Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 271511 AFDILM AREA FORECAST DISCUSSION...COR NATIONAL WEATHER SERVICE WILMINGTON NC 1111 AM EDT SUN JUL 27 2014 .SYNOPSIS... SWELTERING HEAT AND HUMIDITY WILL PREVAIL THE NEXT FEW DAYS AHEAD OF AN APPROACHING AND UNUSUALLY STRONG LATE JULY COLD FRONT. THE FRONT MAY FORCE SEVERAL SEVERE STORMS INTO THE AREA LATE MONDAY. DRY AND UNSEASONABLY COOL AIR WILL OVERSPREAD THE CAROLINAS FROM TUESDAY THROUGH MUCH OF THE UPCOMING WEEK...AS HIGH PRESSURE FROM CENTRAL CANADA DROPS SOUTHEAST AND SETTLES INTO THE REGION. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1055 AM SUNDAY...A MESO-SCALE CONVECTIVE VORTEX IS BECOMING UNRAVELED OVER CENTRAL NORTH CAROLINA THIS LATE MORNING...AND AM ANTICIPATING THE BROKEN LINE OF SHOWERS EXTENDING SOUTHWARD ACROSS OUR WESTERN ZONES CURRENTLY...WILL WEAKEN AND DIMINISH AS IT MOVES TOWARD A FLORENCE SC TO LUMBERTON NC CORRIDOR. THIS FEATURE IS SET TO ENCOUNTER INCREASINGLY UNFAVORABLE CONVECTIVE CONDITIONS WITH EXCEPTIONALLY WARM AIR ALOFT DOMED OVER OUR REGION. THE BROAD SCALE RIDGE LIKELY WINS OUT...AND ISOLATED TO NO ACTIVITY IS ON TAP FOR THE AFTERNOON HOURS AMID A BROILING AIR MASS BY APPARENT FEEL STANDARDS. HEAT ADVISORIES ARE POSTED FOR MOST OF OUR AREA AWAY FROM THE COAST...AND OVERALL HEAT INDICES THIS AFTERNOON WILL RANGE FROM 103 TO 108...HIGHEST SC INTERIOR AND LOWEST IMMEDIATE COASTAL STRIPS. THE LAND-SEA TEMPERATURE DIFFERENTIAL THIS AFTERNOON WILL BECOME THE ENGINE THAT PROPELS A VIGOROUS SEA BREEZE CIRCULATION...AND S WINDS GUSTS ALONG BEACHES OF 20-25 MPH CAN BE EXPECTED BY THE MID AFTERNOON AND PREVAILING INTO EVENING AS THE SYNOPTIC PRESSURE GRADIENT TIGHTENS...SUSTAINING ELEVATED WINDS OVERNIGHT. THIS COUPLED WITH LINGERING TEPID AIR WILL SPELL MILD TO WARM MINIMUM TEMPERATURES MONDAY DAYBREAK WITH INCREASING SW WINDS THROUGH THE COLUMN. POPS/SHRA/TSTMS HOWEVER WILL REMAIN CONFINED TO COASTAL WATERS LATE TONIGHT AS NOCTURNAL BUOYANCY INCREASES OVER THE SEA. WILL NEED TO TAKE A CLOSER LOOK IN THIS POTENTIAL ACTIVITY MOVING ONSHORE INTO THE CAPE FEAR REGION EARLY ON MONDAY. && .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 /15Z SUNDAY THROUGH THURSDAY/... AS OF 12Z...AREAS OF MVFR DUE TO FOG THIS MORNING ACROSS THE AREA...WITH CONDITIONS IMPROVING TO VFR IN THE NEXT FEW HOURS AND CONTINUING THROUGH THE OVERNIGHT HOURS. MVFR POSSIBLE BEFORE THE END OF THE VALID TAF PERIOD DUE TO AREAS OF FOG. MOSTLY MVFR PREVAILS ACROSS THE AREA THIS MORNING DUE TO FOG. EXPECT THIS TO MIX OUT WITHIN THE NEXT HOUR...GIVING WAY TO VFR FOR THE REST OF TODAY. EXPECT INCREASING SOUTHWEST WINDS TODAY AS A PRESSURE GRADIENT TIGHTENS...WITH GUSTS UP TO 20 KT POSSIBLE ALONG THE COAST. COULD NOT ENTIRELY RULE OUT AN ISOLATED THUNDERSTORM OR TWO THIS AFTERNOON...THOUGH ANTICIPATE MAIN CONVECTION TODAY TO REMAIN NORTH OF THE AREA. INTO THE OVERNIGHT HOURS GUSTS WILL SUBSIDE...BUT SUSTAINED WINDS WILL REMAIN AROUND 10 TO 12 KTS. CONDITIONS WILL REMAIN VFR...POSSIBLY DETERIORATING TO MVFR TOWARDS THE END OF THE PERIOD DUE TO FOG. EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE MONDAY. OTHERWISE EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 11 AM SUNDAY...MODERATELY BUMPY CONDITIONS TODAY BUT NO HEADLINES EXPECTED UNTIL THIS EVENING AS SUSTAINED 15-20 KT SW WINDS AND 4-5 FOOT SEAS PREVAIL ON THE WATERS. A FEW TSTMS WILL BE POSSIBLE MAINLY LATE TONIGHT INTO DAYBREAK MONDAY. THE SEA BREEZE ALLOW 20 KT GUSTS TO BECOME COMMON IN THE AFTERNOON AND WINDS LIKELY WILL NOT DROP IN SPEEDS...SO AT MINIMUM AN EXERCISE CAUTION STATEMENT IS LIKELY TONIGHT...AND EVEN POTENTIALLY AN ADVISORY INTO EARLY MONDAY. SEA ENERGY WILL BE DOMINATED BY WIND- WAVES FROM THE SSW 3-4 FT AT 5 SECONDS...AND SE WAVES 1-1.5 FT AT 8-10 SECONDS. 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. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR SCZ017-023-024- 032-033-039-053-055. NC...HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR NCZ087-096-099- 109. MARINE...NONE. && $$ SYNOPSIS...MJC NEAR TERM...MJC SHORT TERM...III LONG TERM...III AVIATION...SGL

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