIDGE AND
OFFSHORE FLOW STILL IN PLACE. MOS GUIDANCE SEEMED TOO COOL IN THIS
PATTERN AND MAY BE HEAVILY INFLUENCED BY CLIMATOLOGY. BUILDING
UPPER HEIGHTS AND STRONGER OFFSHORE FLOW SHOULD RESULT IN AT LEAST
A FEW DEGREES WARMING. HIGH TEMPERATURES WERE TRENDED ABOVE MOS...
WITH WIDESPREAD MID 80S OVER THE INTERIOR.

HIGH PRESSURE ALOFT WILL BEGIN TO SHIFT INLAND SUNDAY NIGHT AND
MONDAY. THERMALLY INDUCED LOW PRESSURE OVER THE INTERIOR OF WRN WA
WILL SHIFT EWD...USHERING IN ONSHORE FLOW MONDAY. TEMPERATURES
WILL TREND COOLER ON MONDAY AND MORE SO ON TUESDAY AS A WEAK
SYSTEM ARRIVES. THIS INITIAL TROUGH WILL FALL APART AS IT
ENCOUNTERS THE RIDGE BUT THERE MAY BE ENOUGH MOISTURE FOR SOME
SHOWERS.

LONG RANGE MODELS WERE IN SURPRISINGLY GOOD AGREEMENT ON THE
WESTERLIES ARRIVING BY MID WEEK. THIS PATTERN CHANGE SHOULD USHER
IN WETTER AND COOL CONDITIONS JUST IN TIME FOR THE FIRST WEEK OF
FALL. SOME MODELS INDICATED IT COULD BE RATHER BREEZY AS WELL.
MERCER

&&

.AVIATION...AN UPPER LEVEL TROUGH OVER THE NORTHEAST PACIFIC WILL
MOVE OVER WESTERN WASHINGTON THURSDAY WITH SOUTHERLY FLOW ALOFT
BECOMING WESTERLY. AT THE SURFACE...WEAK HIGH PRESSURE WILL BE OVER
THE COAST WITH LOWER PRESSURE INLAND. AIR MASS UNSTABLE WITH MID AND
HIGH LEVEL MOISTURE...BECOMING MOIST AT THE LOW LEVELS THURSDAY
MORNING.

KSEA...MOSTLY HIGH CLOUDS THIS EVENING WITH SOME MID LEVEL CEILINGS
IN SHOWERS. CEILING WILL GRADUALLY LOWER OVERNIGHT WITH LOW CLOUDS
THURSDAY MORNING. NORTH WIND 4-8 KNOTS BECOMING SOUTH AFTER
MIDNIGHT. SCHNEIDER

&&

.MARINE...WEAK HIGH PRESSURE WILL BE OVER THE COAST THROUGH THURSDAY
NIGHT. THERE COULD BE A FEW HOURS OF SMALL CRAFT ADVISORY WEST WINDS
IN THE CENTRAL AND EAST STRAIT THURSDAY EVENING AS ONSHORE FLOW
INCREASES A BIT BUT THIS LOOKS PRETTY MARGINAL.

A WEAK FRONT WILL CROSS THE WATERS FRIDAY. OFFSHORE FLOW WILL
DEVELOP FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY NIGHT WITH A
TROUGH JUST OFFSHORE. SOUTHERLY WINDS WILL DEVELOP SUNDAY AND
CONTINUE INTO MONDAY AS A TROUGH APPROACHES FROM THE WEST. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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






000
FXUS66 KSEW 172235 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT WED SEP 17 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL PRODUCE SHOWERS AS IT MOVES
ACROSS THE REGION THROUGH THURSDAY. A TRAILING WEAK UPPER LEVEL
TROUGH WILL PROLONG THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A
STRONG RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY
SKIES AND WARMER WEATHER. ANOTHER WEAK TROUGH WILL TRAVERSE THE AREA
LATE MONDAY INTO TUESDAY...FOLLOWED BY A STRONGER SYSTEM ON
WEDNESDAY.

&&

.SHORT TERM...IR SATELLITE IMAGERY SHOWS A RATHER DISORGANIZED MASS
OF MID/HIGH BASED CLOUDS STREAMING NWD INTO THE REGION. THE UPPER
LOW WHICH HAS FED MOISTURE INTO THE AREA IS BECOMING CUT OFF BUT A
PORTION OF THIS SYSTEM WILL GET PULLED INTO WRN WA TONIGHT. VARIOUS
MODEL TIME-HEIGHTS SHOW THE LOWER LEVELS SLOWLY BECOMING SATURATED
LATER TONIGHT. A NRN STREAM TROUGH WILL PROVIDE INCREASING LIFT WITH
MEASURABLE RAINFALL LIKELY ACROSS MOST THE AREA.

THE 500 MB TROUGH AXIS SHIFTS EWD BY THURSDAY AFTERNOON. MOIST WLY
FLOW WILL STILL PRODUCE SHOWERS IN THE MOUNTAINS. THE BEST CHANCE OF
SHOWERS ACROSS THE LOWLANDS WILL BE EARLY ON...THEN DECREASING
DURING THE AFTERNOON. SOME MESO MODELS AND EVEN THE GFS40 IMPLY A
CONVERGENCE ZONE MAY DEVELOP LATE IN THE AFTERNOON INTO THE EVENING.
THE SURFACE RIDGE W OF PUGET SOUND SUPPORTS THIS IDEA WITH THE FLOW
FAVORING THE N SEATTLE TO EVERETT CORRIDOR. GRADIENTS WEAKEN LATE
THU NIGHT AND ANY CONVERGENCE ZONE ACTIVITY SHOULD DIMINISH.

ANOTHER WEAK TRAILING UPPER TROUGH AND ASSOCIATED FRONT WILL
DISSIPATE AS IT REACHES WRN WA FRIDAY. THERE MAY STILL BE ENOUGH
MOISTURE FOR SOME SHOWERS...ESPECIALLY COAST AND MOUNTAINS IN THE
MORNING. THE FLOW TURNS MORE NWLY FRI AFTERNOON AS UPPER HEIGHTS
START TO BUILD. PARTIAL SUNSHINE IS EXPECTED LATER IN THE DAY WITH
SLIGHTLY WARMER TEMPERATURES.

THE WARMING TREND CONTINUES INTO SATURDAY AS HIGH PRESSURE RAPIDLY
AMPLIFIES OVER THE PAC NW. THERMALLY INDUCED LOW PRESSURE WILL BE
NEAR THE COAST SO OFFSHORE FLOW WILL DRY OUT THE AIR MASS AND ALLOW
FOR A WARMING TREND. SOME AREAS AWAY FROM THE WATER MAY REACH THE
LOW 80S.

.LONG TERM...THE WARMING TREND CONTINUES INTO SUNDAY WITH THE RIDGE
AND OFFSHORE FLOW STILL IN PLACE. MOS GUIDANCE SEEMS TOO COOL IN
THIS PATTERN AND MAY BE HEAVILY INFLUENCED BY CLIMATOLOGY. BUILDING
UPPER HEIGHTS AND STRONGER OFFSHORE FLOW SHOULD RESULT IN AT LEAST A
FEW DEGREES WARMING. HIGH TEMPERATURES ARE TRENDED ABOVE MOS...WITH
WIDESPREAD MID 80S OVER THE INTERIOR.

HIGH PRESSURE ALOFT BEGINS TO SHIFT INLAND SUNDAY NIGHT AND MONDAY.
THERMALLY INDUCED LOW PRESSURE OVER THE INTERIOR OF WRN WA WILL
SHIFT EWD...USHERING IN ONSHORE FLOW MONDAY. TEMPERATURES WILL TREND
COOLER ON MONDAY AND MORE SO ON TUESDAY AS A WEAK SYSTEM ARRIVES.
THIS INITIAL TROUGH WILL FALL APART AS IT ENCOUNTERS THE RIDGE BUT
THERE MAY BE ENOUGH MOISTURE FOR SOME SHOWERS.

LONG RANGE MODELS ARE IN SURPRISINGLY GOOD AGREEMENT ON THE
WESTERLIES ARRIVING BY MID WEEK. THIS PATTERN CHANGE SHOULD USHER IN
WETTER AND COOL CONDITIONS JUST IN TIME FOR THE FIRST WEEK OF FALL.
SOME MODELS INDICATE IT COULD BE RATHER BREEZY AS WELL.  MERCER

&&

.AVIATION...AN UPPER LEVEL TROUGH IS DIGGING OFFSHORE THIS
AFTERNOON...SENDING MID/HIGH LEVEL MOISTURE INTO WESTERN WA. THE
FLOW ALOFT IS SOUTHERLY WITH DIFFLUENT FLOW AND WEAK LIFT OVER THE
REGION. RADAR SHOWS MAINLY LIGHT SHOWERS ACROSS WESTERN WA WITH VFR
CONDITIONS EXPECTED. SHOWERS WILL INCREASE TONIGHT THROUGH THU
MORNING AS THE UPPER LEVEL TROUGH SHIFTS INLAND. 33

KSEA...SHOWERS WILL INCREASE IN COVERAGE TONIGHT 06-12Z AS AN UPPER
LEVEL TROUGH SHIFTS INLAND. LIGHT NORTHERLY WINDS WILL SWITCH TO SLY
06-09Z. 33

&&

.MARINE...A 998 MB LOW IS SPINNING OFF THE NORTHERN CA COAST THIS
AFTERNOON. THIS LOW WILL WEAKEN AS IT MOVES EAST AND INLAND ON
THURSDAY. PRESSURE GRADIENTS AND WINDS WILL REMAIN LIGHT ACROSS
WESTERN WA...EXCEPT WEST WINDS RISING TO 15 TO 25 KT THROUGH THE
STRAIT OF JUAN DE FUCA THU EVENING. A WEAK COLD FRONT WILL CROSS THE
AREA ON FRIDAY WITH ONSHORE FLOW EXPECTED. OFFSHORE FLOW WILL
DEVELOP ON SATURDAY AS AN INVERTED SURFACE TROUGH FORMS ALONG THE
COAST. THIS INVERTED SURFACE TROUGH WILL WEAKEN ON SUN. A SURFACE
TROUGH WILL THEN CROSS THE COASTAL WATERS ON MON. MODELS SHOW A
STRONGER SYSTEM DEVELOPING OVER THE NE PAC MIDWEEK...HOWEVER EXACT
STRENGTH AND TIMING IS STILL UNCLEAR. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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



















000
FXUS66 KSEW 172235 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT WED SEP 17 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL PRODUCE SHOWERS AS IT MOVES
ACROSS THE REGION THROUGH THURSDAY. A TRAILING WEAK UPPER LEVEL
TROUGH WILL PROLONG THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A
STRONG RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY
SKIES AND WARMER WEATHER. ANOTHER WEAK TROUGH WILL TRAVERSE THE AREA
LATE MONDAY INTO TUESDAY...FOLLOWED BY A STRONGER SYSTEM ON
WEDNESDAY.

