845 FXUS62 KILM 292329 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 729 PM EDT SAT SEP 29 2012 .SYNOPSIS... THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL BE ON THE INCREASE THIS WEEKEND AS A COLD FRONT STALLS ACROSS THE EASTERN CAROLINAS. NEXT WEEK WILL REMAIN UNSETTLED AS LOW PRESSURE DEVELOPS ALONG THE GULF COAST AND MOVES ACROSS THE WESTERN CAROLINAS. A COLD FRONT WILL CROSS THE AREA BY LATE WEEK BRINGING DRIER AND COOLER WEATHER. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... AS OF 300 PM SATURDAY...THE COLD FRONT STALLED OUT JUST ALONG NORTHERN TIER OF CWA IN NORTH CAROLINA BASICALLY FROM FAYETTEVILLE TO NEW BERN AND ALSO EXTENDS INTO SOUTH CAROLINA JUST SOUTH OF STATE BORDER INTO GSP AREA. ONE SMALL AREA OF STORMS FIRED ALONG THIS BOUNDARY DOWN INTO ROBESON COUNTY THIS MORNING AND MOVED QUICKLY TOWARD THE COAST. THIS CONVECTION REMAINED SHALLOW WITH NO SIGNIFICANT IMPACT OTHER THAN BRIEF HEAVIER RAIN ACROSS PORTIONS OF ROBESON...BLADEN AND PENDER COUNTIES. MID TO HIGH CLOUDS CONTINUE TO BLANKET AREA WITH ISOLATED SHOWERS DEVELOPING MAINLY OVER NORTH CAROLINA COASTAL ZONES. THIS IS KEEPING TEMPS CLOSER TO 70 OVER RAIN COOLED AIR CLOSE TO FRONT AND CLOSER TO 80 SOUTH OF FRONT THROUGH EARLY THIS AFTERNOON. HRRR CONTINUES TO SHOW BEST COVERAGE IN WARM AND MOIST AIR MASS TO THE SOUTH AND EAST OF FRONT. BEST INSTABILITY LIES IN AREAS TO THE SOUTH AND WEST OF LOCAL CWA WHERE TEMPS REACHING INTO 80S AND DEWPOINTS IN THE MID 60S CLOSE TO 70 WITH GREATER SUNSHINE. TEMPS SHOULD REACH THE LOW TO MID 80S FOR MOST AREAS ESPECIALLY ACROSS SOUTH CAROLINA. INCREASED MOISTURE THROUGH THE COLUMN FROM H7 UP THROUGH MID TO UPPER ATMOSPHERE CREATING PCP WATER VALUES UP TO 1.7 INCHES. MODIFIED SURFACE BASED CAPE REACHING UP AROUND 1100 J/KG THIS AFTERNOON. OVERALL LOOKS LIKE MAIN FOCAL POINT FOR CONVECTION WILL BE ALONG THE FRONT INITIALLY. THEN ALONG SEA BREEZE BOUNDARY THIS AFTERNOON AIDED BY PERTURBATION IN MID TO UPPER LEVELS. AS MID TO UPPER TROUGH SWINGS EAST THROUGH THIS AFTERNOON...MODELS SHOW DECENT SUPPORT AS PERTURBATION MOVES THROUGH AT THE BASE OF THIS TROUGH THIS AFTERNOON INTO THIS EVENING. THIS SHOULD HELP INITIATE SOME STRONGER TSTMS ACROSS LOCAL AREA INTO SOUTH CAROLINA THROUGH THIS EVENING. A STRONG JET RIDING AROUND THE BASE OF THE UPPER TROUGH WILL MOVE EAST ACROSS NORTH CAROLINA THROUGH TONIGHT. THE MID TO UPPER LEVEL SUPPORT MAY COME TOGETHER LATE THIS EVENING TO AROUND MIDNIGHT BEFORE LOCAL AREA ACTUALLY GETS INTO INCREASED SUBSIDENCE AS THE MID TO UPPER TROUGH GIVES A PUSH TO THE COLD FRONT TONIGHT...MOVING OFF THE COAST BY SUNRISE. TEMPS OVERNIGHT WILL BE IN THE MID 60S SOUTH OF FRONT AND DOWN CLOSER TO 60 OVER NORTHERN TIER OF CWA IN SLIGHTLY COOLER AIR BEHIND FRONT. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...AMAZINGLY THE MODELS ARE SIMILAR WITH THE EVOLUTION AND MOVEMENT OF THE 2 UPPER CLOSED LOWS THROUGH EARLY MONDAY...THERE-AFTER THEY DIVERGE FROM ONE ANOTHER. THEY IDENTIFY THE EVOLUTION OF THE UPPER LOW ACROSS TX/OK...THE MUCH WEAKER OF THE 2...AND ITS MOVEMENT TO THE GULF COAST STATES. THE STRONGER CLOSED BORDERLINE CUTOFF UPPER LOW ACROSS SE CANADA IS PROGGED TO DROP TO THE EASTERN GREAT LAKES BY SUNDAY...THEN LIFT SLOWLY ACROSS THE NE STATES THROUGH MONDAY. AT THE SAME TIME...THE WESTERN ATLANTIC UPPER RIDGE BECOMES BETTER ESTABLISHED AND FORCES THE UPPER LOW ACROSS THE GULF COAST STATES TO OPEN UP AND BEGIN LIFTING NORTH BY NORTHEAST LATE MONDAY. WEAK 5H VORTS/IMPULSES WILL EJECT FROM THE SOUTHERN STREAM UPPER LOW AND RESULT WITH WEAK SFC LOWS TRACKING ENE ALONG THE STALLED SFC BOUNDARY. THE UPPER LOW IS PROGGED TO BEGIN LIFTING N BY NE FROM THE GULF OF MEXICO MONDAY THROUGH MONDAY NIGHT...RESULTING WITH THE STALLED SFC BOUNDARY LIFTING NORTHWARD ACROSS THE FA AS A WARM FRONT. THE GULF COAST UPPER LOW PROGGED TO AMPLIFY AND OPEN UP BY THE END OF THIS FORECAST PERIOD. IN TURN...SUBTROPICAL/TROPICAL MOISTURE WILL BE TAPPED AND ADVECT ACROSS THE FA LATE MONDAY INTO MONDAY NIGHT. THE LOWEST CHANCE FOR PCPN THIS PERIOD WILL OCCUR DURING SUNDAY WITH THE AFTERNOON SEA BREEZE BOUNDARY AIDING POPS. THE HIER CHANCE WILL OCCUR FROM MIDDAY MONDAY THROUGH MONDAY NIGHT. FOR MAXES AND MINS...USED THE SLIGHTLY WARMER NAM MOS GUIDANCE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 300 PM SATURDAY...UNSETTLED WEATHER TO PERSIST THROUGH THE FIRST HALF OF THE EXTENDED AS ANOMALOUS 500MB LOW EVOLVES ACROSS THE TN VLY/MID ATLANTIC. AT THE START OF THE PERIOD...VERY DEEP 500MB LOW WILL BE CENTERED ACROSS THE ARKLATEX REGION. IT IS QUITE RARE TO SEE SUCH A DEEP LOW THIS TIME OF YEAR...AND 500MB HEIGHTS SHOW DEPARTURES TO CLIMO OF NEARLY -4 SD'S ACROSS THE GULF! BENEATH THIS TROUGH...A SURFACE LOW WILL MOVE UP THROUGH THE TN VLY AND INTO THE GREAT LAKES WHILE ITS ASSOCIATED WARM FRONT MOVES UP THE EAST COAST. THIS MARKS A PRETTY SIGNIFICANT CHANGE IN SURFACE LOW EVOLUTION FROM PREVIOUS RUNS...BUT SEEMS PLAUSIBLE SINCE THE DEEP TROUGH WILL TEND TO CAPTURE AND SPIN THE SURFACE CYCLONE BACK TO THE WEST...AS OPPOSED TO HAVING IT TRACK INTO THE MID ATLANTIC AND OFF THE COAST. THIS LOW WILL GRADUALLY FILL THROUGH MID WEEK WHILE ITS COLD FRONT SLOWLY WORKS EAST AND THROUGH THE CAROLINAS ON THURSDAY. WITH THE ILM CWA BEING SOUTH OF THE WARM FRONT...AND DEEP SOUTHERLY FLOW ADVECTING TROPICAL MOISTURE INTO THE COLUMN...SHOWERS AND THUNDERSTORMS ARE LIKELY ON TUESDAY AND HAVE BUMPED POP TO LOW-END LIKELY...HIGHEST ALONG THE COAST WHERE AN INVERTED TROUGH WILL HELP FOCUS CONVECTION. SOME GUIDANCE SWINGS THE FRONT THROUGH WITH MUCH DRIER AIR ON WEDNESDAY...BUT WITH UPPER TROUGH LAGGING WELL TO THE WEST...BELIEVE THIS IS TOO FAST AND WILL CONTINUE THE INHERITED SCHC THROUGH THURSDAY BEFORE DRYING BEGINS IN EARNEST FRIDAY AND THE WKND. TO CALL THIS BOUNDARY A COLD FRONT IS A BIT OF A STRETCH SINCE THERE IS LITTLE CAA BEHIND IT...BUT AFTER SEVERAL DAYS OF ABOVE CLIMO TEMPS THROUGH THURSDAY...FRI/SAT WILL RETURN TO MORE SEASONABLE TEMPS IN A MUCH DRIER AIR MASS. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 00Z...ISOLATED SHOWERS AND THUNDERSTORMS OUTSIDE OF OUR AREA HAVE THE POTENTIAL TO AFFECT THE TERMINALS OVER THE NEXT FEW HOURS. GIVEN LOWERED CONFIDENCE ON EXACT TIMING...HAVE KEPT IN TEMPO GROUPS TO ACCOUNT FOR BRIEFLY REDUCED VISIBILITIES AND CIGS IN HEAVIER DOWNPOURS. ANTICIPATE MOST OF THE ACTIVITY TO DISSIPATE...THOUGH CANNOT RULE OUT VCSH THROUGH THE OVERNIGHT HOURS WITH LIGHT AND VARIABLE WINDS AND MVFR/POSSIBLE IFR/ DUE TO LOWERED CIGS AND PATCHY AREAS OF FOG. AFTER DAYBREAK...FOG WILL GRADUALLY DISSIPATE...WITH ANY LINGERING CIGS TO SLOWLY LIFT THROUGH MID MORNING. INTO THE AFTERNOON HOURS...VFR WILL PREVAIL WITH SCT/BKN MID TO HIGH LEVEL CLOUDS AND ISOLATED TO SCATTERED SHRA/TSRA LIKELY THROUGHOUT THE REMAINDER OF THE TAF PERIOD. WINDS WILL BECOME WEST-SOUTHWEST INTO THE AFTERNOON WITH SUSTAINED WINDS AOB 10 KTS. EXTENDED OUTLOOK...UNSETTLED WEATHER ASSOCIATED WITH A STALLED FRONTAL BOUNDARY COULD PRODUCE PERIODS OF TEMPO SUB-VFR CONDITIONS ACROSS THE AREA THROUGH THURSDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM SATURDAY...FAIRLY TRANQUIL MARINE CONDITIONS CONTINUE WITH SEAS REMAINING DOWN AROUND 2 FT OR LESS IN LIGHT SW WINDS AHEAD OF STALLED COLD FRONT REACHING EAST NORTHEAST INTO THE COASTAL WATERS NORTH OF CAPE LOOKOUT. SOME SHOWERS AND TSTORMS CAN BE EXPECTED THIS AFTERNOON THROUGH TONIGHT AS MID TO UPPER TROUGH PUSHES EAST. THE BEST SUPPORT FOR MORE STRONGER AND MORE WIDESPREAD ACTIVITY WILL COME LATER THIS EVENING INTO EARLY OVERNIGHT HOURS AS PERTURBATION GIVES A PUSH TO THE COLD FRONT HELPED OUT BY LAND BREEZE. WINDS WILL VEER AROUND TO THE SW TO W OVERNIGHT AND MAY REACH UP TO 15 KTS BRIEFLY AHEAD OF COLD FRONT TONIGHT BUT WILL BE W-NW BEHIND FRONT AS IT SHIFTS OFF SHORE BY DAYBREAK. SEAS WILL ONLY INCREASE SLIGHTLY UP NEAR 3 FT IN SOUTHERLY PUSH AHEAD OF FRONT. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...EARLY ON...THE STALLED FRONT WILL LIE EITHER ACROSS PORTIONS OF THE ILM WATERS...OR LIKELY JUST SOUTH OF THE WATERS. RATHER WEAK SFC PRESSURE PATTERN AND GRADIENT WILL RESULT WITH VARIABLE WIND DIRECTION...DEPENDING WHAT SIDE OF THE FRONT ONE IS LOCATED...AND SPEEDS AROUND 10 KT. FOR MONDAY THROUGH MONDAY NIGHT...THE STALLED FRONT WILL LIFT NORTHWARD AS A WARM FRONT AS GULF COAST UPPER LOW OPENS UP AND AMPLIFIES. LOOK FOR WINDS TO VEER TO THE E-SE DURING MONDAY...AND BECOME SOUTHERLY LATE MONDAY NIGHT. WITH THE SFC PG PROGGED TO TIGHTEN...WIND SPEEDS WILL INCREASE TO A SOLID 15 KT...POSSIBLY HIGHER...MONDAY NIGHT. SIG. SEAS WILL RUN 2 TO 3 FT THROUGH EARLY MONDAY...AND MAINLY COMPRISED OF A 9-11 SECOND PERIOD EASTERLY GROUND SWELL. LOW PERIOD WIND DRIVEN WAVES WILL BECOME MORE DOMINANT LATE MONDAY INTO MONDAY NIGHT. SIG SEAS TO BUILD TO 3 TO POSSIBLY 5 FT LATE IN THE SHORT TERM. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 300 PM SATURDAY...SOUTHERLY WINDS BEHIND A WARM FRONT...AND AHEAD OF A COLD FRONT...WILL BE 10-15 KTS THROUGH TUESDAY BEFORE VEERING TO THE W/SW WEDNESDAY AT SPEEDS LESS THAN 10 KTS WITH A DISSIPATING COLD FRONT. WINDS BACK AGAIN TO THE SOUTH AS FRONT DISSIPATES OVER THE WATERS LATE WEDNESDAY...BEFORE VEERING FURTHER TO THE NW ON THURSDAY BEHIND A STRONGER COLD FRONT. SEAS WILL BE PRIMARILY CHARACTERIZED BY SOUTHERLY WIND WAVES TUESDAY AND BE 3-4 FT...BEFORE DROPPING THROUGH THE REST OF THE EXTENDED TO 1-3 FT THANKS TO THE SLACKENING WINDS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...DCH NEAR TERM...RGZ SHORT TERM...DCH LONG TERM...JDW AVIATION...SGL