Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 140234 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1034 PM EDT SAT SEP 13 2014 .SYNOPSIS... UNSETTLED WEATHER WILL CONTINUE AS A COLD FRONT MOVES ACROSS THE AREA TONIGHT AND STALLS TO OUR SOUTH. ANOTHER COLD FRONT WILL MOVE ACROSS THE AREA ON TUESDAY PAVING THE WAY FOR SOME LATE WEEK COOLER HIGH PRESSURE. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1030 PM SATURDAY...THE FOCUS FOR HEAVY RAINFALL APPEARS TO SHIFTING INTO NORTHEASTERN SOUTH CAROLINA WHERE THE CONVERGENCE OF REASONABLY LARGE ELEVATED INSTABILITY (CAPE OF 1000-2000 J/KG) AND THE APPROACHING SURFACE COLD FRONT WILL CREATE THE LARGEST POTENTIAL FOR OVERNIGHT FLOODING. WITH CONVECTIVE OUTFLOW BOUNDARIES DOTTING THE REGION THE ACTUAL COLD FRONT IS NOT EASY TO FIND...BUT APPEARS TO BE PUSHING SOUTH ACROSS FAYETTEVILLE AT THE CURRENT TIME. THE FLOOD THREAT IS DIMINISHING ACROSS SOUTHEASTERN NORTH CAROLINA BUT AFTER COLLABORATION WITH NWS OFFICES IN RALEIGH AND NEWPORT/MOREHEAD CITY WE HAVE DECIDED TO LEAVE THE WATCH UP FOR THE ENTIRE REGION FOR NOW. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... A COLD FRONT EXTENDING FROM NORTHEASTERN NORTH CAROLINA THROUGH RALEIGH AND CHARLOTTE WILL DROP SOUTHWARD OVERNIGHT...PUSHING THROUGH ALL OF SE NORTH CAROLINA AND A PORTION OF THE GRAND STRAND AND PEE DEE REGION OF SOUTH CAROLINA BY DAYBREAK SUNDAY. MODELS DISPLAY A VARIETY OF POSITIONS FOR THIS FRONT AT 12Z SUNDAY WITH AN AVERAGE POSITION ACROSS WILLIAMSBURG AND GEORGETOWN COUNTIES IN SC. AHEAD OF THE FRONT THE AIRMASS IS VERY HUMID WITH DEWPOINTS 72-77 AND PRECIPITABLE WATER VALUES 2.1 TO 2.25 INCHES. SHOWERS AND T-STORMS THIS AFTERNOON HAVE DROPPED A RADAR-ESTIMATED 3 INCHES IN SPOTS...ALTHOUGH A WIDESPREAD 0.10 TO 0.50 INCH HAS BEEN MORE COMMON. INSTABILITY IS BECOMING MAINLY ELEVATED WITH CAPE 1000-1500 J/KG. ONE INGREDIENT MISSING FOR THIS BECOMING A MORE WIDESPREAD HEAVY RAIN/FLOODING EVENT IS STORM-RELATIVE INFLOW: 925 AND 850 MB WINDS ARE LESS THAN 10 KNOTS. AT 300 MB NOT ONLY CAN I NOT FIND A FAVORABLY POSITIONED JET STREAK ANYWHERE NEARBY...THERE`S ACTUALLY A RIDGE AXIS OVER THE AREA. WE ARE DEPENDENT SOLELY ON LOW-LEVEL CONVERGENCE WITH THE FRONT AND DEEP OUTFLOW BOUNDARIES TO PRODUCE STORMS. GIVEN THE RECENT DEVELOPMENT OF STORMS ALONG THE FRONT FROM CHARLOTTE EASTWARD TO SOUTH OF RALEIGH...THE FLOOD WATCH WILL REMAIN IN EFFECT. NO SIGNIFICANT CHANGES HAVE BEEN MADE TO FORECAST LOWS WHICH RANGE FROM THE UPPER 60S ACROSS BENNETTSVILLE THROUGH LUMBERTON AND BURGAW...TO THE LOWER 70S NEAR THE COAST.