Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 251916 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 316 PM EDT FRI JUL 25 2014 .SYNOPSIS... A STALLED FRONT ACROSS NORTHEAST SOUTH CAROLINA WILL LIFT NORTH AND DISSIPATE OVERNIGHT INTO SATURDAY. BUILDING HIGH PRESSURE WILL FOLLOW...BRINGING HOT AND HUMID CONDITIONS OVER THE WEEKEND AND MONDAY. ANOTHER UNUSUALLY STRONG COLD FRONT MAY BRING STRONG THUNDERSTORMS LATE MONDAY...FOLLOWED BY COOLER AND DRIER WEATHER TUESDAY...POSSIBLY THROUGH MUCH OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 315 PM FRIDAY...A STALLED FRONT IN THE GEORGETOWN VICINITY HAS IGNITED A TREMENDOUS CONVECTIVE BLOWUP THIS AFTERNOON. LARGE INSTABILITY ON THE ORDER OF 3000 J/KG...SLOW STORM MOVEMENT PARALLEL TO THE FRONTAL BOUNDARY...AND PRECIPITABLE WATER VALUES NEAR 1.9 INCHES ARE ALL VERY HELPFUL FOR PRODUCING HEAVY RAINFALL AND THE POTENTIAL FOR FLOODING. THIS CONVECTIVE ACTIVITY EXTENDS WESTWARD TO JUST SOUTH OF COLUMBIA SC AND WILL LIKELY CONTINUE THROUGH 5-7 PM BEFORE DISSIPATING AS THE AIRMASS BECOMES OVERTURNED AND STABILIZED. INTERESTINGLY...A COUPLE REPORTS OF HAIL HAVE BEEN RECEIVED IN THE PAST HALF HOUR...UNUSUAL TO SAY THE LEAST IN A HUMID AIRMASS WITH FREEZING LEVELS UP AROUND 15.5 KFT. TO THE NORTH IT HAS BEEN AN UNUSUALLY COOL DAY FOR LATE JULY WITH TEMPERATURES ONLY RECENTLY REACHING THE 80S IN WILMINGTON... WHITEVILLE...AND FLORENCE. FOG AND LOW STATUS THAT FOLLOWED THE FRONT SOUTH THIS MORNING HAS SINCE LIFTED INTO A LAYER OF STRATOCUMULUS WITH BASES BETWEEN 1500 AND 3000 FT. MODELS STRUGGLED INITIALLY WITH THE EXCEPTIONAL SOUTHWARD MOVEMENT OF THIS FRONT EARLIER THIS MORNING...AND ARE NOW STRUGGLING WITH THE FRONT`S SLUGGISH RETURN NORTHWARD. THE 12Z NAM HAD VERY POOR INITIALIZATION WITH THIS BOUNDARY. THE 12Z GFS WAS INITIALIZED A LITTLE BETTER BUT I AM ESSENTIALLY USING THE RUC...HRRR...AND 12Z WRF-ARW AND WRF-NMM MODELS FOR WIND DIRECTION FORECASTS TONIGHT. AS SYNOPTIC HIGH PRESSURE MOVES EAST OFF THE MID-ATLANTIC COAST THIS SHOULD INDUCE THE FRONT TO RETURN NORTHWARD...ALBEIT MORE SLOWLY THAN MOST SYNOPTIC GUIDANCE IS INDICATING. WITH RICH LOW-LEVEL MOISTURE AND RELATIVELY DRY AIR IN THE MID-LEVELS...CALM WINDS...AND SLOWLY CLEARING SKIES...IT IS A GOOD SETUP FOR FOG OR LOW STRATUS OVERNIGHT. VISIBILITIES WILL PROBABLY BEGIN DECREASING AFTER MIDNIGHT WITH THE WORST CONDITIONS AROUND DAYBREAK. LOWS SHOULD REACH THE LOWER 70S WITH SOME MID 70S NEAR THE COAST. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 315 PM FRIDAY...MAIN WEEKEND WEATHER HEADLINE IS EXPANDING HEAT AND HUMIDITY. HEAT INDICES/APPARENT TEMPERATURES FACTORING IN ELEVATED DEWPOINT VALUES...YIELDS 97-102 DEGREE INDICES FOR SATURDAY...AND INTO THE BROILER SUNDAY AS MAXIMUM APPARENT TEMPS SUNDAY AFTERNOON CREST TO 104-107 DEGREES. IF CONSISTENCY HOLDS IN THE MAX TEMP FORECAST...THEN WE WILL BE LOOKING AT PROSPECTS OF A HEAT ADVISORY NEEDED ON SUNDAY. PCPN-WISE...BEST CHANCE LOOKS TO BE SATURDAY AS A DECAYING FRONTAL BOUNDARY LIFTS NORTH ACROSS CAPE FEAR AND SE NC. DRY MID-LEVEL AIR WILL PLACE LIMITATIONS OF PCPN EXTENT AND MAGNITUDE SATURDAY...BUT A FEW SHOWERS SHOULD BE EXPECTED