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000
FXUS66 KSEW 220404
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TONIGHT BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY NIGHT. HIGHER PRESSURE ALOFT IS THEN FORECAST TO
BUILD OVER THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND
WARMER DAYTIME TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...UPPER LEVEL LOW PRESSURE IS IN THE PROCESS OF CLOSING
OFF OVER THE PAC NW THIS EVENING. INSTABILITY IS INCREASING AHEAD OF
AND NEAR THE LOW CENTER RESULTING IN THUNDERSTORMS OVER THE SRN B.C.
ROCKIES AND ALSO JUST E OF THE WA CASCADE CREST. A COOL MARINE AIR
MASS RESULTING FROM WEAK ONSHORE FLOW OVER THE WRN WA LOWLANDS WILL
KEEP MOST OF OUR AREA STABLE. IN FACT...AREAS OF MARINE CLOUDS ARE
EXPECTED TO DEVELOP AGAIN LATER TONIGHT AND FRIDAY MORNING BUT WITH
LESS COVERAGE THAN THIS MORNING. NLY FLOW AND COOLER AIR ALOFT
BEHIND THE LOW ON FRIDAY WILL RESULT IN UNSTABLE CONDITIONS OVER THE
MOUNTAINS. MODELS ARE IN GOOD AGREEMENT ON SOME SHOWER ACTIVITY OVER
THE CASCADES AND FOOTHILLS WITH SUB ZERO LI`S BY AFTERNOON
SUPPORTING A THREAT OF THUNDERSTORMS. THE NLY FLOW COULD ALLOW A FEW
SHOWERS TO SPILL INTO THE FAR N INTERIOR BUT PROBABLY NOT MAKING IT
INTO THE PUGET SOUND REGION. THE FORECAST WAS UPDATED THIS EVENING
TO TRIM BACK POPS SLIGHTLY TO JUST THE MOUNTAINS AND FAR N.
GRADIENTS WILL GO FLAT ON FRIDAY WITH MORE SUNSHINE EXPECTED OVER
THE LOWLANDS SO HIGH TEMPERATURES SHOULD REACH THE LOW 70S.

LOW PRESSURE WILL SHIFT EWD FRIDAY NIGHT BUT THE LONG WAVE TROUGH
POSITION WILL REMAIN CENTERED OVER THE ROCKIES. THIS KEEPS WRN WA
UNDER NW FLOW ALOFT BETWEEN THE RIDGE JUST OFFSHORE AND THE TROUGH
FURTHER INLAND. MODELS STILL SHOW 500 MB HEIGHT RISES TO AROUND
5800M BUT NOT AS HIGH AS SOME PREVIOUS RUNS. THE LACK OF ONSHORE
FLOW SHOULD RESULT IN LITTLE MORNING CLOUD COVER. UPPER HEIGHTS
UNDER THIS SCENARIO SUPPORT HIGHS NEAR 80 ON SATURDAY WHICH MATCHES
CURRENT MOS GUIDANCE. A WEAK SHORT WAVE TRAVELING DOWN THE BACK SIDE
OF THE LONG WAVE TROUGH WILL CLIP THE AREA SUNDAY. THE ONLY IMPACT
SHOULD BE TO KEEP UPPER HEIGHTS AND HIGH TEMPERATURES IN CHECK.
EXPECT ANOTHER MOSTLY CLEAR DAY WITH HIGHS NEAR 80. MERCER

.LONG TERM...NO CHANGES FROM PREVIOUS DISCUSSION...THE OVERALL TREND
IN THE GUIDANCE IS FOR THE UPSTREAM UPPER RIDGE TO MOVE ONSHORE TUE
AND THAT MAY BE THE WARMEST DAY OF THE WEEK. THEN THE FLOW ALOFT
BECOMES MORE WESTERLY OR ZONAL YET 500 MB HEIGHTS ARE RELATIVELY
HIGH. THE ACCOMPANYING LOW LEVEL ONSHORE FLOW SHOULD MAINTAIN
DAYTIME TEMPS AT OR A BIT ABOVE SEASONAL AVERAGE INTO THURSDAY
THOUGH THERE IS SOME INDICATION OF SAGGING HEIGHTS ALOFT BEFORE THE
END OF THE WEEK THAT MAY SIGNAL A GRADUAL COOLING TREND AND SOME
INCREASE IN LOW LEVEL ONSHORE FLOW. BUEHNER

&&

.AVIATION...WEAK UPPER LEVEL TROUGH OVER THE AREA TONIGHT WILL SHIFT
EAST FRIDAY MORNING. LIGHT FLOW ALOFT BECOMING NORTHERLY FRIDAY
MORNING. LOW LEVEL FLOW WILL REMAIN WEAKLY ONSHORE.

SATELLITE IMAGERY AT 0330Z/830 PM SHOWS LITTLE IN THE WAY OF STRATUS
ANYWHERE IN THE CWA. CONVECTIVE ACTIVITY REMAINS WELL TO THE NORTH
AND EAST OF THE AREA. LIGHT ONSHORE GRADIENTS CONTINUING OVERNIGHT
INTO FRIDAY MORNING. WITH THE LIGHT ONSHORE FLOW CAN NOT RULE OUT
STRATUS OVER THE INTERIOR FRIDAY MORNING. THE STRATUS THAT DOES FORM
WILL BE SHALLOW AND BURN OFF BY MIDDAY AT THE LATEST. CEILINGS WITH
THE STRATUS LOOK TO BE IN THE 1000-2000 FOOT RANGE.

KSEA...MOSTLY CLEAR SKIES WITH STRATUS REFORMING OVER THE TERMINAL
AROUND 12Z WITH CEILINGS NEAR 1500 FEET. STRATUS SCATTERING OUT BY
LATE MORNING. VARIABLE WINDS 6 KNOTS OR LESS BECOMING NORTHWESTERLY
MIDDAY FRIDAY. FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING. OVER
THE COASTAL WATERS SOUTHERLY FLOW WILL BECOME NORTHWESTERLY FRIDAY.
SURFACE HIGH PRESSURE BUILDING INSIDE OF 140 W WILL TIGHTEN UP
SURFACE GRADIENTS SATURDAY AFTERNOON AND NIGHT OVER THE OUTER
COASTAL WATERS...BOOSTING THE NORTHWESTERLIES ABOVE SMALL CRAFT
CRITERIA. WEST TO NORTHWESTERLY SWELL 3 TO 6 FEET WITH A PERIOD
AROUND 8 SECONDS WILL PERSIST THROUGH THE WEEKEND. FELTON

&&

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

&&

$$

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FOR THE GRAPHICAL AFD...VISIT
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000
FXUS66 KSEW 220404
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TONIGHT BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY NIGHT. HIGHER PRESSURE ALOFT IS THEN FORECAST TO
BUILD OVER THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND
WARMER DAYTIME TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...UPPER LEVEL LOW PRESSURE IS IN THE PROCESS OF CLOSING
OFF OVER THE PAC NW THIS EVENING. INSTABILITY IS INCREASING AHEAD OF
AND NEAR THE LOW CENTER RESULTING IN THUNDERSTORMS OVER THE SRN B.C.
ROCKIES AND ALSO JUST E OF THE WA CASCADE CREST. A COOL MARINE AIR
MASS RESULTING FROM WEAK ONSHORE FLOW OVER THE WRN WA LOWLANDS WILL
KEEP MOST OF OUR AREA STABLE. IN FACT...AREAS OF MARINE CLOUDS ARE
EXPECTED TO DEVELOP AGAIN LATER TONIGHT AND FRIDAY MORNING BUT WITH
LESS COVERAGE THAN THIS MORNING. NLY FLOW AND COOLER AIR ALOFT
BEHIND THE LOW ON FRIDAY WILL RESULT IN UNSTABLE CONDITIONS OVER THE
MOUNTAINS. MODELS ARE IN GOOD AGREEMENT ON SOME SHOWER ACTIVITY OVER
THE CASCADES AND FOOTHILLS WITH SUB ZERO LI`S BY AFTERNOON
SUPPORTING A THREAT OF THUNDERSTORMS. THE NLY FLOW COULD ALLOW A FEW
SHOWERS TO SPILL INTO THE FAR N INTERIOR BUT PROBABLY NOT MAKING IT
INTO THE PUGET SOUND REGION. THE FORECAST WAS UPDATED THIS EVENING
TO TRIM BACK POPS SLIGHTLY TO JUST THE MOUNTAINS AND FAR N.
GRADIENTS WILL GO FLAT ON FRIDAY WITH MORE SUNSHINE EXPECTED OVER
THE LOWLANDS SO HIGH TEMPERATURES SHOULD REACH THE LOW 70S.

LOW PRESSURE WILL SHIFT EWD FRIDAY NIGHT BUT THE LONG WAVE TROUGH
POSITION WILL REMAIN CENTERED OVER THE ROCKIES. THIS KEEPS WRN WA
UNDER NW FLOW ALOFT BETWEEN THE RIDGE JUST OFFSHORE AND THE TROUGH
FURTHER INLAND. MODELS STILL SHOW 500 MB HEIGHT RISES TO AROUND
5800M BUT NOT AS HIGH AS SOME PREVIOUS RUNS. THE LACK OF ONSHORE
FLOW SHOULD RESULT IN LITTLE MORNING CLOUD COVER. UPPER HEIGHTS
UNDER THIS SCENARIO SUPPORT HIGHS NEAR 80 ON SATURDAY WHICH MATCHES
CURRENT MOS GUIDANCE. A WEAK SHORT WAVE TRAVELING DOWN THE BACK SIDE
OF THE LONG WAVE TROUGH WILL CLIP THE AREA SUNDAY. THE ONLY IMPACT
SHOULD BE TO KEEP UPPER HEIGHTS AND HIGH TEMPERATURES IN CHECK.
EXPECT ANOTHER MOSTLY CLEAR DAY WITH HIGHS NEAR 80. MERCER

.LONG TERM...NO CHANGES FROM PREVIOUS DISCUSSION...THE OVERALL TREND
IN THE GUIDANCE IS FOR THE UPSTREAM UPPER RIDGE TO MOVE ONSHORE TUE
AND THAT MAY BE THE WARMEST DAY OF THE WEEK. THEN THE FLOW ALOFT
BECOMES MORE WESTERLY OR ZONAL YET 500 MB HEIGHTS ARE RELATIVELY
HIGH. THE ACCOMPANYING LOW LEVEL ONSHORE FLOW SHOULD MAINTAIN
DAYTIME TEMPS AT OR A BIT ABOVE SEASONAL AVERAGE INTO THURSDAY
THOUGH THERE IS SOME INDICATION OF SAGGING HEIGHTS ALOFT BEFORE THE
END OF THE WEEK THAT MAY SIGNAL A GRADUAL COOLING TREND AND SOME
INCREASE IN LOW LEVEL ONSHORE FLOW. BUEHNER

&&

.AVIATION...WEAK UPPER LEVEL TROUGH OVER THE AREA TONIGHT WILL SHIFT
EAST FRIDAY MORNING. LIGHT FLOW ALOFT BECOMING NORTHERLY FRIDAY
MORNING. LOW LEVEL FLOW WILL REMAIN WEAKLY ONSHORE.

SATELLITE IMAGERY AT 0330Z/830 PM SHOWS LITTLE IN THE WAY OF STRATUS
ANYWHERE IN THE CWA. CONVECTIVE ACTIVITY REMAINS WELL TO THE NORTH
AND EAST OF THE AREA. LIGHT ONSHORE GRADIENTS CONTINUING OVERNIGHT
INTO FRIDAY MORNING. WITH THE LIGHT ONSHORE FLOW CAN NOT RULE OUT
STRATUS OVER THE INTERIOR FRIDAY MORNING. THE STRATUS THAT DOES FORM
WILL BE SHALLOW AND BURN OFF BY MIDDAY AT THE LATEST. CEILINGS WITH
THE STRATUS LOOK TO BE IN THE 1000-2000 FOOT RANGE.

KSEA...MOSTLY CLEAR SKIES WITH STRATUS REFORMING OVER THE TERMINAL
AROUND 12Z WITH CEILINGS NEAR 1500 FEET. STRATUS SCATTERING OUT BY
LATE MORNING. VARIABLE WINDS 6 KNOTS OR LESS BECOMING NORTHWESTERLY
MIDDAY FRIDAY. FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING. OVER
THE COASTAL WATERS SOUTHERLY FLOW WILL BECOME NORTHWESTERLY FRIDAY.
SURFACE HIGH PRESSURE BUILDING INSIDE OF 140 W WILL TIGHTEN UP
SURFACE GRADIENTS SATURDAY AFTERNOON AND NIGHT OVER THE OUTER
COASTAL WATERS...BOOSTING THE NORTHWESTERLIES ABOVE SMALL CRAFT
CRITERIA. WEST TO NORTHWESTERLY SWELL 3 TO 6 FEET WITH A PERIOD
AROUND 8 SECONDS WILL PERSIST THROUGH THE WEEKEND. FELTON

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE/

FOR THE GRAPHICAL AFD...VISIT
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000
FXUS66 KSEW 212241
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
340 PM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TONIGHT BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY NIGHT. HIGHER PRESSURE ALOFT IS THEN FORECAST TO
BUILD OVER THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND
WARMER DAYTIME TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS THE UPPER RIDGE IS NOW INSIDE
145W WITH THE WEAK SHORTWAVE NEAR 130W DIGGING SE. THE SHORTWAVE
SHOULD ROLL INTO THE PACIFIC NW TONIGHT AND DEVELOP INTO A CLOSED
UPPER LOW IN THE PACIFIC NW INTERIOR FRIDAY. ENOUGH COOLING ALOFT
AND INSTABILITY FOR A THREAT OF TSTMS FOR THE NORTH CASCADES THIS
EVENING. AS OF MID AFTERNOON...SEEING SOME POP UP ON DOPPLER WEATHER
RADAR JUST EAST OF THE CASCADE CREST.

AT THE SURFACE...LOW LEVEL ONSHORE FLOW WITH MAINLY WEST TO EAST
PRESSURE GRADIENTS CONTINUES BUT IS WEAKER THAN ON WEDNESDAY. THE
MARINE CLOUDS WITH TOPS BETWEEN 2 AND 3K FT THAT BLANKETED MUCH OF
THE WESTERN WA LOWLANDS THIS MORNING DISSIPATED MIDDAY TODAY.
ANTICIPATE AN INCREASE IN THE MARINE CLOUDS OVERNIGHT WITH THE
INCOMING SHORTWAVE YET THE COOLING ALOFT WILL LIKELY NOT PERMIT
SOLID CLOUD COVER FRIDAY MORNING. THE PRIMARY SHOWER THREAT SHOULD
REMAIN IN THE MOUNTAINS WITH ANOTHER CHANCE OF TSTMS IN THE
CASCADES. YET A SMALL SHOWER THREAT IS POSSIBLE IN THE INTERIOR.

THE PROGS ARE A BIT FASTER IN EXITING THE DEVELOPING UPPER LOW. SO
THE SHOWER THREAT ENDS FRIDAY NIGHT AS RIDGING ALOFT NOSES IN TOWARD
WESTERN WA. SATURDAY PROMISES MORE SUNSHINE AFTER AREAS OF MORNING
CLOUDS WITH DAYTIME TEMPERATURES REBOUNDING. THAT TREND CONTINUES
INTO SUNDAY. THE 00Z ECMWF SHORTWAVE BARRELING THROUGH THE REGION
ON SUNDAY IS NO LONGER THERE AND ALL THE PROGS IMPLY SIMPLY PAUSING
THE RISING HEIGHTS THAT DAY AS WHATEVER IS LEFT OF THAT SHORTWAVE
SLIDES SE AND INLAND IN THE NW FLOW ALOFT. BUEHNER

.LONG TERM...THE OVERALL TREND IN THE GUIDANCE IS FOR THE UPSTREAM
UPPER RIDGE TO MOVE ONSHORE TUE AND THAT MAY BE THE WARMEST DAY OF
THE WEEK. THEN THE FLOW ALOFT BECOMES MORE WESTERLY OR ZONAL YET 500
MB HEIGHTS ARE RELATIVELY HIGH. THE ACCOMPANYING LOW LEVEL ONSHORE
FLOW SHOULD MAINTAIN DAYTIME TEMPS AT OR A BIT ABOVE SEASONAL
AVERAGE INTO THURSDAY THOUGH THERE IS SOME INDICATION OF SAGGING
HEIGHTS ALOFT BEFORE THE END OF THE WEEK THAT MAY SIGNAL A GRADUAL
COOLING TREND AND SOME INCREASE IN LOW LEVEL ONSHORE FLOW. BUEHNER

&&

.AVIATION...THE WEAK UPPER LEVEL TROUGH THAT HAS BEEN MOVING DOWN
THE BRITISH COLUMBIA COAST TODAY WILL PASS OVER WASHINGTON TONIGHT
AND INTO EASTERN OREGON BY SATURDAY MORNING. LIGHT WESTERLY FLOW
WILL BECOME NORTHERLY BY SATURDAY MORNING. LOW LEVEL FLOW WILL
REMAIN ONSHORE AND THE AIR MASS WILL REMAIN SLIGHTLY UNSTABLE THIS
AFTERNOON...MAINLY OVER THE NORTHERN WASHINGTON CASCADES NEAR THE
CREST.

LINGERING STRATUS OVER HOOD CANAL HAS CLEARED AS OF 22Z. THE UPPER
LEVEL TROUGH MOVING INTO THE AREA THIS AFTERNOON HAS NOT BROUGHT
MUCH IN THE WAY OF HIGH CLOUDS...BUT DOES APPEAR TO BE ENHANCING
CONVECTION ALONG THE EAST SLOPES OF THE NORTH WASHINGTON CASCADES. A
CHANCE OF THUNDERSTORMS REMAINS A POSSIBILITY ALONG THE CREST OF THE
CASCADES THIS EVENING...MAINLY NORTH OF KING COUNTY.

KSEA...CLEAR SKIES AND VFR CONDITIONS WILL PERSIST THIS EVENING...
EXPECT LIMITED STRATUS TO FORM AGAIN TONIGHT WITH MVFR CEILINGS 12Z
TO 15Z. SOUTHWEST WINDS 4 TO 8 KNOTS BECOMING LIGHT AND NORTHEAST
AFTER 06Z.

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING. OVER
THE COASTAL WATERS SOUTHERLY FLOW WILL BECOME NORTHWESTERLY FRIDAY.
SURFACE HIGH PRESSURE BUILDING INSIDE OF 140 W WILL TIGHTEN UP
SURFACE GRADIENTS SATURDAY AFTERNOON AND NIGHT OVER THE COASTAL
WATERS...BOOSTING THE NORTHWESTERLIES ABOVE SMALL CRAFT CRITERIA.
WEST TO NORTHWESTERLY SWELL 4 TO 6 FEET AT AROUND 8 SECONDS WILL
PERSIST THROUGH THE WEEKEND.

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE/

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 211813 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
1110 AM PDT THU AUG 21 2014

UPDATED AVIATION KSEA SECTION.

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TODAY BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY. HIGHER PRESSURE ALOFT IS THEN FORECAST TO BUILD OVER
THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND WARMER DAYTIME
TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...UPPER RIDGE IS NOW INSIDE 150W WITH THE WEAK SHORTWAVE
VISIBLE IN THE WATER VAPOR IMAGE NEAR 135W DIGGING SE. 12Z PROGS IN
THUS CONTINUE THE TREND OF DIGGING THIS SHORTWAVE INTO THE PACIFIC
NW LATE TODAY AND DEVELOPING A CLOSED UPPER LOW IN THE INTERIOR FRI.
ENOUGH INSTABILITY LATE TODAY AND HAVE INCLUDED A THREAT OF TSTMS
FOR THE NORTH CASCADES.

