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000
FXUS61 KAKQ 181153
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
753 AM EDT SAT MAY 18 2013

.SYNOPSIS...
A WEAK FRONT REMAINS NEARLY STATIONARY OVER SOUTHWEST VIRGINIA AND NORTH
CAROLINA THROUGH SATURDAY NIGHT. THE FRONT WILL SLOWLY LIFT BACK TO THE
NORTH LATER SUNDAY INTO MONDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
QUASI-STATIONARY FRONT EXTENDS FROM THE MIDWEST INTO THE
OH VALLEY...BENDING AROUND THE LEE SIDE OF THE APPALACHIANS INTO N
CNTRL NC. SHOWERS/THUNDERSTORMS DEVELOPED ALONG THE BOUNDARY LATE
LAST NIGHT...PROGRESSING SLOWLY EWD. WHILE LOW LEVELS REMAINED
FAIRLY DRY DUE TO HIGH PRESSURE JUST OFF THE COAST...PRECIP WATER
VALUES INCREASED TO NEARLY 1.5 INCHES (+1 STD DEV) HELPING
OVERCOME THE DRY LOW LEVELS. IN ADDITION...UPPER LEVEL
DIVERGENCE...MARGINAL ELEVATED CAPE (SHOWALTER INDEX AROUND -4)
AND OMEGA ALOFT HAVE MAINTAINED THE SHOWERS/THUNDERSTORMS THIS
EVENING. EVEN WITH TEMPERATURES AT THE SFC IN THE LOW/MID 60S.
RAINFALL AMOUNTS HAVE GENERALLY RANGED FROM A FEW TENTHS OF AN
INCH UP TO AN INCH AND A HALF. BASED ON OMEGA FIELDS...EXPECT
SHOWERS TO KEEP SLOWLY PROGRESSING NEWD ACROSS THE FA THROUGH
EARLY MORNING...BEFORE COMING TO AN END MID MORNING.

FOR THIS AFTERNOON...UPPER LOW WILL LOCATE OVER THE TN VALLEY. LOW
LEVEL SW FLOW WILL INCREASE BETWEEN LOW PRESSURE OVER THE TN
VALLEY AND HIGH PRESSURE OFF THE SE COAST. RESULT WILL BE
CONTINUED ADVECTION OF ANOMALOUS PRECIP WATER VALUES INTO THE MID
ATLANTIC. ADDITIONAL WEAK IMPULSES WILL ROTATE AROUND THE SE
PERIPHERY OF THE UPPER LOW...EJECTING NEWD INTO THE MID ATLANTIC.
COMBINATION OF WEAK IMPULSES...AFTERNOON HEATING...STALLED
BOUNDARY AND DEEP MOISTURE WILL RESULT IN ADDITIONAL AFTERNOON
AND EVENING SHOWERS AND THUNDERSTORMS. BEST COVERAGE EXPECTED TO
BE OVER THE PIEDMONT THIS AFTERNOON AND THEN PROGRESSING EWD LATE
AFTERNOON INTO THE EVENING. BEST COVERAGE FOR THUNDERSTORMS
EXPECTED TO BE OVER SRN VA...CLOSEST TO BEST THETA E ADVECTION AND
WARMEST AFTERNOON TEMPS (BEST INSTABILITY). QPF AMOUNTS EXPECTED
TO RANGE FROM A FEW TENTHS OVER THE ERN SHORE TO JUST OVER HALF AN
INCH OVER THE PIEDMONT. HOWEVER...LOCALLY HIGHER AMOUNTS EXPECTED
IN HEAVIER SHOWERS/THUNDERSTORMS. ITS BEEN NEARLY A WEEK AND A
HALF SINCE THE LAST WIDESPREAD RAINFALL EVENT SO FFG IS FAIRLY
HIGH...EVEN WITH LAST NIGHTS RAINFALL. THUS...NO PLANS FOR A FFW
THIS AFTERNOON.

MOSTLY CLOUDY SKIES EXPECTED TODAY...BUT CANT RULE OUT A FEW
BREAKS HIS MORNING. NEAR SEASONABLE NORMAL TEMPS TODAY (LOW 70S
NW TO LOW 80S SE). COOLER ALONG THE IMMEDIATE COAST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
WET WEATHER WILL CONTINUE THROUGH THE SHORT TERM AS THE STALLED
FRONT BEGINS TO LIFT NWD AS A WARM FRONT SUN AND MON. MAIN
FORECAST CHALLENGES WILL BE TIED TO PRECIP COVERAGE AND QPF.