&&

.SHORT TERM...IR SATELLITE IMAGERY SHOWS A RATHER DISORGANIZED MASS
OF MID/HIGH BASED CLOUDS STREAMING NWD INTO THE REGION. THE UPPER
LOW WHICH HAS FED MOISTURE INTO THE AREA IS BECOMING CUT OFF BUT A
PORTION OF THIS SYSTEM WILL GET PULLED INTO WRN WA TONIGHT. VARIOUS
MODEL TIME-HEIGHTS SHOW THE LOWER LEVELS SLOWLY BECOMING SATURATED
LATER TONIGHT. A NRN STREAM TROUGH WILL PROVIDE INCREASING LIFT WITH
MEASURABLE RAINFALL LIKELY ACROSS MOST THE AREA.

THE 500 MB TROUGH AXIS SHIFTS EWD BY THURSDAY AFTERNOON. MOIST WLY
FLOW WILL STILL PRODUCE SHOWERS IN THE MOUNTAINS. THE BEST CHANCE OF
SHOWERS ACROSS THE LOWLANDS WILL BE EARLY ON...THEN DECREASING
DURING THE AFTERNOON. SOME MESO MODELS AND EVEN THE GFS40 IMPLY A
CONVERGENCE ZONE MAY DEVELOP LATE IN THE AFTERNOON INTO THE EVENING.
THE SURFACE RIDGE W OF PUGET SOUND SUPPORTS THIS IDEA WITH THE FLOW
FAVORING THE N SEATTLE TO EVERETT CORRIDOR. GRADIENTS WEAKEN LATE
THU NIGHT AND ANY CONVERGENCE ZONE ACTIVITY SHOULD DIMINISH.

ANOTHER WEAK TRAILING UPPER TROUGH AND ASSOCIATED FRONT WILL
DISSIPATE AS IT REACHES WRN WA FRIDAY. THERE MAY STILL BE ENOUGH
MOISTURE FOR SOME SHOWERS...ESPECIALLY COAST AND MOUNTAINS IN THE
MORNING. THE FLOW TURNS MORE NWLY FRI AFTERNOON AS UPPER HEIGHTS
START TO BUILD. PARTIAL SUNSHINE IS EXPECTED LATER IN THE DAY WITH
SLIGHTLY WARMER TEMPERATURES.

THE WARMING TREND CONTINUES INTO SATURDAY AS HIGH PRESSURE RAPIDLY
AMPLIFIES OVER THE PAC NW. THERMALLY INDUCED LOW PRESSURE WILL BE
NEAR THE COAST SO OFFSHORE FLOW WILL DRY OUT THE AIR MASS AND ALLOW
FOR A WARMING TREND. SOME AREAS AWAY FROM THE WATER MAY REACH THE
LOW 80S.

.LONG TERM...THE WARMING TREND CONTINUES INTO SUNDAY WITH THE RIDGE
AND OFFSHORE FLOW STILL IN PLACE. MOS GUIDANCE SEEMS TOO COOL IN
THIS PATTERN AND MAY BE HEAVILY INFLUENCED BY CLIMATOLOGY. BUILDING
UPPER HEIGHTS AND STRONGER OFFSHORE FLOW SHOULD RESULT IN AT LEAST A
FEW DEGREES WARMING. HIGH TEMPERATURES ARE TRENDED ABOVE MOS...WITH
WIDESPREAD MID 80S OVER THE INTERIOR.

HIGH PRESSURE ALOFT BEGINS TO SHIFT INLAND SUNDAY NIGHT AND MONDAY.
THERMALLY INDUCED LOW PRESSURE OVER THE INTERIOR OF WRN WA WILL
SHIFT EWD...USHERING IN ONSHORE FLOW MONDAY. TEMPERATURES WILL TREND
COOLER ON MONDAY AND MORE SO ON TUESDAY AS A WEAK SYSTEM ARRIVES.
THIS INITIAL TROUGH WILL FALL APART AS IT ENCOUNTERS THE RIDGE BUT
THERE MAY BE ENOUGH MOISTURE FOR SOME SHOWERS.

LONG RANGE MODELS ARE IN SURPRISINGLY GOOD AGREEMENT ON THE
WESTERLIES ARRIVING BY MID WEEK. THIS PATTERN CHANGE SHOULD USHER IN
WETTER AND COOL CONDITIONS JUST IN TIME FOR THE FIRST WEEK OF FALL.
SOME MODELS INDICATE IT COULD BE RATHER BREEZY AS WELL.  MERCER

&&

.AVIATION...AN UPPER LEVEL TROUGH IS DIGGING OFFSHORE THIS
AFTERNOON...SENDING MID/HIGH LEVEL MOISTURE INTO WESTERN WA. THE
FLOW ALOFT IS SOUTHERLY WITH DIFFLUENT FLOW AND WEAK LIFT OVER THE
REGION. RADAR SHOWS MAINLY LIGHT SHOWERS ACROSS WESTERN WA WITH VFR
CONDITIONS EXPECTED. SHOWERS WILL INCREASE TONIGHT THROUGH THU
MORNING AS THE UPPER LEVEL TROUGH SHIFTS INLAND. 33

KSEA...SHOWERS WILL INCREASE IN COVERAGE TONIGHT 06-12Z AS AN UPPER
LEVEL TROUGH SHIFTS INLAND. LIGHT NORTHERLY WINDS WILL SWITCH TO SLY
06-09Z. 33

&&

.MARINE...A 998 MB LOW IS SPINNING OFF THE NORTHERN CA COAST THIS
AFTERNOON. THIS LOW WILL WEAKEN AS IT MOVES EAST AND INLAND ON
THURSDAY. PRESSURE GRADIENTS AND WINDS WILL REMAIN LIGHT ACROSS
WESTERN WA...EXCEPT WEST WINDS RISING TO 15 TO 25 KT THROUGH THE
STRAIT OF JUAN DE FUCA THU EVENING. A WEAK COLD FRONT WILL CROSS THE
AREA ON FRIDAY WITH ONSHORE FLOW EXPECTED. OFFSHORE FLOW WILL
DEVELOP ON SATURDAY AS AN INVERTED SURFACE TROUGH FORMS ALONG THE
COAST. THIS INVERTED SURFACE TROUGH WILL WEAKEN ON SUN. A SURFACE
TROUGH WILL THEN CROSS THE COASTAL WATERS ON MON. MODELS SHOW A
STRONGER SYSTEM DEVELOPING OVER THE NE PAC MIDWEEK...HOWEVER EXACT
STRENGTH AND TIMING IS STILL UNCLEAR. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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




















000
FXUS66 KSEW 171549 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT WED SEP 17 2014

.SYNOPSIS...A LARGE UPPER LEVEL TROUGH OFFSHORE APPROACHING WESTERN
WASHINGTON WILL BRING A CHANCE OF SHOWERS TODAY. SHOWERS WILL BECOME
LIKELY TONIGHT AND THURSDAY MORNING AS THE TROUGH MOVES SLOWLY
ACROSS THE AREA. A SMALLER WEAKER UPPER LEVEL TROUGH WILL PROLONG
THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A STRONG UPPER LEVEL
RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY SKIES
AND WARM WEATHER. A WEAK FRONT MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...AN ELONGATED SOUTHERN STREAM UPPER LOW OFF THE W COAST
IS SPREADING MAINLY MID AND HIGH LEVEL CLOUDS INTO WRN WA THIS
MORNING. THE RADAR LOOKS ACTIVE BUT OBS SO FAR ARE NOT SHOWING ANY
PRECIPITATION REACHING THE GROUND. THE BRIGHTER CLOUD TOPS ON IR
IMAGERY ALONG WITH THE COASTAL RADAR IMPLIES THE DEEPER MOISTURE IS
OFF THE COAST AND LIFTING NWD. THE BEST CHANCE FOR ANY THING
MEASURABLE THIS MORNING WILL BE TOWARD THE COAST AND MAYBE A
SPRINKLE INLAND. THE AIR MASS WILL GRADUALLY MOISTEN UP THROUGH THE
DAY AND ESPECIALLY TONIGHT AS THE NORTHERN STREAM FLOW PUSHES THE
SYSTEM INLAND. SHOWERS WILL GRADUALLY INCREASE WITH MOST MODELS
SHOWING WIDESPREAD LIGHT QPF LATER TONIGHT. THE FORECAST WAS UPDATED
TO INCREASE POPS TONIGHT AND ALSO TO BOOST POPS FOR THE COAST AND
MOUNTAINS AS THESE AREAS SHOULD ALMOST CERTAINLY GET MEASURABLE
RAIN.

THE MOISTURE FEED FROM THE SOUTHERN SYSTEM GETS CUT OFF THURSDAY AS
THE NORTHERN STREAM TROUGH BECOMES THE DOMINATE FEATURE. THERE WILL
BE PLENTY OF RESIDUAL MOISTURE...ONSHORE FLOW...AND WEAK LIFT
ASSOCIATED WITH THE TROUGH. A CHANCE OF SHOWERS WILL CONTINUE WITH
THE MOUNTAINS STILL LIKELY TO GET RAIN IN THIS WEAK WESTERLY FLOW
PATTERN. SOME MESO MODELS HINT AT A BRIEF CONVERGENCE ZONE LATER
THURSDAY NIGHT BUT THE PATTERN DOES NOT SEEM TO SUPPORT ANYTHING
WELL ORGANIZED. WILL MAINTAIN THE BROAD BRUSH CHANCE OF SHOWERS
OVERNIGHT.

ANOTHER TRAILING WAVE EMBEDDED IN WESTERLY FLOW WILL ARRIVE FRIDAY.
THIS SYSTEM IS NOT VERY STRONG AND IS BARELY REFLECTED AT THE
SURFACE. MODELS SHOW THE SYSTEM WEAKENING WITH JUST THE REMNANTS
FROM THE FRONT TO MOVE THROUGH. THERE IS ENOUGH MOISTURE TO SUPPORT
A LOW THREAT OF SHOWERS SO THE CURRENT POPS LOOK GOOD. MERCER

.LONG TERM...NO CHANGES FROM PREVIOUS DISCUSSION...GFS AND ECMWF
REMAIN IN GOOD AGREEMENT IN BUILDING A STRONG UPPER LEVEL RIDGE OVER
THE AREA THIS WEEKEND. 500 MB HEIGHTS CLIMB BACK TO AROUND 5850
METERS SATURDAY. NE LOW LEVEL OFFSHORE FLOW DEVELOPS ON SATURDAY AS
A THERMALLY INDUCED SURFACE TROUGH FORMS ALONG THE OREGON COAST.
EASTERLY FLOW WILL DEVELOP SATURDAY NIGHT AS THE SURFACE TROUGH
EXTENDS NORTH ALONG THE WA COAST. MAX TEMPS SHOULD EASILY CLIMB BACK
INTO THE LOWER TO MID 80S ON SUNDAY.