AT THE SURFACE...LOW LEVEL ONSHORE FLOW IS WEAKER THAN AT THIS TIME
ON WED. KSEA-KEAT GRADIENT THIS HOUR IS 5.2 MB VS 7.5 MB WED. MARINE
CLOUDS BLANKET MUCH OF THE WESTERN WA LOWLANDS BUT TOPS ARE BETWEEN
2 AND 3K FT. SO SHOULD HAVE AN EARLIER BREAKOUT...AROUND MIDDAY FOR
MOST LOCATIONS. WILL MASSAGE THE SHORT TERM FORECAST PERIOD.

OTHERWISE...THE FORECAST LOOKS ON TRACK. A THREAT OF SHOWERS MAINLY
IN THE MOUNTAINS FRI AND THEN SOME RIDGING ALOFT OVER THE WEEKEND
FOR MORE SUNSHINE AND WARMER DAYTIME TEMPS. WILL KEEP AN EYE ON WHAT
THE ECMWF SHOWED WITH THE NEXT DIGGING SHORTWAVE ON SUN VS WHAT
OTHER GUIDANCE SHOWED WITH RIDGING IN THE UPCOMING 12Z MODELS.
BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...CONFIDENCE IN THIS
PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS WERE NOT IN VERY
GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF CARVED OUT AN 570 DAM
LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE GFS HAD THE CWA UNDER
THE INFLUENCE OF AN UPPER TROF CENTERED TO OUR EAST. BASED ON THESE
TWO SOLUTIONS...THE MAX TEMP FORECAST FOR SUNDAY IS TOO WARM. FOR
NOW...THOUGHT IT WOULD BE BEST TO LEAVE THINGS UNCHANGED. THE
MORNING CYCLE MIGHT VERY WELL REVERT TO A RIDGE SOLUTION FOR SUNDAY.
NC

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH SLIDING DOWN THE BRITISH
COLUMBIA COAST TODAY WILL HELP THE NORTHWESTERLY FLOW ALOFT BECOME
WESTERLY. LOW LEVEL FLOW WILL REMAIN ONSHORE AND THE AIR MASS WILL
BECOME SLIGHTLY UNSTABLE THIS AFTERNOON.

PRETTY SOLID STRATUS COVERAGE OVER THE LOWLANDS THIS MORNING...WITH
THE EXCEPTION OF WESTERN WHATCOM AND SKAGIT COUNTIES. DESPITE THE
COVERAGE THE STRATUS LAYER NOT TERRIBLY THICK...EXPECT CEILINGS TO
LIFT THROUGH THE REMAINDER OF THE MORNING AND SCATTER OUT MOST
LOCALES AROUND 18Z/11 AM. THE EXCEPTION WILL BE THE COAST...WHICH
WILL BECOME VFR EARLY IN THE AFTERNOON BUT NOT SCATTER OUT UNTIL
LATE IN THE DAY. THE UPPER LEVEL TROUGH APPROACHING THE AREA TODAY
WILL BRING INCREASING HIGH CLOUDS AND A CHANCE OF THUNDERSTORMS TO
THE NORTH CASCADES.

KSEA...STRATUS AND MVFR CEILINGS WILL CONTINUE TO LIFT OVER THE NEXT
FEW HOURS AND SCATTER OUT BY 20Z. CLEARING HAS BEEN A BIT SLOWER
THAN EXPECTED OVER THE CENTRAL SOUND...MORE SOLID BREAKS IN THE
STRATUS WORKING THEIR WAY UP FROM THE SOUTH. CONDITIONS WILL REMAIN
VFR TONIGHT...LOWERING TO MVFR LEVELS EARLY FRIDAY
MORNING...IMPROVING THROUGH MIDDAY. SOUTHWEST WINDS 4 TO 8 KNOTS
BECOMING LIGHT AND NORTHEAST AFTER 06Z.

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING.

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML











000
FXUS66 KSEW 211813 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
1110 AM PDT THU AUG 21 2014

UPDATED AVIATION KSEA SECTION.

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TODAY BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY. HIGHER PRESSURE ALOFT IS THEN FORECAST TO BUILD OVER
THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND WARMER DAYTIME
TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...UPPER RIDGE IS NOW INSIDE 150W WITH THE WEAK SHORTWAVE
VISIBLE IN THE WATER VAPOR IMAGE NEAR 135W DIGGING SE. 12Z PROGS IN
THUS CONTINUE THE TREND OF DIGGING THIS SHORTWAVE INTO THE PACIFIC
NW LATE TODAY AND DEVELOPING A CLOSED UPPER LOW IN THE INTERIOR FRI.
ENOUGH INSTABILITY LATE TODAY AND HAVE INCLUDED A THREAT OF TSTMS
FOR THE NORTH CASCADES.

AT THE SURFACE...LOW LEVEL ONSHORE FLOW IS WEAKER THAN AT THIS TIME
ON WED. KSEA-KEAT GRADIENT THIS HOUR IS 5.2 MB VS 7.5 MB WED. MARINE
CLOUDS BLANKET MUCH OF THE WESTERN WA LOWLANDS BUT TOPS ARE BETWEEN
2 AND 3K FT. SO SHOULD HAVE AN EARLIER BREAKOUT...AROUND MIDDAY FOR
MOST LOCATIONS. WILL MASSAGE THE SHORT TERM FORECAST PERIOD.

OTHERWISE...THE FORECAST LOOKS ON TRACK. A THREAT OF SHOWERS MAINLY
IN THE MOUNTAINS FRI AND THEN SOME RIDGING ALOFT OVER THE WEEKEND
FOR MORE SUNSHINE AND WARMER DAYTIME TEMPS. WILL KEEP AN EYE ON WHAT
THE ECMWF SHOWED WITH THE NEXT DIGGING SHORTWAVE ON SUN VS WHAT
OTHER GUIDANCE SHOWED WITH RIDGING IN THE UPCOMING 12Z MODELS.
BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...CONFIDENCE IN THIS
PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS WERE NOT IN VERY
GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF CARVED OUT AN 570 DAM
LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE GFS HAD THE CWA UNDER
THE INFLUENCE OF AN UPPER TROF CENTERED TO OUR EAST. BASED ON THESE
TWO SOLUTIONS...THE MAX TEMP FORECAST FOR SUNDAY IS TOO WARM. FOR
NOW...THOUGHT IT WOULD BE BEST TO LEAVE THINGS UNCHANGED. THE
MORNING CYCLE MIGHT VERY WELL REVERT TO A RIDGE SOLUTION FOR SUNDAY.
NC

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH SLIDING DOWN THE BRITISH
COLUMBIA COAST TODAY WILL HELP THE NORTHWESTERLY FLOW ALOFT BECOME
WESTERLY. LOW LEVEL FLOW WILL REMAIN ONSHORE AND THE AIR MASS WILL
BECOME SLIGHTLY UNSTABLE THIS AFTERNOON.

PRETTY SOLID STRATUS COVERAGE OVER THE LOWLANDS THIS MORNING...WITH
THE EXCEPTION OF WESTERN WHATCOM AND SKAGIT COUNTIES. DESPITE THE
COVERAGE THE STRATUS LAYER NOT TERRIBLY THICK...EXPECT CEILINGS TO
LIFT THROUGH THE REMAINDER OF THE MORNING AND SCATTER OUT MOST
LOCALES AROUND 18Z/11 AM. THE EXCEPTION WILL BE THE COAST...WHICH
WILL BECOME VFR EARLY IN THE AFTERNOON BUT NOT SCATTER OUT UNTIL
LATE IN THE DAY. THE UPPER LEVEL TROUGH APPROACHING THE AREA TODAY
WILL BRING INCREASING HIGH CLOUDS AND A CHANCE OF THUNDERSTORMS TO
THE NORTH CASCADES.

KSEA...STRATUS AND MVFR CEILINGS WILL CONTINUE TO LIFT OVER THE NEXT
FEW HOURS AND SCATTER OUT BY 20Z. CLEARING HAS BEEN A BIT SLOWER
THAN EXPECTED OVER THE CENTRAL SOUND...MORE SOLID BREAKS IN THE
STRATUS WORKING THEIR WAY UP FROM THE SOUTH. CONDITIONS WILL REMAIN
VFR TONIGHT...LOWERING TO MVFR LEVELS EARLY FRIDAY
MORNING...IMPROVING THROUGH MIDDAY. SOUTHWEST WINDS 4 TO 8 KNOTS
BECOMING LIGHT AND NORTHEAST AFTER 06Z.

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING.

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML










000
FXUS66 KSEW 211612 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TODAY BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY. HIGHER PRESSURE ALOFT IS THEN FORECAST TO BUILD OVER
THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND WARMER DAYTIME
TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...UPPER RIDGE IS NOW INSIDE 150W WITH THE WEAK SHORTWAVE
VISIBLE IN THE WATER VAPOR IMAGE NEAR 135W DIGGING SE. 12Z PROGS IN
THUS CONTINUE THE TREND OF DIGGING THIS SHORTWAVE INTO THE PACIFIC
NW LATE TODAY AND DEVELOPING A CLOSED UPPER LOW IN THE INTERIOR FRI.
ENOUGH INSTABILITY LATE TODAY AND HAVE INCLUDED A THREAT OF TSTMS
FOR THE NORTH CASCADES.

AT THE SURFACE...LOW LEVEL ONSHORE FLOW IS WEAKER THAN AT THIS TIME
ON WED. KSEA-KEAT GRADIENT THIS HOUR IS 5.2 MB VS 7.5 MB WED. MARINE
CLOUDS BLANKET MUCH OF THE WESTERN WA LOWLANDS BUT TOPS ARE BETWEEN
2 AND 3K FT. SO SHOULD HAVE AN EARLIER BREAKOUT...AROUND MIDDAY FOR
MOST LOCATIONS. WILL MASSAGE THE SHORT TERM FORECAST PERIOD.

OTHERWISE...THE FORECAST LOOKS ON TRACK. A THREAT OF SHOWERS MAINLY
IN THE MOUNTAINS FRI AND THEN SOME RIDGING ALOFT OVER THE WEEKEND
FOR MORE SUNSHINE AND WARMER DAYTIME TEMPS. WILL KEEP AN EYE ON WHAT
THE ECMWF SHOWED WITH THE NEXT DIGGING SHORTWAVE ON SUN VS WHAT
OTHER GUIDANCE SHOWED WITH RIDGING IN THE UPCOMING 12Z MODELS.
BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...CONFIDENCE IN THIS
PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS WERE NOT IN VERY
GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF CARVED OUT AN 570 DAM
LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE GFS HAD THE CWA UNDER
THE INFLUENCE OF AN UPPER TROF CENTERED TO OUR EAST. BASED ON THESE
TWO SOLUTIONS...THE MAX TEMP FORECAST FOR SUNDAY IS TOO WARM. FOR
NOW...THOUGHT IT WOULD BE BEST TO LEAVE THINGS UNCHANGED. THE
MORNING CYCLE MIGHT VERY WELL REVERT TO A RIDGE SOLUTION FOR SUNDAY.
NC

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH SLIDING DOWN THE BRITISH
COLUMBIA COAST TODAY WILL HELP THE NORTHWESTERLY FLOW ALOFT BECOME
WESTERLY. LOW LEVEL FLOW WILL REMAIN ONSHORE AND THE AIR MASS WILL
BECOME SLIGHTLY UNSTABLE THIS AFTERNOON.

PRETTY SOLID STRATUS COVERAGE OVER THE LOWLANDS THIS MORNING...WITH
THE EXCEPTION OF WESTERN WHATCOM AND SKAGIT COUNTIES. DESPITE THE
COVERAGE THE STRATUS LAYER NOT TERRIBLY THICK...EXPECT CEILINGS TO
LIFT THROUGH THE REMAINDER OF THE MORNING AND SCATTER OUT MOST
LOCALES AROUND 18Z/11 AM. THE EXCEPTION WILL BE THE COAST...WHICH
WILL BECOME VFR EARLY IN THE AFTERNOON BUT NOT SCATTER OUT UNTIL
LATE IN THE DAY. THE UPPER LEVEL TROUGH APPROACHING THE AREA TODAY
WILL BRING INCREASING HIGH CLOUDS AND A CHANCE OF THUNDERSTORMS TO
THE NORTH CASCADES.

KSEA...STRATUS AND MVFR CEILINGS WILL LIFT OVER THE NEXT FEW HOURS
AND SCATTER OUT BY 18Z. VISIBLE SATELLITE IMAGERY ALREADY SHOWING
SOME CLEARING TO THE NORTH OF THE TERMINAL AS OF 16Z. CONDITIONS
WILL REMAIN VFR THROUGH FRIDAY MORNING. SOUTHWEST WINDS 4 TO 8 KNOTS
BECOMING LIGHT AND NORTHEAST AFTER 06Z.

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING.

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 211612 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL MOVE SOUTHEAST OVER THE
REGION TODAY BRINGING A THREAT OF SHOWERS MAINLY IN THE MOUNTAINS
THROUGH FRIDAY. HIGHER PRESSURE ALOFT IS THEN FORECAST TO BUILD OVER
THE PACIFIC NW OVER THE WEEKEND FOR MORE SUNSHINE AND WARMER DAYTIME
TEMPERATURES...LIKELY CONTINUING WELL INTO NEXT WEEK.

&&

.SHORT TERM...UPPER RIDGE IS NOW INSIDE 150W WITH THE WEAK SHORTWAVE
VISIBLE IN THE WATER VAPOR IMAGE NEAR 135W DIGGING SE. 12Z PROGS IN
THUS CONTINUE THE TREND OF DIGGING THIS SHORTWAVE INTO THE PACIFIC
NW LATE TODAY AND DEVELOPING A CLOSED UPPER LOW IN THE INTERIOR FRI.
ENOUGH INSTABILITY LATE TODAY AND HAVE INCLUDED A THREAT OF TSTMS
FOR THE NORTH CASCADES.

AT THE SURFACE...LOW LEVEL ONSHORE FLOW IS WEAKER THAN AT THIS TIME
ON WED. KSEA-KEAT GRADIENT THIS HOUR IS 5.2 MB VS 7.5 MB WED. MARINE
CLOUDS BLANKET MUCH OF THE WESTERN WA LOWLANDS BUT TOPS ARE BETWEEN
2 AND 3K FT. SO SHOULD HAVE AN EARLIER BREAKOUT...AROUND MIDDAY FOR
MOST LOCATIONS. WILL MASSAGE THE SHORT TERM FORECAST PERIOD.

OTHERWISE...THE FORECAST LOOKS ON TRACK. A THREAT OF SHOWERS MAINLY
IN THE MOUNTAINS FRI AND THEN SOME RIDGING ALOFT OVER THE WEEKEND
FOR MORE SUNSHINE AND WARMER DAYTIME TEMPS. WILL KEEP AN EYE ON WHAT
THE ECMWF SHOWED WITH THE NEXT DIGGING SHORTWAVE ON SUN VS WHAT
OTHER GUIDANCE SHOWED WITH RIDGING IN THE UPCOMING 12Z MODELS.
BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...CONFIDENCE IN THIS
PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS WERE NOT IN VERY
GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF CARVED OUT AN 570 DAM
LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE GFS HAD THE CWA UNDER
THE INFLUENCE OF AN UPPER TROF CENTERED TO OUR EAST. BASED ON THESE
TWO SOLUTIONS...THE MAX TEMP FORECAST FOR SUNDAY IS TOO WARM. FOR
NOW...THOUGHT IT WOULD BE BEST TO LEAVE THINGS UNCHANGED. THE
MORNING CYCLE MIGHT VERY WELL REVERT TO A RIDGE SOLUTION FOR SUNDAY.
NC

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH SLIDING DOWN THE BRITISH
COLUMBIA COAST TODAY WILL HELP THE NORTHWESTERLY FLOW ALOFT BECOME
WESTERLY. LOW LEVEL FLOW WILL REMAIN ONSHORE AND THE AIR MASS WILL
BECOME SLIGHTLY UNSTABLE THIS AFTERNOON.

PRETTY SOLID STRATUS COVERAGE OVER THE LOWLANDS THIS MORNING...WITH
THE EXCEPTION OF WESTERN WHATCOM AND SKAGIT COUNTIES. DESPITE THE
COVERAGE THE STRATUS LAYER NOT TERRIBLY THICK...EXPECT CEILINGS TO
LIFT THROUGH THE REMAINDER OF THE MORNING AND SCATTER OUT MOST
LOCALES AROUND 18Z/11 AM. THE EXCEPTION WILL BE THE COAST...WHICH
WILL BECOME VFR EARLY IN THE AFTERNOON BUT NOT SCATTER OUT UNTIL
LATE IN THE DAY. THE UPPER LEVEL TROUGH APPROACHING THE AREA TODAY
WILL BRING INCREASING HIGH CLOUDS AND A CHANCE OF THUNDERSTORMS TO
THE NORTH CASCADES.

KSEA...STRATUS AND MVFR CEILINGS WILL LIFT OVER THE NEXT FEW HOURS
AND SCATTER OUT BY 18Z. VISIBLE SATELLITE IMAGERY ALREADY SHOWING
SOME CLEARING TO THE NORTH OF THE TERMINAL AS OF 16Z. CONDITIONS
WILL REMAIN VFR THROUGH FRIDAY MORNING. SOUTHWEST WINDS 4 TO 8 KNOTS
BECOMING LIGHT AND NORTHEAST AFTER 06Z.

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. AS IS TYPICAL WITH THIS TYPE OF PATTERN...THE
STRENGTH OF THE ONSHORE FLOW WILL VARY DIURNALLY AS WELL AS WITH A
SERIES OF WEAK SYSTEMS THAT ARE FORECAST TO BRUSH THE REGION OVER
THE NEXT FEW DAYS. EXPECT THE STRONGEST WESTERLY WINDS OVER THE
CENTRAL AND EAST STRAIT DURING THE EVENING AND EARLY MORNING
HOURS...EASING JUST BEFORE DAY BREAK THROUGH THE LATER MORNING.

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








000
FXUS66 KSEW 211059 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SEATTLE WA
359 AM PDT THU AUG 21 2014

CORRECTED TYPOS IN THE SYNOPSIS AND LONG TERM SEGMENTS.

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL DEVELOP OVER THE REGION
DURING THE DAY TODAY...CARVING OUT AN UPPER LOW OVER THE AREA
TONIGHT. THIS UPPER LOW WILL MOVE INTO THE NORTHERN GREAT BASIN LATE
FRIDAY. HIGH PRESSURE ALOFT WILL THEN PREVAIL OVER THE REGION ON
SATURDAY.

&&

.SHORT TERM...
THE SURFACE ONSHORE PRESSURE GRADIENT WAS WEAKER THAN 24 HOURS
AGO...SO THERE WAS NOT MUCH LOW CLOUDS OVER THE CWA AT THIS TIME.
EXPECT THE LOW CLOUDS TO FILL IN A BIT DURING THE NEXT SEVERAL
HOURS...ESPECIALLY OVER THE SOUTHWEST INTERIOR...BEFORE RETREATING
TO THE COASTLINE EARLY THIS AFTERNOON.

MEANWHILE...AN UPPER TROF WILL DIG OVER THE PACIFIC NORTHWEST
DURING THE DAY TODAY. THE AIR MASS WILL BECOME WEAKLY UNSTABLE IN
THE AFTERNOON FOR A RISK OF SHOWERS OVER THE MOUNTAINS. CANNOT
RULE OUT AN ISOLD TSTM OVER THE NORTH CASCADES...NEAR THE CANADIAN
BORDER...LATE TODAY...SO WILL NEED TO WATCH THIS AREA. OTHERWISE...
MAX TEMPS TODAY SHOULD BE ABOUT THE SAME AS THEY WERE YESTERDAY.

AN UPPER LOW WILL DEVELOP OVER THE CWA TONIGHT BEFORE MOVING INTO
THE NORTHERN GREAT BASIN ON FRI. THE MAIN IMPACT THIS SYSTEM WILL
HAVE ON OUR WEATHER WILL BE TOO DESTABILIZE THE AIR MASS FOR A
RISK OF SHOWERS OVER THE INTERIOR. OF COURSE...THERE WILL BE A
THREAT OF TSTMS OVER THE CASCADES.