WEAKENING UPPER LOW EXPECTED TO MEANDER IN THE VICINITY OF THE
CUMBERLAND PLATEAU SUNDAY. POTENT TROUGH TRAVERSING THE PLAINS SUN
WILL AMPLIFY THE RIDGE OVER THE ERN CONUS...HELPING LIFT THE
STALLED BOUNDARY NWD AS A WARM FRONT LATE SAT NIGHT AND SUN. AT
THE SAME TIME...INCREASING SW FLOW (H85 WINDS 20-30 KT) WILL
ADVECT NEARLY +2 STD DEV PRECIP WATER VALUES INTO THE REGION.
ADDITIONAL WEAK IMPULSES WILL EJECT EWD FROM THE UPPER
LOW...COMBINING WITH ABUNDANT MOISTURE FOR ADDITIONAL SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON AND EVENING SUN. THETA-E
ADVECTION AND TEMPS IN THE UPPER 70S/LOW 80S WILL MAINTAIN A
MARGINALLY UNSTABLE AIRMASS (500-1000 J/KG CAPE) OVER SRN
VA...RESULTING IN A GOOD CHANCE FOR AFTERNOON THUNDERSTORMS.
COMBINATION OF CONVECTION AND DEEP MOISTURE COULD LEAD TO A THREAT
OF FLASH FLOODING...ESPECIALLY IF WIDESPREAD RAINFALL OCCURS THIS
AFTERNOON (SAT AFTERNOON).

MIDWEST TROUGH WILL KICK WHATS LEFT OF THE UPPER LOW EWD MONDAY OVER
THE APPALACHIANS...LOCATING OVER THE FA MONDAY. MEANWHILE...THE
WARM FRONT WILL LIFT NORTH OF THE FA. ABUNDANT MOISTURE AND GOOD
DYNAMICS WILL RESULT IN ADDITIONAL SHOWERS AND THUNDERSTORMS.
WARMER TEMPS WILL RESULT IN GREATER INSTABILITY...WITH ADDITIONAL
ROUNDS OF HEAVY RAIN POSSIBLE.

72 HR QPF TOTALS FORECAST TO RANGE FROM OVER 2 INCHES ACROSS THE
PIEDMONT TO JUST OVER HALF AN INCH FOR THE MD ERN SHORE. SE VA/NE
NC COULD SEE TOTALS UPWARDS OF ONE INCH. IN ADDITION TO THE FLASH
FLOOD THREAT...SEVERAL ROUNDS OF RAINFALL OVER THE REGION MAY LEAD
TO RIVER FLOODING CONCERNS.

