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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KAKQ 172000
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
400 PM EDT MON JUN 17 2013

.SYNOPSIS...
-- Changed Discussion --
A WEAK FRONTAL BOUNDARY REMAINS TO THE NORTH OF THE REGION
TONIGHT. THIS FRONT WILL MOVE SOUTHWARD THROUGH THE LOCAL AREA ON
TUESDAY...THEN WASHES OUT OVER THE CAROLINAS ON WEDNESDAY.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --
LATEST WATER VAPOR IMAGERY CONTINUES TO SHOW BROAD CYCLONIC FLOW
OVER THE CNTRL AND ERN CONUS. SEVERAL WEAK VORTICITY MAXIMA WILL
CONTINUE TO TRAVERSE THE FLOW REGIME...WITH THE STRONGEST
SHORTWAVE DIVING DOWN THE BACK SIDE OF THE BROAD UPPER TROUGH OVER
THE NRN PLAINS. OVER THE LOCAL AREA...SHORTWAVE OBSERVED ON WATER
VAPOR CURRENTLY CROSSING ERN VA. SHORTWAVE AND ABUNDANT MOISTURE
(BLENDED TOTAL PRECIP WATERS ~1.8 INCHES)...AS WELL AS LEE SIDE
TROUGHING...HAVE RESULTED IN ISOLATED/SCATTERED
SHOWERS/THUNDERSTORMS OVER THE REGION THIS AFTERNOON. THE MOST
NOTABLE IS CURRENTLY OVER SERN VA/NE NC. BRIEF HEAVY RAINFALL AND
STRONG WINDS UP TO 45 MPH (THANKS TO STEEP LOW LEVEL LAPSE RATES)
HAVE BEEN OBSERVED. HRRR HANDLES THIS AREA OF PRECIP
WELL...PUSHING IT OFFSHORE BY 6PM EDT. ADDITIONAL
ISOLATED/SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO
DEVELOP OVER WRN VA AND THE ERN VA PIEDMONT THROUGH THE
AFTERNOON...PROGRESSING SLOWLY E/SE THROUGH THE EARLY EVENING.
THETA-E ADVECTION AND TEMPS IN THE LOW/MID 80S AND DEWPOINTS IN
THE UPPER 60S WILL MAINTAIN A MARGINALLY UNSTABLE AIRMASS FOR
THUNDERSTORMS. WILL MAINTAIN SLIGHT CHANCE/CHANCE POPS NW AND
CHANCE POPS ACROSS THE SE. GENERALLY PARTLY CLOUDY-MOSTLY CLOUDY
SKIES OVERNIGHT WILL RESULT IN MILD OVERNIGHT TEMPS...GENERALLY IN
THE UPPER 60S INLAND TO LOW 70S ALONG THE COAST.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
-- Changed Discussion --
UPPER LOW WILL CONTINUE TO DIG OVER ERN CANADA TONIGHT/TUES
MORNING...DEEPENING THE UPPER TROUGH OVER THE ERN CONUS. A MORE
POTENT SHORTWAVE (CURRENTLY OVER S CNTRL CANADA) WILL DIVE DOWN
THE BACKSIDE OF THE UPPER TROUGH...LOCATING OVER THE GREAT LAKES
REGION TUES AFTERNOON. ANOTHER SHORTWAVE WILL TRAVERSE THE TN
VALLEY...LIFTING OVER THE MID ATLANTIC LATE TUESDAY. THE
AMPLIFYING UPPER PATTERN WILL RESULT IN INCREASING SWLY FLOW (H85
WINDS INCREASING TO 20-30 KT) AND GOOD MOISTURE TRANSPORT INTO THE
REGION (ESPECIALLY SE VA/NE NC) TUES-WEDS. PRECIP WATER VALUES
PROGGED TO APPROACH 2 INCHES (NEARLY +2 STD DEV) BY TUES
AFTERNOON. MEANWHILE...HEIGHT FALLS WILL RESULT IN THE DEVELOPMENT
OF A SFC LOW OVER THE LOWER MS VALLEY TONIGHT. SFC LOW WILL
PROGRESS EWD TUESDAY...REACHING NRN NC LATE IN THE DAY TUESDAY.
AFOREMENTIONED SHORTWAVE AND DIVERGENCE ALOFT (THANKS TO RRQ OF
DEPARTING 100+ KT UPPER JET) WILL PROVIDE FORCING FOR ASCENT OVER
THE REGION IN ADVANCE OF THE APPROACHING SFC LOW. EXPECT SHOWERS
TO LIFT INTO THE REGION BEGINNING TUES MORNING...AND SPREADING EWD
DURING THE AFTERNOON. THETA-E ADVECTION AND TEMPS IN THE LOW/MID
80S AND DEWPOINTS IN THE UPPER 60S/LOW 70S WILL MAINTAIN A
MARGINALLY UNSTABLE AIRMASS FOR AFTERNOON AND EVENING
THUNDERSTORMS...ESPECIALLY OVER ERN VA/SERN VA/NE NC. STEEP LOW
LEVEL LAPSE RATES AS WELL AS DECENT MID LEVEL LAPSE RATES MAY
RESULT IN STRONG WINDS UNDER THE STRONGEST STORMS. HOWEVER...SHEAR
WILL REMAIN RATHER WEAK...SO ORGANIZED STRONG THUNDERSTORMS ARE
NOT ANTICIPATED. ABUNDANT MOISTURE AND DEEP LIFT WILL RESULT IN
THE POTENTIAL FOR HEAVY RAINFALL.

