Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 290843 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 443 AM EDT WED OCT 29 2014 .SYNOPSIS... ANOTHER WARM DAY ON TAP COMPLEMENTS OF HIGH PRESSURE TODAY. A COLD FRONT MOVING THROUGH TONIGHT WILL BRING SOME RAIN CHANCES AND FAIRLY SEASONABLE WEATHER THURSDAY AND FRIDAY. SATURDAY THEN TURNS BLUSTERY WITH WINTER-LIKE COLD THAT WILL LAST INTO SUNDAY. A VERY GRADUAL MODERATING TREND BEGINS ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 330 AM WEDNESDAY...PREFER THE SLIGHTLY QUICKER/FASTER NAM OVER THE GFS FOR THE ESE MOVEMENT OF THE COLD FRONT...CROSSING THE ILM CWA FROM LATE THIS AFTERNOON AND MOVING OFF THE ILM CWA COASTLINE AROUND MIDNIGHT TONIGHT. POPS WILL REMAIN IN THE LOW TO MID CHANCE CATEGORY GIVEN THE MODEL MOISTURE PROFILES. THE UPPER TROF NEVER REALLY AMPLIFIES ENOUGH TO TAP/ACCESS GULF OF MEXICO MOISTURE TO AID PCPN DEVELOPMENT AND/OR COVERAGE. THUS...MOISTURE ACCOMPANYING THE FRONT WILL BE WORKED ON AS WELL AS THE AVBL LOW LEVEL MOISTURE ACROSS THE FA. IN ADDITION TO NOT GOING ANY HIER WITH POPS ACCOMPANYING THE FRONT IS THE RATHER WEAK DYNAMICS ALOFT. FRONTAL DYNAMICS ITSELF WITH LIKELY BE THE MAIN PLAYER TO AID PCPN ACTIVITY. WITH THE QUICKER MOVEMENT OF THE CFP...THIN TO OPAQUE CLOUDINESS AHEAD OF THE FRONT WILL LIKELY KEEP MAX TEMPS FROM REACHING WELL INTO THE 80S. HOWEVER...THE RECORD HIGHS FOR TODAY ACROSS THE FA ARE BASICALLY IN THE LOW TO MID 80S AND THUS MAY HAVE A SHOT OF BREAKING THEM... LOCATION WED OCT 29 WILMINGTON 82 1984 FLORENCE 84/1974 N. MYRTLE BEACH 83/1991 AFTER THE CFP...LEFTOVER CLOUDS WILL PREVAIL DURING THE PRE-DAWN THU HOURS WITH ANY LEFTOVER LIGHT PCPN LIKELY ENDING BEFORE DAYBREAK. LEANED CLOSER TO THE MILDER GFS MOS GUIDANCE FOR TONIGHTS LOWS EVENTHOUGH THE NAM IS SLIGHTLY QUICKER WITH THE CFP. THINKING IS THE BEST CAA SURGE TO OCCUR LATER TONIGHT AND INTO DAYLIGHT THU.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 3 AM WEDNESDAY...DRY AIR PUSHING IN RAPIDLY FROM POINTS NORTH AND WEST ON THURSDAY BEHIND THE WEDNESDAY NIGHT COLD FRONT. COASTAL LOCALES MAY SEE SOME MORNING SPRINKLES BUT THATS ABOUT IT. FORECAST SOUNDINGS SHOW MID LEVEL DRYING AS WELL DESPITE THE MAIN UPPER TROUGH LINGERING BACK AND A GENERAL SOUTHWESTERLY FLOW. ANOTHER SHEARED OUT LINE OF VORTICITY WILL CROSS THE REGION ON FRIDAY MOVING THROUGH THIS TROUGH WHILE THE MAIN PIECE OF ENERGY STILL DIVING ACROSS THE WESTERN GREAT LAKES. THE LEAD SHORTWAVE WILL MANAGE SOME WEAK CYCLOGENESIS OFFSHORE BUT IT ALL APPEARS TO BE FAR ENOUGH OFFSHORE TO BE OF LITTLE CONSEQUENCE LOCALLY. HIGHS BOTH DAYS CLOSE TO 70 WHICH IS QUITE NEAR CLIMO...BUT WILL HAVE A COOLISH FEEL AFTER THE WARM FEW DAYS PRECEDING THE SHORT TERM. THE COLUMN REMAINS QUITE DRY THROUGH FRIDAY NIGHT BUT THE DYNAMICS TAKING SHAPE ALOFT WILL BE