Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 191739 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 139 PM EDT FRI SEP 19 2014 .SYNOPSIS... A NORTHEASTERLY SURGE WILL PERSIST INTO SATURDAY AS HIGH PRESSURE WEDGES ACROSS THE CAROLINAS. LOW PRESSURE WILL DEVELOP OFF THE EAST COAST OF FLORIDA AND THEN MOVE NORTH...PASSING OFF THE CAROLINA COAST SATURDAY NIGHT AND SUNDAY. THE LOW IS EXPECTED TO REMAIN FAR ENOUGH OFFSHORE SUCH THAT ITS IMPACTS WILL BE LIMITED. A COLD FRONT WILL MOVE ACROSS THE AREA MONDAY. HIGH PRESSURE WILL BUILD BACK DOWN THE COAST ON TUESDAY...BRINGING A COOL AND DRY NORTHEAST FLOW. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM FRIDAY...STRONG HIGH PRESSURE CENTERED ACROSS NEW ENGLAND WILL BEGIN TO WEDGE STRONGLY ACROSS THE EASTERN CAROLINAS TODAY AND THEN PERSIST INTO TONIGHT. MEANTIME...AN INVERTED TROUGH POKING UP THE SOUTHEAST COAST FROM OFFSHORE OF FLORIDA WILL SHARPEN. LOW LEVEL WINDS WILL CONTINUE TO GUST IN THE NEIGHBORHOOD OF 20 TO 25 MPH...HIGHEST AT THE COAST AS A RATHER TIGHT PRESSURE GRADIENT WILL EXIST BETWEEN THE OFFSHORE TROUGH AND THE STRONG AREA OF HIGH PRESSURE. AS THE ONSHORE FLOW INCREASES THROUGH 25 KFT...WOULD EXPECT THE COLUMN TO MOISTEN...BUT MODELS CONTINUE TO SHOW THIS TO BE A VERY GRADUAL UNDERTAKING. AS FAR AS CONVECTION TODAY...WE SHOULD AGAIN SEE SOME ISOLATED DEVELOPMENT ALONG THE RESULTANT SEABREEZE...ACROSS THE CAPE FEAR AREA. A LARGE AREA OF SHOWERS AND THUNDERSTORMS REMAINS OFFSHORE IN ASSOCIATION WITH THE INVERTED TROUGH. SOME OF THIS ACTIVITY SHOULD MIGRATE ONSHORE GIVEN THE PREVAILING FLOW. THE RISK FOR THIS WILL BE HIGHEST ACROSS THE GRAND STAND AND WINYAH BAY AREA AND PERHAPS ALONG THE SOUTH SANTEE RIVER. ALTHOUGH IT IS SLIGHTLY COOLER ALOFT...THE HEATING AT THE SURFACE IS LOWER AND THUS THE INSTABILITY IS LESS TODAY THAN IT WAS EVEN ON THU. THEREFORE...THUNDERSTORMS SHOULD BE FEW...BUT AGAIN THE RISK WILL BE HIGHEST ALONG THE SOUTH CAROLINA COAST. GIVEN THE INVERTED TROUGH WILL BE SHARPENING AND EXPANDING NORTHWARD...EXPECT SHOWERS WILL BECOME MORE NUMEROUS FROM SOUTH TO NORTH TONIGHT. WILL SHOW POPS INCREASING ALONG AND EAST OF A LINE FROM CKI TO EYF...HIGHEST ALONG THE COAST. WILL INCLUDE THUNDERSTORMS ALONG/NEAR THE COAST AS WELL GIVEN THE DEEPENING MOISTURE SUPPLY. HIGHS TODAY WILL BE IN THE LOWER 80S WITH LOWS TONIGHT IN THE 60S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...HIGH PRESSURE WILL BUILD DOWN THE COAST SAT WHILE WEAK TROUGHING ALOFT CONTINUES. SURFACE LOW WILL START TO TAKE SHAPE OFF THE EAST COAST OF FL. THIS LOW DEVELOPS ALONG THE REMAINS OF A STALLED SURFACE BOUNDARY SO INITIALLY IT WILL NOT BE TROPICAL IN NATURE BUT AS IT LIFTS NORTH-NORTHEAST IT MAY ACQUIRE SOME TROPICAL CHARACTERISTICS. NHC CONTINUES TO ADVERTISE A 20% CHANCE OF TROPICAL DEVELOPMENT THROUGH 5 DAYS...BUT EVEN IF THIS FEATURE DEVELOPS INTO A FULL BLOWN TROPICAL SYSTEM IT WILL HAVE A LIMITED AMOUNT OF TIME TO