LOOK FOR AN UPPER RIDGE TO PREVAIL OVER THE REGION FRI NIGHT AND
SATURDAY FOR SUNNIER AND WARMER WEATHER. THE SURFACE PRESSURE
GRADIENT WILL BECOME LIGHT OFFSHORE OR NORTHERLY...THUS ANY LOW
CLOUDS SHOULD BE CONFINED TO THE COAST SATURDAY MORNING. LESS CLOUD
COVER AND A NORTHERLY SURFACE PRESSURE GRADIENT WILL RESULT IN
WARMER TEMPS SATURDAY AFTERNOON.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS
WERE NOT IN VERY GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF
CARVED OUT AN 570 DAM LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE
GFS HAD THE CWA UNDER THE INFLUENCE OF AN UPPER TROF CENTERED TO OUR
EAST. BASED ON THESE TWO SOLUTIONS...THE MAX TEMP FORECAST FOR
SUNDAY IS TOO WARM. FOR NOW...THOUGHT IT WOULD BE BEST TO LEAVE
THINGS UNCHANGED. THE MORNING CYCLE MIGHT VERY WELL REVERT TO A
RIDGE SOLUTION FOR SUNDAY.

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY TODAY AS AN
UPPER LEVEL TROUGH MOVES INTO THE AREA. LOW LEVEL FLOW WILL REMAIN
ONSHORE WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND. AIR MASS STABLE BECOMING SLIGHTLY UNSTABLE
THIS AFTERNOON.

FOG/STRATUS SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST THROUGH
THE CHEHALIS GAP INTO THE HOOD CANAL AREA. THROUGH THE STRAIT THE
STRATUS HAS NOT MADE IT AS FAR AS PORT ANGELES AS OF 10Z. SC DECK
OVER THE CASCADES STARTING TO SPREAD BACK TO THE WEST BUT STILL
EAST OF ALL OF THE TAFS. ONSHORE SURFACE GRADIENTS CONTINUE TO BE
LIGHT WITH ALL OF THE WEST SIDE GRADIENTS A MILLIBAR OR LESS AT 10Z.

CONFIDENCE NOT VERY HIGH IN THE FORECAST THIS MORNING WITH THE LIGHT
GRADIENTS. STRATUS OVER THE CHEHALIS VALLEY AND THE HOOD CANAL IS
SLOWLY MOVING EAST SO WILL GO WITH A TEMPO BROKEN GROUP FOR
KBFI...KSEA AND KOLM BETWEEN 14Z AND 17Z THIS MORNING. FOR THE
REMAINDER OF THE TAFS WILL JUST GO WITH A SCATTERED CLOUD DECK THIS
MORNING. UPPER LEVEL TROUGH MOVING OVER THE AREA THIS AFTERNOON BUT
ONLY HIGH CLOUDS ASSOCIATED WITH THIS FEATURE. WITH THE LIGHT
ONSHORE FLOW CONTINUING THROUGHOUT THE DAY ONLY EXPECTING A COUPLE
OF HOURS OF BREAKOUT ALONG THE COAST LATE IN THE AFTERNOON.

KSEA...CONFIDENCE NOT HIGH ENOUGH TO COMPLETELY ELIMINATE STRATUS
FROM THE TERMINAL THIS MORNING SO WILL GO WITH A TEMPO BROKEN GROUP
BETWEEN 14Z AND 17Z NEAR 2000 FEET. SCATTERED CLOUDS BEFORE 14Z AND
JUST HIGH CLOUDS THIS AFTERNOON INTO THE EVENING HOURS. LIGHT WINDS
BECOMING SOUTHWEST 4 TO 8 KNOTS IN THE AFTERNOON. FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGHER PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND WILL RESULT IN VARYING DEGREES OF ONSHORE FLOW
INTO THE EARLY PART OF NEXT WEEK. THE ONSHORE FLOW IS ONLY STRONG
ENOUGH TO PRODUCE BORDERLINE SMALL CRAFT ADVISORY WINDS FOR
THE CENTRAL AND EASTERN STRAIT IN THE EVENING AND EARLY MORNING
HOURS THE NEXT FEW DAYS. FELTON

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 211059 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SEATTLE WA
359 AM PDT THU AUG 21 2014

CORRECTED TYPOS IN THE SYNOPSIS AND LONG TERM SEGMENTS.

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL DEVELOP OVER THE REGION
DURING THE DAY TODAY...CARVING OUT AN UPPER LOW OVER THE AREA
TONIGHT. THIS UPPER LOW WILL MOVE INTO THE NORTHERN GREAT BASIN LATE
FRIDAY. HIGH PRESSURE ALOFT WILL THEN PREVAIL OVER THE REGION ON
SATURDAY.

&&

.SHORT TERM...
THE SURFACE ONSHORE PRESSURE GRADIENT WAS WEAKER THAN 24 HOURS
AGO...SO THERE WAS NOT MUCH LOW CLOUDS OVER THE CWA AT THIS TIME.
EXPECT THE LOW CLOUDS TO FILL IN A BIT DURING THE NEXT SEVERAL
HOURS...ESPECIALLY OVER THE SOUTHWEST INTERIOR...BEFORE RETREATING
TO THE COASTLINE EARLY THIS AFTERNOON.

MEANWHILE...AN UPPER TROF WILL DIG OVER THE PACIFIC NORTHWEST
DURING THE DAY TODAY. THE AIR MASS WILL BECOME WEAKLY UNSTABLE IN
THE AFTERNOON FOR A RISK OF SHOWERS OVER THE MOUNTAINS. CANNOT
RULE OUT AN ISOLD TSTM OVER THE NORTH CASCADES...NEAR THE CANADIAN
BORDER...LATE TODAY...SO WILL NEED TO WATCH THIS AREA. OTHERWISE...
MAX TEMPS TODAY SHOULD BE ABOUT THE SAME AS THEY WERE YESTERDAY.

AN UPPER LOW WILL DEVELOP OVER THE CWA TONIGHT BEFORE MOVING INTO
THE NORTHERN GREAT BASIN ON FRI. THE MAIN IMPACT THIS SYSTEM WILL
HAVE ON OUR WEATHER WILL BE TOO DESTABILIZE THE AIR MASS FOR A
RISK OF SHOWERS OVER THE INTERIOR. OF COURSE...THERE WILL BE A
THREAT OF TSTMS OVER THE CASCADES.

LOOK FOR AN UPPER RIDGE TO PREVAIL OVER THE REGION FRI NIGHT AND
SATURDAY FOR SUNNIER AND WARMER WEATHER. THE SURFACE PRESSURE
GRADIENT WILL BECOME LIGHT OFFSHORE OR NORTHERLY...THUS ANY LOW
CLOUDS SHOULD BE CONFINED TO THE COAST SATURDAY MORNING. LESS CLOUD
COVER AND A NORTHERLY SURFACE PRESSURE GRADIENT WILL RESULT IN
WARMER TEMPS SATURDAY AFTERNOON.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS
WERE NOT IN VERY GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF
CARVED OUT AN 570 DAM LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE
GFS HAD THE CWA UNDER THE INFLUENCE OF AN UPPER TROF CENTERED TO OUR
EAST. BASED ON THESE TWO SOLUTIONS...THE MAX TEMP FORECAST FOR
SUNDAY IS TOO WARM. FOR NOW...THOUGHT IT WOULD BE BEST TO LEAVE
THINGS UNCHANGED. THE MORNING CYCLE MIGHT VERY WELL REVERT TO A
RIDGE SOLUTION FOR SUNDAY.

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY TODAY AS AN
UPPER LEVEL TROUGH MOVES INTO THE AREA. LOW LEVEL FLOW WILL REMAIN
ONSHORE WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND. AIR MASS STABLE BECOMING SLIGHTLY UNSTABLE
THIS AFTERNOON.

FOG/STRATUS SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST THROUGH
THE CHEHALIS GAP INTO THE HOOD CANAL AREA. THROUGH THE STRAIT THE
STRATUS HAS NOT MADE IT AS FAR AS PORT ANGELES AS OF 10Z. SC DECK
OVER THE CASCADES STARTING TO SPREAD BACK TO THE WEST BUT STILL
EAST OF ALL OF THE TAFS. ONSHORE SURFACE GRADIENTS CONTINUE TO BE
LIGHT WITH ALL OF THE WEST SIDE GRADIENTS A MILLIBAR OR LESS AT 10Z.

CONFIDENCE NOT VERY HIGH IN THE FORECAST THIS MORNING WITH THE LIGHT
GRADIENTS. STRATUS OVER THE CHEHALIS VALLEY AND THE HOOD CANAL IS
SLOWLY MOVING EAST SO WILL GO WITH A TEMPO BROKEN GROUP FOR
KBFI...KSEA AND KOLM BETWEEN 14Z AND 17Z THIS MORNING. FOR THE
REMAINDER OF THE TAFS WILL JUST GO WITH A SCATTERED CLOUD DECK THIS
MORNING. UPPER LEVEL TROUGH MOVING OVER THE AREA THIS AFTERNOON BUT
ONLY HIGH CLOUDS ASSOCIATED WITH THIS FEATURE. WITH THE LIGHT
ONSHORE FLOW CONTINUING THROUGHOUT THE DAY ONLY EXPECTING A COUPLE
OF HOURS OF BREAKOUT ALONG THE COAST LATE IN THE AFTERNOON.

KSEA...CONFIDENCE NOT HIGH ENOUGH TO COMPLETELY ELIMINATE STRATUS
FROM THE TERMINAL THIS MORNING SO WILL GO WITH A TEMPO BROKEN GROUP
BETWEEN 14Z AND 17Z NEAR 2000 FEET. SCATTERED CLOUDS BEFORE 14Z AND
JUST HIGH CLOUDS THIS AFTERNOON INTO THE EVENING HOURS. LIGHT WINDS
BECOMING SOUTHWEST 4 TO 8 KNOTS IN THE AFTERNOON. FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGHER PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND WILL RESULT IN VARYING DEGREES OF ONSHORE FLOW
INTO THE EARLY PART OF NEXT WEEK. THE ONSHORE FLOW IS ONLY STRONG
ENOUGH TO PRODUCE BORDERLINE SMALL CRAFT ADVISORY WINDS FOR
THE CENTRAL AND EASTERN STRAIT IN THE EVENING AND EARLY MORNING
HOURS THE NEXT FEW DAYS. FELTON

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 211030
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL DEVELOP OVER THE
REGION DURING THE DAY TODAY...CARVING AN UPPER LOW OVER THE AREA
TONIGHT. THIS UPPER LOW WILL MOVE INTO THE NORTHERN GREAT BASIN
LATE FRIDAY. HIGH PRESSURE ALOFT WILL THEN PREVAIL OVER THE REGION
ON SATURDAY.

&&

.SHORT TERM...
THE SURFACE ONSHORE PRESSURE GRADIENT WAS WEAKER THAN 24 HOURS
AGO...SO THERE WAS NOT MUCH LOW CLOUDS OVER THE CWA AT THIS TIME.
EXPECT THE LOW CLOUDS TO FILL IN A BIT DURING THE NEXT SEVERAL
HOURS...ESPECIALLY OVER THE SOUTHWEST INTERIOR...BEFORE
RETREATING TO THE COASTLINE EARLY THIS AFTERNOON.

MEANWHILE...AN UPPER TROF WILL DIG OVER THE PACIFIC NORTHWEST
DURING THE DAY TODAY. THE AIR MASS WILL BECOME WEAKLY UNSTABLE IN
THE AFTERNOON FOR A RISK OF SHOWERS OVER THE MOUNTAINS. CANNOT
RULE OUT AN ISOLD TSTM OVER THE NORTH CASCADES...NEAR THE CANADIAN
BORDER...LATE TODAY...SO WILL NEED TO WATCH THIS AREA.
OTHERWISE...MAX TEMPS TODAY SHOULD BE ABOUT THE SAME AS THEY WERE
YESTERDAY.

AN UPPER LOW WILL DEVELOP OVER THE CWA TONIGHT BEFORE MOVING INTO
THE NORTHERN GREAT BASIN ON FRI. THE MAIN IMPACT THIS SYSTEM WILL
HAVE ON OUR WEATHER WILL BE TOO DESTABILIZE THE AIR MASS FOR A
RISK OF SHOWERS OVER THE INTERIOR. OF COURSE...THERE WILL BE A
THREAT OF TSTMS OVER THE CASCADES.

LOOK FOR AN UPPER RIDGE TO PREVAIL OVER THE REGION FRI NIGHT AND
SATURDAY FOR SUNNIER AND WARMER WEATHER. THE SURFACE PRESSURE
GRADIENT WILL BECOME LIGHT OFFSHORE OR NORTHERLY...THUS ANY LOW
CLOUDS SHOULD BE CONFINED TO THE COAST SATURDAY MORNING. LESS
CLOUD COVER AND A NORTHERLY SURFACE GRADIENT WILL RESULT IN
WARMER TEMPS SATURDAY AFTERNOON.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS
WERE NOT IN VERY GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF
CARVED OUT AN 570 DAM LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE
GFS HAD THE CWA UNDER THE INFLUENCE OF AN UPPER TROF CENTERED TO
OUR EAST. BASED ON THESE TWO SOLUTIONS...THE MAX TEMP FORECAST IS
TOO WARM. FOR NOW...THOUGHT IT WOULD BE BEST THE LEAVE THINGS
UNCHANGED. THE MORNING CYCLE MIGHT VERY WELL REVERT TO A RIDGE
SOLUTION FOR SUNDAY.

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY TODAY AS AN
UPPER LEVEL TROUGH MOVES INTO THE AREA. LOW LEVEL FLOW WILL REMAIN
ONSHORE WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND. AIR MASS STABLE BECOMING SLIGHTLY UNSTABLE
THIS AFTERNOON.

FOG/STRATUS SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST THROUGH
THE CHEHALIS GAP INTO THE HOOD CANAL AREA. THROUGH THE STRAIT THE
STRATUS HAS NOT MADE IT AS FAR AS PORT ANGELES AS OF 10Z. SC DECK
OVER THE CASCADES STARTING TO SPREAD BACK TO THE WEST BUT STILL
EAST OF ALL OF THE TAFS. ONSHORE SURFACE GRADIENTS CONTINUE TO BE
LIGHT WITH ALL OF THE WEST SIDE GRADIENTS A MILLIBAR OR LESS AT 10Z.

CONFIDENCE NOT VERY HIGH IN THE FORECAST THIS MORNING WITH THE LIGHT
GRADIENTS. STRATUS OVER THE CHEHALIS VALLEY AND THE HOOD CANAL IS
SLOWLY MOVING EAST SO WILL GO WITH A TEMPO BROKEN GROUP FOR
KBFI...KSEA AND KOLM BETWEEN 14Z AND 17Z THIS MORNING. FOR THE
REMAINDER OF THE TAFS WILL JUST GO WITH A SCATTERED CLOUD DECK THIS
MORNING. UPPER LEVEL TROUGH MOVING OVER THE AREA THIS AFTERNOON BUT
ONLY HIGH CLOUDS ASSOCIATED WITH THIS FEATURE. WITH THE LIGHT
ONSHORE FLOW CONTINUING THROUGHOUT THE DAY ONLY EXPECTING A COUPLE
OF HOURS OF BREAKOUT ALONG THE COAST LATE IN THE AFTERNOON.

KSEA...CONFIDENCE NOT HIGH ENOUGH TO COMPLETELY ELIMINATE STRATUS
FROM THE TERMINAL THIS MORNING SO WILL GO WITH A TEMPO BROKEN GROUP
BETWEEN 14Z AND 17Z NEAR 2000 FEET. SCATTERED CLOUDS BEFORE 14Z AND
JUST HIGH CLOUDS THIS AFTERNOON INTO THE EVENING HOURS. LIGHT WINDS
BECOMING SOUTHWEST 4 TO 8 KNOTS IN THE AFTERNOON. FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGHER PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND WILL RESULT IN VARYING DEGREES OF ONSHORE FLOW
INTO THE EARLY PART OF NEXT WEEK. THE ONSHORE FLOW IS ONLY STRONG
ENOUGH TO PRODUCE BORDERLINE SMALL CRAFT ADVISORY WINDS FOR
THE CENTRAL AND EASTERN STRAIT IN THE EVENING AND EARLY MORNING
HOURS THE NEXT FEW DAYS. FELTON

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 211030
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL DEVELOP OVER THE
REGION DURING THE DAY TODAY...CARVING AN UPPER LOW OVER THE AREA
TONIGHT. THIS UPPER LOW WILL MOVE INTO THE NORTHERN GREAT BASIN
LATE FRIDAY. HIGH PRESSURE ALOFT WILL THEN PREVAIL OVER THE REGION
ON SATURDAY.

&&

.SHORT TERM...
THE SURFACE ONSHORE PRESSURE GRADIENT WAS WEAKER THAN 24 HOURS
AGO...SO THERE WAS NOT MUCH LOW CLOUDS OVER THE CWA AT THIS TIME.
EXPECT THE LOW CLOUDS TO FILL IN A BIT DURING THE NEXT SEVERAL
HOURS...ESPECIALLY OVER THE SOUTHWEST INTERIOR...BEFORE
RETREATING TO THE COASTLINE EARLY THIS AFTERNOON.

MEANWHILE...AN UPPER TROF WILL DIG OVER THE PACIFIC NORTHWEST
DURING THE DAY TODAY. THE AIR MASS WILL BECOME WEAKLY UNSTABLE IN
THE AFTERNOON FOR A RISK OF SHOWERS OVER THE MOUNTAINS. CANNOT
RULE OUT AN ISOLD TSTM OVER THE NORTH CASCADES...NEAR THE CANADIAN
BORDER...LATE TODAY...SO WILL NEED TO WATCH THIS AREA.
OTHERWISE...MAX TEMPS TODAY SHOULD BE ABOUT THE SAME AS THEY WERE
YESTERDAY.

AN UPPER LOW WILL DEVELOP OVER THE CWA TONIGHT BEFORE MOVING INTO
THE NORTHERN GREAT BASIN ON FRI. THE MAIN IMPACT THIS SYSTEM WILL
HAVE ON OUR WEATHER WILL BE TOO DESTABILIZE THE AIR MASS FOR A
RISK OF SHOWERS OVER THE INTERIOR. OF COURSE...THERE WILL BE A
THREAT OF TSTMS OVER THE CASCADES.

LOOK FOR AN UPPER RIDGE TO PREVAIL OVER THE REGION FRI NIGHT AND
SATURDAY FOR SUNNIER AND WARMER WEATHER. THE SURFACE PRESSURE
GRADIENT WILL BECOME LIGHT OFFSHORE OR NORTHERLY...THUS ANY LOW
CLOUDS SHOULD BE CONFINED TO THE COAST SATURDAY MORNING. LESS
CLOUD COVER AND A NORTHERLY SURFACE GRADIENT WILL RESULT IN
WARMER TEMPS SATURDAY AFTERNOON.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT HIGH. THE MEDIUM RANGE SOLUTIONS
WERE NOT IN VERY GOOD AGREEMENT. FOR EXAMPLE...THE LATEST ECMWF
CARVED OUT AN 570 DAM LOW RIGHT OVER THE CWA ON SUNDAY WHEREAS THE
GFS HAD THE CWA UNDER THE INFLUENCE OF AN UPPER TROF CENTERED TO
OUR EAST. BASED ON THESE TWO SOLUTIONS...THE MAX TEMP FORECAST IS
TOO WARM. FOR NOW...THOUGHT IT WOULD BE BEST THE LEAVE THINGS
UNCHANGED. THE MORNING CYCLE MIGHT VERY WELL REVERT TO A RIDGE
SOLUTION FOR SUNDAY.

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY TODAY AS AN
UPPER LEVEL TROUGH MOVES INTO THE AREA. LOW LEVEL FLOW WILL REMAIN
ONSHORE WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND. AIR MASS STABLE BECOMING SLIGHTLY UNSTABLE
THIS AFTERNOON.