THE UPPER LEVEL RIDGE AXIS WILL SHIFT E OVER ID ON SUNDAY. THIS WILL
ALLOW A SKINNY WEAKENING COLD FRONT TO APPROACH THE COAST ON MONDAY.
EARLIER MODELS HELD THE FRONT OFFSHORE UNTIL TUESDAY...BUT THE 00Z
RUNS HAVE IT JUST OFFSHORE ON MONDAY. THIS FRONT WILL NOT AMOUNT TO
MUCH...BUT THE SYSTEM BEHIND IT MAY BRING SOME RAIN BY TUESDAY OR
WEDNESDAY. KAM

&&

.AVIATION...AN UPPER LEVEL TROUGH IS DIGGING OFFSHORE
TODAY...SENDING MID/HIGH LEVEL MOISTURE INTO WESTERN WA. THE FLOW
ALOFT IS SOUTHERLY WITH DIFFLUENT FLOW AND WEAK LIFT OVER THE
REGION. RADAR SHOWS MAINLY LIGHT SHOWERS ACROSS WESTERN WA WITH VFR
CONDITIONS EXPECTED. SHOWERS WILL INCREASE TONIGHT THROUGH THU
MORNING AS THE UPPER LEVEL TROUGH SHIFTS INLAND. 33

KSEA...LIGHT SHOWERS IN THE VICINITY TODAY BUT CIGS/VIS WILL REMAIN
AT VFR. LIGHT NORTHERLY WINDS WILL SWITCH TO SLY EARLY THU MORNING.
33

&&

.MARINE...A 997 MB LOW IS SPINNING OFF THE NORTHERN CA COAST THIS
MORNING. THIS LOW WILL WEAKEN AS IT MOVES EAST AND INLAND ON
THURSDAY. PRESSURE GRADIENTS AND WINDS WILL REMAIN LIGHT ACROSS
WESTERN WA. A WEAK COLD FRONT WILL CROSS THE AREA ON FRIDAY.
OFFSHORE FLOW WILL DEVELOP ON SATURDAY AS AN INVERTED SURFACE TROUGH
FORMS ALONG THE COAST. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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
















000
FXUS66 KSEW 171549 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT WED SEP 17 2014

.SYNOPSIS...A LARGE UPPER LEVEL TROUGH OFFSHORE APPROACHING WESTERN
WASHINGTON WILL BRING A CHANCE OF SHOWERS TODAY. SHOWERS WILL BECOME
LIKELY TONIGHT AND THURSDAY MORNING AS THE TROUGH MOVES SLOWLY
ACROSS THE AREA. A SMALLER WEAKER UPPER LEVEL TROUGH WILL PROLONG
THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A STRONG UPPER LEVEL
RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY SKIES
AND WARM WEATHER. A WEAK FRONT MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...AN ELONGATED SOUTHERN STREAM UPPER LOW OFF THE W COAST
IS SPREADING MAINLY MID AND HIGH LEVEL CLOUDS INTO WRN WA THIS
MORNING. THE RADAR LOOKS ACTIVE BUT OBS SO FAR ARE NOT SHOWING ANY
PRECIPITATION REACHING THE GROUND. THE BRIGHTER CLOUD TOPS ON IR
IMAGERY ALONG WITH THE COASTAL RADAR IMPLIES THE DEEPER MOISTURE IS
OFF THE COAST AND LIFTING NWD. THE BEST CHANCE FOR ANY THING
MEASURABLE THIS MORNING WILL BE TOWARD THE COAST AND MAYBE A
SPRINKLE INLAND. THE AIR MASS WILL GRADUALLY MOISTEN UP THROUGH THE
DAY AND ESPECIALLY TONIGHT AS THE NORTHERN STREAM FLOW PUSHES THE
SYSTEM INLAND. SHOWERS WILL GRADUALLY INCREASE WITH MOST MODELS
SHOWING WIDESPREAD LIGHT QPF LATER TONIGHT. THE FORECAST WAS UPDATED
TO INCREASE POPS TONIGHT AND ALSO TO BOOST POPS FOR THE COAST AND
MOUNTAINS AS THESE AREAS SHOULD ALMOST CERTAINLY GET MEASURABLE
RAIN.

THE MOISTURE FEED FROM THE SOUTHERN SYSTEM GETS CUT OFF THURSDAY AS
THE NORTHERN STREAM TROUGH BECOMES THE DOMINATE FEATURE. THERE WILL
BE PLENTY OF RESIDUAL MOISTURE...ONSHORE FLOW...AND WEAK LIFT
ASSOCIATED WITH THE TROUGH. A CHANCE OF SHOWERS WILL CONTINUE WITH
THE MOUNTAINS STILL LIKELY TO GET RAIN IN THIS WEAK WESTERLY FLOW
PATTERN. SOME MESO MODELS HINT AT A BRIEF CONVERGENCE ZONE LATER
THURSDAY NIGHT BUT THE PATTERN DOES NOT SEEM TO SUPPORT ANYTHING
WELL ORGANIZED. WILL MAINTAIN THE BROAD BRUSH CHANCE OF SHOWERS
OVERNIGHT.

ANOTHER TRAILING WAVE EMBEDDED IN WESTERLY FLOW WILL ARRIVE FRIDAY.
THIS SYSTEM IS NOT VERY STRONG AND IS BARELY REFLECTED AT THE
SURFACE. MODELS SHOW THE SYSTEM WEAKENING WITH JUST THE REMNANTS
FROM THE FRONT TO MOVE THROUGH. THERE IS ENOUGH MOISTURE TO SUPPORT
A LOW THREAT OF SHOWERS SO THE CURRENT POPS LOOK GOOD. MERCER

.LONG TERM...NO CHANGES FROM PREVIOUS DISCUSSION...GFS AND ECMWF
REMAIN IN GOOD AGREEMENT IN BUILDING A STRONG UPPER LEVEL RIDGE OVER
THE AREA THIS WEEKEND. 500 MB HEIGHTS CLIMB BACK TO AROUND 5850
METERS SATURDAY. NE LOW LEVEL OFFSHORE FLOW DEVELOPS ON SATURDAY AS
A THERMALLY INDUCED SURFACE TROUGH FORMS ALONG THE OREGON COAST.
EASTERLY FLOW WILL DEVELOP SATURDAY NIGHT AS THE SURFACE TROUGH
EXTENDS NORTH ALONG THE WA COAST. MAX TEMPS SHOULD EASILY CLIMB BACK
INTO THE LOWER TO MID 80S ON SUNDAY.

THE UPPER LEVEL RIDGE AXIS WILL SHIFT E OVER ID ON SUNDAY. THIS WILL
ALLOW A SKINNY WEAKENING COLD FRONT TO APPROACH THE COAST ON MONDAY.
EARLIER MODELS HELD THE FRONT OFFSHORE UNTIL TUESDAY...BUT THE 00Z
RUNS HAVE IT JUST OFFSHORE ON MONDAY. THIS FRONT WILL NOT AMOUNT TO
MUCH...BUT THE SYSTEM BEHIND IT MAY BRING SOME RAIN BY TUESDAY OR
WEDNESDAY. KAM

&&

.AVIATION...AN UPPER LEVEL TROUGH IS DIGGING OFFSHORE
TODAY...SENDING MID/HIGH LEVEL MOISTURE INTO WESTERN WA. THE FLOW
ALOFT IS SOUTHERLY WITH DIFFLUENT FLOW AND WEAK LIFT OVER THE
REGION. RADAR SHOWS MAINLY LIGHT SHOWERS ACROSS WESTERN WA WITH VFR
CONDITIONS EXPECTED. SHOWERS WILL INCREASE TONIGHT THROUGH THU
MORNING AS THE UPPER LEVEL TROUGH SHIFTS INLAND. 33

KSEA...LIGHT SHOWERS IN THE VICINITY TODAY BUT CIGS/VIS WILL REMAIN
AT VFR. LIGHT NORTHERLY WINDS WILL SWITCH TO SLY EARLY THU MORNING.
33

&&

.MARINE...A 997 MB LOW IS SPINNING OFF THE NORTHERN CA COAST THIS
MORNING. THIS LOW WILL WEAKEN AS IT MOVES EAST AND INLAND ON
THURSDAY. PRESSURE GRADIENTS AND WINDS WILL REMAIN LIGHT ACROSS
WESTERN WA. A WEAK COLD FRONT WILL CROSS THE AREA ON FRIDAY.
OFFSHORE FLOW WILL DEVELOP ON SATURDAY AS AN INVERTED SURFACE TROUGH
FORMS ALONG THE COAST. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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

















000
FXUS66 KSEW 170957 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED TYPO 3RD PARAGRAPH
NATIONAL WEATHER SERVICE SEATTLE WA
230 AM PDT WED SEP 17 2014

.SYNOPSIS...A LARGE UPPER LEVEL TROUGH OFFSHORE APPROACHING WESTERN
WASHINGTON WILL BRING A CHANCE OF SHOWERS TODAY. SHOWERS WILL BECOME
LIKELY TONIGHT AND THURSDAY MORNING AS THE TROUGH MOVES SLOWLY
ACROSS THE AREA. A SMALLER WEAKER UPPER LEVEL TROUGH WILL PROLONG
THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A STRONG UPPER LEVEL
RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY SKIES
AND WARM WEATHER. A WEAK FRONT MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...THE LARGE UPPER LEVEL TROUGH OFFSHORE ALONG 135W THIS
MORNING WILL BRING A SHOWERY PATTERN TO W WA TODAY THROUGH THURSDAY.
IR IMAGERY SHOWS A DISORGANIZED LOOKING LARGE BLOB OF MOISTURE
EMBEDDED IN THE S FLOW ALOFT ON THE E SIDE OF THE TROUGH...ALL
HEADED IN THE GENERAL DIRECTION OF THE PACNW. DISORGANIZED AREAS OF
MOISTURE ARE ALREADY BRINGING SPOTTY LIGHT SHOWERS TO W WA THIS
MORNING. A BIT MORE ORGANIZED BAND WAS W OF THE CENTRAL/S OREGON
COAST AT 09Z/2 AM AND SHOULD REACH W WA THIS AFTERNOON AND THIS
EVENING. MUCH OF THE MOISTURE MOVING N WILL INITIALLY END UP W OF
THE COAST...BUT WILL END UP MOVING ACROSS W WA LATE TONIGHT AND
THURSDAY MORNING AS THE WHOLE UPPER LEVEL TROUGH SHIFTS INLAND. THE
WETTEST PERIOD STILL LOOKS TO BE TONIGHT AND THURSDAY MORNING AS THE
TROUGH AXIS CROSSES THE AREA. LIKELY POPS LOOK GOOD FOR THE COAST
AND N INTERIOR WITH HIGH END CHANCE POPS AROUND THE PUGET SOUND
REGION.

THE UPPER LEVEL TROUGH WILL BE OVER E WA THURSDAY AFTERNOON...BUT A
SURFACE RIDGE BUILDING ALONG THE COAST MAY BRING ENOUGH ONSHORE FLOW
FOR A PUGET SOUND CONVERGENCE ZONE TO FORM. HOWEVER MESOSCALE MODELS
DO NOT OFFER A STRONG CASE FOR A CONVERGENCE ZONE AT THIS POINT.

