Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 181652 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1150 AM EST THU DEC 18 2014 .SYNOPSIS... HIGH PRESSURE WILL RIDGE INTO THE CAROLINAS THROUGH FRIDAY. LOW PRESSURE WILL MOVE NORTHEAST OUT OF THE GULF OF MEXICO FRIDAY NIGHT...AND THEN OFFSHORE THE CAROLINAS ON SATURDAY. THIS SYSTEM WILL BE ACCOMPANIED BY WIDESPREAD RAIN AND BELOW NORMAL TEMPERATURES. WEDGE OF HIGH PRESSURE WILL MAINTAIN COOL AND CLOUDY CONDITIONS INTO EARLY NEXT WEEK. A LARGER STORM SYSTEM WILL APPROACH FOR THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 930 AM THURSDAY...WEAK HIGH PRESSURE CONTINUES TO SLOWLY BUILD INTO THE AREA AS HIGH CLOUDS STREAM ACROSS FROM THE SOUTHWEST. EXPECT INTERVALS OF FILTERED SUNSHINE WITH PERIODS OF BRIGHTER SUNSHINE. THERMAL PROFILES LOOK GOOD FOR HIGH TEMPS. NO CHANGES WITH THE MID MORNING UPDATE. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM THURSDAY...THE QUESTION FOR THE SHORT TERM IS NOT IF IT WILL RAIN...BUT WHEN...AND HOW MUCH. A SOUTHERN STREAM SHORTWAVE WILL MOVE FROM NEW MEXICO FRIDAY MORNING...TO BE OFF THE MID-ATLANTIC COAST SATURDAY NIGHT. WHILE THIS FEATURE WILL DE-AMPLIFY DURING ITS TREK...A DECENT OVERRUNNING PRECIPITATION EVENT WILL ACCOMPANY IT AS THETA-E RIDGING OCCURS IN CONJUNCTION WITH INCREASING ISENTROPIC LIFT ATOP A WEDGE OF HIGH PRESSURE. FRIDAY WILL START CLEAR AND DRY THANKS TO HIGH PRESSURE RIDGING INTO THE REGION FROM THE OH VALLEY...AND WILL GRADUALLY TRANSITION TO A WEDGE-TYPE SETUP FRIDAY NIGHT. WHILE THIS OCCURS...DIFLUENCE WILL BEGIN ALOFT AHEAD OF THE APPROACHING SHORTWAVE...AND THE INCREASING SW FLOW ATOP THE SURFACE WEDGE WILL CREATE ISENTROPIC LIFT AND GRADUALLY SATURATE THE COLUMN. LIFT WILL BEGIN IN EARNEST AT THE 300K LEVEL...BEFORE GRADUALLY INCREASING THROUGH MUCH OF THE COLUMN. BIGGEST QUESTION MARK IS WHEN PRECIP WILL BEGIN LOCALLY. SREF PROBS CONTINUE TO BACK OFF ON ONSET TIME...AND FORECAST PROFILES HAVE FOLLOWED SUIT WITH A LOT OF DRY AIR REMAINING EVEN BY 7AM SATURDAY. FOLLOWING THIS TREND...HAVE CUT BACK POP FRIDAY NIGHT ONCE AGAIN AND FEEL THAT CHC AT BEST IS WARRANTED BEFORE SATURDAY MORNING. SATURDAY HOWEVER...STILL APPEARS TO BE QUITE WET AS COLUMN SATURATION AND DEEP ISENTROPIC LIFT BETWEEN 285K AND 300K CONTINUES. WHILE LIFT WILL BE SUFFICIENT FOR PRECIP...IT IS NOT EXTRAORDINARILY STRONG...AND GUIDANCE DIFFERS ON JUST HOW WIDESPREAD AND HEAVY THE RAINFALL WILL BE. STILL EXPECT ALL LOCATIONS TO EXPERIENCE RAINFALL DURING SATURDAY...AND WILL LEAN ON WPC QPF FOR THE EVENT. ISENTROPIC LIFT SHUTS OFF SATURDAY NIGHT...AND RAPID DRYING OCCURS THEREAFTER. LOW LEVEL MOISTURE REMAINS TRAPPED BENEATH THE WEDGE SATURDAY NIGHT SO VERY LIGHT RAIN/DRIZZLE WILL CONTINUE...BUT THE BULK OF THE QPF WILL OCCUR DURING THE DAYLIGHT HOURS SATURDAY. TEMPS FRIDAY WILL BE SEASONABLE IN THE MID 50S TO AROUND 60...FOLLOWED BY SEASONABLE LOWS A DEGREE OR TWO EITHER SIDE OF 40 FRIDAY NIGHT. MUCH COOLER ON SATURDAY BENEATH THE WEDGE AND CLOUDS/RAINFALL...AND WILL KEEP HIGHS EVEN BELOW THE COOLEST ECMWF MOS NUMBERS. THIS SUGGESTS HIGHS ONLY IN THE UPPER 40S WELL INLAND...TO THE LOW 50S AT THE COAST. SATURDAY NIGHT LOWS WILL JUST A BIT WARMER THAN THOSE EXPERIENCED FRIDAY NIGHT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 330 AM THURSDAY...LOTS OF UNCERTAINTY IN THE EXTENDED...BUT AN INCREASINGLY AMPLIFIED MID-LEVEL PATTERN SUGGESTS THE POTENTIAL FOR A SIGNIFICANT