Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 230003 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 803 PM EDT TUE JUL 22 2014 .SYNOPSIS... A STATIONARY FRONT ALONG THE COAST WILL SLOWLY MOVE INLAND AND DISSIPATE TONIGHT. BERMUDA HIGH PRESSURE WILL BUILD INTO THE AREA WEDNESDAY AND THURSDAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE THURSDAY...STALLING NEAR THE COAST FOR THE WEEKEND. ANOTHER COLD FRONT WILL APPROACH FROM THE NORTHWEST MONDAY OR TUESDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... AS OF 715 PM TUESDAY...LATEST KLTX 88D INDICATES A DIMINISHING TREND TO THE SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE ILM CWA. WITH THE DAYS HEATING OVERWITH...CONVECTION WILL BECOME MORE DIFFICULT TO SUSTAIN. A SLOW MOVING MID-LEVEL S/W TROF OR IMPULSE OFF THE CAROLINA COASTS...IS PROGGED TO PUSH OFF TO THE NORTHEAST OVERNIGHT INTO WEDNESDAY...AWAY FROM THE ILM CWA. ENOUGH FORCING/DYNAMICS FROM THIS UPPER S/W TROF WILL PRODUCE CONVECTION OVER THE ADJACENT ATL WATERS THAT MAY DRIFT ONSHORE...MAINLY FROM LITTLE RIVER INLET NORTH TO SURF CITY DURING THE PRE-DAWN WEDNESDAY HOURS. LATEST SREF MODEL HIGHLIGHTS THIS DIMINISHING TREND TO POPS OVER LAND BUT DOES KEEP PCPN OCCURRING OVER THE ADJACENT ATL WATERS. LOW TO MID 70S FOR TONIGHTS LOWS MAY NEED TO BE BUMPED UP HIER ACROSS THE COASTAL COUNTIES TO THE UPPER 70S ESPECIALLY WITH LATEST SFC DEWPOINTS HOLDING IN THE MID 70S. CLOUDINESS MORE WIDESPREAD AND OPAQUE IN NATURE AT THE MOMENT... WILL SLOWLY THIN OVERNIGHT AND IN TURN COULD LEAD TO SOME PATCHY OR AREAS OF FOG DEVELOPMENT. WILL INCLUDE THE FOG AT THE NEXT UPDATE IF NEEDED. PREVIOUS DISCUSSION............................................... AS OF 330 PM TUESDAY...ITS BEEN A TOUGH DAY DIAGNOSING WHY MORE WIDESPREAD CONVECTION WITH HEAVY RAIN HAS NOT DEVELOPED ACROSS THE AREA. AN UPPER LEVEL LOW NEAR THE MOUTH OF THE MISSISSIPPI RIVER AND AN UPPER RIDGE IN THE EASTERN BAHAMAS ARE LIFTING A TROPICAL MOISTURE PLUME NORTH ACROSS THE CAROLINAS. AN OLD STATIONARY FRONT AT THE SURFACE IS MERGING WITH THE WEAK SEABREEZE BOUNDARY... PROVIDING A LITTLE EXTRA LOW-LEVEL CONVERGENCE. WIND SPEEDS THROUGH THE LOWEST 20KFT OF THE ATMOSPHERE ARE VERY LIGHT WHICH IS LIMITING MOISTURE ADVECTION...ALTHOUGH THE AIRMASS ITSELF REMAINS LOADED WITH MOISTURE AS SHOWN BY PRECIPITABLE WATER VALUES OF 2.1 TO 2.3 INCHES. THE ONLY FACTOR THAT REALLY STICKS OUT IS THAT CONTINUED PRESENCE OF MULTIPLE LARGE CONVECTIVE CLUSTERS OVER THE GULF STREAM FROM SC