FOG/STRATUS SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST THROUGH
THE CHEHALIS GAP INTO THE HOOD CANAL AREA. THROUGH THE STRAIT THE
STRATUS HAS NOT MADE IT AS FAR AS PORT ANGELES AS OF 10Z. SC DECK
OVER THE CASCADES STARTING TO SPREAD BACK TO THE WEST BUT STILL
EAST OF ALL OF THE TAFS. ONSHORE SURFACE GRADIENTS CONTINUE TO BE
LIGHT WITH ALL OF THE WEST SIDE GRADIENTS A MILLIBAR OR LESS AT 10Z.

CONFIDENCE NOT VERY HIGH IN THE FORECAST THIS MORNING WITH THE LIGHT
GRADIENTS. STRATUS OVER THE CHEHALIS VALLEY AND THE HOOD CANAL IS
SLOWLY MOVING EAST SO WILL GO WITH A TEMPO BROKEN GROUP FOR
KBFI...KSEA AND KOLM BETWEEN 14Z AND 17Z THIS MORNING. FOR THE
REMAINDER OF THE TAFS WILL JUST GO WITH A SCATTERED CLOUD DECK THIS
MORNING. UPPER LEVEL TROUGH MOVING OVER THE AREA THIS AFTERNOON BUT
ONLY HIGH CLOUDS ASSOCIATED WITH THIS FEATURE. WITH THE LIGHT
ONSHORE FLOW CONTINUING THROUGHOUT THE DAY ONLY EXPECTING A COUPLE
OF HOURS OF BREAKOUT ALONG THE COAST LATE IN THE AFTERNOON.

KSEA...CONFIDENCE NOT HIGH ENOUGH TO COMPLETELY ELIMINATE STRATUS
FROM THE TERMINAL THIS MORNING SO WILL GO WITH A TEMPO BROKEN GROUP
BETWEEN 14Z AND 17Z NEAR 2000 FEET. SCATTERED CLOUDS BEFORE 14Z AND
JUST HIGH CLOUDS THIS AFTERNOON INTO THE EVENING HOURS. LIGHT WINDS
BECOMING SOUTHWEST 4 TO 8 KNOTS IN THE AFTERNOON. FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGHER PRESSURE OVER THE OFFSHORE WATERS AND
LOWER PRESSURE INLAND WILL RESULT IN VARYING DEGREES OF ONSHORE FLOW
INTO THE EARLY PART OF NEXT WEEK. THE ONSHORE FLOW IS ONLY STRONG
ENOUGH TO PRODUCE BORDERLINE SMALL CRAFT ADVISORY WINDS FOR
THE CENTRAL AND EASTERN STRAIT IN THE EVENING AND EARLY MORNING
HOURS THE NEXT FEW DAYS. FELTON

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

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WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 210418
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT WED AUG 20 2014

.SYNOPSIS...LOW LEVEL ONSHORE FLOW IS EXPECTED TO CONTINUE INTO
FRIDAY MAINTAINING AREAS OF MARINE CLOUDS AND COOLER THAN AVERAGE
TEMPERATURES. A WEAK LOW PRESSURE SYSTEM ALOFT IS EXPECTED TO MOVE
ONSHORE FROM THE GULF OF ALASKA LATER THURSDAY AND FRIDAY BRINGING A
THREAT OF SHOWERS MAINLY TO THE MOUNTAINS. HIGHER PRESSURE ALOFT IS
FORECAST TO BUILD ONSHORE OVER THE WEEKEND AND INTO NEXT WEEK FOR
WARMER WEATHER AND MORE SUNSHINE.

&&

.SHORT TERM...WEAK ONSHORE FLOW AND AN EXISTING MOIST MARINE AIR
MASS WILL RESULT IN AREAS OF LOW CLOUDS DEVELOPING AGAIN LATER
TONIGHT AND THURSDAY MORNING. A SHORT WAVE EMBEDDED IN NW FLOW ALOFT
WILL APPROACH THE AREA ON THURSDAY. THE MAIN EFFECT OF THIS SYSTEM
WILL BE TO DEEPEN THE MARINE LAYER AND ALLOW MARINE STRATUS TO MIX
OUT FASTER THAN THIS MORNING. THE SYSTEM WILL ONLY BRING A LIMITED
AMOUNT OF MID LEVEL MOISTURE BUT THE ASSOCIATED WEAK LIFT COULD
PRODUCE A FEW SHOWERS OVER THE NORTH CASCADES AND EVEN THE FAR N
INTERIOR. THE GFS MOS GUIDANCE SHOWS LOW CHANCE POPS ACROSS MAINLY
NRN PORTIONS OF THE FORECAST AREA WHICH IS ALREADY INDICATED IN THE
FORECAST SO NO UPDATES PLANNED. HIGH TEMPERATURES WILL REMAIN BELOW
AVERAGE IN THE UPPER 60S TO AROUND 70.

MODELS INDICATE THE UPPER LOW WILL CLOSE OFF OVER WA THURSDAY NIGHT
AND SHIFT SE ON FRIDAY. COOLER AIR ALOFT AND A SLIGHT INCREASE IN
LOW/MID LEVEL MOISTURE SHOULD RESULT IN WEAKLY UNSTABLE CONDITIONS
ACROSS THE AREA...ESPECIALLY THE MOUNTAINS. GFS LI VALUES ARE BELOW
ZERO E OF PUGET SOUND AND LOWEST OVER THE CASCADES AND OLYMPICS. THE
BEST CHANCE OF SHOWERS WILL BE IN THE FOOTHILLS AND MOUNTAINS BUT A
FEW SHOWERS OVER THE LOWLANDS CANNOT BE RULED OUT FRIDAY. GRADIENTS
ARE LIGHTER AND MORE NWLY ON FRIDAY WITH LESS CLOUD COVER SO HIGH
TEMPERATURES SHOULD WARM A FEW DEGREES INTO THE LOW/MID 70S AROUND
PUGET SOUND.

HIGH PRESSURE ALOFT OVER THE ERN PAC NUDGES INTO THE PAC NW
SATURDAY. RISING UPPER HEIGHTS AND WEAK NW ONSHORE FLOW SHOULD
RESULT IN DRY WEATHER AND A WARMING TREND. EXPECT SUNSHINE WITH
HIGHS HEADING TOWARD 80 ON SATURDAY. MERCER

.LONG TERM...FROM PREVIOUS DISCUSSION...ALL THE PROGS SEEM TO BE
GENERALLY ON THE SAME PAGE THROUGH WEDNESDAY. THE RIDGING ALOFT AND
WARMING TREND CONTINUES INTO SUNDAY. SO THE WEEKEND LOOKS TO HAVE
MORE SUNSHINE AND HIGH TEMPS RISING TO AROUND OR A BIT ABOVE
AVERAGE. A WEAK SHORTWAVE DIGS SE MONDAY IN THAT NW FLOW ALOFT
SUNDAY NIGHT AND MONDAY. THE PRIMARY IMPACT ON WESTERN WA WILL BE TO
INCREASE LOW LEVEL ONSHORE FLOW FOR A BRIEF COOL DOWN. THEN THE
RIDGE ALOFT REBOUNDS TUESDAY AND WEDNESDAY WITH LOW LEVEL ONSHORE
FLOW AGAIN EASING FOR MORE SUNSHINE AND TEMPS RISING A BIT ABOVE
SEASONAL NORMS. BUEHNER

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY ON THURSDAY
AS AN UPPER LEVEL TROUGH MOVES INTO THE AREA. LOW LEVEL FLOW WILL
REMAIN ONSHORE WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE
WATERS AND LOWER PRESSURE INLAND. AIR MASS STABLE BECOMING SLIGHTLY
UNSTABLE THURSDAY AFTERNOON.

LAST VISIBLE IMAGERY OF THE DAY SHOWED JUST A BROKEN THIN LAYER OF
STRATUS ALONG THE COAST AND SOME SC OVER THE MOUNTAINS. SURFACE
GRADIENTS ARE WEAK ONSHORE WITH KOLM-KHQM AND KOLM-KBLI NEAR 1 MB.
K0TH-KSEA IS LESS THAN A MILLIBAR WITH THE CROSS CASCADE GRADIENT
AROUND PLUS 8 MB. BOTH THE KUIL SOUNDING AND THE VAD WIND PROFILER
AT KATX SHOW LIGHT SOUTHERLY WINDS IN THE LOWER LEVELS. THE KLGX VAD
WIND PROFILE SHOWS WEST NORTHWESTERLY WINDS AT 2000 FEET. WITH THE
ONSHORE GRADIENTS NOT EXPECTED TO INCREASE MUCH MORE OVERNIGHT THE
STRATUS OVER THE INTERIOR THURSDAY MORNING WILL HAVE TO FORM IN
PLACE. THIS DOES NOT BODE WELL FOR A WIDESPREAD DEEP MARINE LAYER
OVER THE INTERIOR IN THE MORNING. WITH THE CEILINGS ALONG THE COAST
IN THE 1400-1800 FOOT RANGE WILL GO FOR CEILINGS OVER THE INTERIOR
THURSDAY MORNING NEAR THIS HEIGHT BUT WILL SLOW DOWN THE ONSET OF
THE STRATUS OVER THE INTERIOR IN THE 06Z TAFS TO CLOSER TO 12Z. WITH
THE LAYER NOT BEING VERY DEEP EXPECT A LATE MORNING OR MIDDAY
BREAKOUT FOR THE INTERIOR WITH A LATER BREAKOUT FOR THE COAST.

KSEA...MOSTLY CLEAR SKIES INTO THE EARLY MORNING HOURS WITH CEILINGS
AROUND 1500 FEET DEVELOPING AROUND 12Z. STRATUS DECK SCATTERING OUT
MIDDAY. SOUTHWEST WINDS 4 TO 8 KNOTS THROUGH THURSDAY AFTERNOON.
FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGH PRESSURE OVER THE OFFSHORE WATERS AND LOWER
PRESSURE INLAND WILL RESULT IN SMALL CRAFT ADVISORY WINDS FOR THE
CENTRAL AND EASTERN STRAIT IN THE EVENING AND EARLY MORNING HOURS.
FELTON

&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

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WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









000
FXUS66 KSEW 210418
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT WED AUG 20 2014

.SYNOPSIS...LOW LEVEL ONSHORE FLOW IS EXPECTED TO CONTINUE INTO
FRIDAY MAINTAINING AREAS OF MARINE CLOUDS AND COOLER THAN AVERAGE
TEMPERATURES. A WEAK LOW PRESSURE SYSTEM ALOFT IS EXPECTED TO MOVE
ONSHORE FROM THE GULF OF ALASKA LATER THURSDAY AND FRIDAY BRINGING A
THREAT OF SHOWERS MAINLY TO THE MOUNTAINS. HIGHER PRESSURE ALOFT IS
FORECAST TO BUILD ONSHORE OVER THE WEEKEND AND INTO NEXT WEEK FOR
WARMER WEATHER AND MORE SUNSHINE.

&&

.SHORT TERM...WEAK ONSHORE FLOW AND AN EXISTING MOIST MARINE AIR
MASS WILL RESULT IN AREAS OF LOW CLOUDS DEVELOPING AGAIN LATER
TONIGHT AND THURSDAY MORNING. A SHORT WAVE EMBEDDED IN NW FLOW ALOFT
WILL APPROACH THE AREA ON THURSDAY. THE MAIN EFFECT OF THIS SYSTEM
WILL BE TO DEEPEN THE MARINE LAYER AND ALLOW MARINE STRATUS TO MIX
OUT FASTER THAN THIS MORNING. THE SYSTEM WILL ONLY BRING A LIMITED
AMOUNT OF MID LEVEL MOISTURE BUT THE ASSOCIATED WEAK LIFT COULD
PRODUCE A FEW SHOWERS OVER THE NORTH CASCADES AND EVEN THE FAR N
INTERIOR. THE GFS MOS GUIDANCE SHOWS LOW CHANCE POPS ACROSS MAINLY
NRN PORTIONS OF THE FORECAST AREA WHICH IS ALREADY INDICATED IN THE
FORECAST SO NO UPDATES PLANNED. HIGH TEMPERATURES WILL REMAIN BELOW
AVERAGE IN THE UPPER 60S TO AROUND 70.

MODELS INDICATE THE UPPER LOW WILL CLOSE OFF OVER WA THURSDAY NIGHT
AND SHIFT SE ON FRIDAY. COOLER AIR ALOFT AND A SLIGHT INCREASE IN
LOW/MID LEVEL MOISTURE SHOULD RESULT IN WEAKLY UNSTABLE CONDITIONS
ACROSS THE AREA...ESPECIALLY THE MOUNTAINS. GFS LI VALUES ARE BELOW
ZERO E OF PUGET SOUND AND LOWEST OVER THE CASCADES AND OLYMPICS. THE
BEST CHANCE OF SHOWERS WILL BE IN THE FOOTHILLS AND MOUNTAINS BUT A
FEW SHOWERS OVER THE LOWLANDS CANNOT BE RULED OUT FRIDAY. GRADIENTS
ARE LIGHTER AND MORE NWLY ON FRIDAY WITH LESS CLOUD COVER SO HIGH
TEMPERATURES SHOULD WARM A FEW DEGREES INTO THE LOW/MID 70S AROUND
PUGET SOUND.

HIGH PRESSURE ALOFT OVER THE ERN PAC NUDGES INTO THE PAC NW
SATURDAY. RISING UPPER HEIGHTS AND WEAK NW ONSHORE FLOW SHOULD
RESULT IN DRY WEATHER AND A WARMING TREND. EXPECT SUNSHINE WITH
HIGHS HEADING TOWARD 80 ON SATURDAY. MERCER

.LONG TERM...FROM PREVIOUS DISCUSSION...ALL THE PROGS SEEM TO BE
GENERALLY ON THE SAME PAGE THROUGH WEDNESDAY. THE RIDGING ALOFT AND
WARMING TREND CONTINUES INTO SUNDAY. SO THE WEEKEND LOOKS TO HAVE
MORE SUNSHINE AND HIGH TEMPS RISING TO AROUND OR A BIT ABOVE
AVERAGE. A WEAK SHORTWAVE DIGS SE MONDAY IN THAT NW FLOW ALOFT
SUNDAY NIGHT AND MONDAY. THE PRIMARY IMPACT ON WESTERN WA WILL BE TO
INCREASE LOW LEVEL ONSHORE FLOW FOR A BRIEF COOL DOWN. THEN THE
RIDGE ALOFT REBOUNDS TUESDAY AND WEDNESDAY WITH LOW LEVEL ONSHORE
FLOW AGAIN EASING FOR MORE SUNSHINE AND TEMPS RISING A BIT ABOVE
SEASONAL NORMS. BUEHNER

&&

.AVIATION...NORTHWESTERLY FLOW ALOFT BECOMING WESTERLY ON THURSDAY
AS AN UPPER LEVEL TROUGH MOVES INTO THE AREA. LOW LEVEL FLOW WILL
REMAIN ONSHORE WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE
WATERS AND LOWER PRESSURE INLAND. AIR MASS STABLE BECOMING SLIGHTLY
UNSTABLE THURSDAY AFTERNOON.

LAST VISIBLE IMAGERY OF THE DAY SHOWED JUST A BROKEN THIN LAYER OF
STRATUS ALONG THE COAST AND SOME SC OVER THE MOUNTAINS. SURFACE
GRADIENTS ARE WEAK ONSHORE WITH KOLM-KHQM AND KOLM-KBLI NEAR 1 MB.
K0TH-KSEA IS LESS THAN A MILLIBAR WITH THE CROSS CASCADE GRADIENT
AROUND PLUS 8 MB. BOTH THE KUIL SOUNDING AND THE VAD WIND PROFILER
AT KATX SHOW LIGHT SOUTHERLY WINDS IN THE LOWER LEVELS. THE KLGX VAD
WIND PROFILE SHOWS WEST NORTHWESTERLY WINDS AT 2000 FEET. WITH THE
ONSHORE GRADIENTS NOT EXPECTED TO INCREASE MUCH MORE OVERNIGHT THE
STRATUS OVER THE INTERIOR THURSDAY MORNING WILL HAVE TO FORM IN
PLACE. THIS DOES NOT BODE WELL FOR A WIDESPREAD DEEP MARINE LAYER
OVER THE INTERIOR IN THE MORNING. WITH THE CEILINGS ALONG THE COAST
IN THE 1400-1800 FOOT RANGE WILL GO FOR CEILINGS OVER THE INTERIOR
THURSDAY MORNING NEAR THIS HEIGHT BUT WILL SLOW DOWN THE ONSET OF
THE STRATUS OVER THE INTERIOR IN THE 06Z TAFS TO CLOSER TO 12Z. WITH
THE LAYER NOT BEING VERY DEEP EXPECT A LATE MORNING OR MIDDAY
BREAKOUT FOR THE INTERIOR WITH A LATER BREAKOUT FOR THE COAST.

KSEA...MOSTLY CLEAR SKIES INTO THE EARLY MORNING HOURS WITH CEILINGS
AROUND 1500 FEET DEVELOPING AROUND 12Z. STRATUS DECK SCATTERING OUT
MIDDAY. SOUTHWEST WINDS 4 TO 8 KNOTS THROUGH THURSDAY AFTERNOON.
FELTON

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGH PRESSURE OVER THE OFFSHORE WATERS AND LOWER
PRESSURE INLAND WILL RESULT IN SMALL CRAFT ADVISORY WINDS FOR THE
CENTRAL AND EASTERN STRAIT IN THE EVENING AND EARLY MORNING HOURS.
FELTON

&&

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

&&

$$

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000
FXUS66 KSEW 202220
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
320 PM PDT WED AUG 20 2014

.SYNOPSIS...LOW LEVEL ONSHORE FLOW IS EXPECTED TO CONTINUE INTO
FRIDAY MAINTAINING AREAS OF MARINE CLOUDS AND COOLER THAN AVERAGE
TEMPERATURES. A WEAK LOW PRESSURE SYSTEM ALOFT IS EXPECTED TO MOVE
ONSHORE FROM THE GULF OF ALASKA LATER THURSDAY AND FRIDAY BRINGING A
THREAT OF SHOWERS MAINLY TO THE MOUNTAINS. HIGHER PRESSURE ALOFT IS
FORECAST TO BUILD ONSHORE OVER THE WEEKEND AND INTO NEXT WEEK FOR
WARMER WEATHER AND MORE SUNSHINE.

&&

.SHORT TERM...THE LONG WAVE RIDGE WAS OVER THE NE PACIFIC THIS
AFTERNOON WHILE A LONG WAVE TROUGH WAS NEAR THE DATELINE. WATER
VAPOR SATELLITE IMAGES SHOWED A WEAK SHORTWAVE MOVING ACROSS THE TOP
OF THE GULF OF ALASKA RIDGE THAT THE PROGS ALL AGREE WILL DIG SE
INTO THE PACIFIC NW THU AND FRI. THIS SYSTEM WILL MAINTAIN LOW LEVEL
ONSHORE FLOW INTO WESTERN WA AND BRING A THREAT OF SHOWERS PRIMARILY
TO THE MOUNTAINS. ENOUGH INSTABILITY TO INCLUDE A THREAT OF TSTMS IN
THE CASCADES AS WELL ON FRIDAY.

WITH THE ONSHORE FLOW...AREAS OF MARINE CLOUDS SHOULD RETURN EACH
NIGHT AND MORNING WITH SOME AFTERNOON CLEARING. IN ADDITION DAYTIME
TEMPERATURES WILL LIKELY REMAIN A BIT BELOW SEASONAL AVERAGES.

