Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 161126 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 626 AM EST TUE DEC 16 2014 .SYNOPSIS... TEMPERATURES WILL RISE WELL ABOVE NORMAL TODAY AHEAD OF AN APPROACHING COLD FRONT THAT WILL CROSS THE COAST TONIGHT. SEASONABLY COOL AND FAIR WEATHER WILL FOLLOW WEDNESDAY THROUGH FRIDAY. AN APPROACHING STORM SYSTEM COULD BRING WET CONDITIONS DURING THE UPCOMING WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 615 AM TUESDAY...DENSE FOG ADVISORY REMAINS IN EFFECT THRU 9 AM...FOR PORTIONS OF THE ILM SC CWA. LATEST IR 11-3.9 MICRON CHANNEL HAS BEEN OUTLINING THE AREA OF FOG ACROSS THE ILM CWA THIS AM. MID TO UPPER LEVEL CLOUDINESS HAS BEGUN PUSHING ACROSS THE ILM CWA...AND WILL LIMIT THE DENSE FOG COVERAGE...LET ALONE FOG COVERAGE IN GENERAL. THE S/W UPPER RIDGE AXIS HAS MOVED WELL OFF THE CAROLINA COASTS THIS AM. ALL EYES TURN TO THE UPPER CLOSED LOW OR OPEN WAVE PUSHING ACROSS THE SOUTHERN GREAT LAKES TODAY...INTO THE NE STATES TONIGHT. ITS UPPER TROF AXIS TO FLATTEN SOME AS IT PUSHES TO THE CAROLINAS LATE TODAY...AND OFF THE CAROLINA COASTS LATE TONIGHT OR EARLY WEDNESDAY. THERE IS A TRAILING MID-LEVEL VORT THAT PUSHES ACROSS THE FA LATE THIS AFTERNOON AND EVENING...WHICH COULD BE THE DIFFERENCE BETWEEN CHANCE OR NO CHANCE FOR PCPN. THE ASSOCIATED SFC COLD FRONT IS PROGGED TO PUSH EAST ACROSS THE ILM CWA EARLY THIS EVENING...AND OFF THE CAROLINA COASTS BY MIDNIGHT WEDNESDAY. WITH THE UPPER FLOW FLATTENING...MOISTURE SOURCES SUCH AS THE GULF OF MEXICO AND THE ATLANTIC WILL BE UNAVAILABLE. AS A RESULT...MOISTURE AVAILABILITY WILL BE LIMITED AND THUS THE FURTHER THE COLD FRONT IS DISPLACED AWAY FROM THE MAIN SFC LOW OVER THE GREAT LAKES...THE LOWER CHANCE FOR PCPN WILL BE ADVERTISED. PCPN TIMING ACROSS THE FA WILL EXTEND FROM MIDDAY THRU EARLY THIS EVENING. THE CLEARING TREND WILL OCCUR FROM LATE THIS EVENING THRU THE OVERNIGHT. AS FOR MAX/MIN TEMPS...WILL LEAN TOWARD THE SLIGHTLY MILDER GFS MOS GUIDANCE...ESPECIALLY WITH TODAYS HIGHS. LOCAL VERIFICATION FOR THE PAST 10 TO 20 DAYS ILLUSTRATES THE NAM MOS HAVING ITS TROUBLES...AND THE GFS MOS HOLDING ITS OWN WITHIN THE TOP 3 PERFORMERS. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 3 AM TUESDAY...PROGRESSIVE MID LEVEL PATTERN AND LOW LEVEL DRY AIR WILL KEEP THE SOUTHEAST DRY THROUGH THE PERIOD. INCREASING MOISTURE ALOFT WILL MANIFEST AS AN INCREASE IN CLOUD COVER LATE WED NIGHT AND THU BUT DRY AIR BELOW 700MB AND LOW LEVEL SUBSIDENCE RULE OUT ANY PRECIP CHANCES. WEAK SHORTWAVE PASSES NORTH OF THE AREA ON THU AND THE RESULTING INCREASE IN MOISTURE BETWEEN 600 AND 700MB SHOULD PRODUCE A MID CLOUD DECK DURING THE AFTERNOON. THIS CLOUD...WHILE NOT RAIN BEARING...WILL COOL TEMPS A BIT AND HIGHS ARE LIKELY TO END UP A DEGREE OR 2 SHORT OF CLIMO IN MOST PLACES. COOLEST AREAS WILL BE ACROSS THE NORTHERN TIER WHERE CLOUDS LIKELY TO BE THICKEST AND MOST PREVALENT. HIGH CLOUDS WILL HELP KEEP LOWS NEAR CLIMO BOTH NIGHTS. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 3 AM TUESDAY...SOUTHERN STREAM SYSTEM STILL PROGGED TO AFFECT THE SOUTHEAST FRI NIGHT THROUGH SAT NIGHT. A LOT ABOUT THIS SYSTEM REMAINS UNCERTAIN AND CONFIDENCE CONTINUES TO RUN LOW. GUIDANCE CONTINUES TO HAVE RUN TO RUN CONSISTENCY PROBLEMS WITH SOLUTIONS RANGING FROM INTERACTION WITH A NORTHERN STREAM SHORTWAVE AND A WELL DEVELOPED SURFACE LOW CROSSING THE LOCAL AREA AND THEN TRAVELING UP THE EAST COAST TO A WEAK WAVE OPENING UP AS IT LIFTS NORTHEAST AND DRAGS A COLD FRONT ACROSS THE AREA. DESPITE THE UNCERTAINTY SOME DETAILS CAN BE GLEANED FROM THE CHAOS. MID LEVEL FLOW OVER THE SOUTHERN CONUS WILL TRANSITION FROM PROGRESSIVE TO AMPLIFIED WITH DEEP SOUTHWEST FLOW ADVECTION MOISTURE OVER THE CAROLINAS. EVEN THE DRIEST SOLUTIONS SHOW ABUNDANT DEEP MOISTURE WITH PRECIPITABLE WATER VALUES APPROACHING 1.25 INCH. IT ALSO APPEARS THAT REGARDLESS OF THE TRACK OR INTENSITY OF THE SURFACE AND MID LEVEL FEATURES THERE WILL NOT BE ANY PRECIP TYPE ISSUES. BEST PRECIP CHANCES REMAIN LATE FRI NIGHT INTO SAT EVENING WHEN ISENTROPIC LIFT AND MOISTURE ARE ON THE INCREASE. THERE SHOULD ALSO BE SOME ENHANCEMENT FROM PVA AHEAD OF THE SHORTWAVE ALONG WITH THE POSSIBILITY OF SURFACE CYCLOGENESIS. INHERITED FORECAST THINKING REMAINS VALID AND PLAN ONLY MINIMAL CHANGES TO PRECIP FORECAST. NEXT WEEK STARTS OFF DRY AS THE SOUTHERN STREAM SYSTEM EXITS. MEDIUM RANGE GUIDANCE IS HINTING AT TRAILING COLD FRONT ENDING UP PARALLEL TO STEERING FLOW WITH THE BOUNDARY STALLED SOMEWHERE OFF THE SOUTHEAST COAST. AS HAS BEEN THE CASE LATELY THERE ARE BIG DIFFERENCES BETWEEN THE GFS/ECMWF WITH RESPECT TO THE LOCATION OF THE BOUNDARY AND ITS IMPACT ON THE CAROLINAS. FOR NOW DO NOT PLAN ANY MAJOR CHANGES TO INHERITED DRY FORECAST FOR NEXT WEEK. TEMPS NEAR CLIMO EARLY IN THE PERIOD WILL TREND BELOW CLIMO NEXT WEEK. THERE WILL BE POTENTIAL FOR TEMPS ABOVE AND BELOW CLIMO DEPENDING ON HOW THE WEEKEND PLAYS OUT. THE POSSIBILITY OF SURFACE LOW CROSSING THE AREA SAT INTO SAT NIGHT COULD LEAD TO A WIDE RANGE IN TEMPS ACROSS THE AREA. A STRONGER LOW WOULD ENHANCE WARMING AHEAD OF THE LOW AS WELL AS ENHANCING COLD ADVECTION IN ITS WAKE SUN. ONCE AGAIN FEEL MAKING LARGE CHANGES GIVEN THE LOW CONFIDENCE AND LACK OF PREFERRED SOLUTION WOULD BE POINTLESS SO WILL CONTINUE WITH INHERITED FORECAST. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/... AS OF 12Z...MOST OF THE FOG WILL BE OUT OF HERE PRETTY EARLY...14Z AT LBT AT THE LATEST AS SOUTHWEST FLOW ALOFT IS INCREASING. LOOK FOR VFR LATER THIS MORNING WITH INCREASING SOUTHWEST FLOW OUT AHEAD OF A COLD FRONT WHICH WILL PUSH TO THE COAST BY EARLY EVENING. THERE WILL BE SOME WEAK CONVECTION IMMEDIATELY AHEAD OF THE FRONT...COVERAGE WILL BE CONFINED MAINLY TO NORTH CAROLINA. CONVECTION IF ANY WILL BE BRIEF...A COUPLE OF HOURS MAX. LOOK FOR A WEST NORTHWEST WIND TONIGHT...POST FRONTAL. EXTENDED OUTLOOK...VFR WED THROUGH FRIDAY. A CHANCE OF RAIN ON SATURDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 615 AM TUESDAY...THE SFC PRESSURE PATTERN AND TIGHTENING GRADIENT AHEAD OF THE COLD FRONT TO YIELD INCREASING SW WINDS TO 10 TO 20 KT ACROSS THE ILM WATERS TODAY. THE CFP IS SLATED TO OCCUR LATE THIS EVENING AND/OR DURING THE OVERNIGHT PERIOD. THE PROGGED SFC PRESSURE PATTERN TO YIELD VEERING WINDS...FROM SW TO W THIS EVENING...AND TO NW DURING THE PRE-DAWN WED HOURS. THE SFC PG WILL REMAIN TIGHTENED...RESULTING IN CONTINUED 10-20 KT WIND SPEEDS. COULD SEE A FEW GUSTS UP TO 25 KT AFTER FROPA BUT NOT ENOUGH OCCURRENCE TO RAISING A SCA. SIGNIFICANT SEAS WILL SEE A BUILDING TREND THIS PERIOD. WIND DRIVEN WAVES WILL BECOME THE DOMINATE PLAYER OF SIGNIFICANT SEAS WITH THE 11 SECOND PERIOD...1 TO 2 FOOT EASTERLY GROUND SWELL REMAINING PRESENT BUT IN THE BACKGROUND. ONCE NW WINDS BECOME DOMINANT LATE TONIGHT...WILL SEE A DIMINISHING TREND TO SEAS NEARSHORE TAKE AFFECT. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 3 AM TUESDAY...WINDS WILL RETAIN AN OFFSHORE COMPONENT FOR THE DURATION OF THE PERIOD WITH WATERS ON EAST SIDE OF ELONGATED SURFACE HIGH EXTENDING SOUTH FROM CANADA. WINDS WILL VARY FROM WEST TO NORTHWEST ON WED/WED NIGHT AND NORTHWEST TO NORTH THU/THU NIGHT. GRADIENT WILL BE ON THE WEAK SIDE WITH SPEEDS AROUND 10 KT FOR MUCH OF THE PERIOD. COMBINATION OF LIGHT WINDS AND OFFSHORE FLOW WILL KEEP SEAS 2 FT OR LESS. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 3 AM TUESDAY...HIGH PRESSURE FRI WILL YIELD TO A DEVELOPING STORM SYSTEM SAT. SURFACE RIDGE AXIS TO THE WEST-NORTHWEST AND WEAK GRADIENT WILL KEEP NORTH TO NORTHEAST FLOW 10 KT OR LESS THROUGH FRI NIGHT. DEVELOPING LOW WILL MOVE ACROSS OR IN THE VICINITY OF THE WATERS SAT. ALTHOUGH DETAILS REMAIN HAZY GRADIENT WILL TIGHTEN WITH THE PASSING LOW AND WINDS WILL BE ON THE INCREASE...ESPECIALLY LATE IN THE PERIOD AS THE LOW PULLS AWAY AND STRENGTHENS. CURRENT FORECAST HAS WINDS HIGHLY VARIABLE SAT WITH OFFSHORE FLOW APPROACHING A SOLID 20 KT LATE SAT NIGHT. SEAS AROUND 2 FT FRI COULD BUILD AS HIGH AS 5 FT LATER SAT. ALTHOUGH NOT CURRENTLY FORECAST CANNOT RULE OUT HEADLINE CRITERIA DEVELOPING LATE SAT OR SAT NIGHT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR SCZ032-033- 039-053>056. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...III NEAR TERM...DCH SHORT TERM...III LONG TERM...III AVIATION...DL MARINE...

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