STRENGTHEN AND STEERING FLOW WOULD KEEP IT OFF THE COAST. ULTIMATE PATH OF THE LOW IS STILL IN QUESTION...WITH HOW CLOSE IT PASSES OFF THE COAST THE MAIN CONCERN. DO NOT THINK ANY SIGNIFICANT WINDS WILL BE REALIZED BUT IT COULD MAKE FOR A CLOUDY/SOGGY SAT...ESPECIALLY ALONG THE IMMEDIATE COAST. OCCASIONAL GUSTS TO 20 MPH ALONG THE COAST ARE A POSSIBILITY. INLAND THERE WILL BE LESS OF A PRECIP THREAT THOUGH ENHANCED NORTHEAST FLOW BETWEEN THE SURFACE HIGH AND THE DEVELOPING LOW WOULD LIKELY MAINTAIN SOME LOWER CLOUDS AND THE PINCH GRADIENT WILL CREATE BREEZY CONDITIONS. WILL CARRY LOW CHC TO SLIGHT CHC POP ALONG THE COAST SAT INTO SAT NIGHT AND DRY INLAND. NORTHEAST FLOW...CLOUDS...AND PRECIP WILL KEEP HIGHS BELOW CLIMO BUT LINGERING CLOUD COVER AND MOISTURE OVERNIGHT WILL HOLD LOWS ABOVE CLIMO. EXITING SURFACE LOW AND MID LEVEL TROUGH IN PLACE LEADS TO DEVELOPMENT OF DEEP WEST TO NORTHWEST FLOW SUN...DRYING THE REGION OUT. PRECIPITABLE WATERS DROP ABOUT AN INCH SAT INTO SUN...FALLING FROM AROUND 1.7 TO AROUND 0.7. THE RESULT WILL BE BEAUTIFUL DAY WITH ABUNDANT SUNSHINE AND HIGHS IN THE MID 80S. DEVELOPMENT OF RETURN FLOW AHEAD OF ADVANCING COLD FRONT WILL HELP KEEP LOWS ABOVE TO WELL ABOVE CLIMO SUN NIGHT THOUGH SKIES SHOULD BE MOSTLY FREE OF CLOUDS. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY...MID LEVEL TROUGH DROPPING SOUTH FROM THE WESTERN GREAT LAKES WILL PUSH A COLD FRONT ACROSS THE AREA MON. WHERE PREVIOUS MEDIUM RANGE GUIDANCE HAD A DECENT AMOUNT OF MID LEVEL MOISTURE THE LAST FEW RUNS HAVE SHOWN A STEADY DECREASE IN MOISTURE ALOFT AND QPF. AT THIS POINT EVEN WITH IDEAL TIMING DURING PEAK HEATING THINK CONVECTION IS GOING TO BE SPOTTY IN NATURE AND HAVE NO PLANS TO CHANGE INHERITED SLIGHT CHC POP. FRONT ENDS UP STALLED OFF THE COAST TUE WITH MODIFIED HIGH BUILDING IN FROM THE PLAINS. MID LEVEL PATTERN OVER THE SOUTHEAST TRANSITIONS TO PROGRESSIVE TUE INTO WED AS THE 5H TROUGH OVER SOUTHEAST CANADA LIFTS NORTHEAST. MOISTURE ALONG THE STALLED FRONT MAY LEAD TO COASTAL CLOUDS AND LIGHT PRECIP DURING THE DAY. SOLUTIONS FOR MID TO LATE WEEK DIVERGE WITH SOME OF THE GUIDANCE SHOWING A COLD FRONT PUSHING SOUTH ON WED AS REINFORCING HIGH BUILDS IN. THIS WOULD KEEP THE REGION COOL AND DRY THROUGH THE END OF THE PERIOD. THE OTHER SOLUTION INVOLVES A COASTAL TROUGH WITH A WEAKER REINFORCING SURFACE HIGH. THE TROUGH AND ASSOCIATED MOISTURE ARE MUCH CLOSER TO THE COAST WITH CLOUDS/PRECIP OVER MUCH OF THE SOUTHEAST. ONLY PLAN MINIMAL CHANGES TO INHERITED FORECAST UNTIL MID TO LATE WEEK DETAILS BECOME A LITTLE CLEARER. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 18Z...STRONG WEDGE WILL CONTINUE THROUGH THE FORECAST PERIOD. GRADIENT WILL BE QUITE STRONG...WITH EAST NORTHEAST WINDS ALONG THE COAST GUSTING TO AROUND 25 KTS. THERE WILL BE SHOWERS ALONG THE PERIPHERY OF THE WEDGE...AND THERE IS A POSSIBILITY OF CONVECTION ALONG THE EXTREME WESTERN PORTION OF THE CWA...AS WELL AS THE COAST. COVERAGE WILL BE QUITE LIMITED HOWEVER. WINDS WILL REMAIN GUSTY TONIGHT...BUT NOT QUITE AS STRONG. A NOCTURNAL ONSHORE SHOWER IS POSSIBLE AT THE MYRTLES NEAR SUNRISE...CONTINUING THROUGH THE END OF THE FORECAST PERIOD WITH INTERMITTENT MVFR CONDITIONS EXPECTED. AS THE LOW AND MOISTURE MOVE NORTHWARD...ILM WILL SEE SOME SCATTERED CONVECTION TOWARD MIDDAY SATURDAY. EXTENDED OUTLOOK...CHANCE OF SHOWERS ALONG THE COAST SAT EVENING. GUSTY NORTHEAST WINDS SAT WILL BECOME NORTHWEST ON SUN AS LOW PRESSURE WELL OFFSHORE MOVES UP THE EAST COAST. SLIGHT CHANCE OF A SHOWER WITH A COLD FRONT MONDAY. VFR TUE AND WED. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM FRIDAY...STRONG HIGH PRESSURE CENTERED ACROSS NEW ENGLAND WILL BEGIN TO WEDGE STRONGLY ACROSS THE EASTERN CAROLINAS TODAY AND THEN PERSIST INTO TONIGHT. MEANTIME...AN INVERTED TROUGH POKING UP THE SOUTHEAST COAST FROM OFFSHORE OF FLORIDA WILL SHARPEN AS IT EXPANDS NORTHWARD. THIS WILL KEEP A RATHER TIGHT PRESSURE GRADIENT IN PLACE. WINDS ARE ALREADY GUSTING NEAR 25 KT AND SEAS...EVEN NEAR SHORE...WERE UP TO 5 FT...SO HAVE RAISED A SMALL CRAFT ADVISORY FOR ALL WATERS THROUGH THE REMAINDER OF TODAY AND INTO SAT MORNING. SUSTAINED NORTHEAST TO EAST WINDS WILL BE UP TO AROUND 20 KT. SEAS WILL BE UP TO 5 TO 7 FT. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...CONFIDENCE IS HIGH IN HIGH PRESSURE BUILDING DOWN THE COAST SAT AS WEAK LOW PRESSURE DEVELOPS OFF THE EAST FL COAST AND STARTS MOVING NORTH-NORTHEAST. HOWEVER...HAVE LOW CONFIDENCE WITH RESPECT TO THE STRENGTH AND PATH THE LOW TAKES. WHILE IT COULD ACQUIRE SOME TROPICAL CHARACTERISTICS AS IT LIFTS NORTH CURRENT CONSENSUS IS THE LOW WILL REMAIN EAST OF THE WATERS. PINCHED GRADIENT BETWEEN THE HIGH AND THE PASSING LOW WILL CAUSE NORTHEAST FLOW IN THE 15 TO 20 KT RANGE SAT INTO SAT NIGHT. WINDS BACK TO NORTHWEST AND THEN WEST-SOUTHWEST AS THE LOW EXITS OFF TO THE NORTH ON SUN. GRADIENT WEAKENS AS THE LOW DEPARTS WITH WIND SPEEDS DROPPING TO 10 TO 15 KT SUN AND UNDER 10 KT SUN NIGHT. 3 TO 5 FT SEAS SAT WILL SUBSIDE TO 2 TO 3 FT BY SUN AFTERNOON AS WINDS BECOME OFFSHORE AND WEAKEN. IF THE LOW ENDS UP A LITTLE CLOSER TO THE COAST LATE SAT SCA CONDITIONS MAY DEVELOP. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 300 AM THURSDAY...SOUTHWEST FLOW OVER THE WATERS MON WILL BECOME OFFSHORE MON NIGHT IN THE WAKE OF AN EXITING COLD FRONT. AHEAD OF AND IMMEDIATELY BEHIND THE FRONT WINDS WILL BE AROUND 10 KT. WINDS VEER TO NORTHEAST LATE MON NIGHT THEN INCREASE TO 15 TO 20 KT TUE AND TUE NIGHT. SEAS 2 TO 3 FT MON INTO TUE WILL BUILD TO 3 TO 5 BY THE END OF THE PERIOD. HEADLINES MAY BE REQUIRED LATE IN THE PERIOD DEPENDING ON THE STRENGTH AND DURATION OF THE SURGE. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT SATURDAY FOR AMZ250-252-254-256. && $$ NEAR TERM...RJD SHORT TERM...III LONG TERM...III AVIATION...DL/RJD

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