AS THE LOW CROSSES NRN NC TUESDAY NIGHT...THE FIRST SHORTWAVE
WILL LIFT OFF THE VA COAST AS THE SECOND SHORTWAVE CROSSES THE OH
VALLEY. HEIGHT FALLS AND FRONTOGENETIC FORCING AROUND THE NRN
PERIPHERY OF THE SFC LOW MAY ENHANCE RAINFALL OVER SRN VA TUES
NIGHT. HAVE OPTED TO INCREASE POPS TO LIKELY ACROSS THAT REGION.
SFC COLD FRONT WILL CROSS THE REGION EARLY WEDS MORNING...SETTLING
OVER THE CAROLINAS WED. WILL MAINTAIN HIGH CHANCE POPS OVER SRN
VA/NRN NC THROUGH EARLY WEDS AFTERNOON. THEREAFTER...HIGH PRESSURE
WILL USHER IN BEHIND THE DEPARTING LOW/SFC FRONT...SHUNTING THE
BEST MOISTURE OFFSHORE BY WEDS NIGHT. WILL KEEP LOW END CHANCE
POPS FOR SCATTERED SHOWERS WEDS AFTERNOON AS THE TROUGH REMAINS
ALONG THE COAST. DRY THURS AS HIGH PRESSURE BUILDS NORTH OF THE
REGION AND MOISTURE SOURCE PUSHES WELL OFFSHORE.

SLIGHTLY BELOW NORMAL TUESDAY (LOW/MID 80S) WILL COOL TO NEARLY
-1 STD DEV WED AND THURS (LOW 80S). LOWS WILL FALL INTO THE LOW
60S...POSSIBLY UPPER 50S SOME LOCALES BY THURS MORNING.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
A RATHER BENIGN PATTERN IS EXPECTED LATE THIS WEEK THROUGH THE
WEEKEND INTO EARLY NEXT WEEK AS HIGH PRESSURE SLOWLY DROPS S OFF THE
MID-ATLANTIC COAST. THERE IS VERY LITTLE POTENTIAL FOR
SHOWER/THUNDERSTORM DEVELOPMENT DUE TO A LACK OF LARGE SCALE FORCING
AND ANY SURFACE FOCUSING MECHANISMS. A GENERAL SHIFT OF THE
LOW-LEVEL FLOW FROM SE-SW WILL PRODUCE A STEADY WARMING TRENDS WITH
HIGHS RISING FROM THE LOW TO MID 80S FRIDAY...TO THE UPPER 80S TO
LOW 90S BY MONDAY. LOW TEMPERATURES SHOULD TREND UPWARD FROM 60-65
EARLY IN THE PERIOD TO THE UPPER 60S/LOW 70S LATE IN THE PERIOD.
-- End Changed Discussion --