THAT SYSTEM DIGS FURTHER SE FRIDAY NIGHT AND SATURDAY WITH ONLY A
LINGERING THREAT OF SHOWERS NEAR THE CASCADE CREST. THE RIDGE
OFFSHORE REBUILDS WITH NW FLOW ALOFT INTO WA. LOW LEVEL ONSHORE FLOW
WEAKENS. ALL THIS PERMITS MORE SUNSHINE AND WARMER DAYTIME
TEMPERATURES ON SATURDAY. BUEHNER

.LONG TERM...ALL THE PROGS SEEM TO BE GENERALLY ON THE SAME PAGE
THROUGH WEDNESDAY. THE RIDGING ALOFT AND WARMING TREND CONTINUES
INTO SUNDAY. SO THE WEEKEND LOOKS TO HAVE MORE SUNSHINE AND HIGH
TEMPS RISING TO AROUND OR A BIT ABOVE AVERAGE. A WEAK SHORTWAVE DIGS
SE MONDAY IN THAT NW FLOW ALOFT SUNDAY NIGHT AND MONDAY. THE PRIMARY
IMPACT ON WESTERN WA WILL BE TO INCREASE LOW LEVEL ONSHORE FLOW FOR
A BRIEF COOL DOWN. THEN THE RIDGE ALOFT REBOUNDS TUESDAY AND
WEDNESDAY WITH LOW LEVEL ONSHORE FLOW AGAIN EASING FOR MORE SUNSHINE
AND TEMPS RISING A BIT ABOVE SEASONAL NORMS. BUEHNER

&&

.AVIATION...FLOW ALOFT WILL REMAIN NORTHWEST TONIGHT...THEN BECOME
WEST EARLY THURSDAY MORNING AS A WEAK UPPER LEVEL SHORTWAVE TROUGH
APPROACHES FROM NORTHWEST. LOW LEVEL FLOW WILL REMAIN ONSHORE WITH
PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND LOWER PRESSURE
INLAND. THE AIR MASS WILL REMAIN STABLE TONIGHT WITH LINGERING LOW
LEVEL MOISTURE. THE APPROACHING...ALBEIT WEAK...UPPER LEVEL
SHORTWAVE TROUGH MAY JUST PRODUCE ENOUGH LIFT TO PRODUCE DRIZZLE
AND/OR LIGHT RAIN FROM THE STRATUS LAYER TOMORROW ESPECIALLY OVER
THE COAST.

SKIES HAVE ALL BUT SCATTERED OUT THIS AFTERNOON...WITH THE EXCEPTION
OF THE SOUTH SOUND WHERE A BKN 3K FT DECK CONTINUES TO LINGER.
EXPECT THE CLOUDS TO CONTINUE TO LIFT AND DISSIPATE OVER THE NEXT
FEW HOURS...REMAINING VFR THROUGH 06Z FOR THE COAST AND 10Z OVER THE
INTERIOR. EXPECT CEILINGS TO LOWER TO MVFR AND IFR LEVELS AGAIN
THURSDAY MORNING...LIFTING LATE IN THE MORNING TO VFR CONDITIONS AND
SCATTERING OUT LATE IN THE AFTERNOON.

KSEA...VFR CONDITIONS WILL PERSIST THROUGH THE EVENING WITH CEILINGS
LOWERING TO MVFR LEVELS AROUND 11Z...AND IMPROVING BY 18Z. SOUTHWEST
WINDS 6 TO 8 KT WILL EAST TO 4 TO 6 KT AND BECOME SOUTH LATE
TONIGHT.

&&

.MARINE...THE VERY STATIC ONSHORE FLOW PATTERN WILL CONTINUE FOR THE
NEXT SEVERAL DAYS. HIGH PRESSURE OVER THE OFFSHORE WATERS AND LOWER
PRESSURE INLAND WILL DRIVE WESTERLY WINDS NEAR SMALL CRAFT ADVISORY
LEVELS THROUGH THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA MOST
EVENINGS.


&&

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

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 201612
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 AM PDT WED AUG 20 2014

.SYNOPSIS...WEAK LOW PRESSURE ALOFT HELPED CREATE STRONGER LOW LEVEL
ONSHORE FLOW FOR MARINE CLOUDS AND COOLER DAYTIME TEMPERATURES
TODAY. ANOTHER LOW PRESSURE SYSTEM ALOFT IS EXPECTED TO SWING
ONSHORE THURSDAY AND FRIDAY THAT WILL BRING A THREAT OF SHOWERS
MAINLY TO THE MOUNTAINS. HIGHER PRESSURE ALOFT IS FORECAST TO BUILD
ONSHORE OVER THE WEEKEND AND INTO NEXT WEEK FOR WARMER WEATHER AND
MORE SUNSHINE.

&&

.SHORT TERM...THE INCOMING WEAK UPPER TROUGH WAS MOVING EAST NEAR
THE IDAHO BORDER THIS MORNING. IT DID INCREASE LOW LEVEL ONSHORE
FLOW LATE YESTERDAY AND OVERNIGHT BRINGING A MARINE LAYER INTO
WESTERN WA. MORNING VISIBLE SATELLITE IMAGES SHOW THE MARINE
DECK IS NOT SOLID - LOTS OF BREAKS IN IT. BASES RANGE FROM 2500 TO
4000 FT WITH TOPS REPORTED FROM KSEA AROUND 7000. ONLY SPOTTY
DRIZZLE REPORTED. WEST TO EAST PRESSURE GRADIENT HAS EASED IN
WESTERN WA BUT STILL STRONG ACROSS THE CASCADES INTO EASTERN WA. SO
THE BOTTOM LINE - AROUND 10 DEG COOLER INLAND TODAY WITH SOME
SUNSHINE AS THE DAY PROGRESSES. NO CHANGE TO THE CURRENT FORECAST
PACKAGE.

LOOKING UPSTREAM...THE LONG WAVE RIDGE IS IN THE NE PACIFIC AND
TROUGH JUST WEST OF THE DATELINE. WATER VAPOR IMAGES SHOW A WEAK
SHORTWAVE MOVING OVER THE TOP OF THE RIDGE APPROACHING 140W IN THE
GULF OF ALASKA. 12Z PROGS IN THUS FAR CONTINUE THE TREND OF DIGGING
THIS SHORTWAVE INTO THE PACNW THU AND FRI FOR CONTINUED LOW LEVEL
ONSHORE FLOW...BELOW AVERAGE DAYTIME TEMPS AND A THREAT OF SHOWERS
MAINLY IN THE MOUNTAINS. BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...NO CHANGES WERE MADE TO
THE INHERITED FORECAST...WHICH ESSENTIALLY REFLECTED NEAR CLIMO. THE
MEDIUM RANGE SOLUTIONS APPEARED TO BE IN BETTER AGREEMENT AND SHOWED
THE CWA UNDER THE INFLUENCE OF AN AMPLIFIED UPPER RIDGE CENTERED
OFFSHORE. NC

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PERSIST TODAY AS A WEAK UPPER
LEVEL TROUGH MOVES INTO IDAHO. LOW LEVEL FLOW WILL REMAIN ONSHORE
WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND LOWER
PRESSURE INLAND. THE AIR MASS WILL REMAIN GENERALLY STABLE...WITH
THE EXCEPTION OF A SLIGHT CHANCE OF SHOWERS OVER THE NORTH CASCADES.

THE AREAS OF 1K TO 2.5K FT LEVEL CLOUDS WILL CONTINUE TO LIFT AND
DISSIPATE THROUGH THE LATE MORNING. THE MID LEVEL CLOUDS...4-5K FT
WILL BECOME SCATTERED TO BROKEN BY LATE AFTERNOON.

KSEA...MVFR CEILINGS WILL LIFT THROUGH THE LATE MORNING TO AROUND
4.5K FT BY THE EARLY AFTERNOON. EXPECT VFR CONDITIONS THROUGH THE
EVENING WITH CEILINGS LOWERING TO MVFR LEVELS EARLY THURSDAY
MORNING. SOUTH WINDS 6 TO 8 KT WILL BECOME SOUTHEAST THIS AFTERNOON
THEN EASE TO 4 TO 6 KT AROUND 06Z/11 PM.

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. EXPECT THE TYPICAL
IMPACTS OF WINDS NEAR SMALL CRAFT ADVISORY LEVELS IN THE CENTRAL AND
EASTERN STRAIT OF JUAN DE FUCA MOST EVENINGS. RIGHT NOW WE ARE
EXPECTING ABOUT 20 KTS THROUGH THE STRAIT THIS EVENING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS...CENTRAL AND EAST
STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML







000
FXUS66 KSEW 201612
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 AM PDT WED AUG 20 2014

.SYNOPSIS...WEAK LOW PRESSURE ALOFT HELPED CREATE STRONGER LOW LEVEL
ONSHORE FLOW FOR MARINE CLOUDS AND COOLER DAYTIME TEMPERATURES
TODAY. ANOTHER LOW PRESSURE SYSTEM ALOFT IS EXPECTED TO SWING
ONSHORE THURSDAY AND FRIDAY THAT WILL BRING A THREAT OF SHOWERS
MAINLY TO THE MOUNTAINS. HIGHER PRESSURE ALOFT IS FORECAST TO BUILD
ONSHORE OVER THE WEEKEND AND INTO NEXT WEEK FOR WARMER WEATHER AND
MORE SUNSHINE.

&&

.SHORT TERM...THE INCOMING WEAK UPPER TROUGH WAS MOVING EAST NEAR
THE IDAHO BORDER THIS MORNING. IT DID INCREASE LOW LEVEL ONSHORE
FLOW LATE YESTERDAY AND OVERNIGHT BRINGING A MARINE LAYER INTO
WESTERN WA. MORNING VISIBLE SATELLITE IMAGES SHOW THE MARINE
DECK IS NOT SOLID - LOTS OF BREAKS IN IT. BASES RANGE FROM 2500 TO
4000 FT WITH TOPS REPORTED FROM KSEA AROUND 7000. ONLY SPOTTY
DRIZZLE REPORTED. WEST TO EAST PRESSURE GRADIENT HAS EASED IN
WESTERN WA BUT STILL STRONG ACROSS THE CASCADES INTO EASTERN WA. SO
THE BOTTOM LINE - AROUND 10 DEG COOLER INLAND TODAY WITH SOME
SUNSHINE AS THE DAY PROGRESSES. NO CHANGE TO THE CURRENT FORECAST
PACKAGE.

LOOKING UPSTREAM...THE LONG WAVE RIDGE IS IN THE NE PACIFIC AND
TROUGH JUST WEST OF THE DATELINE. WATER VAPOR IMAGES SHOW A WEAK
SHORTWAVE MOVING OVER THE TOP OF THE RIDGE APPROACHING 140W IN THE
GULF OF ALASKA. 12Z PROGS IN THUS FAR CONTINUE THE TREND OF DIGGING
THIS SHORTWAVE INTO THE PACNW THU AND FRI FOR CONTINUED LOW LEVEL
ONSHORE FLOW...BELOW AVERAGE DAYTIME TEMPS AND A THREAT OF SHOWERS
MAINLY IN THE MOUNTAINS. BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...NO CHANGES WERE MADE TO
THE INHERITED FORECAST...WHICH ESSENTIALLY REFLECTED NEAR CLIMO. THE
MEDIUM RANGE SOLUTIONS APPEARED TO BE IN BETTER AGREEMENT AND SHOWED
THE CWA UNDER THE INFLUENCE OF AN AMPLIFIED UPPER RIDGE CENTERED
OFFSHORE. NC

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PERSIST TODAY AS A WEAK UPPER
LEVEL TROUGH MOVES INTO IDAHO. LOW LEVEL FLOW WILL REMAIN ONSHORE
WITH PERSISTENT HIGH PRESSURE OVER THE OFFSHORE WATERS AND LOWER
PRESSURE INLAND. THE AIR MASS WILL REMAIN GENERALLY STABLE...WITH
THE EXCEPTION OF A SLIGHT CHANCE OF SHOWERS OVER THE NORTH CASCADES.

THE AREAS OF 1K TO 2.5K FT LEVEL CLOUDS WILL CONTINUE TO LIFT AND
DISSIPATE THROUGH THE LATE MORNING. THE MID LEVEL CLOUDS...4-5K FT
WILL BECOME SCATTERED TO BROKEN BY LATE AFTERNOON.

KSEA...MVFR CEILINGS WILL LIFT THROUGH THE LATE MORNING TO AROUND
4.5K FT BY THE EARLY AFTERNOON. EXPECT VFR CONDITIONS THROUGH THE
EVENING WITH CEILINGS LOWERING TO MVFR LEVELS EARLY THURSDAY
MORNING. SOUTH WINDS 6 TO 8 KT WILL BECOME SOUTHEAST THIS AFTERNOON
THEN EASE TO 4 TO 6 KT AROUND 06Z/11 PM.

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. EXPECT THE TYPICAL
IMPACTS OF WINDS NEAR SMALL CRAFT ADVISORY LEVELS IN THE CENTRAL AND
EASTERN STRAIT OF JUAN DE FUCA MOST EVENINGS. RIGHT NOW WE ARE
EXPECTING ABOUT 20 KTS THROUGH THE STRAIT THIS EVENING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS...CENTRAL AND EAST
STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








000
FXUS66 KSEW 201029
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
329 AM PDT WED AUG 20 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL INFLUENCE THE WEATHER
PATTERN OVER THE AREA THROUGH FRIDAY. THIS WILL RESULT IN SOMEWHAT
UNSETTLED CONDITIONS AND BELOW NORMAL DAYTIME TEMPERATURES. HIGH
PRESSURE ALOFT WILL RETURN THIS WEEKEND.

&&

.SHORT TERM...
THE STRATUS WAS FORMING IN PLACE INSTEAD OF ADVECTING INLAND FROM
THE PACIFIC...THUS THE LOW CLOUDS WERE NOT AS WIDESPREAD ACROSS
THE LOWLANDS AS ONE WOULD EXPECT WITH THE ONSHORE GRADIENT.
HOWEVER...THERE WAS A 5-7K FT CLOUD DECK OVER THE CWA EARLY THIS
MORNING...THUS IT LOOKS LIKE THERE WILL BE QUITE A BIT OF CLOUD
COVER AROUND THROUGH AT LEAST THIS MORNING.

MEANWHILE...THE AXIS OF AN UPPER TROF WILL REMAIN OVER THE NORTHERN
GREAT BASIN THROUGH TONIGHT...RESULTING IN NORTHWEST FLOW ALOFT
AND CONTINUED LOW LEVEL ONSHORE FLOW. IN GENERAL...TEMPS TODAY
SHOULD BE 5-15 DEGREES COOLER THAN YESTERDAY...WITH THE GREATEST
AMOUNT OF COOLING OCCURRING OVER THE LOWLAND INTERIOR.

THE MODELS WERE IN AGREEMENT THAT AN UPPER TROF WILL DIG OVER THE
REGION ON THU...WITH AN UPPER LOW DEVELOPING OVER WESTERN WA THU
NIGHT. THIS LOW WILL THEN MOVE OVER EASTERN WA/EASTERN OREGON
DURING THE DAY FRI...WITH STRONG NORTHERLY FLOW ALOFT DEVELOPING
OVER WESTERN WA IN ITS WAKE. THERE SHOULD BE SOME LIGHT PRECIP
OVER THE CWA THU AND THU NIGHT...WITH POSSIBLY A BETTER CHANCE OF
PRECIP OVER THE INTERIOR ON FRI.

PREDICTING TEMPS THU AND FRI WILL BE SOMEWHAT OF A CHALLENGE.
THERE IS A CHANCE THAT TEMPS COULD END UP A FEW DEGREES COOLER
THAN PREDICTED FOR BOTH DAYS...ESPECIALLY IF THERE IS NOT MUCH
CLEARING IN THE AFTERNOONS.

.LONG TERM...
NO CHANGES WERE MADE TO THE INHERITED FORECAST...WHICH ESSENTIALLY
REFLECTED NEAR CLIMO. THE MEDIUM RANGE SOLUTIONS APPEARED TO BE IN
BETTER AGREEMENT AND SHOWED THE CWA UNDER THE INFLUENCE OF AN
AMPLIFIED UPPER RIDGE CENTERED OFFSHORE.

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PREVAIL THROUGH TONIGHT WITH
AN UPPER TROUGH OVER EASTERN WASHINGTON. AT THE SURFACE... ONSHORE
FLOW WILL CONTINUE WITH HIGH PRESSURE OFFSHORE AND LOWER PRESSURE
INLAND. AIR MASS GENERALLY STABLE.

THERE IS WIDESPREAD AREAS OF MID LEVEL CLOUDS ABOUT 4-5K OVER MUCH
OF THE REGION EARLY THIS MORNING. THERE ARE ALSO SOME AREAS OF LOWER
CLOUDS IN THE 1K-2.5K LEVEL.  EXPECT THE LOWER CLOUDS TO LIFT AND
DISSIPATE BY AFTERNOON WITH THE MID DECK BECOMING SCATTERED TO
BROKEN BY LATE AFTERNOON.

KSEA...THE MID DECK AROUND 4.5K IS PRESENT NOW...BUT THERE ARE LOW
CLOUDS NEAR BY AT KPWT. THE LOW CLOUDS AT ABOUT 1-2K ARE EXPECTED TO
FORM OR DRIFT NEAR THE AIRPORT THIS MORNING. LOWER CLOUDS SHOULD
LIFT OR DISSIPATE BY EARLY AFTERNOON. 13

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. THIS WILL PRODUCE
WINDS NEAR SMALL CRAFT ADVISORY LEVELS IN THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA MOST EVENINGS. RIGHT NOW WE ARE EXPECTING
ABOUT 20 KTS THROUGH THE STRAIT THIS EVENING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE CENTRAL/EASTERN STRAIT
     OF JUAN DE FUCA AND THE COASTAL WATERS FROM CAPE FLATTERY TO
     CAPE SHOALWATER 10 NM OUT TO 60 NM.


&&

$$

WWW.WEATHER.GOV/SEATTLE

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WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 201029
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
329 AM PDT WED AUG 20 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL INFLUENCE THE WEATHER
PATTERN OVER THE AREA THROUGH FRIDAY. THIS WILL RESULT IN SOMEWHAT
UNSETTLED CONDITIONS AND BELOW NORMAL DAYTIME TEMPERATURES. HIGH
PRESSURE ALOFT WILL RETURN THIS WEEKEND.

&&

.SHORT TERM...
THE STRATUS WAS FORMING IN PLACE INSTEAD OF ADVECTING INLAND FROM
THE PACIFIC...THUS THE LOW CLOUDS WERE NOT AS WIDESPREAD ACROSS
THE LOWLANDS AS ONE WOULD EXPECT WITH THE ONSHORE GRADIENT.
HOWEVER...THERE WAS A 5-7K FT CLOUD DECK OVER THE CWA EARLY THIS
MORNING...THUS IT LOOKS LIKE THERE WILL BE QUITE A BIT OF CLOUD
COVER AROUND THROUGH AT LEAST THIS MORNING.

MEANWHILE...THE AXIS OF AN UPPER TROF WILL REMAIN OVER THE NORTHERN
GREAT BASIN THROUGH TONIGHT...RESULTING IN NORTHWEST FLOW ALOFT
AND CONTINUED LOW LEVEL ONSHORE FLOW. IN GENERAL...TEMPS TODAY
SHOULD BE 5-15 DEGREES COOLER THAN YESTERDAY...WITH THE GREATEST
AMOUNT OF COOLING OCCURRING OVER THE LOWLAND INTERIOR.

THE MODELS WERE IN AGREEMENT THAT AN UPPER TROF WILL DIG OVER THE
REGION ON THU...WITH AN UPPER LOW DEVELOPING OVER WESTERN WA THU
NIGHT. THIS LOW WILL THEN MOVE OVER EASTERN WA/EASTERN OREGON
DURING THE DAY FRI...WITH STRONG NORTHERLY FLOW ALOFT DEVELOPING
OVER WESTERN WA IN ITS WAKE. THERE SHOULD BE SOME LIGHT PRECIP
OVER THE CWA THU AND THU NIGHT...WITH POSSIBLY A BETTER CHANCE OF
PRECIP OVER THE INTERIOR ON FRI.

PREDICTING TEMPS THU AND FRI WILL BE SOMEWHAT OF A CHALLENGE.
THERE IS A CHANCE THAT TEMPS COULD END UP A FEW DEGREES COOLER
THAN PREDICTED FOR BOTH DAYS...ESPECIALLY IF THERE IS NOT MUCH
CLEARING IN THE AFTERNOONS.

