Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 190225 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 925 PM EST THU DEC 18 2014 .SYNOPSIS... HIGH PRESSURE OVER THE GREAT LAKES WILL MOVE NORTH OF THE CAROLINAS FRIDAY AND SATURDAY. LOW PRESSURE WILL DEVELOP ALONG THE GULF COAST FRIDAY AND MOVE NORTHEAST ALONG THE CAROLINA COAST SATURDAY... ACCOMPANIED BY RAIN AND COOL TEMPERATURES. A SECOND LOW COULD BRING MORE CLOUDS AND RAIN MONDAY. A COLD FRONT WILL MOVE ACROSS THE AREA TUESDAY NIGHT INTO WEDNESDAY...WITH COLD AND DRY WEATHER EXPECTED ON CHRISTMAS DAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 930 PM THURSDAY...SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES IS PUSHING A CHILLY AIRMASS INTO THE CAROLINAS. 850 MB TEMPS AROUND +6C SHOULD SLIP TO +4C BY DAYBREAK. A LITTLE CIRRUS WILL MOVE ACROSS FROM TIME TO TIME...AS WILL SOME STRATCUMULUS IN THE 5000-7000 FT RANGE CURRENTLY OBSERVED WEST OF I-95. ANALYSIS OF MODEL RH AND ISENTROPIC FIELDS INDICATES THIS STRATOCUMULUS SHOULD HAVE TROUBLE MAKING IT TOO FAR EAST TONIGHT -- A STRIPE OF HIGHER RH (60-75 PERCENT IN THE 800-850 MB LAYER) SHOULD EXTEND DOWN TO THE COAST BY 12Z FRI BUT WITH WEAK ISENTROPIC DOWNGLIDE NOTED THROUGHOUT THE 290-300K THETA SURFACES CLOUDS SHOULD BE ERODING AS THEY PRESS EASTWARD. SKY COVER FORECASTS WILL REMAIN MOSTLY CLEAR NEAR THE COAST WITH PARTLY CLOUDY INLAND. ONLY SMALL TWEAKS HAVE BEEN MADE TO FORECAST LOWS OVERNIGHT...STILL IN THE LOWER TO MID 30S FOR MOST AREAS EXCEPT FOR SOME UPPER 20S ACROSS THE NORMALLY-COLDER POCOSIN SWAMPS OF SE NORTH CAROLINA.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... 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. && .LONG TERM /SUNDAY THROUGH THURSDAY/... 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. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 00Z...EXPECT VFR AT ALL TERMINALS THROUGH THIS TAF PERIOD. MOSTLY CLEAR AND CALM CONDITIONS WILL PREVAIL TONIGHT WITH SOME SCT MID/HIGH CLOUDS STREAMING OVERHEAD. UNFAVORABLE MOISTURE PROFILES AND STRENGTHENING NORTHERLY FLOW JUST BEFORE DAYBREAK DIMINISH THE THREAT OF ANY FOG CONCERNS. AN UPSTREAM UPPER LEVEL DISTURBANCE WILL BRING MORE PASSING CIRRUS DURING THE DAY...ESPECIALLY AFTER 18Z. THE WINDS WILL BE N-NE LESS THAN 10 KT AT ALL SITES ON FRI. EXTENDED OUTLOOK...RAIN LIKELY SAT WITH DEVELOPING MVFR/IFR CIGS POSSIBLY LASTING INTO SUN. CHANCE OF SHOWERS MON AS LOW PRESSURE MOVES UP THE COAST. SHOWERS POSSIBLE LATE TUE AHEAD OF A STRONG COLD FRONT. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 930 PM THURSDAY...HIGH PRESSURE OVER THE WESTERN GREAT LAKES WILL MAINTAIN A LIGHT NORTH WIND ACROSS THE WATERS TONIGHT. WIND SPEEDS SHOULD REMAIN LESS THAN 10 KNOTS. SEAS ARE 1 TO BARELY 2 FEET CURRENTLY. WAVE SPECTRA OUT AT THE FRYING PAN SHOALS ARE EVENLY SPLIT BETWEEN 11 SECOND SE SWELL AND 4 SECOND WIND CHOP. 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...TRA SHORT TERM...RJD LONG TERM...MBB AVIATION...BJR

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