Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 241424 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1024 AM EDT THU JUL 24 2014 .SYNOPSIS...
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HEAT INDEX VALUES SHOULD TOP 100 DEGREES THIS AFTERNOON. A COLD FRONT WILL APPROACH FROM THE NORTHWEST TODAY...BRINGING AN INCREASING RISK FOR STRONG THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT. THIS FRONT WILL STALL ACROSS THE AREA FRIDAY BEFORE DISSIPATING ON SATURDAY. HIGH PRESSURE WILL BRING HOT AND HUMID CONDITIONS SUNDAY AND MONDAY. A STRONG COLD FRONT WILL CROSS THE AREA EARLY TUESDAY...BRINGING COOLER AND DRIER CONDITIONS FOR THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1015 AM THURSDAY...CLEAR SKIES OVER THE AREA THIS MORNING SHOULD TURN PARTLY CLOUDY OVER THE NEXT FEW HOURS. TEMPERATURES ARE SOARING QUICKLY WITH MID TO UPPER 80S ALREADY OBSERVED. THE LATEST FEW HRRR RUNS PLUS THE 00Z NSSL WRF ARE SHOWING A LATER CONVECTIVE INITIATION TIME THAN OUR PREVIOUS FORECAST INDICATED...SO I HAVE SHIFTED THE WINDOW OF HIGHEST FORECAST POPS INTO THE 4 PM TO 10 PM RANGE. THIS ALSO IS WHEN WE COME UNDER THE BEST INFLUENCE OF THE RIGHT-ENTRANCE REGION OF A HEALTHY 300 MB JET EXTENDING FROM THE MID-ATLANTIC INTO THE CANADIAN MARITIMES. NO OTHER SIGNIFICANT CHANGES ARE NEEDED...AND FORECAST TEMPERATURES/DEWPOINTS STILL SUPPORT HEAT INDICES IN THE 100-104 RANGE THIS AFTERNOON. PREVIOUS DISCUSSION FROM 600 AM FOLLOWS... A QUICK MOVING MID-LEVEL SHORTWAVE MOVED ACROSS THE UPSTATE OF SOUTH CAROLINA DURING THE LATE NIGHT AND WAS CURRENTLY MOVING NE ACROSS CENTRAL NORTH CAROLINA. A FEW SHOWERS AND THUNDERSTORMS DEVELOPED IN RESPONSE TO THIS ADDED LIFT AND ARE EXPECTED TO PASS BY TO OUR NORTH THROUGH 9 AM. A WEAKER SECONDARY IMPULSE WAS MOVING NE ACROSS THE EASTERN CAROLINAS...BUT CONVECTION HAS NOT DEVELOPED IN RESPONSE TO THIS FEATURE. A COLD FRONT WILL DROP INTO THE LEE SIDE TROUGH POSITION TODAY AND THE FRONT WILL THEN SLIDE ACROSS THE FORECAST AREA TONIGHT... LIKELY LYING ACROSS SOUTHERN AND EASTERN PORTIONS OF THE FORECAST AREA AT DAYBREAK FRI. THE UPPER TROUGH WILL STILL BE UPSTREAM FRI MORNING. THE ATMOSPHERE WILL BE WARM AND MOIST THROUGH A DEEP LAYER WITH PRECIPITABLE WATER VALUES INCREASING THROUGH THE AFTERNOON/EVE... IN EXCESS OF 2 INCHES...AND ALONG THE COAST...ABOVE 2.25 INCHES. TEMPERATURES ARE EXPECTED TO REACH THE LOWER TO MID 90S TODAY. THIS WILL BRING MIXED LAYER CAPE VALUES IN THE NEIGHBORHOOD OF 2000-2500 J/KG. MID LEVEL LAPSE RATES AND SHEAR VALUES ARE UNIMPRESSIVE...BUT MID-LEVEL WINDS WILL BE ON THE ORDER OF 40 KT. THE