ON SATURDAY AS LOW-LEVEL MOISTURE LINGERS. SUNDAY LOOKS DRYISH WITH WESTERLY FLOW THROUGH MUCH OF THE COLUMN SQUELCHING RAIN CHANCES. BECAUSE OF INTENSE HEAT AT THE SURFACE SUNDAY HOWEVER...AN ISOLATED TSTM CANNOT BE RULED ENTIRELY. DUE TO THE GRADUAL BUILD UP OF HEAT...VERY MILD MINIMUMS SUNDAY AND MONDAY DAYBREAK ARE ANTICIPATED...ESSENTIALLY MIDDLE 70S TO THE LOWER 80S AND MILDEST NEAR THE SEA...PARTICULARLY AS WE SEE STILL SW WINDS HOLDING UP IN THE OVERNIGHT PERIODS...ESPECIALLY LATE SUNDAY INTO EARLY MONDAY. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 315 PM FRIDAY...IMPRESSIVE MID-LEVEL AMPLIFICATION THROUGH THE EXTENDED WILL DRIVE ACTIVE WEATHER THE FIRST PORTION OF THE EXTENDED...BUT QUIET AND COOL CONDITIONS WILL FOLLOW THE MAJORITY OF THE UPCOMING WEEK. MONDAY SHAPING UP TO BE ONE OF THE HOTTEST DAYS OF THE YEAR LOCALLY...AS RETURN FLOW STRENGTH INCREASES...AND 850MB TEMPS CLIMB ABOVE 20C. COMBINE THIS WITH WHAT WILL LIKELY BE A VERY WARM START TO THE DAY (WARM OVERNIGHT LOWS FROM SUNDAY)...AND MONDAY WILL FEATURE WIDESPREAD MID 90S ACROSS THE AREA...WITH UPPER 90S POSSIBLE IN MANY SPOTS. THESE TEMPS COMBINED WITH HIGH DEWPOINTS WILL BRING APPARENT TEMPS TO NEAR HEAT ADVISORY CRITERIA ON MONDAY. THIS WILL BE THE LAST SUMMER-LIKE DAY FOR QUITE SOME TIME THOUGH...AS AN ANOMALOUSLY SHARP TROUGH (UP TO -4 SD) DIVES INTO THE EASTERN CONUS. BENEATH THIS TROUGH A STRONG COLD FRONT WILL CROSS THE LOCAL AREA MONDAY EVE AND NIGHT...MOVING OFFSHORE BY TUESDAY MORNING. A STRONG COLD FRONT DIVING INTO A VERY WARM UNSTABLE AIRMASS WILL SUPPORT THE CHANCE FOR STRONG CONVECTION ON MONDAY...AND SPC IS ALREADY HIGHLIGHTING THE REGION IN THE D4 OUTLOOK. IT IS TOO EARLY TO FOCUS ON DETAILS OF COURSE...BUT A STRONG COLD FRONT IMPINGING ON A HIGHLY UNSTABLE AIRMASS WITH RAPID HEIGHT FALLS AND STRONG MID-LEVEL FLOW IS UNQUESTIONABLY A SOLUTION WHICH SUPPORTS CONVECTION. WILL BUMP TO LIKELY POP MONDAY FOR MUCH OF THE AREA. TO USE THE WORD SIGNIFICANT TO DESCRIBE THE AIR MASS CHANGE FROM MONDAY THROUGH WEDNESDAY MAY BE AN UNDERSTATEMENT...AS 850MB TEMPS DROP FROM AROUND 21C (+2 SD) TO 13C (-2 SD) IN JUST 48 HOURS! WHILE THIS OCCURS...PWATS DROP BELOW 1 INCH BY WEDNESDAY AS WELL...AND THUS THE TUE/WED/THU TIMEFRAME SHOULD BE DRY LOCALLY...ALBEIT WITH TEMPS WELL BELOW NORMAL FOR LATE JULY. ALTHOUGH STRONG CAA EVENTS IN JULY ARE...NOT SURPRISINGLY...RARE...EXPECT GUIDANCE IS OVERDOING TEMP FORECASTS MID WEEK AND WILL UNDERCUT NUMBERS...WITH TEMPS LIKELY 5-10 DEGREES BELOW NORMAL MUCH OF NEXT WEEK. LATE IN THE WEEK...MID-LEVEL TROUGH BEGINS TO WEAKEN...AND STRONG RIDGE OVER THE ATLANTIC BEGINS TO PUSH BACK TO THE WEST DRIVING A RETROGRADING PATTERN INTO FRIDAY...DRIVING WARMING TEMPS BUT INCREASING CHANCES FOR POP. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 18Z...EXPECT VFR THROUGH THIS EVENING WITH INCREASING CHANCES FOR SHRA/TSRA THROUGH THIS AFTERNOON...ESPECIALLY NEAR & SOUTH OF MYRTLE BEACH. MVFR/IFR POSSIBLE LATE OVERNIGHT INTO THE EARLY MORNING HOURS DUE TO FOG/LOW CIGS...IMPROVING TO VFR SATURDAY LATE MORNING. MVFR/IFR CIGS HAVE PERSISTED ACROSS THE AREA..AND MAY CONTINUE TO DO SO AT A FEW OF THE TAF SITES FOR THE NEXT HOUR BEFORE IMPROVING TO MVFR AND THEN VFR AS THE CLOUD LAYER BURNS OFF. NORTHEAST WINDS WILL BECOME SOUTHEAST ALONG THE COAST AROUND 10 KTS LATER THIS AFTERNOON WITH INLAND SITES CONTINUING A LIGHT NORTHEAST WIND. LATEST RADAR IMAGERY DEPICTS INCREASING SHRA/TSRA NEAR GEORGETOWN AND CHARLESTON SC...AND COVERAGE AND CHANCES WILL INCREASE THROUGHOUT THE REST OF THE AFTERNOON AS THE SEA BREEZE AND THE FRONT INTERACT. ANY SHRA/TSRA COULD PRODUCE HEAVY RAINFALL OR FLIGHT CAT RESTRICTIONS...AND WILL TAPER OFF LATER THIS EVENING. OVERNIGHT INTO THE EARLY MORNING HOURS WINDS WILL BECOME LIGHT AND VARIABLE AND MVFR/IFR IS POSSIBLE DUE TO FOG AT ALL SITES...WHICH WILL DISSIPATE SATURDAY MORNING GIVING WAY TO VFR WITH LIGHT WINDS. EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE SUNDAY AND MONDAY. OTHERWISE EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 315 PM FRIDAY...A STALLED FRONT IN THE GEORGETOWN SC VICINITY HAS BEEN THE FOCUS FOR A SIGNIFICANT BLOWUP OF THUNDERSTORM ACTIVITY THIS AFTERNOON. LOOK FOR THIS ACTIVITY TO CONTINUE MOVING EAST-NORTHEASTWARD...AFFECTING LARGE PORTIONS OF THE SOUTH CAROLINA COASTAL WATERS AND POTENTIALLY THE WATERS NEAR AND SOUTH OF CAPE FEAR BEFORE SUNSET. THUNDERSTORM CHANCES ARE MUCH LESS AFTER SUNSET BUT AN ISOLATED SHOWER CANNOT BE RULED OUT EVEN AFTER MIDNIGHT. THE FRONT SHOULD BEGIN TO MOVE NORTHWARD OVERNIGHT...REACHING CAPE FEAR LATER THIS EVENING AND EVENTUALLY MOVING NORTHWARD INTO EASTERN NORTH CAROLINA. WINDS WHICH ARE STILL EASTERLY AT 3 PM SHOULD TURN SOUTHERLY OVERNIGHT...BUT WITH LITTLE INCREASE IN WIND SPEED EXPECTED. SEAS CURRENTLY 2-3 FEET ARE EVENLY SPLIT BETWEEN A 9-SECOND SOUTHEAST SWELL AND SHORTER PERIOD WAVES PRODUCED BY LOCAL WINDS. LITTLE CHANGE IS ANTICIPATED OVERNIGHT. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 315 PM FRIDAY...THE MARINE WEEKEND HEADLINE...INCREASING SW WINDS SATURDAY THROUGH SUNDAY....WITH AN EXERCISE CAUTION MARINE CONDITIONS LIKELY DEVELOPING SUNDAY OR SUNDAY NIGHT....FOR 15-20 KT SW WINDS AND SEAS OF 4-5 FEET. THEREFOR WHILE SATURDAY WILL BE A MANAGEABLE DAY FOR BOATING...SUNDAY WILL BECOME BUMPY AND A BIT MORE HAZARDOUS AS WIND-WAVES CONTINUE TO GROW IN PERSISTENT AND MODERATELY STRONG SW WINDS. ISOLATED TSTMS EXPECTED ON THE WATERS EARLY SATURDAY...AND POTENTIALLY LATE SUNDAY NIGHT OFFSHORE. .LONG TERM /MONDAY THROUGH WEDNESDAY/... AS OF 3 PM THURSDAY...STRONG PRE-FRONTAL FLOW AHEAD OF A COLD FRONT WILL PUSH WINDS UP ABOVE 20 KTS FROM THE SW ON MONDAY...DRIVING SEAS TO 4-6 FT...AND A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED ON MONDAY. THIS FRONT WILL CROSS THE WATERS MONDAY NIGHT...WITH A RAPID WIND SHIFT TO THE NW BY TUESDAY MORNING...AND SPEEDS EASING THROUGH TUESDAY TO 5-10 KTS. WEAK AREA OF HIGH PRESSURE WILL BUILD ACROSS THE WATERS THEREAFTER...CAUSING WINDS TO BECOME NE AROUND 10 KTS. AFTER THE SCA CONDITIONS SUBSIDE MONDAY NIGHT...SEAS WILL BE 2-4 FT THROUGH THE REMAINDER OF THE PERIOD. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MJC NEAR TERM...TRA SHORT TERM...MJC LONG TERM...JDW AVIATION...TRA/SGL

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