Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 271042 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 642 AM EDT SUN JUL 27 2014 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL EXTEND BACK INTO THE CAROLINAS THROUGH MONDAY CREATING VERY HOT AND HUMID CONDITIONS. A HEAT ADVISORY IS IN EFFECT FOR PORTIONS OF THE AREA TODAY. ANOTHER ADVISORY MAY BE REQUIRED FOR MONDAY. STRONG COLD FRONT WILL CROSS THE AREA LATE MONDAY. SHOWERS AND THUNDERSTORMS...SOME OF WHICH MAY BE SEVERE...WILL BE POSSIBLE MONDAY AFTERNOON. MUCH COOLER AND DRIER WEATHER WILL DEVELOP TUESDAY AND CONTINUE THROUGH THE UPCOMING WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 630 AM SUNDAY...MAIN CONCERN TODAY WILL BE THE HEAT. AT THIS POINT...ALL OF THE ILM CWA EXCEPT THE IMMEDIATE COAST AND 2 NC COUNTIES ARE UNDER THE HEAT ADVISORY FOR THIS AFTERNOON. UPSTREAM CONVECTION TO REMAIN JUST NORTH OF THE ILM CWA THIS MORNING AND AFTERNOON AS THE BEST DYNAMICS TO SUPPORT AND ASSOCIATED WITH THE MCS/MCC REMAIN NORTH OF THE FA. THE FA WILL HAVE TO BE DEAL WITH THE CONVECTIVE DEBRIS CLOUDINESS ASSOCIATED WITH THIS SYSTEM. HOW THICK AND/OR OPAQUE THESE CLOUDS REMAIN AS THEY CROSS THE ILM CWA COULD REDUCE TODAYS MAX TEMPS BY 1 TO 3 DEGREES...TO THE LOW TO MID 90S. THIS OF COURSE REMAINS HOT BUT COULD JEOPARDIZE THE BORDERLINE HEAT ADVISORY IN AFFECT FOR THIS AFTERNOON. AMPLIFYING LONGWAVE UPPER TROF ACROSS THE EASTERN 1/3RD TO HALF OF THE U.S. WILL BECOME THE STORY TONIGHT THRU SUBSEQUENT PERIODS. A TIGHTENING SFC PG WILL OCCUR WITH THE PIEDMONT TROF REMAINING ACROSS THE CENTRAL CAROLINAS. LOOK FOR AN ACTIVE SW WIND ACROSS THE FORECAST AREA TONIGHT. THIS WILL KEEP MIN TEMPS UP ACROSS THE REGION WITH A RANGE OF 75-80 DEGREES COMMON. LACK OF DYNAMICS IE. FORCING...TO SUPPORT LET ALONE INITIATE CONVECTION REMAIN THE STORY FROM THIS AFTERNOON THROUGH TONIGHT...AND THUS WILL CONTINUE WITH NO POPS THRU DAYBREAK MON.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 3 AM SUNDAY...STRONG COLD FRONT SLATED TO CROSS THE REGION LATE MON WILL BRING ABOUT A SIGNIFICANT AIR MASS CHANGE FOR TUE. AHEAD OF THE FRONT INCREASING SOUTHWEST FLOW WILL CONTINUE TO PUMP MOISTURE INTO THE SOUTHEAST WHILE 850 TEMPS IN THE LOW 20C RANGE KEEP THE HEAT ON. HIGHS WILL CLIMB INTO THE MID TO UPPER 90S ACROSS MUCH OF THE AREA WHILE STRONG SOUTHWEST FLOW KEEPS THE SEA BREEZE CONFINED TO SMALL CORNERS OF THE FORECAST AREA...MAINLY SE BRUNSWICK. A HEAT ADVISORY MAY BE NEEDED FOR MUCH IF NOT ALL OF THE AREA. STILL APPEARS TO BE POTENTIAL FOR SEVERE WEATHER MON BUT COVERAGE IS LOOKING LESS CERTAIN. A NARROW RIBBON OF DEEPER MOISTURE MAY PUSH OFF THE COAST BEFORE INSTABILITY IS ABLE TO OVERCOME THE WEAKENING MID LEVEL CAP. DESPITE THE QUESTIONABLE MOISTURE THERE WILL STILL BE PLENTY OF INSTABILITY. MLCAPE MON AFTERNOON SHOULD EASILY EXCEED 2500 J/KG...JUST AS 500MB HEIGHTS ARE