BIGGEST RISK WITH THUNDERSTORMS TODAY AND TONIGHT WILL BE FREQUENT LIGHTNING AND HEAVY RAIN...ALTHOUGH STORM MOTIONS ARE MUCH HIGHER THAN EARLIER IN THE WEEK WHICH SHOULD LIMIT THE EXCESSIVE RAINFALL THREAT. HOWEVER...THE DEEPEST CONVECTION WILL BE CAPABLE OF STRONG WIND GUSTS AND AN ISOLATED WET MICROBURST WITH DAMAGING WINDS CAN NOT BE RULED OUT. THUNDERSTORMS MAY DEVELOP ALONG THE COAST AS A RATHER SHARP SEABREEZE BOUNDARY DEVELOPS LATER THIS MORNING/MIDDAY. ELSEWHERE... AFTERNOON THUNDERSTORMS WILL POP AS THE CONVECTIVE TEMPS ARE EXCEEDED. THE CONVECTION SHOULD TEND TO BECOME MORE ORGANIZED MID AND LATE AFTERNOON AS IT MOVES TOWARD THE COAST. WE EXPECT CONVECTION TO LAST WELL INTO THE NIGHT IF NOT THROUGH THE NIGHT AS A MODEST SHORTWAVE ALOFT INTERACTS WITH THE SURFACE FRONT. HEAT INDEX VALUES LATE MORNING AND THIS AFTERNOON WILL REACH 100 DEGREES IN MOST AREAS AND AS HIGH AS 104 DEGREES. OF COURSE...ONCE A STRONG THUNDERSTORM MOVES OVERHEAD...THE HEAT WILL GET KNOCKED DOWN...BUT NOT THE HUMIDITY.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 AM THURSDAY...COLD FRONT STALLED ACROSS THE AREA WILL CONTINUE SHOWER AND THUNDERSTORM CHANCES ON FRIDAY...BUT AT THE SAME TIME DRIER AIR WILL BEGIN TO ADVECT IN FROM THE WEST...DRYING OUT THE MID AND UPR PORTIONS OF THE COLUMN. STILL...WITH THE FRONT IN PLACE...TEMPS RISING TO AROUND 90...AND DEWPOINTS IN THE LOW 70S...THERE WILL BE PLENTY OF FUEL AROUND FOR CONVECTION BEFORE THE DRIER AIR WORKS INTO THE CWA. THUS WILL CARRY CHC POP FRIDAY...HIGHEST ACROSS THE EASTERN PORTIONS OF THE CWA. THE DIURNAL TREND FOR CONVECTION MAY BE A BIT ATYPICAL AS THE DRY AIR INTRUDES OVERHEAD...AND THE HIGHEST COVERAGE OF CONVECTION MAY BE LATE MORNING/EARLY AFTN BEFORE TAPERING OFF INTO THE EVE. THIS FRONT WILL WASH OUT FRIDAY NIGHT LEAVING MOSTLY CLEAR SKY CONDITIONS...BUT AS LIGHT SW FLOW RE-DEVELOPS...MINS WILL FALL ONLY INTO THE MID 70S AT THE COAST...AND TO AROUND 70 INLAND. ANY AIRMASS CHANGE ASSOCIATED WITH THE PRIOR FRONT QUICKLY ERODES SATURDAY...LEAVING A HOT DAY ACROSS THE CWA. FORTUNATELY...THE COLUMN WILL BE DRIER...AND THUS HUMIDITY VALUES WILL BE MUCH LOWER...KEEPING APPARENT TEMPS TO BELOW 100 EVEN AS HIGHS CLIMB TO AROUND 90 AT THE COAST...MID 90S WELL INLAND. WILL CONTINUE WITH THE INHERITED SCHC POP ON SATURDAY SIMPLY DUE TO THE HEAT...BUT ONLY ISOLATED STORMS ARE POSSIBLE AS PWATS DROP TO LESS THAN 1.5 INCHES. INCREASING SW RETURN FLOW SATURDAY NIGHT WILL PREVENT SIGNIFICANT COOLING...AND THUS LOWS SAT NIGHT WILL BE WELL ABOVE NORMAL...UPR 70S AT THE BEACHES TO LOW 70S ONLY WELL INLAND. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 300 AM THURSDAY...A HOT START TO THE PERIOD...BUT IT WILL BE SHORT LIVED AS...ONCE AGAIN...AN ANOMALOUSLY STRONG UPPER TROUGH DIVES ACROSS THE EASTERN CONUS. SUNDAY LOOKS TO BE THE HOTTEST DAY OF THE PERIOD AS SUBTLE MID-LEVEL RIDGING AND STRONG SW RETURN FLOW AROUND A RIDGE OF HIGH PRESSURE PUSH TEMPS INTO THE MID AND MAYBE UPR 90S...AND WE MAY EXPERIENCE OUR FIRST HEAT ADVISORY OF 2014 (HEAT INDEX OF 105 OR GREATER). ALTHOUGH HUMIDITY WILL INCREASE ON SUNDAY AS WELL...CONVECTIVE COVERAGE MAY BE QUITE LIMITED DUE TO SOME MID-LEVEL DRY AIR PERSISTING...AND A LID WITHIN A LOW-LEVEL THERMAL RIDGE. MONDAY WILL BE SIMILAR...ALTHOUGH A DEGREE OR 2 COOLER AS CLOUD COVER INCREASES AND MID-LEVEL HEIGHTS DECREASE AHEAD OF AN ADVANCING COLD FRONT. INCREASING POP IS WARRANTED MONDAY AS WELL...WITH THE BEST CHANCE OCCURRING MONDAY NIGHT AS THE COLD FRONT MOVES INTO THE AREA. LOWS BOTH NIGHTS WILL BE ABOVE NORMAL IN MID AND UPR 70S. BIG AIR MASS CHANGE OCCURS THEREAFTER AS -3 SD TROUGH DROPS INTO THE MIDWEST...DRIVING A STRONG COLD FRONT INTO THE CWA AND OFFSHORE DURING TUESDAY. THIS TROUGH WILL PRODUCE LOWERED HEIGHTS ALL THE WAY INTO THE GULF OF MEXICO THROUGH THE MIDDLE OF NEXT WEEK...BUT FORTUNATELY FOR THE AREA THE TROUGH AXIS REMAINS DISPLACED WEST OF THE COASTAL CAROLINAS. WHILE DRIER AND COOLER AIR IS ANTICIPATED TUE/WED...WITH TEMPS RUNNING SEVERAL DEGREES BELOW NORMAL...LOCALLY WE WILL NOT BE AS COOL AS OUR NEIGHBORS WELL WEST. LOWER POP IS EXPECTED THROUGH MID-WEEK...BUT INCREASING E/NE FLOW MAY ALLOW FOR RESIDUAL RAIN CHANCES TO PERSIST ALONG THE COAST THROUGH THE END OF THE PERIOD. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... AS OF 12Z...POSSIBLE MVFR/IFR IN ANY HEAVY DOWNPOURS THIS AFTERNOON AND EVENING AS CHANCES FOR SHRA/TSRA INCREASING THROUGHOUT THE DAY...ALONG WITH PATCHY FOG POSSIBLE BEFORE DAYBREAK ON FRIDAY. OTHERWISE EXPECT VFR. WITH SOUTHWEST WINDS AOB 10 KTS...VFR PREVAILS THIS MORNING ACROSS THE AREA...WITH THE EXCEPTION OF KLBT WHICH IS EXPERIENCING IFR DUE TO LOW CIGS. WOULD NOT ENTIRELY RULE OUT A VERY BRIEF PERIOD OF IFR AT KFLO AS WELL IN THE NEXT HOUR OR TWO AS LOW CIGS MOVE ABOUT THE INLAND AREAS AS SEEN FROM LATEST 11.9-3.9 SATELLITE IMAGERY. AFTER 14Z...EXPECT ALL SITES TO BE VFR WITH SOUTHWEST WINDS AOB 12 KTS AHEAD OF AN APPROACHING COLD FRONT AND GUSTS INCREASING TO AROUND 20 KTS BEGINNING OVER THE NEXT FEW HOURS. CHANCES WILL INCREASE FOR SHOWERS AND THUNDERSTORMS THROUGHOUT THE DAY WITH THE COLD FRONT...AND THOUGH THUNDERSTORMS WILL TAPER OFF THIS EVENING...ANTICIPATE SHOWERS