STORM SYSTEM DURING THE MIDDLE OF NEXT WEEK. WEDGE OF HIGH PRESSURE REMAINING IN PLACE SUN/MON WILL KEEP TEMPERATURES COOL...AND MOISTURE TRAPPED NEAR THE SURFACE. EVEN BY D4/D5 GUIDANCE EXHIBITS CONSIDERABLE UNCERTAINTY INTO RAIN CHANCES...BUT WILL LEAN ON THE MORE OPTIMISTIC GUIDANCE AND KEEP SUN/MON MOSTLY DRY LOCALLY. SHOULD NOTE THE GFS HAS A STRONG COASTAL TROUGH ON MONDAY ON WHICH A LOW PRESSURE DEVELOPS...SLINGING A DECENT QPF EVENT INTO THE EASTERN CAROLINAS...BUT THIS HAS LIMITED ENSEMBLE SUPPORT AND IS A NEW OPERATIONAL SOLUTION. THUS WILL KEEP THE INHERITED SCHC/LOW CHC SUN/MON WITH TEMPS JUST BELOW SEASONABLE NORMS. THEREAFTER IT DOES APPEAR A LARGE STORM SYSTEM WILL DEVELOP BENEATH A DEEP TROUGH AND MOVE UP THROUGH THE EASTERN PART OF THE COUNTRY FOR TUE/WED /CHRISTMAS EVE/. THE STRENGTH OF FEATURES CANNOT BE GLEANED WITH ANY CERTAINTY THIS FAR OUT...BUT MODEL CONSENSUS SUPPORTS A STRONG LOW PRESSURE MOVING WEST OF THE LOCAL AREA AS THE PARENT SHORTWAVE CLOSES OFF. WPC IS HIGHLIGHTING THE POTENTIAL FOR A SIGNIFICANT RAIN EVENT...AND SPC IS ALREADY NOTING STRONG TO SEVERE STORM POSSIBILITIES AS WELL. THE INHERITED LOOKS GOOD AND WILL MAKE ONLY MINOR CHANGES ATTM. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AS OF 18Z...LOOK FOR MAINLY A CIRRUS CEILING OVER THE NEXT 24 HOURS...AFTER WHICH CEILINGS WILL LOWER IN ADVANCE OF THE NEXT SYSTEM. NORTHERLY FLOW THIS AFTERNOON...GENERALLY LESS THAN 10 KTS. NO WEATHER TO SPEAK ABOUT WITH NO FOG EXPECTED TONIGHT AS MOISTURE PROFILES ARE UNFAVORABLE. FRIDAY...THICKENING HIGH CLOUDS IN ADVANCE OF A WEAK SYSTEM THAT WILL DEVELOP OVER THE SOUTHEASTERN US. EXTENDED OUTLOOK...VFR THROUGH FRIDAY. GOOD CHANCE OF RAIN ON SATURDAY WITH POSSIBLE MVFR/IFR CONDITIONS. A SLIGHT CHANCE OF PRECIP ON SUN...WITH A BETTER CHANCE MON AND TUE. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 930 AM THURSDAY...NORTH WINDS OF 10-15 KNOTS...MOSTLY ON THE LOWER END OF THE RANGE AND SEAS OF 2-3 FEET CONTINUE ACROSS THE WATERS. A SLIGHT DECREASE IN BOTH IS ANTICIPATED THROUGH THE DAY. NO CHANGES TO THE FORECAST WITH THE MID MORNING UPDATE. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM THURSDAY...HIGH PRESSURE WILL RIDGE DOWN INTO THE AREA FRIDAY...DEVELOPING INTO A WEDGE FRIDAY NIGHT AND ON SATURDAY. AT THE SAME TIME...A LOW PRESSURE WILL DEVELOP OVER...OR JUST EAST...OF THE WATERS. THESE FEATURES TOGETHER WILL DRIVE A SLOWLY TIGHTENING GRADIENT...AND CAUSE WINDS TO INCREASE SLOWLY WHILE REMAINING FROM THE N/NE. FRIDAY...NORTH WINDS WILL BE AROUND 10 KTS...BEFORE RISING TO 10-15 KTS SATURDAY WHILE VEERING MORE TO THE NE. WAVE HEIGHTS WILL BUILD ON THE INCREASING WINDS...FROM 1-2 FT FRIDAY TO 3-4 FT SATURDAY...WITH A NORTHERLY WIND CHOP PREDOMINANT IN THE SPECTRUM. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 330 AM THURSDAY...NE WINDS SUNDAY WILL BE 10-15 KTS BEHIND A LOW PRESSURE MOVING OFF TO THE NORTHEAST...BUT LEAVING A PINCHED GRADIENT THANKS TO A WEDGE OF HIGH PRESSURE JUST INLAND FROM THE COAST. A COASTAL TROUGH WILL TRY TO DEVELOP ON MONDAY WHICH WILL CAUSE THE GRADIENT TO WEAKEN...AND WINDS WILL BACK TO THE N/NW AT 5-10 KTS. SEAS WILL BE HIGHEST ON SUNDAY WITH 2-4 FT WAVE HEIGHTS EXPECTED...FALLING TO 1-3 FT LATE MONDAY DUE TO THE LIGHTER AND MORE OFFSHORE WINDS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...SHK SHORT TERM...JDW LONG TERM...JDW AVIATION...DL

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