Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 231420 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1019 AM EDT SAT AUG 23 2014 .SYNOPSIS... A COLD FRONT WILL MOVE SOUTH ACROSS THE AREA TODAY. THIS FRONT WILL BRING A GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS TODAY...BEFORE COOLER AND DRIER AIR FILTERS INTO THE REGION FOR SUNDAY. HIGH PRESSURE EXPANDING SOUTH FROM NEW ENGLAND WILL MAINTAIN COOLER AND DRIER WEATHER FOR THE FIRST HALF OF NEXT WEEK WITH A RETURN TO MORE SEASONABLE WEATHER LATER IN THE WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1000 AM SATURDAY...AMPLIFIED MID-LEVEL PATTERN SHAPING UP TODAY AS A LARGE RIDGE OF HIGH PRESSURE STRENGTHENS ACROSS THE MS VLY...WHILE A DEEPENING TROUGH DIVES ACROSS THE EAST COAST. THIS LEAVES A REGION OF NW FLOW ENTRENCHED BETWEEN THESE TWO FEATURES...FLOWING DIRECTLY ACROSS THE LOCAL AREA. TWO SEPARATE MID-LEVEL IMPULSES EVIDENT ON WV IMAGERY...ONE OVER TN...AND THE OTHER ACROSS IA...ARE CRESTING THE RIDGE AND WILL DROP SE TODAY IN A "RING OF FIRE" TYPE EVENT...LIKELY SPAWNING CONVECTION LOCALLY THIS EVENING. AT THE SURFACE...BACK DOOR COLD FRONT...WHILE WEAK...IS CURRENTLY LOCATED BASICALLY ALONG THE NC/SC BORDER...AND WILL WAVER IN THE VICINITY INTO TONIGHT BEFORE A STRONG PUSH OF NE WINDS DRIVES IT SOUTH OF THE AREA. MOST CHALLENGING ASPECT OF THE FORECAST TODAY IS HOW CONVECTION WILL EVOLVE LOCALLY. ALTHOUGH INSTABILITY IS MUCH LESS THAN THE PAST FEW DAYS THANKS TO CLOUD COVER AND COOLER TEMPERATURES...ENOUGH WILL BE PRESENT THAT BOUNDARIES WILL DRIVE UPDRAFTS INTO SHOWERS AND STORMS TODAY. CONVECTION WILL INITIALLY BE FAVORED IN THE NE ZONES WHERE PWATS ARE HIGHER...AND SOME MID-LEVEL DRY AIR WILL HELP STEEPEN LAPSE RATES...BUT EVENTUALLY ALL OF THE AREA WILL SEE DEVELOPMENT. STILL HARD TO TIME EXACTLY WHEN AND WHERE THE MOST WIDESPREAD CONVECTION WILL OCCUR...BUT THE HIGH RES GUIDANCE ARW/HRRR/WRF ALL HAVE SIMILAR EVOLUTION WITH MOST WIDESPREAD/STRONGEST CONVECTION DROPPING SE THROUGH THE CWA THIS EVENING. HAVE HIGHEST POP DURING THIS TIMEFRAME. DO NOT EXPECT SEVERE STORMS TODAY...BUT SPC DOES HIGHLIGHT THE AREA EVEN IN THE GENERAL RISK FOR ISOLATED STRONGER STORMS TYPICAL IN NW FLOW REGIMES. THUNDERSTORMS WILL BEGIN TO WANE NOCTURNALLY...BUT HIGH PWAT AND CONTINUED MID-LEVEL FORCING BENEATH SHORTWAVES WILL LIKELY KEEP SHOWERS GOING MUCH OF THE NIGHT BEFORE DRYING BEGINS FROM NE TO SW LATE. TEMPS TODAY WILL RANGE CONSIDERABLY FROM NE TO SW ACROSS THE CWA. HIGHS IN THE FAR S/SW ZONES WILL CLIMB WELL INTO THE 90S...COMBINING WITH HIGH DEWPOINTS TO PRODUCE HEAT INDICES OF 100-104 DEGREES. HIGHS ACROSS THE NC COUNTIES WILL RISE ONLY INTO THE UPPER 80S IN THE FAR NE ZONES...TO THE LOW 90S NEAR THE SC BORDER. ALTHOUGH COOL/DRY ADVECTION WILL BEGIN LATE TONIGHT...IT WILL NOT OCCUR FAST ENOUGH TO INFLUENCE MINS MUCH...SO LOWS WILL REMAIN ABOVE NORMAL...AROUND 70 IN THE FAR NORTH TO THE MID 70S NEAR THE SOUTH SANTEE RIVER.