TO PERSIST INTO THE EARLY OVERNIGHT HOURS. BRIEF PERIODS OF MVFR/IFR ARE POSSIBLE IN ANY SHRA/TSRA ESPECIALLY WITH HEAVIER DOWNPOURS AND LOWER CIGS. LATE OVERNIGHT INTO THE EARLY MORNING HOURS...MVFR IS POSSIBLE DUE TO PATCHY FOG. EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE THROUGH FRIDAY...AS WELL AS SUNDAY AND MONDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1015 AM THURSDAY...WEST-SOUTHWEST WINDS ARE ALREADY GUSTING TO 20 KNOTS AT THE OCEAN CREST PIER ON OAK ISLAND...WITH 12-15 KNOTS PREVAILING ELSEWHERE. NO SIGNIFICANT CHANGES ARE NEEDED TO THE PREVIOUS FORECAST...EXCEPT FOR LOWERING SEA HEIGHTS BY ABOUT 1 FOOT INITIALLY BASED ON AVAILABLE BUOY DATA. PREVIOUS DISCUSSION FROM 600 AM FOLLOWS... A TIGHTER PRESSURE GRADIENT WILL BE REALIZED TODAY INTO THIS EVENING AS A RATHER IMPRESSIVE TROUGH FOR THIS TIME OF YEAR APPROACHES. SOUTHWEST SUSTAINED WIND SPEEDS ARE EXPECTED TO REACH 20 KT WITH GUSTS TO 25 KT. SEAS TODAY ARE EXPECTED TO REACH UP TO 4 TO 5 FT...WITH SOME 6 FT SEAS POSSIBLE ACROSS THE OUTERMOST WATERS LATE DAY AND THIS EVE. AT THIS TIME...WILL ISSUE A SMALL CRAFT SHOULD EXERCISE CAUTION HEADLINE. THE FRONTAL ZONE SHOULD BE NEARING THE WATERS LATE TONIGHT AND EXPECT THE WIND DIRECTION OVERNIGHT WILL VEER TO A MORE WESTERLY DIRECTION WITH WIND SPEEDS DECREASING TO 10 TO 15 KT. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 AM THURSDAY...WESTERLY WINDS WILL BEGIN THE PERIOD AS A COLD FRONT WAVERS JUST OFF THE COAST. THIS FRONT WILL LIFT SLOWLY BACK TO THE NORTH DURING FRIDAY...WITH WINDS REMAINING LIGHT...AROUND 10 KTS...BUT BACKING TO THE SW THROUGH SUNDAY MORNING. THEREAFTER...WINDS WILL INCREASE THROUGH SATURDAY AS THE PRESSURE GRADIENT TIGHTENS ABOUT AROUND HIGH PRESSURE RIDGING BACK TOWARDS THE COAST...WITH SPEEDS RISING FROM THE SW TO AROUND 15 KTS. SEAS WILL BE 3-4 FT EARLY FRIDAY...AND RISE AGAIN TO 3-4 FT LATE SATURDAY. IN BETWEEN 1-3 FT SEAS WILL BE COMMON THANKS TO THE EXTENDED PERIOD OF LIGHTER WINDS. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 300 AM THURSDAY...HIGH PRESSURE OFFSHORE RIDGING TOWARDS THE COAST...AND A STRONG COLD FRONT SLOWLY APPROACHING FROM THE NW...WILL PINCH THE GRADIENT SUNDAY AND MONDAY. THIS DRIVES SW WINDS UP TO 20 KTS OR MORE BOTH DAYS...AND PUSHES WIND-DRIVEN SEAS UP TO 4-6 FT. AN SCA MAY BE NEEDED FOR AN EXTENDED PORTION OF THIS PERIOD AHEAD OF THE COLD FRONT WHICH IS PROGGED TO CROSS THE WATERS BY TUESDAY MORNING.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RJD/TRA SHORT TERM...JDW LONG TERM...JDW AVIATION...SGL

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