SOUTH TO FLORIDA. WITH SO MUCH SUSTAINED UPWARD VERTICAL MOTION CENTERED THERE...THERE HAS TO BE A CORRESPONDING DOWNWARD VERTICAL MOTION LOCATED DOWNSTREAM OVER OUR HEADS. THE FLOOD WATCH HAS BEEN CANCELLED EARLY AS A RESULT. SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO THE EARLY EVENING...BUT COVERAGE AND RAINFALL RATES WILL BE MUCH LOWER THAN THOUGHT THIS MORNING. THE MID-LEVEL FLOW WILL VEER A LITTLE MORE TONIGHT AS THE BAHAMAS RIDGE BUILDS A LITTLE MORE WESTWARD ACROSS FLORIDA. THE MEAN FLOW SHOULD REMAIN ORIENTED ONSHORE FOR THE CAPE FEAR REGION...AND FOR THE SOUTHPORT/WILMINGTON AREA I WILL INDICATE AN INCREASING TREND IN POPS AFTER MIDNIGHT. 12Z MODELS SHOW NOCTURNAL MARINE CONVECTION PASSING VERY CLOSE TO CAPE FEAR IN THE 06-12Z TIME FRAME. BOTH GFS AND NAM MOS SHOWED A PRONOUNCED COOL BIAS LAST NIGHT SO I HAVE ADJUSTED MY FORECAST LOWS UPWARD. LOWS SHOULD RANGE FROM AROUND 73 INLAND TO 75 AT THE COAST. LIKE LAST NIGHT WIDESPREAD LOW STRATUS AND SOME FOG WILL PROBABLY DEVELOP BY MIDNIGHT. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... AS OF 330 PM TUESDAY...UPPER LOW OVER THE GULF COAST WILL CONTINUE RETROGRADING ON WEDNESDAY...ALLOWING A 500 MB RIDGE TO BRIEFLY BUILD INTO THE SOUTHEAST. MID LEVEL FLOW WILL BECOME MORE WESTERLY DURING THE AFTERNOON/EVENING HOURS...FINALLY BRINGING AN END TO THE CONTINUOUS CHANNEL OF DEEP MOISTURE THAT HAS FUNNELED INTO THE AREA OVER THE PAST COUPLE DAYS. MOST ONGOING SHOWER ACTIVITY WEDNESDAY MORNING WILL BE OFFSHORE...BUT WILL MENTION HIGHER POPS ALONG THE COAST EARLY. PWAT VALUES WILL REMAIN IN THE 2.0 INCH RANGE DURING THE DAY...SO STILL EXPECT ISOLATED TO SCATTERED CONVECTION IN THE AFTN ALONG THE SEA BREEZE. BUT OVERALL PCPN COVERAGE SHOULD BE LESS WIDESPREAD THAN WE HAVE SEEN OVER THE PAST COUPLE DAYS. 500 MB HEIGHTS WILL GRADUALLY FALL ON THURSDAY AHEAD OF AN APPROACHING COLD FRONT. RAIN CHANCES INCREASE AGAIN LATE THURSDAY INTO EARLY FRIDAY AS THE FRONT NEARS OUR FORECAST AREA. BY 12Z FRIDAY THE BOUNDARY WILL BE DRAPED ACROSS THE CAROLINAS...PERHAPS EVEN BISECTING OUR FORECAST AREA AS IT STALLS. THE SFC PRESSURE GRADIENT WILL TIGHTEN BETWEEN BERMUDA HIGH PRESSURE AND A PRE-FRONTAL TROUGH...WITH STRENGTHENING S-SW WINDS THROUGH THE PERIOD. 1000-500 MB THICKNESSES INDICATE A WARMING TREND AS THE FLOW ACQUIRES A MORE WESTERLY COMPONENT. EXPECT HIGHS TO CLIMB INTO THE LOW 90S WEDNESDAY AND MID 90S THURSDAY ACROSS OUR INLAND ZONES... WITH HEAT INDICES NEARING OR EXCEEDING TRIPLE DIGITS. LOW TEMPS BOTH NIGHTS WILL BE IN THE MID 70S. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 330 AM TUESDAY...COLD FRONT MAY BE HUNG UP RIGHT ALONG THE COAST FRI MORNING BUT NAM WANTS TO PUSH IT SOUTH AND EAST OF AREA LEAVING HIGH PRESSURE IN CONTROL. NOT CONFIDENT THAT THE BOUNDARY WILL GET TOO FAR SOUTH AS H5 TROUGH LIFTS NORTH LEAVING A VERY BROAD MID TO UPPER TROUGH ANCHORED OVER THE GREAT LAKES MAINTAINING MORE OF A SW FLOW ALOFT AND NOT GIVING MUCH OF PUSH TO THE COLD FRONT. THEREFORE WILL KEEP FRONT JUST TO OUR NORTHWEST ON FRI. DEEP SW FLOW WILL KEEP A WARMER AND MORE HUMID AIR MASS OVER THE AREA LEAVING POTENTIAL FOR LOCALIZED CONVECTION THROUGH THE WEEKEND. MID TO UPPER TROUGH WILL DIG DOWN FROM THE GREAT LAKES COME MONDAY PUSHING ANOTHER COLD FRONT INTO THE CAROLINAS. THIS WILL PRODUCE MORE WIDESPREAD CONVECTION IN INCREASED UPPER LEVEL SUPPORT LATER ON MONDAY. ONCE AGAIN UPPER LEVEL TROUGH WILL REMAIN TO OUR WEST LEAVING A FLOW RUNNING MORE PARALLEL TO FRONT AND NOT GIVING IT TOO STRONG OF A PUSH THROUGH THE AREA. THEREFORE MAY NOT SEE TOO MUCH OF AN AIR MASS CHANGE BEHIND FRONT. OVERALL EXPECT GREATEST POTENTIAL FOR MORE WIDESPREAD CONVECTION EARLY FRI AND AGAIN MON AFTN INTO EARLY TUES...BUT EXPECT MORE TYPICAL DIURNAL TYPE SHWR ACTIVITY MOST DAYS. SOME DRIER AIR SHOULD MAKE IT INTO INLAND AREAS ON FRI AND ON TUES BEHIND FRONTS...BUT WILL MOST LIKELY REMAIN JUST TO THE WEST OF FORECAST AREA. TEMPS WILL BASICALLY BE ABOVE CLIMO WITH OVERNIGHT LOWS IN THE 70S AND DAY TIME HIGHS INTO THE 90S MOST DAYS WITH LOWER TEMPS EXPECTED. AS TROUGH DIGS DOWN THURS INTO FRI AND AGAIN MON INTO TUES MAY SEE BELOW NORMAL TEMPS IN LOWERED H5 HEIGHTS. && .AVIATION /23Z TUESDAY THROUGH SUNDAY/... AS OF 00Z...CONVECTION IS OVER FOR THE MOST PART...HOWEVER SOME NOCTURNAL SHOWERS ARE POSSIBLE NEAR THE COAST THROUGH THE OVERNIGHT HOURS. STILL A LOT OF CONVECTIVE DEBRIS...HOWEVER MOST OF THAT WILL BE DISSIPATING IN A FEW HOURS...ALLOWING MODERATE RADIATIONAL COOLING TO COMMENCE. FOG WILL RETURN TO THE REGION...HOWEVER LOW LEVEL MOISTURE IS NOT AS PREVALENT AS LAST NIGHT SO WILL BACK OFF A BIT ON THE INTENSITY AT THIS TIME. COULD SEE POCKETS OF IFR...AS WELL AS STRATUS. WEDNESDAY...AN IMPULSE WILL MOVE UP THE COAST...AND COASTAL TERMINALS ARE EXPECTED TO SEE CONVECTION START FAIRLY EARLY IN THE DAY...BECOMING MORE INTENSE BY EARLY AFTERNOON WITH THUNDER EXPECTED. WEAK SOUTHWEST FLOW TOMORROW. EXTENDED OUTLOOK...CHANCE OF SHOWERS/TSTMS WILL PERSIST THROUGH THE EXTENDED PERIOD. EXPECT PREDOMINANTLY VFR CONDITIONS WITH TEMPO PERIODS OF MVFR/IFR CIGS/VSBYS IN STORMS. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 745 PM TUESDAY...LATEST SFC PRESSURE PATTERN REMAINS SOMEWHAT CHAOTIC...HENCE THE VARIABLE WIND DIRECTION AT TIMES. THE SFC PG TO REMAIN RELAXED THIS EVENING. TOWARDS DAYBREAK WEDNESDAY...THE SFC PG IS PROGGED TO TIGHTEN AS THE ILM WATERS BECOMES NESTLED BETWEEN STRONG BERMUDA HIGH PRESSURE CENTERED WELL OFF THE SE U.S. COAST...AND A STRENGTHENING PIEDMONT TROF ACROSS THE CENTRAL CAROLINAS. OVERALL...WINDS PROGGED TO VEER TO THE SSE THRU WSW DIRECTIONS. SPEEDS TO INCREASE TO 10-15 KT. SIGNIFICANT SEAS WILL BE A PRODUCT OF A SOMEWHAT DECAYED 2 FOOT SE GROUND SWELL EXHIBITING 8 TO 9 SECOND PERIODS...AND BUILDING 2 TO 3 FOOT WIND DRIVEN WAVES AT 5 TO 6 SECOND PERIODS. PREVIOUS DISCUSSION................................................ AS OF 330 PM TUESDAY...AN OLD STATIONARY FRONT THAT HAS BEEN STALLED NEAR THE COAST ALL DAY SHOULD LARGELY DISSIPATE TONIGHT...LEAVING SLOWLY VEERING WIND PATTERN IN ITS WAKE. BY THIS EVENING WINDS EVERYWHERE SHOULD BE TURNING SOUTHERLY AND WILL INCREASE TO 10-12 KNOTS NEARSHORE AND 15 KNOTS OFFSHORE. SEAS ARE CURRENTLY 2-3 FEET MAINLY IN A SOUTHEAST 7 SECOND SWELL. THIS WILL BE SUPPLEMENTED BY A SHORT PERIOD WIND CHOP OVERNIGHT...BUT WITH LITTLE SIGNIFICANT INCREASE IN SEA HEIGHTS. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 330 PM TUESDAY...SOUTHWEST WINDS AROUND 15 KTS WILL PREVAIL WEDNESDAY AFTN THROUGH THURSDAY AS THE GRADIENT IS PINCHED BETWEEN BERMUDA HIGH PRESSURE AND A PRE-FRONTAL TROUGH. SEAS WILL BE 3-4 FT...BUILDING TO 4-5 FT ON THURSDAY ACROSS AMZ250/252 WHERE WINDS MAY GUST TO 20 KTS. THE DOMINANT WAVE GROUP WILL BE A 5-6 SECOND SOUTHERLY WIND CHOP. WINDS AND SEAS WILL RELAX A BIT TOWARD THE END OF THE PERIOD AS A COLD FRONT DROPPING SOUTHWARD NEARS THE COAST. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 330 AM TUESDAY...COLD FRONT REACHES INTO THE CAROLINAS EARLY FRI BUT WILL MOST LIKELY STALL AND DISSIPATE OVER INLAND CAROLINAS OVER THE WEEKEND. EXPECT TO MAINTAIN A SW FLOW AROUND BERMUDA HIGH WEAKENING AS GRADIENT RELAXES THROUGH FRIDAY INTO SATURDAY AS FRONT DISSIPATES OVER THE CAROLINAS. SEAS UP TO 3 TO 5 FT EARLY FRI WILL FALL BACK DOWN TO 2 TO 4 FT THROUGH LATE FRI INTO SATURDAY. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...BJR NEAR TERM...DCH/TRA SHORT TERM...BJR LONG TERM...MBB AVIATION...DL

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