W FLOW ALOFT OVER THE NE PACIFIC BEHIND THE TROUGH WILL DRIVE
ANOTHER UPPER LEVEL SHORTWAVE TROUGH ACROSS THE AREA THURSDAY NIGHT
AND FRIDAY MORNING FOR A CONTINUING CHANCE OF SHOWERS. THE 00Z
MODELS HAVE TRENDED A BIT STRONGER WITH THIS WAVE. THE CHANCE OF
SHOWERS HAS BEEN KEPT THROUGH FRIDAY NIGHT...ALTHOUGH THEY COULD
TAPER OFF BY FRIDAY EVENING. KAM

.LONG TERM...GFS AND ECMWF REMAIN IN GOOD AGREEMENT IN BUILDING A
STRONG UPPER LEVEL RIDGE OVER THE AREA THIS WEEKEND. 500 MB HEIGHTS
CLIMB BACK TO AROUND 5850 METERS SATURDAY. NE LOW LEVEL OFFSHORE
FLOW DEVELOPS ON SATURDAY AS A THERMALLY INDUCED SURFACE TROUGH
FORMS ALONG THE OREGON COAST. EASTERLY FLOW WILL DEVELOP SATURDAY
NIGHT AS THE SURFACE TROUGH EXTENDS NORTH ALONG THE WA COAST. MAX
TEMPS SHOULD EASILY CLIMB BACK INTO THE LOWER TO MID 80S ON SUNDAY.

THE UPPER LEVEL RIDGE AXIS WILL SHIFT E OVER ID ON SUNDAY. THIS WILL
ALLOW A SKINNY WEAKENING COLD FRONT TO APPROACH THE COAST ON MONDAY.
EARLIER MODELS HELD THE FRONT OFFSHORE UNTIL TUESDAY...BUT THE 00Z
RUNS HAVE IT JUST OFFSHORE ON MONDAY. THIS FRONT WILL NOT AMOUNT TO
MUCH...BUT THE SYSTEM BEHIND IT MAY BRING SOME RAIN BY TUESDAY OR
WEDNESDAY. KAM

&&

.AVIATION...AN UPPER TROUGH WILL APPROACH THE PACNW TODAY. THERE IS
SW FLOW ALOFT WITH CONSIDERABLE MID LEVEL MOISTURE AND SCATTERED
LIGHT SHOWERS. GRADIENTS HAVE BECOME LIGHT AND WITHOUT ONSHORE
FLOW IT IS NOT LIKELY THAT AREAS OF LOW CLOUDS WILL DEVELOP THIS
MORNING BUT THERE MIGHT BE PATCHY LOW CLOUDS AND FOG ON THE COAST
THIS MORNING.

KSEA...MID LEVEL CLOUDS. INCREASING AND THICKENING WITH A FEW LIGHT
SHOWERS. LIGHT AND VARIABLE WIND.

&&

.MARINE...LIGHT PRESSURE GRADIENTS TODAY AND THU AS A FAIRLY WEAK
WEATHER SYSTEM MOVES THROUGH THE REGION. OFFSHORE FLOW WILL DEVELOP
OVER THE WEEKEND.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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














000
FXUS66 KSEW 170957 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED TYPO 3RD PARAGRAPH
NATIONAL WEATHER SERVICE SEATTLE WA
230 AM PDT WED SEP 17 2014

.SYNOPSIS...A LARGE UPPER LEVEL TROUGH OFFSHORE APPROACHING WESTERN
WASHINGTON WILL BRING A CHANCE OF SHOWERS TODAY. SHOWERS WILL BECOME
LIKELY TONIGHT AND THURSDAY MORNING AS THE TROUGH MOVES SLOWLY
ACROSS THE AREA. A SMALLER WEAKER UPPER LEVEL TROUGH WILL PROLONG
THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A STRONG UPPER LEVEL
RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY SKIES
AND WARM WEATHER. A WEAK FRONT MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...THE LARGE UPPER LEVEL TROUGH OFFSHORE ALONG 135W THIS
MORNING WILL BRING A SHOWERY PATTERN TO W WA TODAY THROUGH THURSDAY.
IR IMAGERY SHOWS A DISORGANIZED LOOKING LARGE BLOB OF MOISTURE
EMBEDDED IN THE S FLOW ALOFT ON THE E SIDE OF THE TROUGH...ALL
HEADED IN THE GENERAL DIRECTION OF THE PACNW. DISORGANIZED AREAS OF
MOISTURE ARE ALREADY BRINGING SPOTTY LIGHT SHOWERS TO W WA THIS
MORNING. A BIT MORE ORGANIZED BAND WAS W OF THE CENTRAL/S OREGON
COAST AT 09Z/2 AM AND SHOULD REACH W WA THIS AFTERNOON AND THIS
EVENING. MUCH OF THE MOISTURE MOVING N WILL INITIALLY END UP W OF
THE COAST...BUT WILL END UP MOVING ACROSS W WA LATE TONIGHT AND
THURSDAY MORNING AS THE WHOLE UPPER LEVEL TROUGH SHIFTS INLAND. THE
WETTEST PERIOD STILL LOOKS TO BE TONIGHT AND THURSDAY MORNING AS THE
TROUGH AXIS CROSSES THE AREA. LIKELY POPS LOOK GOOD FOR THE COAST
AND N INTERIOR WITH HIGH END CHANCE POPS AROUND THE PUGET SOUND
REGION.

THE UPPER LEVEL TROUGH WILL BE OVER E WA THURSDAY AFTERNOON...BUT A
SURFACE RIDGE BUILDING ALONG THE COAST MAY BRING ENOUGH ONSHORE FLOW
FOR A PUGET SOUND CONVERGENCE ZONE TO FORM. HOWEVER MESOSCALE MODELS
DO NOT OFFER A STRONG CASE FOR A CONVERGENCE ZONE AT THIS POINT.

W FLOW ALOFT OVER THE NE PACIFIC BEHIND THE TROUGH WILL DRIVE
ANOTHER UPPER LEVEL SHORTWAVE TROUGH ACROSS THE AREA THURSDAY NIGHT
AND FRIDAY MORNING FOR A CONTINUING CHANCE OF SHOWERS. THE 00Z
MODELS HAVE TRENDED A BIT STRONGER WITH THIS WAVE. THE CHANCE OF
SHOWERS HAS BEEN KEPT THROUGH FRIDAY NIGHT...ALTHOUGH THEY COULD
TAPER OFF BY FRIDAY EVENING. KAM

.LONG TERM...GFS AND ECMWF REMAIN IN GOOD AGREEMENT IN BUILDING A
STRONG UPPER LEVEL RIDGE OVER THE AREA THIS WEEKEND. 500 MB HEIGHTS
CLIMB BACK TO AROUND 5850 METERS SATURDAY. NE LOW LEVEL OFFSHORE
FLOW DEVELOPS ON SATURDAY AS A THERMALLY INDUCED SURFACE TROUGH
FORMS ALONG THE OREGON COAST. EASTERLY FLOW WILL DEVELOP SATURDAY
NIGHT AS THE SURFACE TROUGH EXTENDS NORTH ALONG THE WA COAST. MAX
TEMPS SHOULD EASILY CLIMB BACK INTO THE LOWER TO MID 80S ON SUNDAY.

THE UPPER LEVEL RIDGE AXIS WILL SHIFT E OVER ID ON SUNDAY. THIS WILL
ALLOW A SKINNY WEAKENING COLD FRONT TO APPROACH THE COAST ON MONDAY.
EARLIER MODELS HELD THE FRONT OFFSHORE UNTIL TUESDAY...BUT THE 00Z
RUNS HAVE IT JUST OFFSHORE ON MONDAY. THIS FRONT WILL NOT AMOUNT TO
MUCH...BUT THE SYSTEM BEHIND IT MAY BRING SOME RAIN BY TUESDAY OR
WEDNESDAY. KAM

&&

.AVIATION...AN UPPER TROUGH WILL APPROACH THE PACNW TODAY. THERE IS
SW FLOW ALOFT WITH CONSIDERABLE MID LEVEL MOISTURE AND SCATTERED
LIGHT SHOWERS. GRADIENTS HAVE BECOME LIGHT AND WITHOUT ONSHORE
FLOW IT IS NOT LIKELY THAT AREAS OF LOW CLOUDS WILL DEVELOP THIS
MORNING BUT THERE MIGHT BE PATCHY LOW CLOUDS AND FOG ON THE COAST
THIS MORNING.

KSEA...MID LEVEL CLOUDS. INCREASING AND THICKENING WITH A FEW LIGHT
SHOWERS. LIGHT AND VARIABLE WIND.

&&

.MARINE...LIGHT PRESSURE GRADIENTS TODAY AND THU AS A FAIRLY WEAK
WEATHER SYSTEM MOVES THROUGH THE REGION. OFFSHORE FLOW WILL DEVELOP
OVER THE WEEKEND.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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













000
FXUS66 KSEW 170926
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 AM PDT WED SEP 17 2014

.SYNOPSIS...A LARGE UPPER LEVEL TROUGH OFFSHORE APPROACHING WESTERN
WASHINGTON WILL BRING A CHANCE OF SHOWERS TODAY. SHOWERS WILL BECOME
LIKELY TONIGHT AND THURSDAY MORNING AS THE TROUGH MOVES SLOWLY
ACROSS THE AREA. A SMALLER WEAKER UPPER LEVEL TROUGH WILL PROLONG
THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A STRONG UPPER LEVEL
RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY SKIES
AND WARM WEATHER. A WEAK FRONT MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...THE LARGE UPPER LEVEL TROUGH OFFSHORE ALONG 135W THIS
MORNING WILL BRING A SHOWERY PATTERN TO W WA TODAY THROUGH THURSDAY.
IR IMAGERY SHOWS A DISORGANIZED LOOKING LARGE BLOB OF MOISTURE
EMBEDDED IN THE S FLOW ALOFT ON THE E SIDE OF THE TROUGH...ALL
HEADED IN THE GENERAL DIRECTION OF THE PACNW. DISORGANIZED AREAS OF
MOISTURE ARE ALREADY BRINGING SPOTTY LIGHT SHOWERS TO W WA THIS
MORNING. A BIT MORE ORGANIZED BAND WAS W OF THE CENTRAL/S OREGON
COAST AT 09Z/2 AM AND SHOULD REACH W WA THIS AFTERNOON AND THIS
EVENING. MUCH OF THE MOISTURE MOVING N WILL INITIALLY END UP W OF
THE COAST...BUT WILL END UP MOVING ACROSS W WA LATE TONIGHT AND
THURSDAY MORNING AS THE WHOLE UPPER LEVEL TROUGH SHIFTS INLAND. THE
WETTEST PERIOD STILL LOOKS TO BE TONIGHT AND THURSDAY MORNING AS THE
TROUGH AXIS CROSSES THE AREA. LIKELY POPS LOOK GOOD FOR THE COAST
AND N INTERIOR WITH HIGH END CHANCE POPS AROUND THE PUGET SOUND
REGION.

THE UPPER LEVEL TROUGH WILL BE OVER E WA FRIDAY AFTERNOON...BUT A
SURFACE RIDGE BUILDING ALONG THE COAST MAY BRING ENOUGH ONSHORE FLOW
FOR A PUGET SOUND CONVERGENCE ZONE TO FORM. HOWEVER MESOSCALE MODELS
DO NOT OFFER A STRONG CASE FOR A CONVERGENCE ZONE AT THIS POINT.

