Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 182027 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 327 PM EST THU DEC 18 2014 .SYNOPSIS...
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HIGH PRESSURE WILL RIDGE INTO THE CAROLINAS THROUGH FRIDAY. LOW PRESSURE WILL DEVELOP ALONG THE WESTERN GULF COAST ON FRIDAY AND TRACK EAST ALONG THE GULF COAST...MOVING OFF THE SOUTHEAST COAST BY SATURDAY NIGHT. THIS SHOULD BRING A PERIOD OF RAIN AND BELOW NORMAL TEMPERATURES. A WEDGE OF HIGH PRESSURE WILL MAINTAIN COOL AND CLOUDY CONDITIONS INTO EARLY NEXT WEEK. AN OFFSHORE STORM SYSTEM MAY BRING RAIN ON MONDAY. A COLD FRONT WILL MOVE ACROSS THE AREA TUESDAY NIGHT INTO WEDNESDAY. COLD AND DRY WEATHER IS EXPECTED ON CHRISTMAS.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 300 PM THURSDAY...A WEAK PRESSURE GRADIENT WILL PREVAIL AT THE SURFACE UNDER A FLAT MID LEVEL PATTERN ALOFT. MID AND HIGH LEVEL MOISTURE WILL CONTINUE TO STREAM BY IN INTERVALS FROM THE SOUTHWEST. THE ONLY FORECAST CHALLENGE IS TEMPERATURES. THE NAM AND GFS ARE IN REALLY GOOD AGREEMENT WITH WIDESPREAD LOWER 30S. I HAVE ADDED A MARGINAL RADIATIONAL COMPONENT WHICH LOWERS READINGS SLIGHTLY IN THE FAVORED AREAS. POSSIBILITY FOR FOG LOOKS MINIMAL AS THE VERY DRY BOUNDARY LAYER AND MID LEVEL CLOUDS SHOULD PRECLUDE THREAT.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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AS OF 300 PM THURSDAY...STILL LOOKS LIKE IT WILL RAIN SAT...BUT THE MODELS HAVE NOT ONLY BEEN GUIDING US TO A SLOWER PROGRESSION... BUT NOW A DRIER AND MORE SUPPRESSED SOLUTION FOR OUR FORECAST AREA. GIVEN THAT...HAVE DECIDED TO DIAL BACK SOME ON BOTH POPS AND QPF. NEVERTHELESS...A SOUTHERN STREAM SHORTWAVE WILL MOVE OUT OF THE SOUTHWESTERN U.S. FRI AND THEN ACROSS THE MID SOUTH AND SOUTHEAST FRI NIGHT AND SAT. HIGH PRESSURE IS EXPECTED TO BEGIN WEDGING INTO THE CAROLINAS ON SAT WHICH WILL ALLOW A SHALLOW N TO NE FLOW THROUGH 3 KFT TO BE TOPPED BY A DEEP W OR WSW FLOW. THE FLOW ALOFT IS MARGINALLY MOIST AND THIS ALLOWS PRECIPITABLE WATER VALUES TO CLIMB TO AROUND THREE-QUARTERS OF AN INCH. THE SYNOPTIC SETUP DOES ALLOW ISENTROPIC UPGLIDE TO INCREASE AND THE COMBINATION DOES SUPPORT HIGH POPS. HOWEVER...THE LOWEST 3-5 KFT DO SHOW INDICATIONS OF HANGING ONTO THE DRY AIR IN THIS RATHER QUICK HITTING SYSTEM. THEREFORE...WILL FORECAST LIKELY TO CATEGORICAL POPS AT THIS TIME WITH QPF AMOUNTS ON THE ORDER OF ONE TENTH TO A QUARTER OF AN INCH. OTHERWISE...FRIDAY WILL SHOW INCREASING CLOUDS...ESPECIALLY OF THE HIGH VARIETY WITH CLOUDS LOWERING THROUGH THE AFTERNOON AND EVE. IT WILL BE SOLIDLY CLOUDY LATER FRI NIGHT AND SAT. CLOUDS MAY BEGIN TO PARTIALLY ERODE FROM INLAND TO THE COAST SAT NIGHT AS DRIER AIR TRIES TO WORK IN...ALTHOUGH WE MAY BE LEFT WITH CONSIDERABLE STRATUS FOR MUCH OF THE NIGHT. TEMPS ON FRI WILL BE NEAR NORMAL...MID AND UPPER 50S. HOWEVER... SAT IS SHAPING UP TO BE A CHILLY DAY WITH TEMPS ONLY REACHING THE UPPER 40S TO LOWER 50S. AN ALL LIQUID EVENT WITH LOWS FRI NIGHT MAINLY IN THE 40S AND UPPER 30S TO LOWER 40S SAT NIGHT.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