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...TEMPERATURES A BIT BELOW CLIMO ON SUNDAY...MORESO OVER NWRN ZONES...WITH COLD FRONT NEARLY STALLED TO OUR SOUTH. SHOWERS AND MAYBE SHALLOW CONVECTION STILL SCATTERED ABOUT THE REGION WITH SLIGHT CONCENTRATION OVER SRN REGIONS WHERE THERE SHOULD BE MORE MOISTURE AND A THINNER SURFACED-BASED STABLE LAYER. THE BOUNDARY WEAKENS OFF TO OUR SOUTH HEADING INTO MONDAY BUT ITS ASSOCIATED MOISTURE LINGERS AND EVEN APPEARS TO WASH BACK NORTHWARD A BIT. AREA-WIDE CHANCE POPS WILL CONTINUE AND AFTERNOON TEMPERATURES SHOULD RECOVER BACK TO CLIMO IF NOT A TAD HIGHER. RAIN CHANCES LINGER AND POSSIBLY EVEN RISE SLIGHTLY MONDAY NIGHT AS A COLD FRONT APPROACHES FROM THE NORTHWEST. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 3 PM SATURDAY...COLD FRONT MOVES ACROSS THE AREA TUE WITH NORTHERLY LOW LEVEL WINDS AND WEST TO NORTHWEST FLOW ALOFT HELPING DRY THE AREA OUT. FRONT WILL PUSH SOUTHEAST OF THE AREA BEFORE STALLING BUT JUST HOW FAR REMAINS THE CRUX OF NEXT WEEKS FORECAST. RECENT GFS RUNS HAVE COME INTO LINE WITH PREVIOUS THINKING AND ECMWF/WPC SOLUTIONS WHICH HAVE THE FRONT STALLING FARTHER OFF THE COAST. WORTH NOTING MOST OF THE GFS ENSEMBLE MEMBERS ALSO SUPPORT THIS SOLUTION...WITH A DECENT MID LEVEL TROUGH AXIS NEAR OR JUST OFF THE COAST MID TO LATE NEXT WEEK. AIR MASS BEHIND THE FRONT IS OF CANADIAN ORIGIN WITH TEMPERATURES DROPPING BELOW CLIMO BY THE END OF THE PERIOD DESPITE INCREASING SUNSHINE AS THE REGION DRIES OUT. PLAN TO HOLD ONTO SLIGHT CHC/LOW CHC POP FOR WED DUE TO LINGERING MOISTURE AND AGAIN THU WITH BOTH GFS/ECMWF SHOWING WEAK MID LEVEL IMPULSE AND LOW PRESSURE MOVING NORTHEAST ALONG THE STALLED FRONT. THE LOW IS LIKELY TOO FAR OFF THE COAST TO DIRECTLY AFFECT THE AREA BUT IT WILL ENHANCE LOW/MID LEVEL MOISTURE OVER THE REGION AHEAD OF THE SHORTWAVE. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 00Z...THE RADAR HAS QUIETED DOWN A BIT THIS EVENING AFTER WIDELY SCATTERED CONVECTION EARLIER TODAY. WITH THE COLD FRONT STILL LOCATED JUST TO OUR NORTH...MORE SHOWERS/ISO TSTMS ARE POSSIBLE THIS EVENING...MAINLY BEFORE 06Z. STILL WATCHING A LINE OF TSRA ACROSS EAST CENTRAL NC...AND HAVE INCLUDED VCTS FOR KFLO/KLBT TONIGHT IN CASE THESE STORMS HOLD TOGETHER. HAVE ALSO MAINTAINED VCSH FOR THE COASTAL TERMS AS PERIODS OF -RA ARE POSSIBLE FROM THE EARLIER STORMS. ALTHOUGH LIGHT/CALM WINDS AND DEWPOINTS IN THE 70S APPEAR FAVORABLE FOR FOG...PLENTY OF DEBRIS CLOUD COVER SHOULD LIMIT THE OVERALL FOG THREAT TONIGHT. AS THE COLD FRONT MOVES ACROSS OUR CWA EARLY SUN MORNING...EXPECT WIDESPREAD MVFR/IFR CIGS TO DEVELOP...BEGINNING WITH KLBT/KILM AROUND 09Z. FCST SOUNDINGS INDICATE THE FRONTAL INVERSION WILL BE RIGHT AROUND 1KFT...AND GFS/NAM MOS GUIDANCE ARE SPLIT ON WHETHER CIGS WILL DROP TO IFR LEVELS. SO FOR NOW...WILL INCLUDE SCT IFR STRATUS WITH PREVAILING MVFR CIGS JUST ABOVE 1KFT THROUGH THE MORNING. SOME TEMPO IFR CIGS MAY BE ADDED WITH THE NEXT ISSUANCE. NORTHEAST WINDS AOB 10 KT WILL PREVAIL BEHIND THE FRONT ON SUN AS MVFR CIGS PERSIST THROUGH THE DAY. WILL KEEP INHERITED VCSH FOR SUN AS THE COLUMN REMAINS QUITE MOIST EVEN BEHIND THE FRONT. EXTENDED OUTLOOK...CHANCE OF AFTERNOON SHOWERS/TSTMS AND TEMPO MVFR THROUGH TUESDAY. EXPECT VFR WEDNESDAY AND THURSDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM SATURDAY...NO SIGNIFICANT CHANGES ARE NEEDED TO THE FORECAST THIS EVENING. OVERNIGHT SHOWERS AND T-STORM CHANCES WILL INCREASE FOR THE SOUTH CAROLINA WATERS LATE TONIGHT AS ACTIVITY IN THE PEE DEE REGION SHIFTS SOUTHEASTWARD. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... THE COLD FRONT CURRENTLY EXTENDS EAST-TO-WEST ACROSS NORTH CAROLINA FROM NEAR ELIZABETH CITY TO RALEIGH AND TO JUST SOUTH OF CHARLOTTE. THIS BOUNDARY WILL SLIP SOUTHWARD OVERNIGHT AND DEFINITELY SHOULD PUSH THROUGH THE NORTH CAROLINA WATERS BY DAYBREAK SUNDAY. ALONG THE SOUTH CAROLINA COAST MODELS DISPLAY QUITE A BIT OF SPREAD WITH THEIR PREDICTED FRONTAL POSITIONS BUT IT APPEARS THE BOUNDARY WILL BE NEAR MYRTLE BEACH AT DAYBREAK...WITH NORTH TO NORTHEAST WINDS DEVELOPING. SEAS CURRENTLY ONLY 1 FOOT MAY BUILD TOWARD 2 FEET LATE TONIGHT. THE ONLY PRECIPITATION ACROSS THE COASTAL WATERS SO FAR AS BEEN LIGHT SHOWERS FROM DECAYING THUNDERSTORMS DROPPING SOUTHEASTWARD. AS THE FRONT APPROACHES OVERNIGHT LOOK FOR SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS TO DEVELOP...SOME WITH LOCALLY HEAVY RAINFALL. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...LIGHT NORTHEASTERLY POST-FRONTAL WINDS ON SUNDAY APPEAR TO STAY CAPPED AT ABOUT 10 KTS. LOCAL SWAN RUNS UTILIZING SUCH LIGHT WINDS AND IN THE ABSENCE OF SWELLS KEEPS US AT 2 FT OR LESS FOR SEAS. THE MAIN NAVIGATION WOE WILL THUS BE ANY VSBY RESTRICTIONS CAUSED BY RAINFALL. AS THE BOUNDARY REMAINS TO OUR SOUTH AND FALLS APART ON MONDAY WINDS WILL GROW EVEN LIGHTER ESPECIALLY OVER SRN ZONES...CLOSER TO ITS REMAINS. THE LIGHT NE FLOW SHOULD REMAIN OVER NRN ZONES BUT THE WASHED OUT PRESSURE PATTERN OVER SRN WATERS SHOULD FAVOR LIGHT AND VARIABLE FLOW OR EVEN A LATE DAY WEAK S TO SW COMPONENT. SEAS WILL REMAIN MINIMAL. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 3 PM SATURDAY...PROLONGED PERIOD OF NORTHEAST FLOW ON TAP BEHIND COLD FRONT WHICH WILL PUSH OFFSHORE EARLY TUE. GRADIENT WILL TIGHTEN UP TUE NIGHT INTO WED AS SURFACE HIGH BUILDS IN BEHIND THE FRONT...INCREASING NORTHEAST FLOW TO A SOLID 15 KT WED. SURFACE WAVE DEVELOPING ALONG THE FRONT STALLED WELL OFFSHORE WILL FURTHER ENHANCE THE GRADIENT WED NIGHT AND THU. A PERIOD OF SOLID 20 KT NORTHEAST WINDS IS LIKELY THU. PROLONGED AND INCREASING NORTHEAST FLOW WILL BUILD SEAS FROM AROUND 2 FT TUE TO 4 TO 6 FT...AND POSSIBLY HIGHER...BY THE END OF THE PERIOD. HEADLINES SEEM LIKELY AS EARLY AS WED MORNING.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...FLOOD WATCH THROUGH LATE TONIGHT FOR SCZ017-023-024-032-033- 039-053>056. NC...FLOOD WATCH THROUGH LATE TONIGHT FOR NCZ087-096-099-105>110. MARINE...NONE. && $$ SYNOPSIS...MBB NEAR TERM...TRA SHORT TERM...MBB LONG TERM...III AVIATION...BJR

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