W FLOW ALOFT OVER THE NE PACIFIC BEHIND THE TROUGH WILL DRIVE
ANOTHER UPPER LEVEL SHORTWAVE TROUGH ACROSS THE AREA THURSDAY NIGHT
AND FRIDAY MORNING FOR A CONTINUING CHANCE OF SHOWERS. THE 00Z
MODELS HAVE TRENDED A BIT STRONGER WITH THIS WAVE. THE CHANCE OF
SHOWERS HAS BEEN KEPT THROUGH FRIDAY NIGHT...ALTHOUGH THEY COULD
TAPER OFF BY FRIDAY EVENING. KAM

.LONG TERM...GFS AND ECMWF REMAIN IN GOOD AGREEMENT IN BUILDING A
STRONG UPPER LEVEL RIDGE OVER THE AREA THIS WEEKEND. 500 MB HEIGHTS
CLIMB BACK TO AROUND 5850 METERS SATURDAY. NE LOW LEVEL OFFSHORE
FLOW DEVELOPS ON SATURDAY AS A THERMALLY INDUCED SURFACE TROUGH
FORMS ALONG THE OREGON COAST. EASTERLY FLOW WILL DEVELOP SATURDAY
NIGHT AS THE SURFACE TROUGH EXTENDS NORTH ALONG THE WA COAST. MAX
TEMPS SHOULD EASILY CLIMB BACK INTO THE LOWER TO MID 80S ON SUNDAY.

THE UPPER LEVEL RIDGE AXIS WILL SHIFT E OVER ID ON SUNDAY. THIS WILL
ALLOW A SKINNY WEAKENING COLD FRONT TO APPROACH THE COAST ON MONDAY.
EARLIER MODELS HELD THE FRONT OFFSHORE UNTIL TUESDAY...BUT THE 00Z
RUNS HAVE IT JUST OFFSHORE ON MONDAY. THIS FRONT WILL NOT AMOUNT TO
MUCH...BUT THE SYSTEM BEHIND IT MAY BRING SOME RAIN BY TUESDAY OR
WEDNESDAY. KAM

&&

.AVIATION...AN UPPER TROUGH WILL APPROACH THE PACNW TODAY. THERE IS
SW FLOW ALOFT WITH CONSIDERABLE MID LEVEL MOISTURE AND SCATTERED
LIGHT SHOWERS. GRADIENTS HAVE BECOME LIGHT AND WITHOUT ONSHORE
FLOW IT IS NOT LIKELY THAT AREAS OF LOW CLOUDS WILL DEVELOP THIS
MORNING BUT THERE MIGHT BE PATCHY LOW CLOUDS AND FOG ON THE COAST
THIS MORNING.

KSEA...MID LEVEL CLOUDS. INCREASING AND THICKENING WITH A FEW LIGHT
SHOWERS. LIGHT AND VARIABLE WIND.

&&

.MARINE...LIGHT PRESSURE GRADIENTS TODAY AND THU AS A FAIRLY WEAK
WEATHER SYSTEM MOVES THROUGH THE REGION. OFFSHORE FLOW WILL DEVELOP
OVER THE WEEKEND.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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










000
FXUS66 KSEW 170926
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 AM PDT WED SEP 17 2014

.SYNOPSIS...A LARGE UPPER LEVEL TROUGH OFFSHORE APPROACHING WESTERN
WASHINGTON WILL BRING A CHANCE OF SHOWERS TODAY. SHOWERS WILL BECOME
LIKELY TONIGHT AND THURSDAY MORNING AS THE TROUGH MOVES SLOWLY
ACROSS THE AREA. A SMALLER WEAKER UPPER LEVEL TROUGH WILL PROLONG
THE CHANCE OF SHOWERS THROUGH FRIDAY NIGHT. A STRONG UPPER LEVEL
RIDGE WILL BUILD OVER THE REGION THIS WEEKEND BRINGING SUNNY SKIES
AND WARM WEATHER. A WEAK FRONT MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...THE LARGE UPPER LEVEL TROUGH OFFSHORE ALONG 135W THIS
MORNING WILL BRING A SHOWERY PATTERN TO W WA TODAY THROUGH THURSDAY.
IR IMAGERY SHOWS A DISORGANIZED LOOKING LARGE BLOB OF MOISTURE
EMBEDDED IN THE S FLOW ALOFT ON THE E SIDE OF THE TROUGH...ALL
HEADED IN THE GENERAL DIRECTION OF THE PACNW. DISORGANIZED AREAS OF
MOISTURE ARE ALREADY BRINGING SPOTTY LIGHT SHOWERS TO W WA THIS
MORNING. A BIT MORE ORGANIZED BAND WAS W OF THE CENTRAL/S OREGON
COAST AT 09Z/2 AM AND SHOULD REACH W WA THIS AFTERNOON AND THIS
EVENING. MUCH OF THE MOISTURE MOVING N WILL INITIALLY END UP W OF
THE COAST...BUT WILL END UP MOVING ACROSS W WA LATE TONIGHT AND
THURSDAY MORNING AS THE WHOLE UPPER LEVEL TROUGH SHIFTS INLAND. THE
WETTEST PERIOD STILL LOOKS TO BE TONIGHT AND THURSDAY MORNING AS THE
TROUGH AXIS CROSSES THE AREA. LIKELY POPS LOOK GOOD FOR THE COAST
AND N INTERIOR WITH HIGH END CHANCE POPS AROUND THE PUGET SOUND
REGION.

THE UPPER LEVEL TROUGH WILL BE OVER E WA FRIDAY AFTERNOON...BUT A
SURFACE RIDGE BUILDING ALONG THE COAST MAY BRING ENOUGH ONSHORE FLOW
FOR A PUGET SOUND CONVERGENCE ZONE TO FORM. HOWEVER MESOSCALE MODELS
DO NOT OFFER A STRONG CASE FOR A CONVERGENCE ZONE AT THIS POINT.

W FLOW ALOFT OVER THE NE PACIFIC BEHIND THE TROUGH WILL DRIVE
ANOTHER UPPER LEVEL SHORTWAVE TROUGH ACROSS THE AREA THURSDAY NIGHT
AND FRIDAY MORNING FOR A CONTINUING CHANCE OF SHOWERS. THE 00Z
MODELS HAVE TRENDED A BIT STRONGER WITH THIS WAVE. THE CHANCE OF
SHOWERS HAS BEEN KEPT THROUGH FRIDAY NIGHT...ALTHOUGH THEY COULD
TAPER OFF BY FRIDAY EVENING. KAM

.LONG TERM...GFS AND ECMWF REMAIN IN GOOD AGREEMENT IN BUILDING A
STRONG UPPER LEVEL RIDGE OVER THE AREA THIS WEEKEND. 500 MB HEIGHTS
CLIMB BACK TO AROUND 5850 METERS SATURDAY. NE LOW LEVEL OFFSHORE
FLOW DEVELOPS ON SATURDAY AS A THERMALLY INDUCED SURFACE TROUGH
FORMS ALONG THE OREGON COAST. EASTERLY FLOW WILL DEVELOP SATURDAY
NIGHT AS THE SURFACE TROUGH EXTENDS NORTH ALONG THE WA COAST. MAX
TEMPS SHOULD EASILY CLIMB BACK INTO THE LOWER TO MID 80S ON SUNDAY.

THE UPPER LEVEL RIDGE AXIS WILL SHIFT E OVER ID ON SUNDAY. THIS WILL
ALLOW A SKINNY WEAKENING COLD FRONT TO APPROACH THE COAST ON MONDAY.
EARLIER MODELS HELD THE FRONT OFFSHORE UNTIL TUESDAY...BUT THE 00Z
RUNS HAVE IT JUST OFFSHORE ON MONDAY. THIS FRONT WILL NOT AMOUNT TO
MUCH...BUT THE SYSTEM BEHIND IT MAY BRING SOME RAIN BY TUESDAY OR
WEDNESDAY. KAM

&&

.AVIATION...AN UPPER TROUGH WILL APPROACH THE PACNW TODAY. THERE IS
SW FLOW ALOFT WITH CONSIDERABLE MID LEVEL MOISTURE AND SCATTERED
LIGHT SHOWERS. GRADIENTS HAVE BECOME LIGHT AND WITHOUT ONSHORE
FLOW IT IS NOT LIKELY THAT AREAS OF LOW CLOUDS WILL DEVELOP THIS
MORNING BUT THERE MIGHT BE PATCHY LOW CLOUDS AND FOG ON THE COAST
THIS MORNING.

KSEA...MID LEVEL CLOUDS. INCREASING AND THICKENING WITH A FEW LIGHT
SHOWERS. LIGHT AND VARIABLE WIND.

&&

.MARINE...LIGHT PRESSURE GRADIENTS TODAY AND THU AS A FAIRLY WEAK
WEATHER SYSTEM MOVES THROUGH THE REGION. OFFSHORE FLOW WILL DEVELOP
OVER THE WEEKEND.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

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000
FXUS66 KSEW 170328
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
830 PM PDT TUE SEP 16 2014

.SYNOPSIS...LOWER PRESSURE ALOFT WILL BRING A THREAT OF SHOWERS INTO
FRIDAY WITH SHOWERS MOST LIKELY WEDNESDAY NIGHT AND THURSDAY. HIGHER
PRESSURE ALOFT IS FORECAST TO BUILD OVER THE REGION THIS WEEKEND FOR
A RETURN TO WARMER AND DRIER WEATHER.

&&

.SHORT TERM...UPPER TROUGH WAS APPROACHING 135W FROM THE WEST THIS
EVENING WITH THE DOWNSTREAM UPPER RIDGE OVER THE NORTHERN ROCKIES.
SOUTHERLY FLOW ALOFT OVER WA WITH EMBEDDED SHORTWAVES AND SPOTTY
LIGHT SHOWERS IN THE MID AND HIGH LEVEL MOISTURE. THE KSLE AND KUIL
RAOBS SHOW THE AIR MASS IS GETTING MORE MOIST - PRIMED IF YOU WISH.
WILL UPDATE THE EVENING FORECAST TO REFLECT A SMALL THREAT OF LIGHT
SHOWERS OVERNIGHT INTO WED MORNING.

THE LOW LEVEL ONSHORE FLOW IS NOW MAINLY WEST TO EAST WITH STRONGER
GRADIENTS ACROSS THE CASCADES. WITH THE MID AND HIGH LEVEL CLOUDS
PRESENT...MARINE CLOUDS WED MORNING WILL LIKELY BE MORE LIMITED IN
BOTH SPACE AND TIME.

00Z PROGS IN THUS FAR CONTINUE THE TREND OF TRACKING THE UPPER
TROUGH ONSHORE BY THU THOUGH WEAKENING WITH TIME. BEST THREAT OF
SHOWERS APPEARS TO BE THE 12 HOUR PERIOD FROM 06Z-18Z THURSDAY. THEN
THE WESTERLY FLOW ALOFT SHOULD LIMIT WHAT SHOWERS ARE LEFT IN THE
MOUNTAINS.

HIGH TEMPS TODAY WERE DOWN ABOUT 10-20 DEGREES FROM MONDAY.
WEDNESDAY AND THURSDAY HIGHS SHOULD BE A BIT BELOW MID SEPTEMBER
SEASONAL READINGS.