.LONG TERM...
NO CHANGES WERE MADE TO THE INHERITED FORECAST...WHICH ESSENTIALLY
REFLECTED NEAR CLIMO. THE MEDIUM RANGE SOLUTIONS APPEARED TO BE IN
BETTER AGREEMENT AND SHOWED THE CWA UNDER THE INFLUENCE OF AN
AMPLIFIED UPPER RIDGE CENTERED OFFSHORE.

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PREVAIL THROUGH TONIGHT WITH
AN UPPER TROUGH OVER EASTERN WASHINGTON. AT THE SURFACE... ONSHORE
FLOW WILL CONTINUE WITH HIGH PRESSURE OFFSHORE AND LOWER PRESSURE
INLAND. AIR MASS GENERALLY STABLE.

THERE IS WIDESPREAD AREAS OF MID LEVEL CLOUDS ABOUT 4-5K OVER MUCH
OF THE REGION EARLY THIS MORNING. THERE ARE ALSO SOME AREAS OF LOWER
CLOUDS IN THE 1K-2.5K LEVEL.  EXPECT THE LOWER CLOUDS TO LIFT AND
DISSIPATE BY AFTERNOON WITH THE MID DECK BECOMING SCATTERED TO
BROKEN BY LATE AFTERNOON.

KSEA...THE MID DECK AROUND 4.5K IS PRESENT NOW...BUT THERE ARE LOW
CLOUDS NEAR BY AT KPWT. THE LOW CLOUDS AT ABOUT 1-2K ARE EXPECTED TO
FORM OR DRIFT NEAR THE AIRPORT THIS MORNING. LOWER CLOUDS SHOULD
LIFT OR DISSIPATE BY EARLY AFTERNOON. 13

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. THIS WILL PRODUCE
WINDS NEAR SMALL CRAFT ADVISORY LEVELS IN THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA MOST EVENINGS. RIGHT NOW WE ARE EXPECTING
ABOUT 20 KTS THROUGH THE STRAIT THIS EVENING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE CENTRAL/EASTERN STRAIT
     OF JUAN DE FUCA AND THE COASTAL WATERS FROM CAPE FLATTERY TO
     CAPE SHOALWATER 10 NM OUT TO 60 NM.


&&

$$

WWW.WEATHER.GOV/SEATTLE

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WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 200354
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT TUE AUG 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
MAINTAIN NORTHWEST FLOW ALOFT AND MODERATE LOW LEVEL ONSHORE FLOW
OVER WESTERN WASHINGTON THIS WEEK. SMALL WEAK UPPER LEVEL TROUGHS
BRUSHING THE AREA MAY BRING A FEW SHOWERS TO MAINLY THE CASCADES AT
TIMES. THE ONSHORE FLOW WILL BRING MOSTLY CLOUDY SKIES TO THE
LOWLANDS WITH PARTIAL AFTERNOON CLEARING. THE UPPER LEVEL TROUGH
WILL SHIFT EAST THIS WEEKEND ALLOWING AN UPPER LEVEL RIDGE TO BUILD
INLAND FOR A SMALL WARMING AND DRYING TREND.

&&

.SHORT TERM...A WEAK UPPER LEVEL TROUGH BROUGHT A FEW SHOWERS AND
THUNDERSTORMS TO EASTERN WA TODAY...BUT NOT MUCH ACTIVITY ON THE
WESTSIDE. THERE IS LOW LEVEL CONVERGENCE OVER KING COUNTY JUST LIKE
THE MESOSCALE MODELS SHOWED BUT NO SHOWERS ON THE RADAR. ALL THAT IS
SHOWING UP IS A FLAT MID LEVEL DECK OVER THE NORTH AND CENTRAL
SOUND. SO WITH THAT IN MIND...UPDATED THE FORECAST TO REMOVE THE
MENTION OF SHOWERS IN THE INTERIOR AND CASCADES. ALSO ABSENT IS THE
MARINE LAYER OFFSHORE...BUT THIS MAY FORM IN PLACE OVERNIGHT THEN
SPREAD INLAND.

NORTHWEST FLOW WILL PREVAIL ON WED AS AN UPPER LEVEL RIDGE BUILDS
OVER THE NE PAC. A WEAK DISTURBANCE OVER B.C. MAY TRIGGER A FEW
SHOWERS IN THE NORTH CASCADES. LOW CLOUDS MAY LINGER IN THE INTERIOR
THROUGH WED AFTERNOON WHICH WILL KEEP TEMPS A FEW DEGREES COOLER
THAN NORMAL.

THE UPPER LEVEL RIDGE WILL CONTINUE TO BUILD OFFSHORE ALONG 140W ON
THURSDAY WITH THE FLOW ALOFT TURNING MORE NORTHERLY. THIS WILL ALLOW
AN UPPER LOW TO DRIFT SOUTH AND SPIN OVER THE PAC NW THU NIGHT AND
FRIDAY. TEMPS WILL REMAIN A FEW DEGREES BELOW NORMAL DURING THE
PERIOD...WITH SHOWERS MAINLY IN THE CASCADES. 33

.LONG TERM...PREVIOUS DISCUSSION...THE UPPER LEVEL LOW OVER THE
PACIFIC NW ON FRIDAY WILL SHIFT E OVER ID BY SATURDAY
MORNING...ALLOWING AN OFFSHORE UPPER LEVEL RIDGE TO BUILD EASTWARD
OVER THE AREA. WITH WEAK ONSHORE FLOW FRIDAY AND SATURDAY NIGHTS AND
DRIER NW FLOW ALOFT ON SATURDAY...SKIES WILL BE MOSTLY SUNNY WITH
MAX TEMPS WARMING BACK TO THE 70S TO LOWER 80S. BOTH THE GFS AND
ECMWF BRING AN UPPER LEVEL SHORTWAVE TROUGH DOWN OVER W WA ON
SUNDAY. AT THIS POINT THE SHORTWAVE LOOKS MAINLY DRY WITH JUST AN
INCREASE IN MID/HI CLOUD COVER EXPECTED. ONSHORE FLOW WILL PROBABLY
INCREASE SUNDAY NIGHT AND MONDAY. KAM

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PREVAIL THROUGH WEDNESDAY WITH
AN UPPER TROUGH OVER THE PACIFIC NORTHWEST. AT THE SURFACE...ONSHORE
FLOW WILL CONTINUE WITH HIGH PRESSURE OFFSHORE AND LOWER PRESSURE
INLAND. AIR MASS GENERALLY STABLE.

THERE ARE AREAS OF MID LEVEL CLOUDS OVER THE AREA THIS EVENING...
MOSTLY OVER THE CASCADES AND IN A CONVERGENCE ZONE OVER CENTRAL
PUGET SOUND. LOW CLOUDS ARE EXPECTED TO FORM AT THE COAST AND SPREAD
INLAND WEDNESDAY MORNING UNDER MODERATE ONSHORE FLOW.

KSEA...MID CLOUDS THIS EVENING WITH A WEAK PUGET SOUND CONVERGENCE
ZONE TO THE NORTH. LOW CLOUDS ARE EXPECTED TO DEVELOP LATE
TONIGHT...THEN BURN OFF BY EARLY AFTERNOON WEDNESDAY. SOUTHERLY WIND
4-8 KNOTS. THERE IS A SMALL CHANCE THE WIND COULD SWITCH TO NORTH
FOR A COUPLE OF HOURS THIS EVENING IF THE CONVERGENCE ZONE SAGS A
LITTLE FARTHER SOUTH. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. THIS WILL PRODUCE
SMALL CRAFT ADVISORY WEST WINDS IN THE CENTRAL AND EASTERN STRAIT OF
JUAN DE FUCA MOST EVENINGS.

ONSHORE FLOW WILL BE STRONGEST THIS EVENING IN THE WAKE OF AN UPPER
LEVEL TROUGH. MARGINAL GALE FORCE WEST WINDS ARE POSSIBLE THIS
EVENING IN THE CENTRAL AND EASTERN STRAIT. THERE WILL ALSO BE SOME
SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE OUTER COASTAL WATERS
THROUGH WEDNESDAY MORNING. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
    .SMALL CRAFT ADVISORY OUTER COASTAL WATERS...ADMIRALTY INLET...
     NORTHERN INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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







000
FXUS66 KSEW 200354
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT TUE AUG 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
MAINTAIN NORTHWEST FLOW ALOFT AND MODERATE LOW LEVEL ONSHORE FLOW
OVER WESTERN WASHINGTON THIS WEEK. SMALL WEAK UPPER LEVEL TROUGHS
BRUSHING THE AREA MAY BRING A FEW SHOWERS TO MAINLY THE CASCADES AT
TIMES. THE ONSHORE FLOW WILL BRING MOSTLY CLOUDY SKIES TO THE
LOWLANDS WITH PARTIAL AFTERNOON CLEARING. THE UPPER LEVEL TROUGH
WILL SHIFT EAST THIS WEEKEND ALLOWING AN UPPER LEVEL RIDGE TO BUILD
INLAND FOR A SMALL WARMING AND DRYING TREND.

&&

.SHORT TERM...A WEAK UPPER LEVEL TROUGH BROUGHT A FEW SHOWERS AND
THUNDERSTORMS TO EASTERN WA TODAY...BUT NOT MUCH ACTIVITY ON THE
WESTSIDE. THERE IS LOW LEVEL CONVERGENCE OVER KING COUNTY JUST LIKE
THE MESOSCALE MODELS SHOWED BUT NO SHOWERS ON THE RADAR. ALL THAT IS
SHOWING UP IS A FLAT MID LEVEL DECK OVER THE NORTH AND CENTRAL
SOUND. SO WITH THAT IN MIND...UPDATED THE FORECAST TO REMOVE THE
MENTION OF SHOWERS IN THE INTERIOR AND CASCADES. ALSO ABSENT IS THE
MARINE LAYER OFFSHORE...BUT THIS MAY FORM IN PLACE OVERNIGHT THEN
SPREAD INLAND.

NORTHWEST FLOW WILL PREVAIL ON WED AS AN UPPER LEVEL RIDGE BUILDS
OVER THE NE PAC. A WEAK DISTURBANCE OVER B.C. MAY TRIGGER A FEW
SHOWERS IN THE NORTH CASCADES. LOW CLOUDS MAY LINGER IN THE INTERIOR
THROUGH WED AFTERNOON WHICH WILL KEEP TEMPS A FEW DEGREES COOLER
THAN NORMAL.

THE UPPER LEVEL RIDGE WILL CONTINUE TO BUILD OFFSHORE ALONG 140W ON
THURSDAY WITH THE FLOW ALOFT TURNING MORE NORTHERLY. THIS WILL ALLOW
AN UPPER LOW TO DRIFT SOUTH AND SPIN OVER THE PAC NW THU NIGHT AND
FRIDAY. TEMPS WILL REMAIN A FEW DEGREES BELOW NORMAL DURING THE
PERIOD...WITH SHOWERS MAINLY IN THE CASCADES. 33

.LONG TERM...PREVIOUS DISCUSSION...THE UPPER LEVEL LOW OVER THE
PACIFIC NW ON FRIDAY WILL SHIFT E OVER ID BY SATURDAY
MORNING...ALLOWING AN OFFSHORE UPPER LEVEL RIDGE TO BUILD EASTWARD
OVER THE AREA. WITH WEAK ONSHORE FLOW FRIDAY AND SATURDAY NIGHTS AND
DRIER NW FLOW ALOFT ON SATURDAY...SKIES WILL BE MOSTLY SUNNY WITH
MAX TEMPS WARMING BACK TO THE 70S TO LOWER 80S. BOTH THE GFS AND
ECMWF BRING AN UPPER LEVEL SHORTWAVE TROUGH DOWN OVER W WA ON
SUNDAY. AT THIS POINT THE SHORTWAVE LOOKS MAINLY DRY WITH JUST AN
INCREASE IN MID/HI CLOUD COVER EXPECTED. ONSHORE FLOW WILL PROBABLY
INCREASE SUNDAY NIGHT AND MONDAY. KAM

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PREVAIL THROUGH WEDNESDAY WITH
AN UPPER TROUGH OVER THE PACIFIC NORTHWEST. AT THE SURFACE...ONSHORE
FLOW WILL CONTINUE WITH HIGH PRESSURE OFFSHORE AND LOWER PRESSURE
INLAND. AIR MASS GENERALLY STABLE.

THERE ARE AREAS OF MID LEVEL CLOUDS OVER THE AREA THIS EVENING...
MOSTLY OVER THE CASCADES AND IN A CONVERGENCE ZONE OVER CENTRAL
PUGET SOUND. LOW CLOUDS ARE EXPECTED TO FORM AT THE COAST AND SPREAD
INLAND WEDNESDAY MORNING UNDER MODERATE ONSHORE FLOW.

KSEA...MID CLOUDS THIS EVENING WITH A WEAK PUGET SOUND CONVERGENCE
ZONE TO THE NORTH. LOW CLOUDS ARE EXPECTED TO DEVELOP LATE
TONIGHT...THEN BURN OFF BY EARLY AFTERNOON WEDNESDAY. SOUTHERLY WIND
4-8 KNOTS. THERE IS A SMALL CHANCE THE WIND COULD SWITCH TO NORTH
FOR A COUPLE OF HOURS THIS EVENING IF THE CONVERGENCE ZONE SAGS A
LITTLE FARTHER SOUTH. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. THIS WILL PRODUCE
SMALL CRAFT ADVISORY WEST WINDS IN THE CENTRAL AND EASTERN STRAIT OF
JUAN DE FUCA MOST EVENINGS.

ONSHORE FLOW WILL BE STRONGEST THIS EVENING IN THE WAKE OF AN UPPER
LEVEL TROUGH. MARGINAL GALE FORCE WEST WINDS ARE POSSIBLE THIS
EVENING IN THE CENTRAL AND EASTERN STRAIT. THERE WILL ALSO BE SOME
SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE OUTER COASTAL WATERS
THROUGH WEDNESDAY MORNING. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
    .SMALL CRAFT ADVISORY OUTER COASTAL WATERS...ADMIRALTY INLET...
     NORTHERN INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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






000
FXUS66 KSEW 192154
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
254 PM PDT TUE AUG 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
MAINTAIN NORTHWEST FLOW ALOFT AND MODERATE LOW LEVEL ONSHORE FLOW
OVER WESTERN WASHINGTON THIS WEEK. SMALL WEAK UPPER LEVEL TROUGHS
BRUSHING THE AREA MAY BRING A FEW SHOWERS TO MAINLY THE CASCADES AT
TIMES. THE ONSHORE FLOW WILL BRING MOSTLY CLOUDY SKIES TO THE
LOWLANDS WITH PARTIAL AFTERNOON CLEARING. THE UPPER LEVEL TROUGH
WILL SHIFT EAST THIS WEEKEND ALLOWING AN UPPER LEVEL RIDGE TO BUILD
INLAND FOR A SMALL WARMING AND DRYING TREND.

&&

.SHORT TERM...AN UPPER LEVEL LONGWAVE TROUGH HAS SET UP OVER E WA
TODAY...WHICH WILL GIVE W WA NW FLOW ALOFT FOR THE NEXT COUPLE DAYS.
MESOSCALE MODELS STILL SHOW SOME CONVECTION DEVELOPING OVER THE
OLYMPICS THIS AFTERNOON AND EVENING AND SATELLITE IMAGERY SHOW
CUMULUS HAS BEGUN TO INCREASE. INCREASING SW ONSHORE FLOW IS
BEGINNING TO DEVELOP OVER S PUGET SOUND AND NW FLOW COMING DOWN FROM
THE EASTERN STRAIT COULD ADD SOME CONVERGENCE TO THE MIX. I WILL
KEEP PARTLY CLOUDY SKIES AND A CHANCE OF SHOWERS OVER CENTRAL PUGET
SOUND THIS EVENING...ALTHOUGH CONFIDENCE IS NOT VERY HIGH.

THE AIR MASS OVER THE CASCADES HAS BECOME UNSTABLE THIS AFTERNOON
WITH CUMULUS DEVELOPING. A FEW SHOWERS ARE EXPECTED. CONVECTION WILL
PROBABLY BE DEEPER OVER THE FAR NE CASCADES SO AN ISOLATED
THUNDERSTORM WOULD NOT BE SURPRISING BUT IS STILL UNLIKELY.

THE NW FLOW ALOFT WILL BE MAINLY DRY THROUGH FRIDAY...BUT SMALL
WEAK UPPER LEVEL SHORTWAVE TROUGHS EMBEDDED IN THE NW FLOW MAY BRING
A FEW SHOWERS TO THE CASCADES AT TIMES AS THEY BRUSH THE AREA. THE
UPPER LEVEL TROUGH WILL DEEPEN INTO AN UPPER LEVEL LOW OVER CENTRAL
WA THURSDAY NIGHT AND FRIDAY. NE FLOW ALOFT AROUND THE LOW ON FRIDAY
COULD BRING A MORE UNSTABLE AIR MASS AND MORE WIDESPREAD SHOWERS
OVER THE CASCADES BY FRIDAY AFTERNOON. IT IS POSSIBLE THAT SOME
SHOWERS COULD SPREAD W OUT OVER THE LOWLANDS BUT THE MODELS DO NOT
SHOW THAT JUST YET. FRIDAY AFTERNOON AND EVENING WILL PROBABLY BE
THE BEST BET FOR THUNDERSTORMS OVER THE CASCADES. IT IS JUST A BIT
EARLY TO JUMP ON THE THUNDERSTORMS...BUT IF THE MODELS REMAIN
CONSISTENT FOR A COUPLE MORE RUNS THEY WILL BE ADDED TO THE
FORECAST.

THE OTHER IMPACT OF THE UPPER TROUGH WILL BE TO MAINTAIN A SW
DIRECTION TO THE LOW LEVEL ONSHORE FLOW THE NEXT COUPLE OF DAYS. A
DEEPER MARINE LAYER WILL FORM TONIGHT SO STRATUS WEDNESDAY MORNING
SHOULD COVER JUST ABOUT ALL W WA...AND SHOULD BE DEEP ENOUGH SO THAT
SOME DRIZZLE IS POSSIBLE. WEAK CONVERGENCE OVER CENTRAL PUGET SOUND
SHOULD INCREASE THE CHANCE OF DRIZZLE THERE. NOT MUCH BREAKOUT IS
EXPECTED WEDNESDAY AFTERNOON...BUT THERE COULD BE SOME LATE
AFTERNOON SUN BREAKS. ONSHORE FLOW WEDNESDAY NIGHT WILL NOT BE AS
STRONG BUT STRATUS IN THE DEEPER MARINE LAYER SHOULD ONCE AGAIN
COVER THE W WA LOWLANDS. THE STRATUS IS EXPECTED TO BREAK UP MORE ON
THURSDAY AND FRIDAY FOR PARTLY TO MOSTLY SUNNY CONDITIONS IN THE
AFTERNOON.

THE UPPER LEVEL TROUGH AND ONSHORE FLOW COMBINED WILL COOL MAX TEMPS
BACK TO THE LOWER 70S OVER THE INTERIOR...WHICH IS NEAR OR SLIGHTLY
BELOW NORMAL. KAM

.LONG TERM...THE UPPER LEVEL LOW OVER THE PACIFIC NW ON FRIDAY WILL
SHIFT E OVER ID BY SATURDAY MORNING...ALLOWING AN OFFSHORE UPPER
LEVEL RIDGE TO BUILD EASTWARD OVER THE AREA. WITH WEAK ONSHORE FLOW
FRIDAY AND SATURDAY NIGHTS AND DRIER NW FLOW ALOFT ON
SATURDAY...SKIES WILL BE MOSTLY SUNNY WITH MAX TEMPS WARMING BACK TO
THE 70S TO LOWER 80S. BOTH THE GFS AND ECMWF BRING AN UPPER LEVEL
SHORTWAVE TROUGH DOWN OVER W WA ON SUNDAY. AT THIS POINT THE
SHORTWAVE LOOKS MAINLY DRY WITH JUST AN INCREASE IN MID/HI CLOUD
COVER EXPECTED. ONSHORE FLOW WILL PROBABLY INCREASE SUNDAY NIGHT AND
MONDAY. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH WILL DIG SE THROUGH THE
INTERIOR PAC NW TONIGHT. LIGHT WLY FLOW ALOFT...BECOMING NWLY ON
WED. ATMOSPHERE GENERALLY STABLE...AND SOMEWHAT MOIST IN THE LOWER
AND MID LEVELS.

