Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 191023 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 623 AM EDT TUE AUG 19 2014 .SYNOPSIS... A COLD FRONT APPROACHING FROM THE NORTH WILL STALL OVER THE AREA THROUGH MID-WEEK...BRINGING A PERIOD OF UNSETTLED AFTERNOON AND EVENING WEATHER. A BUILDING UPPER RIDGE WILL BRING HOT CONDITIONS MID TO LATE WEEK...AND HEAT ADVISORIES MAY BE NEEDED FOR PORTIONS OF THE AREA WEDNESDAY AND THURSDAY. A BACK DOOR COLD FRONT AND UPPER TROUGH WILL DROP INTO THE AREA BY THE WEEKEND...BRINGING A PERIOD OF UNSETTLED BUT COOLER CONDITIONS. && .NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM TUESDAY...A S/W MID-LEVEL TROF AND ASSOCIATED SFC LOW WILL EXIT OFF THE OUTER BANKS THIS MORNING. SOME WEAK SUBSIDENCE LEFT BEHIND WILL AFFECT THE ILM CWA AND HOLD OFF ANY PCPN DEVELOPMENT UNTIL LATER THIS AFTERNOON. A SECOND MID-LEVEL S/W TROF WILL ROUND THE BASE OF THE UPPER TROF THIS MORNING...AND TRACK TO THE ENE ACROSS THE FORECAST AREA THIS AFTERNOON AND TONIGHT. CONVECTION WILL ACTUALLY LAST WELL INTO TONIGHT AND/OR INTO THE PRE-DAWN WED HOURS BEFORE ALL IS SAID AND DONE. ON THE MESOSCALE...SEA BREEZE INDUCED CONVECTION WILL HOLD OFF UNTIL THE MID-AFTERNOON HRS BEFORE FIRING UP. OVERALL...PREFER THE NAM SOLUTION WITH REGARD TO THE MOVEMENT AND EFFECTS OF THE NEXT MID- LEVEL S/W TROF POISED TO MOVE ACROSS THE FA. WILL LEAN TOWARD THE NAM MOS GUIDANCE FOR MAX/MIN TEMPS THRU TONIGHT...AND A MODIFIED NAM MOS GUIDANCE FOR POPS EXTENDING WELL INTO TONIGHT. MAX TEMPS ACROSS THE FA TODAY WILL LIKELY EXCEED 90 DEGREES FOR THE 3RD DAY IN A ROW. COMBINED WITH PROGGED DEWPOINTS IN THE 70 TO 75 RANGE...AFTERNOON HEAT INDEX VALUES WILL BE AROUND 100 DEGREES...EXCEPT FOR THE SOUTHERNMOST PORTIONS OF THE ILM CWA...WHERE HEAT INDICES WILL REACH 103 DEGREES. FOR HEAT ADVISORY THRESHOLDS TO BE MET...HEAT INDICES MUST REACH 105 DEGREES OR HIGHER. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...HEAT AND HUMIDITY STILL EXPECTED FOR THE SHORT TERM...AS 5H RIDGE BUILDS OVERHEAD AND SURFACE HIGH REMAINS ANCHORED OFFSHORE. A BRIEF PERIOD OF N/NW WINDS BEHIND A WEAK COLD FRONT WILL START WEDNESDAY...BUT THIS WILL HAVE LITTLE IMPACT TO TEMPERATURES SINCE THE AIR MASS BEHIND THIS FEATURE IS BASICALLY THE SAME AS AHEAD OF IT. TEMPS ARE EXPECTED TO SOAR INTO THE 90S EVEN TO THE BEACHES THANKS TO W/NW FLOW JUST ABOVE THE SURFACE PINNING THE SEA BREEZE. WHILE ISOLATED CONVECTION WILL BE POSSIBLE WEDNESDAY SIMPLY DUE TO THE HIGH INSTABILITY CAUSED BY THE HEAT/HUMIDITY...SOMEWHAT DRIER AIR ABOVE 700MB WILL LIMIT COVERAGE...AND ONLY SCHC POP IS WARRANTED. ANY CONVECTION WILL BE STRONGLY DIURNALLY FORCED...AND THUS WILL WANE AFTER DARK...LEAVING A WARM BUT CLEAR NIGHT WITH MINS ONLY