SATELLITE IMAGERY MUCH FURTHER WEST ACROSS THE NORTH PACIFIC SHOWS A
STRONG SHORTWAVE NEAR 150E THAT IS EXPECTED TO ZIP UNDER THE
ALEUTIAN UPPER LOW AND HELP BUILD RIDGING OVER OUR REGION BY THE END
OF THE WEEK. BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...THE WEEKEND WILL SEE A
STRONG UPPER RIDGE WITH OFFSHORE SURFACE FLOW. MODEL HEIGHTS ARE IN
THE MID 580S. THIS IS A SUNNY AND WARM PATTERN. FOR NOW HAVE BOOSTED
TEMPS INTO THE 70S AND LOW 80S FOR SATURDAY. FOR SUNDAY THE FORECAST
CALLS FOR MORE WIDESPREAD 80S. ON MONDAY SURFACE FLOW TURNS WEAKLY
ONSHORE AND HEIGHTS FALL IN RESPONSE TO AN APPROACHING SYSTEM.
MONDAY IS LIKELY TO REMAIN DRY BUT CLOUDS WILL INCREASE MONDAY NIGHT
AND A CHANCE OF SHOWERS APPEARS IN THE TUESDAY FORECAST. BURKE

&&

.AVIATION...AN UPPER TROUGH WILL APPROACH THE PACNW WED. SW FLOW
ALOFT WITH MAINLY INCREASING MID LEVEL MOISTURE. STRATUS MAINLY ON
THE COAST...BUT SOME AREAS OF MARINE STRATUS MAY PUSH INTO THE
INTERIOR BY DAYBREAK WED.

KSEA...MAINLY MID LVL CLOUDS...INCREASING AND THICKENING. THERE IS A
CHANCE OF LOW CLOUDS PUSHING IN FROM THE COAST...BUT IF IT MAKES IT
ONLY FOR A COUPLE OR THREE HOURS THROUGH MID MORNING WED.

&&

.MARINE...ONSHORE FLOW WILL BECOME FAIRLY LIGHT THROUGH WED AND THU
AS WEATHER SYSTEMS MOVING THROUGH THE AREA ARE EXPECTED TO BE RATHER
WEAK. OFFSHORE FLOW DEVELOPS SAT AND SUN WITH BREEZY EAST WINDS
DEVELOPING AT THE W ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS
WEEKEND.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
     THROUGH MIDNIGHT TONIGHT.

&&

$$

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000
FXUS66 KSEW 162129
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 PM PDT TUE SEP 16 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING A CHANCE OF SHOWERS TO
THE AREA WEDNESDAY THROUGH FRIDAY NIGHT...WITH SHOWERS MOST LIKELY
ON THURSDAY. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
WEEKEND FOR WARMER AND DRY WEATHER.

&&

.SHORT TERM...MID AND HIGH CLOUDS FROM AN UPPER LOW OFF NORTHERN
CALIFORNIA HAVE BEEN STREAMING INTO WASHINGTON FROM THE SOUTHWEST.
THIS TREND WILL CONTINUE TONIGHT AND WEDNESDAY. SURFACE FLOW IS
ONSHORE WHICH WILL ALLOW MARINE STRATUS INLAND OVERNIGHT. THE UPSHOT
IS A FORECAST FOR INCREASING CLOUDS TONIGHT AND MOSTLY CLOUDY SKIES
WEDNESDAY. MODELS ALSO BEGIN BRINGING SOME MOISTURE INTO THE AREA
TOMORROW...ENOUGH FOR A CHANCE OF SHOWERS IN THE AFTERNOON. THE
CLOUDS WILL KEEP HIGH TEMPERATURES IN THE LOW TO MID 70S INLAND WITH
MAINLY 60S ON THE COAST.

A STRONGER IMPULSE ARRIVES WEDNESDAY NIGHT AND THURSDAY. SHOWERS ARE
LIKELY OVER WESTERN SECTIONS WEDNESDAY NIGHT AND ARE LIKELY
EVERYWHERE THURSDAY. TEMPERATURES WILL TAKE ANOTHER DIP WITH HIGHS
MOSTLY IN THE 60S AND LOW 70S THURSDAY. RAINFALL AMOUNTS WILL BE
LIGHT BUT COULD SUM TO A COUPLE OF TENTHS OF AN INCH BY THURSDAY
NIGHT OR SO. A PUGET SOUND CONVERGENCE ZONE PATTERN IS EVIDENT IN
MESOSCALE MODELS THURSDAY NIGHT.

FLOW ALOFT REMAINS WESTERLY FRIDAY...ALLOWING ANOTHER IMPULSE TO
REACH THE AREA AND KEEPING A CHANCE OF SHOWERS IN THE FORECAST.
THERE SHOULD BE LESS CLOUD COVER OVERALL AND HIGH TEMPERATURES WILL
REBOUND A BIT INTO MOSTLY 70S. BY FRIDAY NIGHT MODELS BUILD A STRONG
UPPER RIDGE THAT SHOULD GIVE A CLEARING AND DRYING TREND. BURKE

.LONG TERM...THE WEEKEND WILL SEE A STRONG UPPER RIDGE WITH OFFSHORE
SURFACE FLOW. MODEL HEIGHTS ARE IN THE MID 580S. THIS IS A SUNNY AND
WARM PATTERN. FOR NOW HAVE BOOSTED TEMPS INTO THE 70S AND LOW 80S
FOR SATURDAY. FOR SUNDAY THE FORECAST CALLS FOR MORE WIDESPREAD 80S.
ON MONDAY SURFACE FLOW TURNS WEAKLY ONSHORE AND HEIGHTS FALL IN
RESPONSE TO AN APPROACHING SYSTEM. MONDAY IS LIKELY TO REMAIN DRY
BUT CLOUDS WILL INCREASE MONDAY NIGHT AND A CHANCE OF SHOWERS
APPEARS IN THE TUESDAY FORECAST. BURKE

&&

.AVIATION...HIGH PRESSURE ALOFT OVER THE PAC NW WILL SHIFT INLAND ON
WED AS A BROAD UPPER TROUGH APPROACHES THE REGION. LIGHT TO
MODERATE SW FLOW ALOFT. MOISTURE WILL INCREASE IN THE MID/UPPER
LEVELS AGAIN LATER TONIGHT AND WED AHEAD OF THE SYSTEM. THE LOW
LEVELS WILL REMAIN MOIST WITH PATCHY MVFR STRATUS POSSIBLE IN THE
MORNING AT ANY OF THE TAF SITES. KHQM AND KCLM WILL HAVE MORE
EXTENSIVE MVFR STRATUS OVERNIGHT INTO WED MORNING DUE TO WLY ONSHORE
FLOW.

KSEA...ANOTHER SURGE OF MID/HIGH CLOUDS WILL ARRIVE LATE TONIGHT AND
WED. PATCHY MVFR STRATUS COULD ALSO FORM AT OR NEAR THE TERMINAL FOR
A FEW HOURS WED MORNING. ONSHORE FLOW WITH S TO SW WIND LESS THAN 10
KT...BECOMING LIGHT BY WED MORNING...THEN SWITCHING THE N-NWLY LATE
IN THE AFTERNOON. DTM

&&

.MARINE...SMALL CRAFT WINDS TO 25 KT WILL CONTINUE THROUGH ABOUT
MIDNIGHT BEFORE DECREASING. AFTER THE MARINE PUSH THIS EVENING...
THE ONSHORE FLOW WILL BE FAIRLY LIGHT AS WEATHER SYSTEMS MOVING
THROUGH THE AREA ARE EXPECTED TO BE RATHER WEAK. OFFSHORE FLOW
DEVELOPS SAT AND SUN WITH BREEZY CONDITIONS AT THE W ENTRANCE TO THE
STRAIT. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
     THROUGH MIDNIGHT TONIGHT.

&&

$$

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000
FXUS66 KSEW 161548
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT TUE SEP 16 2014

.SYNOPSIS...ONSHORE FLOW WILL BRING CLOUDS AND LOWER TEMPERATURES
TODAY. AN UPPER LEVEL TROUGH WILL BRING A CHANCE OF SHOWERS TO THE
AREA WEDNESDAY THROUGH FRIDAY NIGHT...WITH SHOWERS MOST LIKELY ON
THURSDAY. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
WEEKEND FOR WARMER AND DRY WEATHER.

&&

.SHORT TERM...SATELLITE AND RADAR IMAGES SHOW A WEAK SHORT WAVE
CONSISTING MAINLY OF MID AND HIGH LEVEL CLOUDS MOVING SOUTH TO NORTH
THROUGH WESTERN WASHINGTON THIS MORNING. SO FAR THERE HAVE BEEN
SEVERAL TRACE AMOUNTS IN SPRINKLES BUT ONLY ONE INSTANCE OF
MEASURABLE PRECIPITATION...0.01 INCH AT KOLM. THIS BAND OF CLOUDS
WILL BE OUT OF THE STATE BY NOON OR SO. SOME MARINE STRATUS THAT
PENETRATED PART WAY INLAND OVER THE SOUTHWEST WILL ALSO RETREAT TO
THE COAST. SURFACE FLOW HAS BEEN SOLIDLY ONSHORE SINCE LAST NIGHT SO
HIGHS TODAY WILL BE CONSIDERABLY LOWER THAN YESTERDAY...MAINLY 70S
INLAND AND 60S COAST.

FORECAST REMAINS UNCHANGED WITH WEDNESDAY THROUGH FRIDAY HAVING AT
LEAST A CHANCE OF SHOWERS...AND SHOWERS MOST LIKELY ON THURSDAY. AN
UPPER LEVEL LOW OFF THE NORTHERN CALIFORNIA COAST WILL SPIN IMPULSES
NORTHEAST EACH DAY. BY THURSDAY AN UPPER LEVEL TROUGH IS MOVING
THROUGH WESTERN WASHINGTON. BURKE

.LONG TERM...PREVIOUS DISCUSSION...THE UPPER LEVEL TROUGH WILL MOVE
OVER E WA THURSDAY EVENING WITH DIMINISHING SHOWERS OVER W WA.
HOWEVER ANOTHER WEAKER UPPER LEVEL SHORTWAVE TROUGH MOVING ONSHORE
WILL PROLONG THE CHANCE OF SHOWERS INTO FRIDAY EVENING. GFS AND
ECMWF AGREE WELL ON BUILDING A STRONG UPPER LEVEL RIDGE JUST
OFFSHORE FRIDAY NIGHT THEN MOVING IT INLAND ON SATURDAY. THIS WILL
BRING ANOTHER PERIOD OF E-NE LOW LEVEL OFFSHORE FLOW...WHICH COULD
PUSH MAX TEMPS BACK UP INTO THE 80S THIS WEEKEND...PARTICULARLY ON
SUNDAY. BOTH MODELS HAVE THE RIDGE SHIFTING E OVER W MT SUNDAY NIGHT
ALLOWING A WEAKENING FRONT TO APPROACH THE COAST ON MONDAY. HOWEVER
THE FRONT COULD BE WEAK AND SLOW ENOUGH TO EKE OUT A MOSTLY SUNNY
DRY MONDAY AS WELL. KAM

&&

.AVIATION...A WEAK UPPER TROUGH OVER WA TODAY WILL LIFT NE OF THE
AREA TONIGHT. BROADER LOW PRESSURE ALOFT WILL REMAIN OFFSHORE
THROUGH WED. LIGHT SW FLOW ALOFT. THE AIR MASS IS MOIST AND WEAKLY
UNSTABLE THIS MORNING...JUST ENOUGH TO BREAK UP SOME OF THE LOWER
STRATUS DECK ACROSS THE LOWLANDS. MID CLOUDS AND A FEW ISOLATED
SHOWERS WILL DECREASE LATER TODAY. THE AIR MASS WILLS STABILIZE
TONIGHT WITH ANY PATCHY MVFR STRATUS SHORT LIVED WED MORNING.
ANOTHER SURGE OF MID AND UPPER LEVEL MOISTURE WILL ARRIVE LATE
TONIGHT AND WED. A FEW HIGH BASED SHOWERS WILL AGAIN BE POSSIBLE.

