-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 191452
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1052 AM EDT WED JUN 19 2013

.SYNOPSIS...
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A COLD FRONT WILL SLOWLY PROGRESS THROUGH THE REGION LATE TODAY
AND TONIGHT. THE FRONT WILL STALL JUST SOUTH OF THE AREA THURSDAY
AND LINGER THROUGH SATURDAY...AS HIGH PRESSURE BUILDS FROM THE
NORTH. THE CENTER OF HIGH PRESSURE WILL THEN SLIP INTO THE
ATLANTIC EARLY NEXT WEEK.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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LATE THIS MORNING...RADAR IMAGERY SHOWS THE FIRST SHOWERS STARTING
TO DEVELOP ACROSS THE REGION. OVERALL...NO NOTEWORTHY CHANGES TO
THE PREVIOUS FORECAST THINKING AS THE FORECAST AREA STILL LOOKS TO
BE IN A GOOD SET UP FOR THE DEVELOPMENT OF NUMEROUS SHOWERS AND
THUNDERSTORMS. MORNING UPPER AIR ANALYSIS SHOWS A WELL DEFINED 70+
KNOT 300 MB JET OVER THE NORTHEAST THAT EXTENDS BACK TO THE
SOUTHWEST ACROSS MUCH OF EASTERN VIRGINIA. THIS PLACES THE AREA IN
THE RIGHT ENTRANCE REGION WHICH SHOULD PROVIDE AMPLE UPPER LEVEL
SUPPORT IN THE FORM OF DIVERGENCE ALOFT. AT 500 MB A BROAD TROUGH
AXIS REMAINS TO THE WEST WITH SHORTWAVE ENERGY PROGGED TO APPROACH
THROUGH THE AFTERNOON. FINALLY...AT THE SURFACE A WEST-SOUTHWEST
TO EAST-NORTHEAST COLD FRONT IS DRAPED JUST NORTH OF THE FORECAST
AREA AND IS LOOSELY DEFINED ALONG THE NORTHERN EXTENT OF THE 70
DEGREE DEWPOINT GRADIENT. THIS FRONT SHOWS UP PRETTY WELL ON
VISIBLE SATELLITE IMAGERY AS MARKED BY MORE CONVECTIVE LOOKING
CLOUDS EXTENDING FROM EASTERN NORTH CAROLINA TO LOUISIANA. ALL
THESE FACTORS WILL COME TOGETHER AND RESULT IN NUMEROUS COVERAGE
OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...WHICH
SHOULD START DEVELOPING QUICKLY AROUND NOON. GIVEN THE REALLY HIGH
LOW LEVEL THICKNESSES AND THE FACT THAT TEMPS STARTED OFF THE DAY
IN THE UPPER 70S TO NEAR 80...IT WILL NOT TAKE LONG FOR TEMPS TO
REACH THEIR HIGHS IN THE UPPER 80S. THE DEGREE OF LOW AND MID
LEVEL FLOW IS AROUND 20-25 KNOTS FROM THE WEST AND
SOUTHWEST...WHICH WILL KEEP STORMS MOVING ROUGHLY PARALLEL TO THE
ORIENTATION OF THE FRONT. PWATS ARE QUITE HIGH...IN EXCESS OF 2
INCHES. GIVEN THE AMOUNT OF AMBIENT MOISTURE AND LACK OF MID LEVEL
DRY AIR...THE OVERALL SEVERE THREAT IS PRETTY LOW. HOWEVER...WE
CAN/T RULE OUT A WET MICROBURST WITH BOUNDARY INTERACTIONS. THE
MAIN THREAT CONTINUES TO BE LOCALLY EXCESSIVE RAINFALL DUE TO THE
HIGH PWATS...OVERALL COVERAGE OF STORMS...AND WET ANTECEDENT
CONDITIONS. WILL MAINTAIN THE CURRENT HWO WORDING.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
THE FRONT SHOULD CONTINUE TO SAG THROUGH THE FORECAST AREA TONIGHT
WITH WEAK WIND SHIFTS IN A LIGHT PRES FIELD. DEEP CONVECTION SHOULD
DIMINISH THIS EVENING BUT MAY LINGER A BIT LONGER IS SE GEORGIA WHERE
A WEAK SURFACE WAVE IS FORECAST TO MOVE OFF THE COAST AFTER MIDNIGHT.
WE LOWERED POPS OVER INLAND AREAS OF SOUTH CAROLINA TO SLIGHT CHANCE
LATER TONIGHT AND MAINTAINED A CHANCE POPS ALL NIGHT ALONG COASTAL
SE GEORGIA.