HI TEMPS WILL GENERALLY RANGE FROM THE LOW/MID 70S NORTH TO LOW
80S SOUTH (NEAR SEASONABLE NORMS) SUN. COOLER ALONG THE IMMEDIATE
COAST. WARMER MONDAY WITH HIGHS GENERALLY IN THE LOW 80S.
AGAIN...COOLER ALONG THE IMMEDIATE COAST.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
LONG TERM PERIOD WILL FEATURE PERIODS OF UNSETTLED WX AND ABOVE
NORMAL HI/LO TEMPS ON AVG. FOR TUE...MID-LVL S/W TROF PUSHES
OFFSHORE ERLY IN THE DAY WITH A CHC FOR SHWRS MAINLY OVER SE AREAS.
DECREASING CLDS DURING THE AFTN WITH TEMPS CLIMBING INTO THE MID
80S. S/SW FLOW CONTINUES WED AND THU LEADING TO CONTINUED WARM TEMPS
(HIGHS IN THE MID TO UPR 80S) AND A CHC FOR MAINLY DIURNAL SHWRS/TSTMS
WITH WEAK SFC TROFS OVER THE AREA. BEST CHC FOR RAIN WILL BE FRI AS
A COLD FRNT ADVANCES TOWARDS THE AREA. WILL CAP POPS AT 40% FOR
NOW WITH HOW FAR OUT IN TIME THIS IS ALBEIT FAIRLY GOOD
CONSISTENCY AMONGST MODEL GUIDANCE WITH THE FRNTAL TIMING. HI
TEMPS ONLY IN THE UPR 70S TO NEAR 80 FRI DUE TO PRECIP AND
WIDESPREAD CLOUDINESS.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
THE AREA OF SHOWERS WHICH MOVED ACROSS CENTRAL VA...TIDEWATER AND
NC NC ARE PUSHING OFFSHORE. ONLY A FEW STRAY SHOWERS ARE EXPECTED
THROUGH THE MORNING HOURS AND VSBYS SHOULD REMAIN 5SM OR BETTER
IN ANY LIGHT SHOWERS. CEILING THIS MORNING WILL BE A MIX OF MVFR
AND VFR. BY MID TO LATE MORNING EXPECT MOST LOCATION TO IMPROVE TO
VFR WITH CEILINGS AOB 3KFT. THIS MAY BE SHORT LIVED FOR A PERIOD
LATE THIS MORNING AND EARLY AFTERNOON AS A A WEAK WARM FRONT WILL
SLOWLY LIFT SW- NE ACROSS THE REGION TODAY INTO TONIGHT. ADDITIONAL
SCT SHRA/TSRA WILL DEVELOP THIS AFTERNOON WITH INCREASING SELY
FLOW. SHOWERS WILL INCREASE IN COVERAGE THROUGH THE AFTERNOON AND EVENING.
VFR CONDITIONS SHOULD GENERALLY PREVAIL LATE THIS MORNING INTO
EARLY AFTERNOON WITH THE EXCEPTION OF REDUCED VSBY IN MODERATE
SHOWERS WHICH START TO DEVELOP AROUND 17-19Z. STATISTICAL
GUIDANCE ALONG WITH FORECAST SOUNDINGS SUGGEST THE POTENTIAL FOR
IFR STRATUS LATER TONIGHT...ESPECIALLY FOR RIC/PHF/SBY. THE
POTENTIAL FOR SHRA/TSRA CONTINUES SUNDAY INTO EARLY NEXT WEEK AS
MOIST SE TO SW FLOW CONTINUES TO AFFECT THE REGION.

&&

.MARINE...
A WEAK FRONTAL BOUNDARY ACROSS THE REGION IS BEGINNING TO SLOWLY
LIFT NE AS A WARM FRONT EARLY THIS MORNING. THIS SLOW PROCESS IS
EXPECTED TO CONTINUE THROUGH THE DAY INTO TONIGHT. MEANWHILE...HIGH
PRESSURE WILL REMAIN ANCHORED OFF CAPE COD AS TROUGH OF LOW PRESSURE
APPROACHES FROM THE WEST. THIS WILL RESULT IN A TIGHTENING PRESSURE
GRADIENT ACROSS THE REGION LATER THIS AFTERNOON INTO TONIGHT. A
10-15KT ESE WIND IS EXPECTED TO APPROACH 20KT LATER THIS AFTERNOON
THROUGH THIS EVENING FOR THE BAY/LOWER JAMES. SIMILAR SPEEDS ARE
EXPECTED FOR THE OCEAN. HOWEVER...THE ONSHORE COMPONENT TO THE WIND
SHOULD ALLOW SEAS TO BUILD TO 5FT LATER TODAY INTO TONIGHT...MAINLY
N OF CAPE CHARLES. HENCE SCA FLAGS HAVE BEEN RAISED FOR THE
AFOREMENTIONED AREAS BEGINNING AT 20Z/4PM THIS AFTERNOON AND
CONTINUING THROUGH 04Z/12AM FOR THE BAY/LOWER JAMES AND 10Z/6AM FOR
THE OCEAN. THE WARM FRONT FINALLY CLEARS THE REGION LATER SUNDAY
AFTN/EVE ALLOWING FOR THE WIND TO SHIFT TO S AND EVENTUALLY SW.
SPEEDS SHOULD GENERALLY REMAIN AOB 15KT. HOWEVER...A BRIEF INCREASE
IS POSSIBLE MONDAY AFTN/EVE AS LOW PRESSURE TRACKS N OF THE REGION.
SEAS SHOULD LARGELY BE 3-4FT WITH ~2FT WAVES.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO MIDNIGHT EDT
     TONIGHT FOR ANZ630>632-634-638.
     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EDT
     SUNDAY FOR ANZ650-652-654.

&&

$$
SYNOPSIS...LKB
NEAR TERM...SAM
SHORT TERM...SAM
LONG TERM...MAS
AVIATION...AJZ/JAO
MARINE...AJZ