KSEA...MVFR STRATUS WILL BRIEFLY AFFECT THE TERMINAL THIS
MORNING...OTHERWISE MID AND HIGH CLOUDS TODAY. ANOTHER SURGE OF
MID/HIGH CLOUDS MAY ARRIVE LATE TONIGHT AND WED. PATCHY MVFR STRATUS
COULD ALSO FORM AT OR NEAR THE TERMINAL FOR A FEW HOURS WED MORNING.
ONSHORE FLOW TODAY WITH S TO SW WIND LESS THAN 10 KT. DTM

&&

.MARINE...A WLY PUSH IS UNDERWAY IN THE STRAIT OF JUAN DE FUCA THIS
MORNING. SMALL CRAFT WINDS TO 25 KT ARE LIKELY THROUGH ABOUT
MIDNIGHT BEFORE DECREASING. AFTER THE MARINE PUSH TODAY THE ONSHORE
FLOW WILL BE FAIRLY LIGHT AS WEATHER SYSTEMS MOVING THROUGH THE AREA
ARE EXPECTED TO BE RATHER WEAK. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
     THROUGH MIDNIGHT TONIGHT.

&&

$$

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000
FXUS66 KSEW 161548
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT TUE SEP 16 2014

.SYNOPSIS...ONSHORE FLOW WILL BRING CLOUDS AND LOWER TEMPERATURES
TODAY. AN UPPER LEVEL TROUGH WILL BRING A CHANCE OF SHOWERS TO THE
AREA WEDNESDAY THROUGH FRIDAY NIGHT...WITH SHOWERS MOST LIKELY ON
THURSDAY. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
WEEKEND FOR WARMER AND DRY WEATHER.

&&

.SHORT TERM...SATELLITE AND RADAR IMAGES SHOW A WEAK SHORT WAVE
CONSISTING MAINLY OF MID AND HIGH LEVEL CLOUDS MOVING SOUTH TO NORTH
THROUGH WESTERN WASHINGTON THIS MORNING. SO FAR THERE HAVE BEEN
SEVERAL TRACE AMOUNTS IN SPRINKLES BUT ONLY ONE INSTANCE OF
MEASURABLE PRECIPITATION...0.01 INCH AT KOLM. THIS BAND OF CLOUDS
WILL BE OUT OF THE STATE BY NOON OR SO. SOME MARINE STRATUS THAT
PENETRATED PART WAY INLAND OVER THE SOUTHWEST WILL ALSO RETREAT TO
THE COAST. SURFACE FLOW HAS BEEN SOLIDLY ONSHORE SINCE LAST NIGHT SO
HIGHS TODAY WILL BE CONSIDERABLY LOWER THAN YESTERDAY...MAINLY 70S
INLAND AND 60S COAST.

FORECAST REMAINS UNCHANGED WITH WEDNESDAY THROUGH FRIDAY HAVING AT
LEAST A CHANCE OF SHOWERS...AND SHOWERS MOST LIKELY ON THURSDAY. AN
UPPER LEVEL LOW OFF THE NORTHERN CALIFORNIA COAST WILL SPIN IMPULSES
NORTHEAST EACH DAY. BY THURSDAY AN UPPER LEVEL TROUGH IS MOVING
THROUGH WESTERN WASHINGTON. BURKE

.LONG TERM...PREVIOUS DISCUSSION...THE UPPER LEVEL TROUGH WILL MOVE
OVER E WA THURSDAY EVENING WITH DIMINISHING SHOWERS OVER W WA.
HOWEVER ANOTHER WEAKER UPPER LEVEL SHORTWAVE TROUGH MOVING ONSHORE
WILL PROLONG THE CHANCE OF SHOWERS INTO FRIDAY EVENING. GFS AND
ECMWF AGREE WELL ON BUILDING A STRONG UPPER LEVEL RIDGE JUST
OFFSHORE FRIDAY NIGHT THEN MOVING IT INLAND ON SATURDAY. THIS WILL
BRING ANOTHER PERIOD OF E-NE LOW LEVEL OFFSHORE FLOW...WHICH COULD
PUSH MAX TEMPS BACK UP INTO THE 80S THIS WEEKEND...PARTICULARLY ON
SUNDAY. BOTH MODELS HAVE THE RIDGE SHIFTING E OVER W MT SUNDAY NIGHT
ALLOWING A WEAKENING FRONT TO APPROACH THE COAST ON MONDAY. HOWEVER
THE FRONT COULD BE WEAK AND SLOW ENOUGH TO EKE OUT A MOSTLY SUNNY
DRY MONDAY AS WELL. KAM

&&

.AVIATION...A WEAK UPPER TROUGH OVER WA TODAY WILL LIFT NE OF THE
AREA TONIGHT. BROADER LOW PRESSURE ALOFT WILL REMAIN OFFSHORE
THROUGH WED. LIGHT SW FLOW ALOFT. THE AIR MASS IS MOIST AND WEAKLY
UNSTABLE THIS MORNING...JUST ENOUGH TO BREAK UP SOME OF THE LOWER
STRATUS DECK ACROSS THE LOWLANDS. MID CLOUDS AND A FEW ISOLATED
SHOWERS WILL DECREASE LATER TODAY. THE AIR MASS WILLS STABILIZE
TONIGHT WITH ANY PATCHY MVFR STRATUS SHORT LIVED WED MORNING.
ANOTHER SURGE OF MID AND UPPER LEVEL MOISTURE WILL ARRIVE LATE
TONIGHT AND WED. A FEW HIGH BASED SHOWERS WILL AGAIN BE POSSIBLE.

KSEA...MVFR STRATUS WILL BRIEFLY AFFECT THE TERMINAL THIS
MORNING...OTHERWISE MID AND HIGH CLOUDS TODAY. ANOTHER SURGE OF
MID/HIGH CLOUDS MAY ARRIVE LATE TONIGHT AND WED. PATCHY MVFR STRATUS
COULD ALSO FORM AT OR NEAR THE TERMINAL FOR A FEW HOURS WED MORNING.
ONSHORE FLOW TODAY WITH S TO SW WIND LESS THAN 10 KT. DTM

&&

.MARINE...A WLY PUSH IS UNDERWAY IN THE STRAIT OF JUAN DE FUCA THIS
MORNING. SMALL CRAFT WINDS TO 25 KT ARE LIKELY THROUGH ABOUT
MIDNIGHT BEFORE DECREASING. AFTER THE MARINE PUSH TODAY THE ONSHORE
FLOW WILL BE FAIRLY LIGHT AS WEATHER SYSTEMS MOVING THROUGH THE AREA
ARE EXPECTED TO BE RATHER WEAK. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
     THROUGH MIDNIGHT TONIGHT.

&&

$$

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000
FXUS66 KSEW 160953
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
252 AM PDT TUE SEP 16 2014

.SYNOPSIS...ONSHORE FLOW WILL BRING COOLER TEMPERATURES TO WESTERN
WASHINGTON TODAY ALONG WITH AREAS OF MORNING LOW CLOUDS. AN UPPER
LEVEL TROUGH WILL BRING A CHANCE OF SHOWERS TO THE AREA WEDNESDAY
THROUGH FRIDAY NIGHT...WITH SHOWERS MOST LIKELY ON THURSDAY. AN
UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS WEEKEND FOR WARMER
AND DRY WEATHER.

&&

.SHORT TERM...A SW MARINE PUSH OVERNIGHT HAS BROUGHT AREAS OF
STRATUS INLAND THIS MORNING. STRATUS REACHED SHELTON AROUND MIDNIGHT
AND WITH KSHN WINDS BLOWING SW 15-25KT SHOULD SPREAD THE LOW CLOUDS
ACROSS MOST OF PUGET SOUND THIS MORNING. THE SMALL UPPER LEVEL
TROUGH THAT HAS TRIGGERED THE MARINE PUSH WAS CENTERED OVER ASTORIA
AT 09Z/2 AM AND WAS HEADED QUICKLY NORTH. A SMALL AREA OF SHOWERS
WAS ALONG THE N OREGON COAST ALONG WITH A SOLO LIGHTNING STRIKE AT
0745Z. THIS SHOWER AREA IS SMALL ENOUGH TO FIZZLE OUT THIS MORNING
AS THE UPPER LEVEL TROUGH MOVES DEEPER INTO THE UPPER LEVEL RIDGE
CENTERED OVER THE PACNW...BUT STILL BEARS WATCHING.

THE NAM12 AND ARW-W BOUNDARY LAYER RH FORECASTS SEEMED A REASONABLE
INDICATOR FOR STRATUS COVERAGE TODAY. LOW CLOUDS WILL PROBABLY
BLANKET PUGET SOUND THIS MORNING WITH A LITTLE BIT SPREADING E OF
LAKE WASHINGTON...BUT SHOULD BURN OFF OVER THE SOUND THIS AFTERNOON.
HOWEVER THE STRATUS WILL BE DEEP ENOUGH ALONG THE COAST AND ONSHORE
FLOW PERSISTENT ENOUGH SO THAT STRATUS WILL PROBABLY NOT BURN OFF
OVER THE LOWER CHEHALIS VALLEY TODAY. THE RATHER SPARSE MID AND HIGH
CLOUDS FROM THE UPPER LEVEL TROUGH WILL NOT ADD MUCH TO THE OVERALL
CLOUD COVER. MAX TEMPS WILL BE A LITTLE TRICKY TODAY...WITH STRONGER
COOLING EXPECTED IN THE STRATUS AREAS...ESPECIALLY ALONG THE COAST
AND OVER THE LOWER CHEHALIS.

MAX TEMPS WEDNESDAY WERE ALSO TROUBLESOME. THE ONSHORE FLOW WILL BE
ABOUT AS STRONG TONIGHT AND WEDNESDAY MORNING. THE MARINE LAYER WILL
BE DEEPER AND WILL SPREAD ACROSS MOST OF W WA...BUT INSTABILITY FROM
THE UPPER LEVEL TROUGH APPROACHING FROM OFFSHORE SHOULD HELP THE
CLOUD COVER BREAK UP A BIT WEDNESDAY AFTERNOON. FOR MAX TEMPS THIS
MEANS THAT LOCATIONS TODAY WHERE THE STRATUS IS MOST PERSISTENT
COULD VERY WELL BE SLIGHTLY WARMER ON WEDNESDAY GIVEN A BETTER MIXED
MARINE LAYER. LOCATIONS THAT ARE STRATUS FREE TODAY...MAY END UP
BEING A LITTLE COOLER BECAUSE OF THE GREATER COVERAGE OF CLOUDS ON
WEDNESDAY.