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 AM SATURDAY...RIDGE BECOMES HIGHLY AMPLIFIED UP THE MISSISSIPPI VALLEY INTO THE NORTHEAST EARLY NEXT WEEK AND BUILDS EASTWARD WITH TIME. AT THE SAME TIME SURFACE HIGH PRESSURE BUILDS DOWN FROM THE NORTH. INCREASING SUBSIDENCE AND DRY AIR WILL ACT TO INHIBIT CONVECTION. OVERALL MOISTURE THROUGH THE COLUMN WILL BE DIMINISHING WITH PCP WATER VALUES DROPPING FROM CLOSE TO 2 INCHES EARLY SUNDAY DOWN TO 1.25 BY SUN NIGHT AND LESS THAN AN INCH BY MONDAY MORNING. MAY FEEL MORE LIKE EARLY FALL-LIKE WEATHER FOR THE START OF THE WEEK WITH COOLER AND DRIER NORTHERLY FLOW OFFSET SLIGHTLY BY LATE SUMMER SUNSHINE...WITH TEMPS REACHING BELOW NORMAL INTO THE LOW TO MID 80S. ANY CLOUDS EARLY SUNDAY WILL DISSIPATE AS DEWPOINT TEMPS DROP FROM NEAR 70 DOWN TO NEAR 60 BY MONDAY MORNING. THESE LOWER DEWPOINT TEMPS WILL ALLOW TEMPS TO DROP INTO THE MID 60S MOST PLACES OVERNIGHT. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 300 AM SATURDAY...CONTINUED COOL AND DRY WEATHER THROUGH MID WEEK AS HIGH PRESSURE RIDGES DOWN FROM THE NORTHEAST INTO THE CAROLINAS AND UPPER RIDGE CONTINUES TO BUILD EASTWARD. THE COOLER NORTHEAST FLOW WILL BE OFFSET BY PLENTY OF SUNSHINE TO PRODUCE TEMPS NEAR NORMAL...IN THE MID 80S. 850 TEMPS AND LOW LEVEL THICKNESSES WILL BE ON THE RISE AS RIDGE BUILDS OVER THE SOUTHEAST AND H5 HEIGHTS INCREASE WED. MOISTURE MAY BE ON THE RISE BY LATE WED INTO THURS DEPENDING ON THE EXACT TRACK OF TROPICAL SYSTEM FORECAST TO MOVE UP THROUGH THE OFF SHORE ATLANTIC WATERS TO OUR EAST LATE WED/THURS TIME FRAME. THE ECMWF CONTINUES TO THE BE THE FASTEST AND FURTHEST EAST WITH THE SYSTEM WHILE THE GFS REMAINS THE SLOWEST AND FARTHEST WEST. AT THIS POINT LOOKS LIKE MAIN EFFECTS OF THIS TROPICAL SYSTEM WILL BE ALONG THE COAST WITH INCREASED ON SHORE WINDS AND SWELLS THROUGH MID WEEK. HIGH PRESSURE SHOULD HOLD OVER LAND WITH RIDGE HOLDING STRONG ALOFT. FOR NOW IT LOOKS LIKE THIS SHOULD HELP TO SUPPRESS SHWR ACTIVITY THROUGH MUCH OF THE WEEK BUT MAY SEE SOME CLOUDS AND SHOWERS MOVE ON SHORE...MAINLY OVER COASTAL AREAS AS TROPICAL SYSTEM PASSES TO OUR EAST THROUGH MID WEEK. GFS ALSO SHOWS COLD FRONT MOVING INTO THE CAROLINAS FROM THE NW BY THE WEEKEND. TEMPS NEAR OR BELOW NORMAL TO START WILL BEGIN TO MODERATE AS MOISTURE INCREASES THROUGH THE COLUMN THURS INTO FRI WITH DEEPER ON SHORE FLOW. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... AS OF 12Z...A COLD FRONT WAS LOCATED IN THE VICINITY OF THE TERMINALS THIS MORNING. MVFR CIGS WERE OCCURRING AT KILM AND WILL MOVE INTO KLBT OVER THE NEXT HOUR OR TWO. MVFR VSBYS IN BR WERE OCCURRING AT KCRE/KMYR. MOST SHRA/TSRA HAS BEEN OCCURRING WELL BEHIND THE FRONT NE OF KILM. THE BOUNDARY WILL SHIFT SOUTH OF ALL TERMINALS THIS EVENING. WIDESPREAD LIGHT SHOWERS WITH ISOLATED TO WIDELY SCT HEAVIER SHRA/TSRA EXPECTED ALONG AND BEHIND THE FRONT MAINLY DURING THE AFTERNOON. HEAVIER SHRA/TSRA POTENTIAL SHOULD SHIFT SWRD AS THE EVENING APPROACHES. THERE IS LOW CONFIDENCE ON TIMING OF THE HEAVIER SHRA/TSRA IN THE TAFS. LIGHT WINDS EARLY THIS MORNING WILL EAST BEHIND THE FRONT LESS THAN 10 KT. KCRE/KMYR WILL LIKELY SEE E-SE WINDS IN THE AFTN BEHIND A SEA BREEZE BEFORE THE FRONT PASSES THROUGH IN THE EVENING. ISOLATED SHOWERS WILL LINGER INTO THE OVERNIGHT HOURS NEAR KCRE/KMYR. POST FRONTAL MVFR CIGS ARE EXPECTED WITH REASONABLE CONFIDENCE OF POST-FRONTAL IFR CIGS AT KFLO/KLBT OVERNIGHT. EXTENDED OUTLOOK...MVFR/IFR CIGS/VSBYS POSSIBLE SUN MORNING. OTHERWISE EXPECT VFR TO PREVAIL SUN THROUGH WED AS HIGH PRESSURE RIDGES OVER THE EAST COAST IN THE WAKE OF THE COLD FRONT. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM SATURDAY...WEAK COLD FRONT IS BISECTING THE WATERS THIS MORNING...LEAVING E/NE WINDS ACROSS THE NC WATERS...WITH A MORE EASTERLY DIRECTION OFF THE SC COAST. THIS FRONT WILL WAVER IN THE AREA BEFORE FINALLY PUSHING SOUTH OF THE WATERS LATE TONIGHT. AS THIS FRONT PUSHES SOUTH...WINDS WILL BECOME FROM THE NE ALL WATERS...AND BEGIN TO INCREASE AS A SURGE DEVELOPS LOCALLY. WINDS THROUGH MOST OF THE DAY WILL BE LIGHT...BUT WILL INCREASE TO 10-15 KTS BY THE END OF THE PERIOD. WAVE HEIGHTS WILL BE JUST 1-2 FT DURING THE DAYLIGHT HOURS AND THE BEGINNING OF THE TONIGHT PERIOD...BEFORE THE RISING WINDS PUSH SEAS TO 2-4 FT...HIGHEST ACROSS AMZ250. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 AM SATURDAY...NORTHERLY SURGE AS COOL AND DRY HIGH PRESSURE BUILDS DOWN FROM THE NORTHEAST. WINDS WILL RISE SHARPLY THROUGH SUNDAY UP TO 15 TO 20 KTS ACROSS THE WATERS. THE INCREASE IN WINDS WILL IN TURN PRODUCE AN INCREASE IN SEAS UP CLOSE TO SCA THRESHOLDS BY SUN EVENING. SEAS WILL REMAIN UP CLOSE TO 4 TO 6 FT OVER A GOOD PORTION OF OUR LOCAL COASTAL WATERS THROUGH MONDAY NIGHT AND BEYOND IN PERSISTENT STRONG NORTHEASTERLY WINDS. LONG TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 300 AM SATURDAY...HIGH PRESSURE BUILDING DOWN FROM THE NORTHEAST THROUGH THE CAROLINAS WILL PROVIDE A CONTINUOUS NORTHEAST FLOW UP TO 15 TO 20 KTS THROUGH MID WEEK. THIS WILL KEEP SEAS UP TO 4 TO 6 FT POSSIBLY INCREASING FURTHER WED INTO THURS DUE TO INCREASING SWELLS FROM A TROPICAL SYSTEM MOST PROBABLY MOVING NORTH THROUGH THE OFF SHORE WATERS. AT THIS TIME MUCH UNCERTAINTY STILL EXISTS CONCERNING THE DEVELOPMENT AND FATE OF THIS POTENTIAL TROPICAL SYSTEM.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...RGZ NEAR TERM...JDW SHORT TERM...RGZ LONG TERM...RGZ AVIATION...MRR MARINE...JDW/RGZ

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