STARTING TO FALL. FORECAST AREA IS IN A SOMEWHAT FAVORABLE LOCATION WITH RESPECT TO THE POSITION OF JETTING ALOFT...THOUGH BOTH GFS/NAM PORTRAY A WEAKER JET WHEN COMPARED TO LAST NIGHT. THERE WILL ALSO BE A 25 KT LOW LEVEL JET TAKING SHAPE IN THE AFTERNOON. ALL OF THIS SUGGESTS STORMS THAT DO DEVELOP WILL HAVE POTENTIAL FOR STRONG UPDRAFTS AND DAMAGING WIND ALONG WITH LARGE HAIL. JUST NOT SURE WHAT COVERAGE IS GOING TO BE LIKE GIVEN THE INCREASING DRY AIR ALOFT. SPC SLIGHT RISK CONTINUES FOR MUCH OF THE FORECAST AREA ON MON. SIGNIFICANT AIR MASS CHANGE ON TAP FOR TUE...SO MUCH THAT IT WILL FEEL LIKE FALL HAS ARRIVED EARLY. NORTHERLY FLOW BEHIND THE FRONT WILL KEEP HIGHS IN THE MID 80S IN MOST AREAS BUT MORE SIGNIFICANTLY HUMIDITY VALUES WILL FALL. DEWPOINTS WILL DROP WELL INTO THE 60S WITH PRECIPITABLE WATER VALUES DOWN AROUND 1 INCH...MORE THAN -2 SD FROM WHAT IS TYPICAL FOR THE END OF JULY. GIVEN THE AMOUNT OF DRY AIR AND SOME WEAK SUBSIDENCE FROM CONVERGENCE ALOFT DO NOT SEE MUCH CHANCE FOR PRECIP TUE. WILL CONTINUE TO CARRY THE INHERITED DRY BUT NOT ZERO POP FORECAST. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 3 AM SUNDAY...UNUSUALLY STRONG MID LEVEL TROUGH WILL REMAIN IN PLACE OVER THE EASTERN CONUS THROUGH THE PERIOD. 5H TROUGH AXIS JUST WEST OF THE AREA WILL MAINTAIN DEEP WESTERLY FLOW...PREVENTING ANY APPRECIABLE MOISTURE RETURN. INSTEAD DEEP DRY AIR HOLDS ON FOR MUCH OF THE PERIOD WITH PRECIPITABLE WATER VALUES RUNNING BETWEEN 1 AND 1.25 INCHES INTO FRI. TROUGH DIGS A LITTLE LATE IN THE PERIOD AS 5H RIDGE OVER THE ATLANTIC TRIES TO EXPAND WEST. FLOW ALOFT BACKS FROM WEST TO SOUTHWEST RESULTING IN A SLOW BUT STEADY INCREASE IN MOISTURE NEXT WEEKEND. PRECIP CHANCES WILL BE INCREASING LATE IN THE PERIOD BUT THE EXTENT OF THE INCREASE REMAINS UNCERTAINTY. WHILE THERE IS CERTAINLY POTENTIAL FOR SHORTWAVES ROUNDING THE BASE OF THE MID LEVEL TROUGH CANNOT SAY IF ANY WILL ACTUALLY EXIST GIVEN THE TIME FRAME. WILL MAINTAIN DRY FORECAST WED WITH SILENT POP THU/FRI AND LOW CHC FOR SAT. TEMPERATURES WILL RUN BELOW CLIMO THROUGH THE PERIOD WITH HIGHS EXPECTED TO REMAIN BELOW 90 WHILE LOWS DROP INTO THE MID 60S. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 06Z...PREDOMINATELY VFR CONDITIONS FOR THE PRE-DAWN SUNDAY HRS. THE EXCEPTION WILL BE MVFR ACROSS SITES WHERE WINDS DROP OFF ALLOWING FOG TO TEMPORARILY DEVELOP. WINDS AT THE COASTAL TERMS SHOULD STAY AT 5 KT OR HIER LIMITING FOG FORMATION. FOR SUNDAY...SOUTHWESTERLY FLOW WILL QUICKLY PICK UP DUE TO A TIGHTENING SFC PG. EXPECT SW 10G15KT EXCEPT THE COASTAL TERMS WILL SEE WINDS BACK TO SSW 10G20KT FROM THE SEA BREEZE. MODELS KEEP THIS INCREASED FLOW WELL INTO SUNDAY NIGHT. SOME ISOLATED CONVECTION COULD BE INITIATED ALONG THE SEA BREEZE AND ALSO THE PIEDMONT TROUGH INLAND. WHATS CONCERNING IS THE MCC/MCS WEST OF THE APPALACHIAN MOUNTAINS ATTM. MODELS WANT TO TAKE IT APART AS IT CROSSES THE MOUNTAINS WITH THE BEST DYNAMICS LEFTOVER TO PASS WELL NORTH OF THE TERMINALS DURING SUNDAY AFTN/EVENG. WILL HIGHLIGHT THE PASSAGE OF MID AND UPPER LEVEL DEBRIS CLOUDINESS FROM THIS SYSTEM. EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE MONDAY. OTHERWISE EXPECT VFR. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM SUNDAY...PROGRESSIVELY INCREASING SW WINDS AND SLOWLY BUILDING SIGNIFICANT SEAS WILL RULE THE NEAR TERM PERIOD. MAY NEED TO ISSUE A SCEC FOR TONIGHT AND LATER PERIODS...OR POSSIBLY GO STRAIGHT WITH A SCA WITH WINDS/SEAS ON THE CUSP OF PRODUCING SCA CONDITIONS TONIGHT AND LIKELY DURING MONDAY. MODELS AGREE THAT THE SFC PRESSURE PATTERN AND TIGHTENING GRADIENT WILL YIELD SW WINDS THAT INCREASE TO 15 TO 20 KT DURING TODAY...AND 15 TO 20 KT...POSSIBLY AS HIGH AS SUSTAINED 25 KT LATER TONIGHT. WILL ATLEAST HAVE FEW/OCCASIONAL GUSTS UP TO 25 KT TONIGHT. SIGNIFICANT SEAS WILL BUILD UP TO 4 FT TODAY...3 TO 5 FT TONIGHT...AND POSSIBLY UP TO 6 FT OFF CAPE FEAR ACROSS FRYING PAN SHOALS LATE TONIGHT. WIND DRIVEN WAVES EXHIBITING 3 TO 6 SECOND PERIODS WILL BECOME THE DOMINATE PLAYER FOR SIGNIFICANT SEAS. THE ESE-SE DOMINATE GROUND SWELL OF THE PAST WEEK WILL REMAIN EVIDENT ACROSS THE AREA WATERS JUST SMALLER IN HEIGHT...VIA CURRENT BUOY DATA AND LATEST WAVEWATCH3 MODEL DATA. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 AM SUNDAY...STRONG SOUTHWEST FLOW AHEAD OF ADVANCING COLD FRONT WILL PROBABLY REQUIRE HEADLINES FOR THE WATERS AT SOME POINT MON. EVENT MAY END UP AS A MARGINAL SCA...BUT CONFIDENCE IS NOT HIGH ENOUGH TO GO WITH A HEADLINE AT THIS POINT IN TIME. WINDS WILL LIKELY FALL SHORT OF 25 KT BUT EXTENDED PERIOD OF SOUTHWEST FLOW COMBINED WITH INCREASING SPEEDS MON COULD PUSH SEAS OVER 6 FT BY MID AFTERNOON. FRONT MOVES ACROSS THE WATERS MON NIGHT WITH OFFSHORE FLOW IN ITS WAKE. BRIEF PERIOD WITH PINCHED GRADIENT BEHIND THE FRONT WILL SEE NORTHWEST FLOW INCREASE TO 10 TO 15 KT BUT BY MID MORNING TUE SPEEDS WILL BE UNDER 10 KT WITH VARIABLE DIRECTION. DEVELOPMENT OF OFFSHORE FLOW BEHIND THE FRONT WILL DROP SEAS FROM 4 TO 6 FT PRE FRONT TO 2 TO 3 FT BY TUE MORNING. SEAS WILL REMAIN 2 TO 3 FT THROUGH THE END OF THE PERIOD. LONG TERM /WEDNESDAY THROUGH THURSDAY/... AS OF 3 AM SUNDAY...NORTHEAST FLOW AROUND 10 KT WED WILL INCREASE TO 10 TO 15 KTS THU AS HIGH PRESSURE TO THE WEST EXPANDS EAST AND GRADIENT BECOMES MORE DEFINED. SEAS 2 TO 3 FT ON WED BUILD TO 3 TO 4 FT BY THU AFTERNOON.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...HEAT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR SCZ017-023-024-032-033-039-053-055. NC...HEAT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR NCZ087-096-099-109. MARINE...NONE. && $$ SYNOPSIS...III NEAR TERM...DCH SHORT TERM...III LONG TERM...III AVIATION...DCH

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