OVERALL THE MODELS REMAIN IN GENERAL AGREEMENT WITH THE LARGE UPPER
LEVEL TROUGH CURRENTLY OFFSHORE ALONG 140W EJECTING E THIS WEEK.
SPOTTY SHOWERS WILL PROBABLY SPREAD TO THE COAST WEDNESDAY MORNING
AND THEN INLAND WEDNESDAY AFTERNOON. THE UPPER LEVEL TROUGH AXIS
WILL MOVE ACROSS THE AREA WEDNESDAY EVENING AND THURSDAY MORNING FOR
THE GREATEST SHOWER POTENTIAL AND LIKELY POPS. THURSDAY SHOULD BE
THE COOLEST DAY WITH THE COOLER AIR MASS FROM THE TROUGH RIGHT
OVERHEAD. KAM

.LONG TERM...THE UPPER LEVEL TROUGH WILL MOVE OVER E WA THURSDAY
EVENING WITH DIMINISHING SHOWERS OVER W WA. HOWEVER ANOTHER WEAKER
UPPER LEVEL SHORTWAVE TROUGH MOVING ONSHORE WILL PROLONG THE CHANCE
OF SHOWERS INTO FRIDAY EVENING. GFS AND ECMWF AGREE WELL ON BUILDING
A STRONG UPPER LEVEL RIDGE JUST OFFSHORE FRIDAY NIGHT THEN MOVING IT
INLAND ON SATURDAY. THIS WILL BRING ANOTHER PERIOD OF E-NE LOW LEVEL
OFFSHORE FLOW...WHICH COULD PUSH MAX TEMPS BACK UP INTO THE 80S THIS
WEEKEND...PARTICULARLY ON SUNDAY. BOTH MODELS HAVE THE RIDGE
SHIFTING E OVER W MT SUNDAY NIGHT ALLOWING A WEAKENING FRONT TO
APPROACH THE COAST ON MONDAY. HOWEVER THE FRONT COULD BE WEAK AND
SLOW ENOUGH TO EKE OUT A MOSTLY SUNNY DRY MONDAY AS WELL. KAM

&&

.AVIATION...LOW CLOUDS COAST AND AREAS OF LOW CLOUDS IN PUGET SOUND
THIS MORNING. SOME OF THE MARINE STRATUS MAY PUSH EAST IN THE STRAIT
THIS MORNING BUT MORE LIKELY WILL HOLD OFF TIL THE STRONGER PUSH
THIS AFTERNOON. IN THE AREAS THAT DO NOT SEE MORNING LOW
CLOUDS...MAINLY NORTH OF EVERETT...THERE WILL ONLY BE SOME MID AND
HIGH CLOUDS. THE RIDGE IS MOVING EAST AND THERE IS SW FLOW ALOFT.
AREAS OF LOW CLOUDS SHOULD DEVELOP AGAIN TONIGHT AND WED MORNING.

KSEA...MORNING LOW CLOUDS ARE EXPECTED...THEN JUST SOME MID AND HIGH
CLOUDS. WITH ONSHORE FLOW THE BREEZE WILL REMAIN S TO SW.

&&

.MARINE...ONSHORE FLOW...AND A DECENT WLY PUSH IS LIKELY IN THE
STRAIT OF JUAN DE FUCA THIS AFTERNOON AND EVENING. AFTER THE MARINE
PUSH TODAY THE ONSHORE FLOW WILL BE FAIRLY LIGHT AS WEATHER SYSTEMS
MOVING THROUGH THE AREA ARE EXPECTED TO BE RATHER WEAK.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
FROM NOON TODAY TIL MIDNIGHT TONIGHT.

&&

$$

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000
FXUS66 KSEW 160953
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
252 AM PDT TUE SEP 16 2014

.SYNOPSIS...ONSHORE FLOW WILL BRING COOLER TEMPERATURES TO WESTERN
WASHINGTON TODAY ALONG WITH AREAS OF MORNING LOW CLOUDS. AN UPPER
LEVEL TROUGH WILL BRING A CHANCE OF SHOWERS TO THE AREA WEDNESDAY
THROUGH FRIDAY NIGHT...WITH SHOWERS MOST LIKELY ON THURSDAY. AN
UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS WEEKEND FOR WARMER
AND DRY WEATHER.

&&

.SHORT TERM...A SW MARINE PUSH OVERNIGHT HAS BROUGHT AREAS OF
STRATUS INLAND THIS MORNING. STRATUS REACHED SHELTON AROUND MIDNIGHT
AND WITH KSHN WINDS BLOWING SW 15-25KT SHOULD SPREAD THE LOW CLOUDS
ACROSS MOST OF PUGET SOUND THIS MORNING. THE SMALL UPPER LEVEL
TROUGH THAT HAS TRIGGERED THE MARINE PUSH WAS CENTERED OVER ASTORIA
AT 09Z/2 AM AND WAS HEADED QUICKLY NORTH. A SMALL AREA OF SHOWERS
WAS ALONG THE N OREGON COAST ALONG WITH A SOLO LIGHTNING STRIKE AT
0745Z. THIS SHOWER AREA IS SMALL ENOUGH TO FIZZLE OUT THIS MORNING
AS THE UPPER LEVEL TROUGH MOVES DEEPER INTO THE UPPER LEVEL RIDGE
CENTERED OVER THE PACNW...BUT STILL BEARS WATCHING.

THE NAM12 AND ARW-W BOUNDARY LAYER RH FORECASTS SEEMED A REASONABLE
INDICATOR FOR STRATUS COVERAGE TODAY. LOW CLOUDS WILL PROBABLY
BLANKET PUGET SOUND THIS MORNING WITH A LITTLE BIT SPREADING E OF
LAKE WASHINGTON...BUT SHOULD BURN OFF OVER THE SOUND THIS AFTERNOON.
HOWEVER THE STRATUS WILL BE DEEP ENOUGH ALONG THE COAST AND ONSHORE
FLOW PERSISTENT ENOUGH SO THAT STRATUS WILL PROBABLY NOT BURN OFF
OVER THE LOWER CHEHALIS VALLEY TODAY. THE RATHER SPARSE MID AND HIGH
CLOUDS FROM THE UPPER LEVEL TROUGH WILL NOT ADD MUCH TO THE OVERALL
CLOUD COVER. MAX TEMPS WILL BE A LITTLE TRICKY TODAY...WITH STRONGER
COOLING EXPECTED IN THE STRATUS AREAS...ESPECIALLY ALONG THE COAST
AND OVER THE LOWER CHEHALIS.

MAX TEMPS WEDNESDAY WERE ALSO TROUBLESOME. THE ONSHORE FLOW WILL BE
ABOUT AS STRONG TONIGHT AND WEDNESDAY MORNING. THE MARINE LAYER WILL
BE DEEPER AND WILL SPREAD ACROSS MOST OF W WA...BUT INSTABILITY FROM
THE UPPER LEVEL TROUGH APPROACHING FROM OFFSHORE SHOULD HELP THE
CLOUD COVER BREAK UP A BIT WEDNESDAY AFTERNOON. FOR MAX TEMPS THIS
MEANS THAT LOCATIONS TODAY WHERE THE STRATUS IS MOST PERSISTENT
COULD VERY WELL BE SLIGHTLY WARMER ON WEDNESDAY GIVEN A BETTER MIXED
MARINE LAYER. LOCATIONS THAT ARE STRATUS FREE TODAY...MAY END UP
BEING A LITTLE COOLER BECAUSE OF THE GREATER COVERAGE OF CLOUDS ON
WEDNESDAY.

OVERALL THE MODELS REMAIN IN GENERAL AGREEMENT WITH THE LARGE UPPER
LEVEL TROUGH CURRENTLY OFFSHORE ALONG 140W EJECTING E THIS WEEK.
SPOTTY SHOWERS WILL PROBABLY SPREAD TO THE COAST WEDNESDAY MORNING
AND THEN INLAND WEDNESDAY AFTERNOON. THE UPPER LEVEL TROUGH AXIS
WILL MOVE ACROSS THE AREA WEDNESDAY EVENING AND THURSDAY MORNING FOR
THE GREATEST SHOWER POTENTIAL AND LIKELY POPS. THURSDAY SHOULD BE
THE COOLEST DAY WITH THE COOLER AIR MASS FROM THE TROUGH RIGHT
OVERHEAD. KAM

.LONG TERM...THE UPPER LEVEL TROUGH WILL MOVE OVER E WA THURSDAY
EVENING WITH DIMINISHING SHOWERS OVER W WA. HOWEVER ANOTHER WEAKER
UPPER LEVEL SHORTWAVE TROUGH MOVING ONSHORE WILL PROLONG THE CHANCE
OF SHOWERS INTO FRIDAY EVENING. GFS AND ECMWF AGREE WELL ON BUILDING
A STRONG UPPER LEVEL RIDGE JUST OFFSHORE FRIDAY NIGHT THEN MOVING IT
INLAND ON SATURDAY. THIS WILL BRING ANOTHER PERIOD OF E-NE LOW LEVEL
OFFSHORE FLOW...WHICH COULD PUSH MAX TEMPS BACK UP INTO THE 80S THIS
WEEKEND...PARTICULARLY ON SUNDAY. BOTH MODELS HAVE THE RIDGE
SHIFTING E OVER W MT SUNDAY NIGHT ALLOWING A WEAKENING FRONT TO
APPROACH THE COAST ON MONDAY. HOWEVER THE FRONT COULD BE WEAK AND
SLOW ENOUGH TO EKE OUT A MOSTLY SUNNY DRY MONDAY AS WELL. KAM

&&

.AVIATION...LOW CLOUDS COAST AND AREAS OF LOW CLOUDS IN PUGET SOUND
THIS MORNING. SOME OF THE MARINE STRATUS MAY PUSH EAST IN THE STRAIT
THIS MORNING BUT MORE LIKELY WILL HOLD OFF TIL THE STRONGER PUSH
THIS AFTERNOON. IN THE AREAS THAT DO NOT SEE MORNING LOW
CLOUDS...MAINLY NORTH OF EVERETT...THERE WILL ONLY BE SOME MID AND
HIGH CLOUDS. THE RIDGE IS MOVING EAST AND THERE IS SW FLOW ALOFT.
AREAS OF LOW CLOUDS SHOULD DEVELOP AGAIN TONIGHT AND WED MORNING.

KSEA...MORNING LOW CLOUDS ARE EXPECTED...THEN JUST SOME MID AND HIGH
CLOUDS. WITH ONSHORE FLOW THE BREEZE WILL REMAIN S TO SW.

&&

.MARINE...ONSHORE FLOW...AND A DECENT WLY PUSH IS LIKELY IN THE
STRAIT OF JUAN DE FUCA THIS AFTERNOON AND EVENING. AFTER THE MARINE
PUSH TODAY THE ONSHORE FLOW WILL BE FAIRLY LIGHT AS WEATHER SYSTEMS
MOVING THROUGH THE AREA ARE EXPECTED TO BE RATHER WEAK.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
FROM NOON TODAY TIL MIDNIGHT TONIGHT.

&&

$$

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