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
A LINE OF SCATTERED SHOWERS AND THUNDERSTORMS WILL RE-DEVELOP ALONG
A WEAK TROUGH THIS AFTN FROM GENERALLY KSBY TO KRIC TO KRAH...AND
WILL MOVE EAST OF THIS LINE INTO MID-EVENING. CIGS AND VIS MAY LOWER
BRIEFLY INTO MVFR/IFR RANGES UNDER STRONGER STORM CORES...HOWEVER VFR
CONDITIONS SHOULD PREVAIL. SHOWER ACTIVITY IS EXPECTED TO DIMINISH
SHORTLY AFTER 18/0000Z DUE TO LOSS OF DAYTIME HEATING...WITH
LINGERING SHOWERS OVER NE NC AND FAR SE VA POSSIBLE OVERNIGHT. FOG
IS ALSO EXPECTED TO DEVELOP TWD DAYBREAK AT KRIC/KSBY/KPHF/KECG...
AND THEN DISSIPATE QUICKLY AFTER 18/1200-1300Z.

CONDITIONS REMAIN UNSETTLED ON TUE AS A MORE ORGANIZED AREA OF LOW
PRESSURE APPROACHES THE MID ATLANTIC REGION. THERE ARE SOME TIMING
DIFFERENCES AS TO WHEN THE LOW CROSSES THE AREA...HOWEVER ANOTHER
ROUND OF SHOWERS AND THUNDERSTORMS SHOULD BE ANTICIPATED DURING THE
AFTN AND EVENING HOURS. ONCE AGAIN...A BRIEF REDUCTION TO CIGS/VIS
SHOULD BE EXPECTED UNDER STRONGER STORM CORES.

&&

.MARINE...
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A DISSIPATING BOUNDARY IS PRESENTLY DROPPING ACROSS SE VA/NE NC THIS
AFTERNOON. ANY WIND SHIFT IS VERY LOCALIZED AT THIS TIME...WITH SW
FLOW RECOVERING N OF THE BOUNDARY...WHICH SHOULD CONTINUE OVERNIGHT
ACROSS THE MARINE AREA. A COLD FRONT IS SITUATED FROM THE EASTERN
GREAT LAKES THROUGH NEW ENGLAND AND THIS IS EXPECTED TO MOVE SOUTH
INTO PA TONIGHT AS LOW PRESSURE LIFTS ENE INTO THE TENNESSEE VALLEY.
NUMERICAL MODEL SOLUTIONS DIVERGE THROUGH THE DAY TUESDAY AS THE
19/12Z GFS LIFTS THE LOW ENE INTO W-CENTRAL NC WHILE THE 19/12Z NAM
LAGS THE LOW BACK OVER TN AT 00Z WEDNESDAY. THE 19/12Z ECMWF HAS
COME MORE INTO LINE WITH THE GFS IN TRACKING THE LOW ACROSS NC
TUESDAY NIGHT AND OFF THE COAST WEDNESDAY MORNING. IF THIS TIMING
VERIFIES THE WIND WOULD LIKELY SHIFT TO NNE FROM N-S LATE TUESDAY
NIGHT INTO WEDNESDAY MORNING AND REMAIN NNE/NE THROUGH THURSDAY HIGH
PRESSURE BUILDS OVER NEW ENGLAND AND LOW PRESSURE LINGERS OFF THE
COAST. SCA WIND SPEEDS ARE POSSIBLE FOR THE BAY/SOUND/RIVERS LATE
TUESDAY NIGHT INTO WEDNESDAY WHILE ONSHORE FLOW HAS THE POTENTIAL TO
BUILD SEAS TO 5 FT WEDNESDAY INTO WEDNESDAY NIGHT. NO SCA FLAGS AT
THIS POINT GIVEN THE UNCERTAINTY AND THAT THE EARLIEST COMMENCEMENT
OF SCA CONDITIONS WOULD LIKELY BE LATE 3RD PERIOD INTO 4TH PERIOD.
THE HIGH SLOWLY SINKS S OFF THE COAST LATE IN THE WEEK INTO NEXT
WEEKEND WITH THE WIND VEERING FROM NE-S AND REMAINING AOB 15KT.
-- End Changed Discussion --

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...JDM
NEAR TERM...SAM
SHORT TERM...SAM
LONG TERM...AJZ
AVIATION...BMD
MARINE...AJZ