STRONGER SOUTHWEST ONSHORE FLOW IS EXPECTED TONIGHT WITH MORE
EXTENSIVE LOW CLOUDS FOR THE INTERIOR BY WEDNESDAY MORNING. EXPECT
AREAS OF IFR OR LOW MVFR CEILINGS TO DEVELOP...THEN SCATTER ACROSS
THE INTERIOR DURING THE AFTERNOON.

A PUGET SOUND CONVERGENCE ZONE MAY DEVELOP OVER FAR N KING OR
SOUTHERN SNOHOMISH COUNTY EARLY THIS EVENING. THE KPAE TERMINAL HAS
THE BEST CHANCE OF PRECIPITATION AND BRIEF MVFR CIGS...THOUGH
CONFIDENCE IN THESE DETAILS ARE LOW.

KSEA...A PUGET SOUND CONVERGENCE ZONE MAY RESULT IN SOME SCT-BKN
CLOUD COVER AROUND 5K FT DEVELOPING THIS EVENING. ANY PRECIPITATION
MOST LIKELY WILL REMAIN N OF THE TERMINAL. LOW CLOUDS ARE EXPECTED
LATER TONIGHT WITH THE MARINE PUGH. SOUTH TO SOUTHWEST WIND 4-8
KNOTS.

&&

.MARINE...STRONGER SOUTHWESTERLY ONSHORE FLOW WILL PREVAIL TONIGHT
BEHIND A WEAK UPPER LEVEL DISTURBANCE. RACE ROCKS REACHED 32 KT AT 2
PM SO A GALE WARNING WILL BE IN EFFECT FOR THE CENTRAL AND EAST
STRAIT LATE THIS AFTERNOON AND THIS EVENING. THE FLOW ADJACENT TO
THE EAST ENTRANCE TONIGHT SUPPORTS SMALL CRAFT WINDS IN THE NRN
PORTION OF ADMIRALTY INLET AND THE SRN PORTION OF THE N INTERIOR. IN
ADDITION...NORTHWESTERLY GRADIENT WILL TIGHTEN TONIGHT THROUGH
WEDNESDAY MORNING SUPPORTING SMALL CRAFT WINDS OVER THE OUTER
COASTAL WATERS.

SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE NEXT
SEVERAL DAYS OVER THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE WINDS IN THE STRAIT SHOULD BE STRONGEST TONIGHT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
     SMALL CRAFT ADVISORY OUTER COASTAL WATERS...ADMIRALTY INLET...
     AND NORTHERN INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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











000
FXUS66 KSEW 192154
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
254 PM PDT TUE AUG 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
MAINTAIN NORTHWEST FLOW ALOFT AND MODERATE LOW LEVEL ONSHORE FLOW
OVER WESTERN WASHINGTON THIS WEEK. SMALL WEAK UPPER LEVEL TROUGHS
BRUSHING THE AREA MAY BRING A FEW SHOWERS TO MAINLY THE CASCADES AT
TIMES. THE ONSHORE FLOW WILL BRING MOSTLY CLOUDY SKIES TO THE
LOWLANDS WITH PARTIAL AFTERNOON CLEARING. THE UPPER LEVEL TROUGH
WILL SHIFT EAST THIS WEEKEND ALLOWING AN UPPER LEVEL RIDGE TO BUILD
INLAND FOR A SMALL WARMING AND DRYING TREND.

&&

.SHORT TERM...AN UPPER LEVEL LONGWAVE TROUGH HAS SET UP OVER E WA
TODAY...WHICH WILL GIVE W WA NW FLOW ALOFT FOR THE NEXT COUPLE DAYS.
MESOSCALE MODELS STILL SHOW SOME CONVECTION DEVELOPING OVER THE
OLYMPICS THIS AFTERNOON AND EVENING AND SATELLITE IMAGERY SHOW
CUMULUS HAS BEGUN TO INCREASE. INCREASING SW ONSHORE FLOW IS
BEGINNING TO DEVELOP OVER S PUGET SOUND AND NW FLOW COMING DOWN FROM
THE EASTERN STRAIT COULD ADD SOME CONVERGENCE TO THE MIX. I WILL
KEEP PARTLY CLOUDY SKIES AND A CHANCE OF SHOWERS OVER CENTRAL PUGET
SOUND THIS EVENING...ALTHOUGH CONFIDENCE IS NOT VERY HIGH.

THE AIR MASS OVER THE CASCADES HAS BECOME UNSTABLE THIS AFTERNOON
WITH CUMULUS DEVELOPING. A FEW SHOWERS ARE EXPECTED. CONVECTION WILL
PROBABLY BE DEEPER OVER THE FAR NE CASCADES SO AN ISOLATED
THUNDERSTORM WOULD NOT BE SURPRISING BUT IS STILL UNLIKELY.

THE NW FLOW ALOFT WILL BE MAINLY DRY THROUGH FRIDAY...BUT SMALL
WEAK UPPER LEVEL SHORTWAVE TROUGHS EMBEDDED IN THE NW FLOW MAY BRING
A FEW SHOWERS TO THE CASCADES AT TIMES AS THEY BRUSH THE AREA. THE
UPPER LEVEL TROUGH WILL DEEPEN INTO AN UPPER LEVEL LOW OVER CENTRAL
WA THURSDAY NIGHT AND FRIDAY. NE FLOW ALOFT AROUND THE LOW ON FRIDAY
COULD BRING A MORE UNSTABLE AIR MASS AND MORE WIDESPREAD SHOWERS
OVER THE CASCADES BY FRIDAY AFTERNOON. IT IS POSSIBLE THAT SOME
SHOWERS COULD SPREAD W OUT OVER THE LOWLANDS BUT THE MODELS DO NOT
SHOW THAT JUST YET. FRIDAY AFTERNOON AND EVENING WILL PROBABLY BE
THE BEST BET FOR THUNDERSTORMS OVER THE CASCADES. IT IS JUST A BIT
EARLY TO JUMP ON THE THUNDERSTORMS...BUT IF THE MODELS REMAIN
CONSISTENT FOR A COUPLE MORE RUNS THEY WILL BE ADDED TO THE
FORECAST.

THE OTHER IMPACT OF THE UPPER TROUGH WILL BE TO MAINTAIN A SW
DIRECTION TO THE LOW LEVEL ONSHORE FLOW THE NEXT COUPLE OF DAYS. A
DEEPER MARINE LAYER WILL FORM TONIGHT SO STRATUS WEDNESDAY MORNING
SHOULD COVER JUST ABOUT ALL W WA...AND SHOULD BE DEEP ENOUGH SO THAT
SOME DRIZZLE IS POSSIBLE. WEAK CONVERGENCE OVER CENTRAL PUGET SOUND
SHOULD INCREASE THE CHANCE OF DRIZZLE THERE. NOT MUCH BREAKOUT IS
EXPECTED WEDNESDAY AFTERNOON...BUT THERE COULD BE SOME LATE
AFTERNOON SUN BREAKS. ONSHORE FLOW WEDNESDAY NIGHT WILL NOT BE AS
STRONG BUT STRATUS IN THE DEEPER MARINE LAYER SHOULD ONCE AGAIN
COVER THE W WA LOWLANDS. THE STRATUS IS EXPECTED TO BREAK UP MORE ON
THURSDAY AND FRIDAY FOR PARTLY TO MOSTLY SUNNY CONDITIONS IN THE
AFTERNOON.

THE UPPER LEVEL TROUGH AND ONSHORE FLOW COMBINED WILL COOL MAX TEMPS
BACK TO THE LOWER 70S OVER THE INTERIOR...WHICH IS NEAR OR SLIGHTLY
BELOW NORMAL. KAM

.LONG TERM...THE UPPER LEVEL LOW OVER THE PACIFIC NW ON FRIDAY WILL
SHIFT E OVER ID BY SATURDAY MORNING...ALLOWING AN OFFSHORE UPPER
LEVEL RIDGE TO BUILD EASTWARD OVER THE AREA. WITH WEAK ONSHORE FLOW
FRIDAY AND SATURDAY NIGHTS AND DRIER NW FLOW ALOFT ON
SATURDAY...SKIES WILL BE MOSTLY SUNNY WITH MAX TEMPS WARMING BACK TO
THE 70S TO LOWER 80S. BOTH THE GFS AND ECMWF BRING AN UPPER LEVEL
SHORTWAVE TROUGH DOWN OVER W WA ON SUNDAY. AT THIS POINT THE
SHORTWAVE LOOKS MAINLY DRY WITH JUST AN INCREASE IN MID/HI CLOUD
COVER EXPECTED. ONSHORE FLOW WILL PROBABLY INCREASE SUNDAY NIGHT AND
MONDAY. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH WILL DIG SE THROUGH THE
INTERIOR PAC NW TONIGHT. LIGHT WLY FLOW ALOFT...BECOMING NWLY ON
WED. ATMOSPHERE GENERALLY STABLE...AND SOMEWHAT MOIST IN THE LOWER
AND MID LEVELS.

STRONGER SOUTHWEST ONSHORE FLOW IS EXPECTED TONIGHT WITH MORE
EXTENSIVE LOW CLOUDS FOR THE INTERIOR BY WEDNESDAY MORNING. EXPECT
AREAS OF IFR OR LOW MVFR CEILINGS TO DEVELOP...THEN SCATTER ACROSS
THE INTERIOR DURING THE AFTERNOON.

A PUGET SOUND CONVERGENCE ZONE MAY DEVELOP OVER FAR N KING OR
SOUTHERN SNOHOMISH COUNTY EARLY THIS EVENING. THE KPAE TERMINAL HAS
THE BEST CHANCE OF PRECIPITATION AND BRIEF MVFR CIGS...THOUGH
CONFIDENCE IN THESE DETAILS ARE LOW.

KSEA...A PUGET SOUND CONVERGENCE ZONE MAY RESULT IN SOME SCT-BKN
CLOUD COVER AROUND 5K FT DEVELOPING THIS EVENING. ANY PRECIPITATION
MOST LIKELY WILL REMAIN N OF THE TERMINAL. LOW CLOUDS ARE EXPECTED
LATER TONIGHT WITH THE MARINE PUGH. SOUTH TO SOUTHWEST WIND 4-8
KNOTS.

&&

.MARINE...STRONGER SOUTHWESTERLY ONSHORE FLOW WILL PREVAIL TONIGHT
BEHIND A WEAK UPPER LEVEL DISTURBANCE. RACE ROCKS REACHED 32 KT AT 2
PM SO A GALE WARNING WILL BE IN EFFECT FOR THE CENTRAL AND EAST
STRAIT LATE THIS AFTERNOON AND THIS EVENING. THE FLOW ADJACENT TO
THE EAST ENTRANCE TONIGHT SUPPORTS SMALL CRAFT WINDS IN THE NRN
PORTION OF ADMIRALTY INLET AND THE SRN PORTION OF THE N INTERIOR. IN
ADDITION...NORTHWESTERLY GRADIENT WILL TIGHTEN TONIGHT THROUGH
WEDNESDAY MORNING SUPPORTING SMALL CRAFT WINDS OVER THE OUTER
COASTAL WATERS.

SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE NEXT
SEVERAL DAYS OVER THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE WINDS IN THE STRAIT SHOULD BE STRONGEST TONIGHT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
     SMALL CRAFT ADVISORY OUTER COASTAL WATERS...ADMIRALTY INLET...
     AND NORTHERN INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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












000
FXUS66 KSEW 191626
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
926 AM PDT TUE AUG 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
MAINTAIN NORTHWEST FLOW ALOFT AND MODERATE LOW LEVEL ONSHORE FLOW
OVER WESTERN WASHINGTON THIS WEEK. SMALL WEAK UPPER LEVEL TROUGHS
BRUSHING THE AREA MAY BRING A FEW SHOWERS TO MAINLY THE CASCADES AT
TIMES. THE ONSHORE FLOW WILL BRING MOSTLY CLOUDY SKIES TO THE
LOWLANDS WITH PARTIAL AFTERNOON CLEARING. THE UPPER LEVEL TROUGH
WILL SHIFT EAST THIS WEEKEND ALLOWING AN UPPER LEVEL RIDGE TO BUILD
INLAND FOR A SMALL WARMING AND DRYING TREND.

&&

.SHORT TERM...AN UPPER LEVEL LONGWAVE TROUGH IS IN THE PROCESS OF
SETTING UP OVER E WA THIS MORNING...WHICH WILL GIVE W WA NW FLOW
ALOFT FOR THE NEXT COUPLE DAYS. AN UPPER LEVEL SHORTWAVE TROUGH WAS
JUST MOVING PAST W WA THIS MORNING AND THE ASSOCIATED HIGH CLOUDS
HAVE MOVED E. AS IT TURNED OUT THERE IS NOT MUCH LOWER LEVEL
MOISTURE ADVECTING INLAND BEHIND THE TROUGH...SO SKIES WILL BE
MOSTLY SUNNY OVER INLAND AREAS TODAY. STRATUS WILL STILL PLAGUE THE
COAST.

THE MESOSCALE MODELS SHOW SOME CONVECTION DEVELOPING OVER THE
OLYMPICS THIS AFTERNOON...AND W-NW MID LEVEL FLOW MAY PUSH SOME OF
THE RESULTING SHOWERS OUT OVER THE CENTRAL KITSAP PENINSULA. HOWEVER
CONFIDENCE FOR MUCH SHOWER ACTIVITY IS NOT HIGH.

THE NW FLOW ALOFT WILL BE MAINLY DRY THROUGH THURSDAY...BUT SMALL
WEAK UPPER LEVEL SHORTWAVE TROUGHS EMBEDDED IN THE NW FLOW MAY BRING
A FEW SHOWERS TO THE CASCADES AT TIMES AS THEY BRUSH THE AREA. THE
FAR NE CORNER OF THE CASCADES IS MOST LIKELY TO HAVE SHOWER
ACTIVITY...AND THERE MAY BE ENOUGH INSTABILITY FOR AN ISOLATED
THUNDERSTORM TO FORM THIS AFTERNOON.

THE OTHER IMPACT OF THE UPPER TROUGH WILL BE TO SHIFT THE LOW LEVEL
ONSHORE FLOW TO SW...WHICH WILL ALLOW A DEEPER MARINE LAYER TO FORM
OVER JUST ABOUT ALL THE W WA LOWLANDS BY WEDNESDAY MORNING. ONSHORE
FLOW LAST NIGHT WAS NOT THAT STRONG BUT PUSHED STRATUS UP THE LOWER
CHEHALIS VALLEY AS FAR AS SHELTON THIS MORNING. PRESSURE GRADIENTS
THIS MORNING ARE ALREADY 1 TO 1.5 MB AHEAD OF YESTERDAY AND THE
AST-SEA AND HQM-SEA GRADIENTS DEFINITELY INDICATE A SW DIRECTION.
THE STRATUS ALONG THE COAST AND OVER THE LOWER CHEHALIS VALLEY WILL
HAVE A TOUGHER TIME BREAKING OUT THIS AFTERNOON.

THE MARINE LAYER WEDNESDAY MORNING SHOULD COVER JUST ABOUT ALL W
WA...AND SHOULD BE DEEP ENOUGH SO THAT SOME DRIZZLE IS POSSIBLE. A
CONVERGENCE ZONE WILL ALSO SET UP OVER CENTRAL PUGET SOUND WHICH
SHOULD INCREASE THE CHANCE OF DRIZZLE THERE. NOT MUCH BREAKOUT IS
EXPECTED WEDNESDAY AFTERNOON...BUT THERE COULD BE SOME LATE
AFTERNOON SUN BREAKS. ONSHORE FLOW WEDNESDAY NIGHT WILL NOT BE AS
STRONG BUT STRATUS IN THE DEEPER MARINE LAYER SHOULD ONCE AGAIN
COVER THE W WA LOWLANDS. THE STRATUS IS EXPECTED TO BREAK UP MORE ON
THURSDAY FOR PARTLY SUNNY CONDITIONS IN THE AFTERNOON.

THE UPPER LEVEL TROUGH AND ONSHORE FLOW COMBINED WILL COOL MAX TEMPS
BACK TO THE LOWER 70S OVER THE INTERIOR...WHICH IS NEAR OR SLIGHTLY
BELOW NORMAL. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 330 AM AFD...CONFIDENCE IN
THIS PERIOD WAS NOT VERY HIGH DUE TO DISAGREEMENT IN THE MEDIUM
RANGE SOLUTIONS. FOR EXAMPLE...THE GFS HAD THE REGION MORE UNDER THE
INFLUENCE OF AN UPPER TROF LATE IN THE PERIOD WHEREAS THE ECMWF KEPT
AN UPPER RIDGE OVER THE AREA. THE CURRENT FORECAST REFLECTS
CLIMO...WHICH IS PROBABLY A GOOD WAY TO GO FOR NOW.

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH OVER THE REGION TODAY WILL DIG
SE THROUGH THE INTERIOR PAC NW TONIGHT. LIGHT W-NW FLOW ALOFT.
ATMOSPHERE GENERALLY STABLE...AND SOMEWHAT MOIST IN THE LOWER AND
MID LEVELS.

VISIBLE SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST...SOME OF
THE STRAIT...THE LOWER CHEHALIS GAP AND PARTIALLY INTO THE EXTREME
SW PART OF PUGET SOUND. THIS IS LESS EXTENSIVE THAN EXPECTED AND IS
NOT EXPECTED TO REACH THE INLAND TERMINALS TODAY. A STRONGER MARINE
PUSH IS EXPECTED TONIGHT WITH MORE EXTENSIVE LOW CLOUDS FOR THE
INTERIOR BY WEDNESDAY MORNING.

A PUGET SOUND CONVERGENCE ZONE WILL LIKELY FORM OVER KING OR
SOUTHERN SNOHOMISH COUNTY LATE THIS AFTERNOON...LINGER INTO THE
EVENING...THEN WEAKEN AFTER MIDNIGHT TONIGHT. THE KPAE TERMINAL HAS
THE BEST CHANCE OF PRECIPITATION AND BRIEF MVFR CIGS...THOUGH
CONFIDENCE IN THESE DETAILS ARE LOW.

KSEA...VFR SKIES THROUGH MOST OF THE DAY WITH MARINE CLOUDS WELL S
OF THE TERMINAL THIS MORNING. A CONVERGENCE ZONE COULD PRODUCE SOME
BRIEF MVFR CLOUDS LATE THIS AFTERNOON AND EVENING...BUT MOST LIKELY
DEVELOPING JUST N OF THE TERMINAL. LOW CLOUDS ARE EXPECTED LATER
TONIGHT WITH THE MARINE PUGH. SOUTH TO SOUTHWEST WIND 3-6 KNOTS.
WINDS COULD SWITCH TO NORTH FOR A FEW HOURS THIS EVENING IF THE
CONVERGENCE ZONE COMES DOWN...THEN SWITCH BACK TO SLY. DTM

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. A WEAK UPPER LEVEL
DISTURBANCES PASSING TO THE NORTH TODAY WILL CAUSE THE ONSHORE FLOW
TO INCREASE.

SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE NEXT
SEVERAL DAYS OVER THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE WINDS IN THE STRAIT SHOULD BE STRONGEST TONIGHT. THE CURRENT
FORECAST FOR TONIGHT FOR THE CENTRAL AND EAST EASTERN STRAIT IS FOR
HIGH END SMALL CRAFT ADVISORY STRENGTH BUT THERE IS A CHANCE IT
COULD HIT GALE. THERE SHOULD ALSO BE SOME SMALL CRAFT ADVISORY WINDS
OVER THE INLAND WATERS ADJACENT TO THE STRAIT THIS EVENING.

