Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211043 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 643 AM EDT TUE APR 21 2015 .SYNOPSIS... A COLD FRONT WILL MOVE OFF THE COAST AROUND DAYBREAK. DRY AND SEASONABLE HIGH PRESSURE WILL BUILD ACROSS THE AREA TODAY AND WEDNESDAY. ANOTHER COLD FRONT WILL CROSS THE COAST EARLY THURSDAY FOLLOWED BY MORE SEASONABLE WEATHER FRIDAY. A STORM SYSTEM MAY AFFECT THE AREA SATURDAY. COOLER HIGH PRESSURE WILL FOLLOW INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 630 AM TUESDAY...FOR THE FIRST TIME IN RECENT MEMORY THERE IS VIRTUALLY NO CHANCE FOR RAIN TODAY. A COLD FRONT IS MAKING ITS WAY EAST ACROSS ELIZABETHTOWN...MARION AND FLORENCE CURRENTLY. THE BOUNDARY SHOULD BE MOVING ACROSS THE BEACHES WITHIN THE NEXT 1-2 HOURS. MUCH DRIER AIR WILL BUILD IN ON WESTERLY WINDS...DROPPING RELATIVE HUMIDITY DOWN TOWARD 30 PERCENT THIS AFTERNOON. DESPITE 850 MB TEMPS FALLING TO +5C TO +7C...STRONG SUNSHINE SHOULD STILL BOOST HIGHS IN THE MID 70S FOR MOST AREAS. FOR TONIGHT HIGH PRESSURE ALONG THE GULF COAST SHOULD MOVE EAST TO COASTAL GEORGIA. SINCE WE`RE NORTH OF THE RIDGE THIS MEANS THE GRADIENT WILL SUPPORT A GENERALLY WESTERLY WIND. IN THE UPPER LEVELS CHANNELED VORTICITY SHOULD REMAIN NORTH OF THE CAROLINAS WITH INSUFFICIENT MOISTURE EXPECTED FOR CLOUDS. THIS MEANS RADIATIONAL COOLING SHOULD PROCEED UNINHIBITED...AND LOWS SHOULD FALL INTO THE 48-52 RANGE...EXCEPT SOME MID TO UPPER 50S AT THE BEACHES.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 AM TUESDAY...LARGE CLOSED LOW SPINNING ACROSS SE CANADA WILL DRIVE NEARLY FLAT/ZONAL FLOW ACROSS THE CAROLINAS THROUGH MID- WEEK. THIS WILL CREATE FAIRLY SEASONABLE AND QUIET WEATHER...BUT A WEAK COLD FRONT IS PROGGED TO DROP ACROSS THE AREA VERY EARLY THURSDAY. HIGH PRESSURE WILL BE OFFSHORE WEDNESDAY WITH RETURN FLOW AHEAD OF THE COLD FRONT DRIVING TEMPS TOWARDS 80 BENEATH A LOT OF SUNSHINE. CLOUD COVER WILL GRADUALLY INCREASE WED NIGHT INTO THURSDAY AS THE COLD FRONT APPROACHES FROM THE NW...DRIVEN BY A PIECE OF VORT ENERGY ROTATING AROUND THE LARGE CANADIAN VORTEX. GUIDANCE STILL SUGGESTING ONLY A SMALL CHANCE FOR SHOWERS WITH THIS FEATURE AS FORCING IS WEAK AND THE COLUMN REMAINS DRY. WILL KEEP INHERITED SCHC POP FOR THURSDAY...BUT NOT EXPECTING WIDESPREAD OR SIGNIFICANT RAINFALL THURSDAY. HOWEVER...CLOUDS AND ANY SHOWERS WILL KEEP TEMPS THURSDAY A BIT COOLER THAN WED...WITH WIDESPREAD MID 70S EXPECTED. DRYING WILL OCCUR THURSDAY NIGHT...ALLOWING TEMPS TO FALL WELL INTO THE 50S...A SOLID 5+ DEGREES COOLER THAN WED NIGHT LOWS. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 300 AM TUESDAY...BIGGEST CONCERN FOR THE EXTENDED IS A SIGNIFICANT LOW PRESSURE SYSTEM PROGGED TO MOVE ACROSS THE SOUTHEAST AND TAP GULF MOISTURE DURING SATURDAY. STILL LOTS OF UNCERTAINTY DUE TO LACK OF MODEL AGREEMENT...AND WHILE THE GFS HAS BEEN CONSISTENT BRINGING MOISTURE IN FRIDAY NIGHT WITH SOAKING RAINS ON SATURDAY...THE ECMWF IS SLOWER AND MORE SUPPRESSED WITH THE BAROCLINIC GRADIENT LEADING TO LESS QPF AND A BETTER FRI NIGHT/SATURDAY. IT IS GETTING LATE IN THE YEAR FOR SUCH AN EQUATORWARD PUSH OF THE BAROCLINIC GRADIENT...SO THE ECMWF MAY BE TOO SUPPRESSED...BUT WILL MAKE VERY LITTLE CHANGE TO INHERITED AND MAINTAIN A SPLIT OF THE GUIDANCE WHICH AGREES WITH CURRENT WPC FORECASTS. THEREAFTER...COOLER WEATHER WILL PREVAIL AS DRYING OCCURS SUNDAY...AND THESE BELOW NORMAL TEMPS WILL PERSIST THROUGH THE END OF THE PERIOD EVEN BENEATH FULL LATE-APRIL INSOLATION. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 06Z...AREA OF HIGH CLOUDS IS EXITING THE COASTAL AREAS WITH DRIER AIR NOTED IN WATER VAPOR STREAMING INTO THE REGION FROM THE WEST AND SOUTHWEST. AS A RESULT...HIGH CONFIDENCE THAT VFR CONDITIONS WILL PREVAIL TONIGHT THROUGH TUESDAY NIGHT. OTHERWISE... WINDS WILL VEER WITH THE APPROACH OF THE FRONT THROUGH THE EARLY MORNING HOURS TUESDAY. EXTENDED OUTLOOK...EXPECT VFR WITH POSSIBLE SHOWERS THURSDAY AND SATURDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM TUESDAY...THE COLD FRONT WILL REACH THE BEACHES ABOUT 1-2 HOURS AFTER SUNRISE. THIS WILL FINALLY END THE BREEZY SOUTHWEST WINDS WE HAVE EXPERIENCED OVERNIGHT...REPLACING IT WITH GENTLER WEST WINDS THIS MORNING. WITH LOTS OF SUNSHINE AN AFTERNOON SEABREEZE SHOULD DEVELOP...BACKING NEARSHORE WINDS AROUND TO THE SOUTHWEST. HIGH PRESSURE OVER THE GULF COAST WILL MOVE SLOWLY EAST TO COASTAL GEORGIA BY DAYBREAK WEDNESDAY. THIS WILL MAINTAIN THE WESTERLY WIND TONIGHT. SEAS CURRENTLY 4-5 FEET ACROSS THE NC WATERS AND 3-5 FEET ACROSS THE SC WATERS WILL DIMINISH TO 2-3 FEET THIS AFTERNOON AND TONIGHT. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...HIGH PRESSURE OFFSHORE WILL MAINTAIN SW RETURN FLOW WEDNESDAY...BUT SPEEDS INCREASE THROUGH THE DAY THANKS TO A PINCHING GRADIENT AHEAD OF A COLD FRONT. WIND SPEEDS WILL RISE TO 15-20 KTS WED NIGHT BEFORE SHIFTING TO THE NW EARLY THURSDAY BEHIND THE FRONT. THESE NW WINDS WILL PERSIST AND BE LIGHT MOST OF THURSDAY...BUT VEER MORE TO THE NORTH AND INCREASE LATE TO 10-15 KTS. WAVE HEIGHTS WILL BE HIGHEST IMMEDIATELY AHEAD OF THE FRONTAL PASSAGE...RISING TO 3-4 FT WITH A SW WIND CHOP AND SE GROUND SWELL COMPRISING THE SPECTRUM. N/NW WINDS THURSDAY WILL PUSH HIGHEST SEAS AWAY FROM SHORE...LEAVING 1-3 FT WAVES IN THE COASTAL WATERS. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 300 AM TUESDAY...A COLD FRONT WILL WAVER BACK AND FORTH ACROSS THE WATERS FRIDAY...LEAVING HIGHLY VARIABLE WIND DIRECTIONS...FROM NORTH EARLY...TO SW LATE...AND THEN TO N/NE SATURDAY MORNING. FORTUNATELY THE DIFFUSE GRADIENT ALLOWING THIS TO OCCUR WILL KEEP SPEEDS AROUND 10 KTS EXCEPT VERY EARLY FRIDAY WHEN THEY MAY REACH 15 KTS. THESE N/NE WINDS WILL PERSIST SATURDAY AHEAD OF A LOW PRESSURE SYSTEM APPROACHING FROM THE SW...BUT THE GRADIENT REMAINS LAX SO SPEEDS WILL HOVER AROUND 10 KTS. WITH THE LIGHT GRADIENT IN PLACE AND NO SIGNIFICANT SWELL...SEAS WILL BE MOSTLY 2-3 FT THROUGH THE PERIOD...ALTHOUGH A BIT OF AN AMPLIFICATION IS POSSIBLE LATE SATURDAY.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...TRA SHORT TERM...JDW LONG TERM...JDW AVIATION...TRA MARINE...TRA/JDW

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