IN THE MID 70S...UPR 70S AT THE BEACHES. THURSDAY IS EXPECTED TO BE THE HOTTEST DAY OF THE WEEK WITH WIDESPREAD MID 90S LIKELY...WITH SOME LOW 90S AT THE BEACHES AND UPR 90S ACROSS THE PEE DEE REGION. THESE TEMPERATURES COMBINED WITH HIGH DEWPOINT VALUES WILL LIKELY NECESSITATE A HEAT ADVISORY FOR PORTIONS OF THE CWA ON THURSDAY. THE PATTERN BEGINS TO CHANGE ON THURSDAY THOUGH...AS THE RIDGE AMPLIFIES AND MIGRATES TO THE WEST...ALLOWING FOR A TROUGH TO DEVELOP AND DIVE DOWN THE EAST COAST. THE GFS CONTINUES TO BE A FAST OUTLIER...BUT LOWERING HEIGHTS THURSDAY EVE COMBINED WITH INCREASING MOISTURE WILL LIKELY ALLOW FOR MORE WIDESPREAD CONVECTION THURSDAY AFTN AND THURSDAY NIGHT...WITH THE HIGHEST POP ACROSS THE NORTHERN TIER. THIS AGREES WELL WITH INHERITED AND WILL MAKE ONLY MINIMAL CHANGES. LOWS THURSDAY NIGHT WILL AGAIN BE ELEVATED...FALLING TO A DEGREE OR TWO EITHER SIDE OF 75. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 AM TUESDAY...SIGNIFICANT MID-LEVEL PATTERN AMPLIFICATION WILL LEAD TO A PERIOD OF UNSETTLED WEATHER...FOLLOWED BY COOLER THAN NORMAL TEMPS LATE IN THE WEEKEND INTO EARLY NEXT WEEK. EXPANSIVE RIDGE WILL BECOME CENTERED ACROSS THE MS VLY AND BLOOM NORTHEAST...WHILE A DEEP TROUGH DIVES ALONG THE EAST COAST. THIS CREATES A COOLING TREND BEGINNING FRIDAY WITH SEASONABLE TEMPS DROPPING TO BELOW NORMAL BY SUNDAY. ADDITIONALLY...THE TRANSITIONAL PERIOD...FRI/SAT...LOOK TO BE UNSETTLED WITH HIGHER THAN CLIMO POP WARRANTED AS A BACK DOOR COLD FRONT DROPS INTO AN OTHERWISE HUMID AND UNSTABLE AIR MASS FRIDAY...AND THEN ONLY SLOWLY CROSSING THE REGION ON SATURDAY. WITH UPPER IMPULSES CRESTING THE TROUGH AND RACING TOWARDS THE AREA ON NW FLOW...AND A SURFACE BOUNDARY IN THE VICINITY...THUNDERSTORMS CAN BE EXPECTED FRIDAY AND SATURDAY...ALTHOUGH AT THIS TIME IT IS TOO EARLY TO PINPOINT TEMPORALLY OR SPATIALLY THE MOST LIKELY LOCATIONS...OTHER THAN SUGGESTING A DIURNAL ENHANCEMENT. BY SUNDAY AND INTO NEXT WEEK...THE FRONT WILL BE SOUTH OF THE AREA AS THE TROUGH CONTINUES TO PUSH SOUTH...LEAVING COOLER BUT DRIER WEATHER FOR THE END OF THE PERIOD. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... AS OF 06Z...POTENTIAL FOR MVFR DUE TO FOG OVERNIGHT...ESPECIALLY THE INLAND TERMINALS WHERE WINDS DROP BELOW 3 KT. OTHERWISE EXPECT VFR WITH AFTERNOON/EVENING SHRA/TSRA ON TUESDAY. VFR PREVAILS SOUTH-SOUTHWEST WINDS VEERING TO WSW 5 KT OR LESS. COULD POTENTIALLY SEE FOG DEVELOPMENT DURING THE EARLY TUE MORNING HOURS BUT GIVEN LOWER CONFIDENCE HAVE ONLY INTRODUCED TEMPO GROUPINGS ATTM...AND MAINLY ACROSS THE INLAND TERMS. AFTER DAYBREAK...EXPECT VFR WITH ISOLATED TO SCATTERED TSRA/SHRA TO POP ALONG THE SEA BREEZE EARLY TO MID-AFTERNOON HOURS. DYNAMICS WITH AN UPPER S/W TROF TO PASS ACROSS