THURSDAY AND FRIDAY...THE DESCENDING FRONT WILL STALL NEAR THE
FLORIDA/GEORGIA BORDER LATE IN THE WEEK...AS IT BECOMES PARALLEL TO
WEAK FLOW ALOFT. ALTHOUGH SURFACE HIGH PRESSURE WILL STEADILY BUILD
FROM THE NORTH AT THE SAME TIME...WAVES OF LOW PRESSURE DEVELOPING
ALONG THE MEANDERING FRONT WILL LIKELY KEEP IT IN PLACE. THE SURFACE
PATTERN WILL EVENTUALLY TAKE THE SHAPE OF AN INLAND WEDGE AND
COASTAL TROUGH TYPE SCENARIO. AS A RESULT...THE FAVORED AREAS FOR
DAYTIME CONVECTIVE COVERAGE WILL BE ALONG THE COAST AND ACROSS
SOUTHEAST GEORGIA COUNTIES CLOSEST TO THE LINGERING BOUNDARY AND
COASTAL TROUGH. PRECIPITATION POTENTIAL WILL THEN SHIFT INTO THE
NEARSHORE WATERS EACH NIGHT...WHERE BEST CONVERGENCE AND INSTABILITY
WILL BE FOUND AFTER SUNSET. THERE REMAINS SOME UNCERTAINTY REGARDING
DETAILS IN THUNDERSTORM CHANCES BOTH THURSDAY AND FRIDAY...AS
COVERAGE WILL BE HIGHLY DEPENDENT ON THE EXACT LOCATION/TRACK OF
SURFACE WAVES AND THEIR ABILITY TO PULL THE FRONT CLOSER/FARTHER
FROM THE FORECAST AREA. THUS PREFER TO CAP POPS IN THE 30 PERCENT
RANGE THROUGH FRIDAY...HIGHEST SOUTH AND EAST. HIGH TEMPERATURES
COULD TREND A DEGREE OR TWO BELOW SEASONAL NORMALS CONSIDERING
NORTHEAST FLOW IN THE INLAND WEDGE PATTERN. EXPECT TEMPERATURES TO
PEAK IN THE MID TO UPPER 80S AWAY FROM THE LOCALLY COOLER COASTLINE.