INCREDIBLY STRONG. THE AFOREMENTIONED GREAT LAKES SHORTWAVE DIVES INTO THE CAROLINAS AND BECOMES ONE OF THE STRONGEST VORTICITY CENTERS I CAN REMEMBER SEEING IN QUITE A WHILE LOCALLY. AHEAD OF IT THERE SHOULD BE AN INCREASE IN WARM ADVECTION CLOUDINESS BUT OVERALL IT APPEARS TO BE TOO DRY FOR MEANINGFUL RAIN CHANCES. THERE ARE BIG DIFFERENCES BETWEEN VARIOUS MODELS AS TO WHETHER OR NOT THE HEART OF THE STRONG COLD ADVECTION ARRIVES LATE FRIDAY NIGHT. THE WRF IS NOTABLY SLOWER AND HOLDS IT OFF UNTIL SATURDAY. THE GFS IS USUALLY TOO FAST TO BRING THE COLD AIR ESP WHEN IT HAS TO NEGOTIATE OVER THE MOUNTAINS. EVEN SO...FRIDAY NIGHT LOWS MAY HAVE TO BE ADJUSTED DOWNWARD SHOULD THE MODEL VERIFY. BY 12Z SATURDAY IT HAS ALREADY SWUNG SOME FRIGHTFULLY STRONG CAA THROUGH THE REGION AND HAS A POCKET OF 850MB -5C OVER WESTERN ZONES. THE (OLDER 12Z) ECMWF ARGUES FOR FASTER AS WELL. IN THE END IT WILL LIKELY TAKE BETTER SAMPLING OF THE MAIN VORT BY UA STATIONS TO RESOLVE THESE DISCREPANCIES. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 3 AM WEDNESDAY...FIRST TASTE OF WINTER ARRIVES WITH THE MONTH OF NOVEMBER ON SATURDAY. EXTREME VORT CENTER PASSING BY JUST TO THE NORTH. SO STRONG IN FACT THAT IT MAY WRING OUT A FEW SHOWERS OVER NRN ZONES OUT OF AN OTHERWISE DRY COLUMN. MOS NUMBERS CONTINUE TO SEEMINGLY STRUGGLE WITH THE MAGNITUDE OF THE COLD AIR IN SHOWING HIGHS A `MERE` 10 DEGREES BELOW CLIMO/LOW 60S. GIVEN THE LOW LEVEL COLD AIR WITH 850MB TEMPS ANYWHERE FROM -2C TO -5C THROUGH MUCH OF THE DAY EVEN A WELL MIXED AFTERNOON MAY STRUGGLE TO ATTAIN HIGHS IN THE MID 50S. AND IT WILL BE WELL MIXED WITH GUSTY WESTERLY WINDS. BL WINDS MAY BE AS HIGH AS 30 MPH WHICH COULD REPRESENT PEAK GUSTS FOR SOME DOWNRIGHT NASTY WIND CHILLS. THE MAGNITUDE OF THE COLD ABATES ON SUNDAY FROM AN ADVECTION STANDPOINT BUT SHALLOWER MIXING DUE TO LIGHT WINDS WILL STILL YIELD HUGE TEMPERATURE DEVIATIONS FROM CLIMO. SUNDAY NIGHT ALSO LOOKS LIKE A GOOD CANDIDATE FOR RADIATIONAL COOLING AND TEMPERATURES LOW ENOUGH TO SUPPORT FROST...EVEN THOUGH RH VALUES MAY NOT. THE HIGH MOVES OVERHEAD MONDAY AND TUESDAY BOTH SURFACE AND ALOFT MAKING FOR MINIMAL TEMPERATURE ADVECTION. THE MODERATION OF THE AIRMASS WILL THUS BE SLOW, MORE A PROCESS OF SOLAR HEATING THAN THERMAL ADVECTION. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... AS OF 06Z...CONDITIONS ARE EXPECTED TO DETERIORATE TO MVFR TO POSSIBLY IFR FROM LOW CEILINGS ASSOCIATED WITH A LOW STRATUS DECK THROUGH 14Z. OTHERWISE EXPECT VFR DURING DAYLIGHTS WED HRS. MVFR/IFR CONDITIONS POSSIBLE DURING THE LAST FEW HRS OF THE 06Z ISSUANCE PERIOD DUE TO POSSIBLE -SHRA AHEAD OF AN APPROACHING COLD FRONT. ANTICIPATE A LOW STRATUS CLOUD CEILING OVER WIDESPREAD FOG. ACTIVE WINDS AND LOW LEVEL JET WILL KEEP THE FOG TO A MINIMUM BUT WILL ALLOW A LOW STRATUS SCT-BKN DECK