THE FA LATE THIS AFTERNOON AND EVENING WHICH WILL FURTHER AID TSRA DEVELOPMENT. WILL INDICATE BEST TIME FOR CONVECTION WITH TEMPO GROUPINGS DURING THE LATE AFTERNOON THRU EARLY EVENING. WEST-SOUTHWEST WINDS AT 5 KT OR LESS IN THE MORNING WILL BECOME SOUTH-SOUTHWEST IN THE AFTERNOON WITH SUSTAINED WINDS BETWEEN 8-13 KT AND GUSTS UP TO 20 KTS ACROSS MAINLY THE COASTAL TERMS AFTER THE SEA BREEZE CIRCULATION SETS UP. EXTENDED OUTLOOK...CHC AFTERNOON/EVENING SHRA/TSRA THROUGH THE PERIOD. SUB-VFR FOG AND/OR CEILINGS WILL BE POSSIBLE DURING THE EARLY MORNING HOURS EACH DAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM TUESDAY...A STALLED BOUNDARY LYING EAST-WEST...WILL REMAIN NORTH OF THE AREA WATERS TODAY THROUGH TONIGHT. THE SFC PRESSURE PATTERN AND SOMEWHAT TIGHTENED GRADIENT SOUTH OF THIS BOUNDARY WILL YIELD SW-WSW WINDS AT 15 KT OR LESS THRU OUT THIS PERIOD. THE SEA BREEZE CIRCULATION THIS AFTERNOON AND EARLY EVENING MAY ADD AN ADDITIONAL 5 KT AND/OR GUSTS AT OR ABOVE 20 KT TO THE NEAR SHORE WATERS. SIGNIFICANT SEAS WILL RANGE BETWEEN 2 AND 4 FT...POSSIBLY UP TO 5 FT DURING THE PEAK OF THE SEA BREEZE LATE THIS AFTN AND EVENING. WIND DRIVEN WAVES AT 4 TO 6 SECOND PERIODS WILL DOMINATE THE SEAS SPECTRUM...WITH VERY LITTLE INPUT FROM THE ESE 1 TO POSSIBLY 2 FOOT GROUND SWELL. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...A BRIEF PERIOD OF W/NW WINDS WILL START WEDNESDAY BEHIND A WEAK COLD FRONT...BUT THESE WILL QUICKLY RETURN TO A SW DIRECTION THANKS TO HIGH PRESSURE OFFSHORE...AND THEN PERSIST THROUGH THE END OF THE PERIOD. THE GRADIENT REMAINS RATHER WEAK HOWEVER...SO WINDS WILL BE LESS THAN 10 KTS MOST OF THE PERIOD...INCREASING TO 10-15 KTS THURSDAY NIGHT AHEAD OF ANOTHER COLD FRONT. SEAS WILL BE 2-4 FT FIRST THING WEDNESDAY...BUT WILL FALL TO 1-2 FT MOST OF THE SHORT TERM BEFORE A SLIGHT INCREASE WITH THE HIGHER WINDS THURSDAY NIGHT. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 300 AM TUESDAY...COLD FRONT WILL SLOWLY DROP ACROSS THE WATERS BY LATE FRIDAY...CAUSING A WIND SHIFT FROM S/SW AT 5-10 KTS...TO N/NE AT 5-10 KTS...BY SATURDAY MORNING. THIS WIND SHIFT WILL OCCUR FIRST ACROSS AMZ250...AND THEN DROP S/SW THROUGH FRIDAY NIGHT...AND BY SATURDAY MORNING ALL WATERS WILL BE EXPERIENCING LIGHT N/NE WINDS. A SURGE BEHIND THIS BOUNDARY WILL THEN PUSH WIND SPEEDS UP TO 10-15 KTS SATURDAY...REMAINING FROM THE NE. WAVE HEIGHTS FRIDAY WILL BE OF LOW AMPLITUDE...1-2 FT...BUT A CONFUSED SPECTRUM WILL DEVELOP AS THE WIND SHIFT OCCURS. SEAS WILL BUILD SLOWLY ON SATURDAY TO 2-3 FT WITH A NE WIND CHOP BECOMING PREDOMINANT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...DCH SHORT TERM...JDW LONG TERM...JDW AVIATION...DCH

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