SATURDAY...THE GFS AND ECMWF SOLUTIONS DIVERGE FURTHER INTO THE
WEEKEND REGARDING THE POTENTIAL FOR THE COASTAL TROUGH TO SHIFT
INLAND AND SUPPORT HIGHER RAIN CHANCES ON SATURDAY. THE MORE
AGGRESSIVE GFS SUGGESTS BETTER SHOWER/THUNDERSTORM COVERAGE...A
RESULT OF THE TROUGH MOVING OVER LAND AREAS AS WEAK SHORTWAVE
ENERGY TRACKS NORTH THROUGH THE FORECAST AREA. WILL COMPROMISE
BETWEEN THE TWO SOLUTIONS BY CONTINUING TO CAP RAIN POTENTIAL
AROUND 30 PERCENT...WHILE INCLUDING THE MAJORITY OF THE FORECAST
AREA WITHIN THESE SOLID CHANCES POPS. A MORE EAST/SOUTHEAST FLOW
WITHIN THIS TRANSITIONING SURFACE PATTERN WILL ALLOW TEMPERATURES
TO GENERALLY WARM A DEGREE OR TWO...REACHING THE UPPER 80S INLAND.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
THE INLAND WEDGE/COASTAL TROUGH PATTERN WILL TRANSITION ON
SUNDAY...AS THE TROUGH DAMPENS AND/OR MOVES INLAND WHILE THE
CENTER OF HIGH PRESSURE SETTLES OVER THE ATLANTIC. THE FORECAST
AREA WILL THEN REMAIN ALONG THE WESTERN PERIPHERY OF THE ATLANTIC
HIGH PRESSURE INTO EARLY NEXT WEEK...WITH A WEAK INLAND SURFACE
TROUGH DEVELOPING TOWARD THE MID WEEK PERIOD. HAVE INDICATED A
MORE SEASONAL CONVECTIVE SCENARIO....WITH THUNDERSTORMS GENERALLY
DEVELOPING ALONG AND INLAND OF THE SEABREEZE EACH
AFTERNOON...DIMINISHING IN COVERAGE AND/OR RE-DEVELOPING OVER THE
WATERS EACH NIGHT. 500 MB HEIGHTS PEAK EARLY NEXT WEEK...EVIDENCE
THAT THE INITIALLY WEAK UPPER LEVEL PATTERN WILL TRANSITION INTO
BROAD RIDGING ALOFT. AS A RESULT...EXPECT A GRADUAL WARMING TREND
THROUGH THE PERIOD. HIGH TEMPERATURES AROUND 90 DEGREES AWAY FROM
THE COASTLINE SUNDAY WILL INCREASE INTO THE LOWER 90S MONDAY
THROUGH WEDNESDAY.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
MAIN ISSUES TODAY ARE TIMING CONVECTION INITIATION WHICH AT THIS
POINT SEEMS PRETTY CERTAIN ALONG THE COASTAL CORRIDOR TODAY. THIS
MORNING/S KCHS SOUNDING SHOWED JUST ENOUGH CAP TO HOLD UNTIL
MIDDAY AND THIS SEEMS REASONABLE GIVEN LATEST MODEL TIMING TRENDS.
WE HAVE TEMPO THUNDER AT BOTH TERMINALS THIS AFTERNOON AND LATER
UPDATES WILL ZERO IN ON VSBYS AND POTENTIAL FOR +RA. TONIGHT THERE
COULD BE MORE SHOWERS IN THE AREA AND ISOLATED STORMS IN SE
GEORGIA. IT LOOKS LIKE MVFR OR LOWER CIGS WILL FOLLOW A FROPA
THROUGH THE AREA TONIGHT. LOWER CLOUDS REACHING KSAV A BIT LATER
AND HAVE OPTED TO HOLD OFF MENTIONS THERE FOR NOW.

EXTENDED AVIATION...MVFR CIGS/VSBYS POSSIBLE THROUGH THE PERIOD
WITHIN ISOLATED TO SCATTERED SHOWERS AND/OR THUNDERSTORMS.

&&

.MARINE...
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TODAY...SEAS WILL BEGIN A SLOW DIMINISHING TREND AS WIND WAVE
SUBSIDES. THE MAIN THREAT TO MARINERS LATER TODAY MAY BE STRONG
TSTMS ADVANCING OFF THE COAST...PARTICULARLY IN SOUTH CAROLINA.
THESE STORMS COULD PRODUCE LOCALLY LOW VSBYS IN HEAVY RAIN AND
DEADLY LIGHTNING STRIKES.

THURSDAY THROUGH SUNDAY...NORTHEAST FLOW WILL PREVAIL THURSDAY AND
FRIDAY...AS THE MARINE ZONES BECOME LOCATED BETWEEN INLAND HIGH
PRESSURE AND A DEVELOPING COASTAL TROUGH. WIND SPEEDS COULD INCREASE
TO 15 TO 20 KT AT TIMES WITHIN A MODERATE PRESSURE GRADIENT...YET
CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA. THE SURFACE HIGH WILL SLIP INTO THE ATLANTIC OVER THE
WEEKEND...WHILE THE COASTAL TROUGH EITHER DAMPENS OR MOVES ONSHORE.
WINDS WILL DIMINISH SLIGHTLY AND VEER MORE EAST/SOUTHEAST SATURDAY
AND SUNDAY ACCORDINGLY.
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&&

.CHS WATCHES/WARNINGS/ADVISORIES...
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GA...NONE.
SC...NONE.
MARINE...NONE.
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&&

$$

SYNOPSIS...
NEAR TERM...BSH
SHORT TERM...WMS
LONG TERM...WMS
AVIATION...
MARINE...WMS