WITH BASES AT 5H TO 1K FOOT THRU 14Z. 1-2 HRS AFTER DAYBREAK...CONDITIONS WILL IMPROVE TO VFR AND CLOUDS AT ALL LEVELS WILL CONTINUE TO INCREASE THROUGHOUT THE REST OF THE MORNING AND AFTN AHEAD OF AN APPROACHING COLD FRONT. EXPECT SSW-SW WINDS AROUND 5 KT THIS AM...INCREASING TO AROUND 10 KTS BY MIDDAY THRU THE AFTN. BKN CU-SC CLOUD DECK THIS EVENING MAY PRODUCE SHRA ACROSS THE FA AS DYNAMICS ASSOCIATED AND AHEAD OF THE APPROACHING COLD FRONT REACH THE FA LATE IN THE ISSUANCE PERIOD. TIMING ISSUES REMAIN AND AS A RESULT WILL ENTERTAIN VICINITY SHRA FOR NOW AFTER 00Z 10/30. WILL VEER THE WINDS TO WESTERLY THIS EVENING. EXTENDED OUTLOOK...SHOWERS MVFR/IFR POSSIBLE 6-12Z THURSDAY AS A COLD FRONT PUSHES ACROSS THE CAROLINAS AND OFF THE COAST. VFR LATER THU THRU FRIDAY WITH A SLIGHT CHANCE OF MVFR SHOWERS SATURDAY MORNING. VFR AND BREEZY SATURDAY AFTERNOON INTO SUNDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 10:40 PM TUESDAY...LIGHT WINDS WITH SEAS OF UNDER 2 FT CONTINUE OVER THE WATERS THIS EVENING. NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. PREVIOUS DISCUSSION FOLLOWS: SOUTHWEST FLOW CONTINUES OVERNIGHT WITH SURFACE HIGH CENTERED EAST OF THE WATERS. AS THE HIGH MOVES FARTHER EAST THE GRADIENT WILL BECOME MORE DEFINED. THIS...COMBINED WITH STRONG LOW LEVEL JET...WILL PUSH SOUTHWEST FLOW TO A SOLID 15 KT LATE TONIGHT. GUSTS AROUND 20 KT WILL BE POSSIBLE EARLY WED MORNING. INCREASED SOUTHWEST FLOW WILL BUILD SEAS FROM 1 TO 2 FT THIS AFTERNOON TO 2 TO 3 FT OVERNIGHT. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 3 AM WEDNESDAY...COLD FRONT WILL SIT OFF THE COAST THROUGH THE PERIOD...WAITING FOR A STRONG UPPER LOW CROSSING THE WESTERN GREAT LAKES. WINDS WILL BE OUT OF THE NORTH THROUGH THE PERIOD. WIND SPEED FORECAST IS SLIGHTLY PROBLEMATIC AS A WAVE OF LOW PRESSURE DEVELOPS ALONG THE WELL-OFFSHORE BOUNDARY. SOME GUIDANCE HINTING AT A MAINTAINED WIND SPEED WHEREAS THE GFS SHOWS THAT THE APPROACH OF THE NEXT STRONG SYSTEM ACTUALLY CAUSES LOCAL WINDS TO DIMINISH. FLAGS LIKELY IN EFFECT ON FRIDAY HOWEVER AS SMALL CRAFT CONDITIONS EXPECTED TO MATERIALIZE SATURDAY. LONG TERM /SATURDAY THROUGH SUNDAY/... AS OF 3 AM WEDNESDAY...VERY STRONG UPPER LOW CROSSING BY JUST TO OUR NORTH ON SATURDAY. A NEW LOW CROSSES THE REGION ALONG WITH A SECONDARY COLD FRONT. VERY COLD AIR ADVECTION AND DEEP MIXING THEN ENSUES WITH VERY STRONG LOW LEVEL WIND FIELDS IN PLACE. ADVISORY APPEARS LIKELY AND GALE FORCE WIND GUSTS TOUGH TO RULE OUT. FLAGS SHOULD CARRY INTO PART OF SUNDAY BUT CONDITIONS WILL BE WANING AS THE LOW RAPIDLY ACCELERATES WHILE DEEPENING. IT MAY SEND SOME BACKSWELL TOWARDS THE CAROLINAS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MBB NEAR TERM...DCH SHORT TERM...MBB LONG TERM...MBB AVIATION...DCH/SGL

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