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AS OF 300 PM THURSDAY...SUNDAY APPEARS TO BE RAIN-FREE BUT STILL RATHER CLOUDY WITH NO REAL IMPETUS FOR LOW LEVEL MOISTURE TO BE ROUTED OUT FOLLOWING THE SATURDAY SYSTEM. THIS MAY CHANGE AS SOON AS SUNDAY NIGHT HOWEVER AS A VERY WEAK UPPER IMPULSE LEADS TO A LITTLE CYCLOGENESIS ALONG THE FRONT SITTING OFF THE COAST. FOR A FEW RUNS NOW THE GFS HAS BEEN QUITE WET LOCALLY WITH THIS SYSTEM AND NOW THE CMC IS ON BOARD. WILL RAISE POPS BUT NOT GO WITH QUITE THE BULLISH RAINFALL AMOUNTS SHOWN GIVEN THE WEAK FORCING OVERALL AND TO A LESSER EXTENT THE BACKING OFF TREND SEEN IN MODELS WITH THE SATURDAY SYSTEM. ATTENTION THEN TURNS WESTWARD ON TUESDAY AS A DEEP TROUGH DIGS INTO THE MIDDLE OF THE NATION. THE SURFACE BOUNDARY MAY REACH THE MOUNTAINS BY EVE BUT LOCALLY THIS SHOULD MEAN ONE DRY DAY. STRONG DYNAMICS START TO IMPINGE UPON OUR AREA TUESDAY NIGHT AND MAX OUT WEDNESDAY ALTHOUGH THE FRONT AND DEEP MOISTURE LONG GONE/WELL OFFSHORE BY MORNING. WEDNESDAY`S COLD AIR ADVECTION MAY BE STRONG ENOUGH FOR NON-DIURNAL TEMP CURVES AND WED NIGHT THROUGH THURSDAY NIGHT SHOULD BE RATHER CHILLY.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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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.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM THURSDAY...THE WEAK PRESSURE GRADIENT THAT RESIDES OVER THE COASTAL WATERS WILL WEAKEN FURTHER THROUGH THE AFTERNOON AND OVERNIGHT HOURS. NORTH TO NORTHEAST WINDS CURRENTLY RUNNING NEAR TEN KNOTS WILL DROP TO THE SINGLE DIGITS AND PERSIST THROUGH 1200 UTC FRIDAY. SEAS...COMPRISED OF A VERY SUBTLE 10 SECOND SWELL COMPONENT AND FOUR SECOND WIND WAVE WILL CONTINUE TO BE 1-2 FEET. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 PM THURSDAY...N WINDS FRI WILL VEER TO NNE AND NE FRI NIGHT WITH NE WINDS PERSISTING THROUGH SAT NIGHT. WIND SPEEDS WILL BE UP TO 10 TO 15 KT...ESPECIALLY IN THE WAKE OF A SOUTHERN STREAM SYSTEM SAT NIGHT. SEAS WILL BE 2 FT OR SO INTO FRI NIGHT WITH 3 TO 4 FT SEAS BECOMING MORE COMMON DURING SAT AND ESPECIALLY SAT NIGHT. LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 300 PM THURSDAY...SUNDAY SHOULD BRING A FAIRLY LIGHT GRADIENT WITH HIGH PRESSURE HOLDING ON TO OUR NORTH AND A WEAK TROUGH OFF THE COAST. THE OFFSHORE TROUGH WILL CREEP CLOSER TO THE COAST SUNDAY NIGHT. AS THIS IMPULSE PASSES TO OUR NORTH AN AREA OF EXITING LOW PRESSURE WILL BE DEVELOPING. NORMALLY THIS WOULD OFFER AN OPPORTUNITY FOR A BIT OF A SURGE IN WINDS AND SEAS BUT THIS DOES NOT PAN OUT THIS TIME. FLOW WILL TURN SLIGHTLY OFFSHORE BUT NOT PICK UP IN SPEED. BACKING WINDS EXPECTED MOST OF TUESDAY AS A FAIRLY STRONG COLD FRONT APPROACHES FROM THE WEST.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RJD SHORT TERM...SHK LONG TERM...MBB AVIATION...DL

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