LASTLY...THERE WILL BE SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE
OUTER COASTAL WATERS AT TIMES FOR THE NEXT COUPLE OF DAYS.
SCHNEIDER/DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE
     FUCA...OUTER COASTAL WATERS...ADMIRALTY INLET...AND NORTHERN
     INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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








000
FXUS66 KSEW 191626
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
926 AM PDT TUE AUG 19 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL
MAINTAIN NORTHWEST FLOW ALOFT AND MODERATE LOW LEVEL ONSHORE FLOW
OVER WESTERN WASHINGTON THIS WEEK. SMALL WEAK UPPER LEVEL TROUGHS
BRUSHING THE AREA MAY BRING A FEW SHOWERS TO MAINLY THE CASCADES AT
TIMES. THE ONSHORE FLOW WILL BRING MOSTLY CLOUDY SKIES TO THE
LOWLANDS WITH PARTIAL AFTERNOON CLEARING. THE UPPER LEVEL TROUGH
WILL SHIFT EAST THIS WEEKEND ALLOWING AN UPPER LEVEL RIDGE TO BUILD
INLAND FOR A SMALL WARMING AND DRYING TREND.

&&

.SHORT TERM...AN UPPER LEVEL LONGWAVE TROUGH IS IN THE PROCESS OF
SETTING UP OVER E WA THIS MORNING...WHICH WILL GIVE W WA NW FLOW
ALOFT FOR THE NEXT COUPLE DAYS. AN UPPER LEVEL SHORTWAVE TROUGH WAS
JUST MOVING PAST W WA THIS MORNING AND THE ASSOCIATED HIGH CLOUDS
HAVE MOVED E. AS IT TURNED OUT THERE IS NOT MUCH LOWER LEVEL
MOISTURE ADVECTING INLAND BEHIND THE TROUGH...SO SKIES WILL BE
MOSTLY SUNNY OVER INLAND AREAS TODAY. STRATUS WILL STILL PLAGUE THE
COAST.

THE MESOSCALE MODELS SHOW SOME CONVECTION DEVELOPING OVER THE
OLYMPICS THIS AFTERNOON...AND W-NW MID LEVEL FLOW MAY PUSH SOME OF
THE RESULTING SHOWERS OUT OVER THE CENTRAL KITSAP PENINSULA. HOWEVER
CONFIDENCE FOR MUCH SHOWER ACTIVITY IS NOT HIGH.

THE NW FLOW ALOFT WILL BE MAINLY DRY THROUGH THURSDAY...BUT SMALL
WEAK UPPER LEVEL SHORTWAVE TROUGHS EMBEDDED IN THE NW FLOW MAY BRING
A FEW SHOWERS TO THE CASCADES AT TIMES AS THEY BRUSH THE AREA. THE
FAR NE CORNER OF THE CASCADES IS MOST LIKELY TO HAVE SHOWER
ACTIVITY...AND THERE MAY BE ENOUGH INSTABILITY FOR AN ISOLATED
THUNDERSTORM TO FORM THIS AFTERNOON.

THE OTHER IMPACT OF THE UPPER TROUGH WILL BE TO SHIFT THE LOW LEVEL
ONSHORE FLOW TO SW...WHICH WILL ALLOW A DEEPER MARINE LAYER TO FORM
OVER JUST ABOUT ALL THE W WA LOWLANDS BY WEDNESDAY MORNING. ONSHORE
FLOW LAST NIGHT WAS NOT THAT STRONG BUT PUSHED STRATUS UP THE LOWER
CHEHALIS VALLEY AS FAR AS SHELTON THIS MORNING. PRESSURE GRADIENTS
THIS MORNING ARE ALREADY 1 TO 1.5 MB AHEAD OF YESTERDAY AND THE
AST-SEA AND HQM-SEA GRADIENTS DEFINITELY INDICATE A SW DIRECTION.
THE STRATUS ALONG THE COAST AND OVER THE LOWER CHEHALIS VALLEY WILL
HAVE A TOUGHER TIME BREAKING OUT THIS AFTERNOON.

THE MARINE LAYER WEDNESDAY MORNING SHOULD COVER JUST ABOUT ALL W
WA...AND SHOULD BE DEEP ENOUGH SO THAT SOME DRIZZLE IS POSSIBLE. A
CONVERGENCE ZONE WILL ALSO SET UP OVER CENTRAL PUGET SOUND WHICH
SHOULD INCREASE THE CHANCE OF DRIZZLE THERE. NOT MUCH BREAKOUT IS
EXPECTED WEDNESDAY AFTERNOON...BUT THERE COULD BE SOME LATE
AFTERNOON SUN BREAKS. ONSHORE FLOW WEDNESDAY NIGHT WILL NOT BE AS
STRONG BUT STRATUS IN THE DEEPER MARINE LAYER SHOULD ONCE AGAIN
COVER THE W WA LOWLANDS. THE STRATUS IS EXPECTED TO BREAK UP MORE ON
THURSDAY FOR PARTLY SUNNY CONDITIONS IN THE AFTERNOON.

THE UPPER LEVEL TROUGH AND ONSHORE FLOW COMBINED WILL COOL MAX TEMPS
BACK TO THE LOWER 70S OVER THE INTERIOR...WHICH IS NEAR OR SLIGHTLY
BELOW NORMAL. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 330 AM AFD...CONFIDENCE IN
THIS PERIOD WAS NOT VERY HIGH DUE TO DISAGREEMENT IN THE MEDIUM
RANGE SOLUTIONS. FOR EXAMPLE...THE GFS HAD THE REGION MORE UNDER THE
INFLUENCE OF AN UPPER TROF LATE IN THE PERIOD WHEREAS THE ECMWF KEPT
AN UPPER RIDGE OVER THE AREA. THE CURRENT FORECAST REFLECTS
CLIMO...WHICH IS PROBABLY A GOOD WAY TO GO FOR NOW.

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH OVER THE REGION TODAY WILL DIG
SE THROUGH THE INTERIOR PAC NW TONIGHT. LIGHT W-NW FLOW ALOFT.
ATMOSPHERE GENERALLY STABLE...AND SOMEWHAT MOIST IN THE LOWER AND
MID LEVELS.

VISIBLE SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST...SOME OF
THE STRAIT...THE LOWER CHEHALIS GAP AND PARTIALLY INTO THE EXTREME
SW PART OF PUGET SOUND. THIS IS LESS EXTENSIVE THAN EXPECTED AND IS
NOT EXPECTED TO REACH THE INLAND TERMINALS TODAY. A STRONGER MARINE
PUSH IS EXPECTED TONIGHT WITH MORE EXTENSIVE LOW CLOUDS FOR THE
INTERIOR BY WEDNESDAY MORNING.

A PUGET SOUND CONVERGENCE ZONE WILL LIKELY FORM OVER KING OR
SOUTHERN SNOHOMISH COUNTY LATE THIS AFTERNOON...LINGER INTO THE
EVENING...THEN WEAKEN AFTER MIDNIGHT TONIGHT. THE KPAE TERMINAL HAS
THE BEST CHANCE OF PRECIPITATION AND BRIEF MVFR CIGS...THOUGH
CONFIDENCE IN THESE DETAILS ARE LOW.

KSEA...VFR SKIES THROUGH MOST OF THE DAY WITH MARINE CLOUDS WELL S
OF THE TERMINAL THIS MORNING. A CONVERGENCE ZONE COULD PRODUCE SOME
BRIEF MVFR CLOUDS LATE THIS AFTERNOON AND EVENING...BUT MOST LIKELY
DEVELOPING JUST N OF THE TERMINAL. LOW CLOUDS ARE EXPECTED LATER
TONIGHT WITH THE MARINE PUGH. SOUTH TO SOUTHWEST WIND 3-6 KNOTS.
WINDS COULD SWITCH TO NORTH FOR A FEW HOURS THIS EVENING IF THE
CONVERGENCE ZONE COMES DOWN...THEN SWITCH BACK TO SLY. DTM

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. A WEAK UPPER LEVEL
DISTURBANCES PASSING TO THE NORTH TODAY WILL CAUSE THE ONSHORE FLOW
TO INCREASE.

SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE NEXT
SEVERAL DAYS OVER THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE WINDS IN THE STRAIT SHOULD BE STRONGEST TONIGHT. THE CURRENT
FORECAST FOR TONIGHT FOR THE CENTRAL AND EAST EASTERN STRAIT IS FOR
HIGH END SMALL CRAFT ADVISORY STRENGTH BUT THERE IS A CHANCE IT
COULD HIT GALE. THERE SHOULD ALSO BE SOME SMALL CRAFT ADVISORY WINDS
OVER THE INLAND WATERS ADJACENT TO THE STRAIT THIS EVENING.

LASTLY...THERE WILL BE SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE
OUTER COASTAL WATERS AT TIMES FOR THE NEXT COUPLE OF DAYS.
SCHNEIDER/DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE
     FUCA...OUTER COASTAL WATERS...ADMIRALTY INLET...AND NORTHERN
     INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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









000
FXUS66 KSEW 191030
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT TUE AUG 19 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL INFLUENCE THE WEATHER
PATTERN OVER THE AREA THROUGH THURSDAY. THIS WILL RESULT IN
SOMEWHAT UNSETTLED CONDITIONS. THE MAIN IMPACTS WILL BE COOLER
TEMPERATURES AND CLOUDIER SKIES.

&&

.SHORT TERM...
AN UPPER TROF WAS MOVING OVER THE REGION AT THIS TIME. THIS
SYSTEM WAS SLIGHTLY STRONGER THAN WHAT THE MODELS HAD ADVERTISED
AND HAS TRIGGERED ISOLATED TSTMS OVER THE NORTHERN PART OF THE CWA
EARLY THIS MORNING. THERE IS A POSSIBILITY THAT THIS ACTIVITY
MIGHT BECOME A LITTLE MORE WIDESPREAD DURING THE NEXT FEW HOURS...
THUS WILL KEEP AN EYE ON IT. IN THE MEANTIME...THE RISK OF TSTMS
HAS BEEN CONFINED TO THE NORTHERN ZONES FOR NOW.

WESTERN WA WILL REMAIN UNDER THE INFLUENCE OF AN UPPER TROF DURING
THIS PERIOD FOR SOMEWHAT UNSETTLED CONDITIONS. THE MAIN IMPACTS
WILL BE COOLER TEMPS AND MORE CLOUD COVER. HOWEVER THERE WILL BE A
CHANCE OF PRECIP OVER PARTS OF THE CWA EACH DAY.

THE SURFACE ONSHORE PRESSURE GRADIENT WILL TIGHTEN THIS AFTERNOON...
LEADING TO THE DEVELOPMENT OF A PUGET SOUND CONVERGENCE ZONE
/PSCZ/ LATER THIS AFTERNOON. THE PSCZ SHOULD PERSIST OVERNIGHT.
THE NAM AND WRF-GFS DIFFERED ON THE EXACT PLACEMENT OF THE
PSCZ...SO BROAD-BRUSHED THE FORECAST TO INDICATE THAT THE PSCZ
WILL AFFECT THE NORTHERN AND CENTRAL PUGET SOUND REGION. LATER
SHIFTS CAN FINE-TUNE THE FORECAST IF NEEDED. THE ONSHORE FLOW WILL
TIGHTEN ON THU AFTER RELAXING SOME ON WED...RESULTING IN THE
REDEVELOPMENT OF A PSCZ.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT VERY HIGH DUE TO DISAGREEMENT IN
THE MEDIUM RANGE SOLUTIONS. FOR EXAMPLE...THE GFS HAD THE REGION
MORE UNDER THE INFLUENCE OF AN UPPER TROF LATE IN THE PERIOD
WHEREAS THE ECMWF KEPT AN UPPER RIDGE OVER THE AREA. THE CURRENT
FORECAST REFLECTS CLIMO...WHICH IS PROBABLY A GOOD WAY TO GO FOR
NOW.

&&

.AVIATION...A BROAD UPPER LEVEL TROUGH WILL SETTLE OVER THE PACIFIC
NORTHWEST TODAY AND TONIGHT WITH WEST TO NORTHWEST FLOW ALOFT. AT
THE SURFACE...ONSHORE FLOW WILL PREVAIL WITH HIGH PRESSURE OFFSHORE
AND LOWER PRESSURE INLAND. AIR MASS STABLE.

STRATUS AT THE COAST WILL SPREAD PARTIALLY INLAND THROUGH THE
CHEHALIS GAP THIS MORNING. A STRONGER PUSH IS EXPECTED TONIGHT WITH
MORE EXTENSIVE LOW CLOUDS FOR THE INTERIOR BY WEDNESDAY MORNING.

A PUGET SOUND CONVERGENCE ZONE WILL LIKELY FORM OVER KING OR
SOUTHERN SNOHOMISH COUNTY LATE THIS AFTERNOON...LINGER INTO THE
EVENING...THEN WEAKEN AFTER MIDNIGHT TONIGHT.

KSEA...COASTAL STRATUS WILL PROBABLY NOT MAKE IT TO THE TERMINAL
THIS MORNING. A CONVERGENCE ZONE COULD BRING SOME LOWER CEILINGS
LATE THIS AFTERNOON AND EVENING. LOW CLOUDS ARE EXPECTED LATER
TONIGHT. SOUTH TO SOUTHWEST WIND 3-6 KNOTS. WINDS COULD SWITCH TO
NORTH FOR A FEW HOURS THIS EVENING IF THE CONVERGENCE ZONE COMES
DOWN. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. A WEAK UPPER LEVEL
DISTURBANCES PASSING TO THE NORTH TODAY WILL CAUSE THE ONSHORE FLOW
TO INCREASE.

SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE NEXT
SEVERAL DAYS OVER THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE WINDS IN THE STRAIT SHOULD BE STRONGEST TONIGHT. THE CURRENT
FORECAST FOR TONIGHT FOR THE CENTRAL AND EAST EASTERN STRAIT IS FOR
HIGH END SMALL CRAFT ADVISORY STRENGTH BUT THERE IS A CHANCE IT
COULD HIT GALE. THERE SHOULD ALSO BE SOME SMALL CRAFT ADVISORY WINDS
OVER THE INLAND WATERS ADJACENT TO THE STRAIT THIS EVENING.

LASTLY...THERE WILL BE SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE
OUTER COASTAL WATERS AT TIMES FOR THE NEXT COUPLE OF DAYS. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE COASTAL WATERS FROM
     JAMES ISLAND TO CAPE SHOALWATER FROM 10 NM OUT TO 60 NM...
     THE CENTRAL/EASTERN STRAIT OF JUAN DE FUCA...THE NORTHERN
     INLAND WATERS AND ADMIRALTY INLET.

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 191030
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT TUE AUG 19 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL INFLUENCE THE WEATHER
PATTERN OVER THE AREA THROUGH THURSDAY. THIS WILL RESULT IN
SOMEWHAT UNSETTLED CONDITIONS. THE MAIN IMPACTS WILL BE COOLER
TEMPERATURES AND CLOUDIER SKIES.

&&

.SHORT TERM...
AN UPPER TROF WAS MOVING OVER THE REGION AT THIS TIME. THIS
SYSTEM WAS SLIGHTLY STRONGER THAN WHAT THE MODELS HAD ADVERTISED
AND HAS TRIGGERED ISOLATED TSTMS OVER THE NORTHERN PART OF THE CWA
EARLY THIS MORNING. THERE IS A POSSIBILITY THAT THIS ACTIVITY
MIGHT BECOME A LITTLE MORE WIDESPREAD DURING THE NEXT FEW HOURS...
THUS WILL KEEP AN EYE ON IT. IN THE MEANTIME...THE RISK OF TSTMS
HAS BEEN CONFINED TO THE NORTHERN ZONES FOR NOW.

WESTERN WA WILL REMAIN UNDER THE INFLUENCE OF AN UPPER TROF DURING
THIS PERIOD FOR SOMEWHAT UNSETTLED CONDITIONS. THE MAIN IMPACTS
WILL BE COOLER TEMPS AND MORE CLOUD COVER. HOWEVER THERE WILL BE A
CHANCE OF PRECIP OVER PARTS OF THE CWA EACH DAY.

THE SURFACE ONSHORE PRESSURE GRADIENT WILL TIGHTEN THIS AFTERNOON...
LEADING TO THE DEVELOPMENT OF A PUGET SOUND CONVERGENCE ZONE
/PSCZ/ LATER THIS AFTERNOON. THE PSCZ SHOULD PERSIST OVERNIGHT.
THE NAM AND WRF-GFS DIFFERED ON THE EXACT PLACEMENT OF THE
PSCZ...SO BROAD-BRUSHED THE FORECAST TO INDICATE THAT THE PSCZ
WILL AFFECT THE NORTHERN AND CENTRAL PUGET SOUND REGION. LATER
SHIFTS CAN FINE-TUNE THE FORECAST IF NEEDED. THE ONSHORE FLOW WILL
TIGHTEN ON THU AFTER RELAXING SOME ON WED...RESULTING IN THE
REDEVELOPMENT OF A PSCZ.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT VERY HIGH DUE TO DISAGREEMENT IN
THE MEDIUM RANGE SOLUTIONS. FOR EXAMPLE...THE GFS HAD THE REGION
MORE UNDER THE INFLUENCE OF AN UPPER TROF LATE IN THE PERIOD
WHEREAS THE ECMWF KEPT AN UPPER RIDGE OVER THE AREA. THE CURRENT
FORECAST REFLECTS CLIMO...WHICH IS PROBABLY A GOOD WAY TO GO FOR
NOW.

&&

.AVIATION...A BROAD UPPER LEVEL TROUGH WILL SETTLE OVER THE PACIFIC
NORTHWEST TODAY AND TONIGHT WITH WEST TO NORTHWEST FLOW ALOFT. AT
THE SURFACE...ONSHORE FLOW WILL PREVAIL WITH HIGH PRESSURE OFFSHORE
AND LOWER PRESSURE INLAND. AIR MASS STABLE.

STRATUS AT THE COAST WILL SPREAD PARTIALLY INLAND THROUGH THE
CHEHALIS GAP THIS MORNING. A STRONGER PUSH IS EXPECTED TONIGHT WITH
MORE EXTENSIVE LOW CLOUDS FOR THE INTERIOR BY WEDNESDAY MORNING.

A PUGET SOUND CONVERGENCE ZONE WILL LIKELY FORM OVER KING OR
SOUTHERN SNOHOMISH COUNTY LATE THIS AFTERNOON...LINGER INTO THE
EVENING...THEN WEAKEN AFTER MIDNIGHT TONIGHT.

KSEA...COASTAL STRATUS WILL PROBABLY NOT MAKE IT TO THE TERMINAL
THIS MORNING. A CONVERGENCE ZONE COULD BRING SOME LOWER CEILINGS
LATE THIS AFTERNOON AND EVENING. LOW CLOUDS ARE EXPECTED LATER
TONIGHT. SOUTH TO SOUTHWEST WIND 3-6 KNOTS. WINDS COULD SWITCH TO
NORTH FOR A FEW HOURS THIS EVENING IF THE CONVERGENCE ZONE COMES
DOWN. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. A WEAK UPPER LEVEL
DISTURBANCES PASSING TO THE NORTH TODAY WILL CAUSE THE ONSHORE FLOW
TO INCREASE.

SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE NEXT
SEVERAL DAYS OVER THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE WINDS IN THE STRAIT SHOULD BE STRONGEST TONIGHT. THE CURRENT
FORECAST FOR TONIGHT FOR THE CENTRAL AND EAST EASTERN STRAIT IS FOR
HIGH END SMALL CRAFT ADVISORY STRENGTH BUT THERE IS A CHANCE IT
COULD HIT GALE. THERE SHOULD ALSO BE SOME SMALL CRAFT ADVISORY WINDS
OVER THE INLAND WATERS ADJACENT TO THE STRAIT THIS EVENING.

LASTLY...THERE WILL BE SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE
OUTER COASTAL WATERS AT TIMES FOR THE NEXT COUPLE OF DAYS. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE COASTAL WATERS FROM
     JAMES ISLAND TO CAPE SHOALWATER FROM 10 NM OUT TO 60 NM...
     THE CENTRAL/EASTERN STRAIT OF JUAN DE FUCA...THE NORTHERN
     INLAND WATERS AND ADMIRALTY INLET.

&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






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