Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201900 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 300 PM EDT MON OCT 20 2014 .SYNOPSIS... HIGH PRESSURE OVERHEAD WILL SLIP OFF SHORE THROUGH TUESDAY AS A COLD FRONT APPROACHES FROM THE WEST. THIS DRY COLD FRONT WILL CROSS THE AREA TUESDAY NIGHT...BRINGING COOLER TEMPERATURES MID WEEK. HIGH PRESSURE WILL DOMINATE THE WEATHER THROUGH EARLY NEXT WEEK...WITH LITTLE OR NO RAIN EXPECTED. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM MONDAY...SURFACE ANALYSIS SHOWS HIGH PRESSURE OVERHEAD BUT THE CENTER OF THIS AIRMASS IS PROGRESSING EASTWARD QUICKLY. IN THE MID AND UPPER LEVELS A STRONG SYSTEM IS DIVING SOUTH ACROSS THE OHIO VALLEY. THE EVENING WILL FEATURE A TRANSITION FROM THE DECREASING DIURNALLY-DRIVEN CUMULUS FIELDS TO AN INCREASE IN STRATIFORM CLOUDINESS MAINLY ALONG THE COAST. THE UPPER WAVE WILL TRY TO GRAB SOME MOISTURE THAT WILL BE GATHERING WELL OFFSHORE. FOR THE MOST PART THIS WILL BE CONFINED TO CLOUDINESS BUT A FEW SPRINKLES CANNOT BE RULED OUT. A CONTINUATION OF FAIRLY DRY MID LEVELS SHOULD PRECLUDE MEASURABLE RAINFALL. THE HIGH MOVING OFF THE COAST PAIRED WITH THE CLOUD COVER WILL KEEP TEMPERATURES MUCH MILDER THAN LAST NIGHT WITH LOWS RANGING FROM UPPER 40S OVER NWRN ZONES (WHERE THERE SHOULD BE FAR FEWER CLOUDS) TO MID 50S ALONG THE IMMEDIATE COAST. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...HIGH PRESSURE WILL SLIP FARTHER OFF SHORE AS A COLD FRONT APPROACHES FROM THE WEST ON TUESDAY. OVERALL MOISTURE RETURN WILL BE LIMITED AS WINDS VEER AHEAD OF THE FRONT THROUGH TUES WITH AN INCREASING DOWNSLOPE WESTERLY COMPONENT TO THE FLOW THROUGH THE LOW TO MID LEVELS OF THE ATMOSPHERE AS TROUGH DIGS DOWN FROM THE NORTH ALOFT. EXPECT PCP WATER VALUES TO REMAIN BELOW AN INCH THROUGH TUES. AS VORT MOVES THROUGH THE MAIN H5 TROUGH ON TUES IT WILL PRODUCE SOME CLOUDS AND PCP TUES MORNING IN CONVERGENCE ALONG TROUGH JUST OFF SHORE BEFORE MOVING OFF TO THE EAST BY THE AFTN. PCP SHOULD REMAIN JUST EAST AND WILL LEAVE JUST SOME CLOUDS TUES MORNING FOR COASTAL LOCALES. MID TO UPPER TROUGH DIGGING DOWN FROM THE NORTH WILL PUSH THIS FRONT THROUGH THE CAROLINAS TUES NIGHT. A DEEP N-NW FLOW OF COOLER AND DRIER AIR WILL BUILD IN BEHIND FRONT AS MID TO UPPER TROUGH ROTATES SLOWLY AROUND THROUGH THE SOUTHEAST FINALLY LIFTING OFF TO THE NORTHEAST BY THURS MORNING. DECENT DYNAMICS WILL ROTATE AROUND THE TROUGH THROUGH THE CAROLINAS ON WED BUT NOT ENOUGH MOISTURE TO WORK WITH TO PRODUCE MORE THAN SOME CLOUDS...MAINLY OVER NORTHEAST NC. PCP WATER VALUES DROP TO LESS THAN A HALF INCH BY WED MORNING. TEMPS WILL REBOUND ON TUES IN WARMER AND SLIGHTLY MOISTER SW TO W FLOW WITH AFTN HIGHS REACHING THE UPPER HALF OF 70S. DECENT HEIGHT FALLS INTO WED WITH DEEP DRYING AND COOLING BEHIND FRONT WILL LEAD TO TEMPS BEING KNOCKED BACK DOWN AND MOST TEMPS WILL REMAIN IN THE 60S FOR WED IN COOL NORTHERLY FLOW AT THE SFC. DRY AIR WITH LOW DEWPOINTS WILL ALLOW TEMPS TO DROP DOWN INTO THE 40S MOST PLACES WED NIGHT...ALTHOUGH WINDS WILL STAY UP A LITTLE WITHOUT THE BEST RADIATIONAL COOLING. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 300 PM MONDAY...MODIFYING HIGH PRESSURE WILL BE THE DOMINANT FEATURE IN THE PERIOD. ALOFT THE MID LEVEL PATTERN OVER MUCH OF THE CONUS REMAINS AMPLIFIED WITH TROUGHING OVER THE EAST EARLY IN THE PERIOD TRANSITIONING TO RIDGING BY THE END OF THE PERIOD. DEEP NORTHWEST FLOW ALOFT WILL KEEP MID LEVELS DRY WHILE SLOW DEVELOPMENT OF LOW LEVEL RETURN FLOW WILL LIMIT AVAILABILITY OF LOW LEVEL MOISTURE. BASED ON THIS WILL MAINTAIN INHERITED DRY FORECAST THROUGH THE END OF THE PERIOD. COMBINATION OF LOW LEVEL NORTHERLY FLOW AND MID LEVEL TROUGHING AT THE START OF THE PERIOD WILL KEEP HIGHS NEAR TO BELOW CLIMO. AS MID LEVEL RIDGE BUILDS AND LOW LEVEL RETURN FLOW DEVELOPS EARLY NEXT WEEK HIGHS WILL CLIMB ABOVE CLIMO. DEEP DRY AIR AND WEAK GRADIENT WILL ALLOW FOR AT LEAST SOME RADIATIONAL COOLING EACH NIGHT. THIS WILL KEEP LOWS NEAR TO BELOW CLIMO FOR MUCH OF THE PERIOD. && .AVIATION /18Z MONDAY THROUGH FRIDAY/... AS OF 18Z...EXPECT VFR TO PREVAIL THROUGH THE VALID TAF PERIOD AS HIGH PRESSURE BUILDS OVER THE AREA. GENERALLY SOUTH WINDS AROUND 5 TO 10 KTS WILL CONTINUE THROUGH THE REST OF TODAY...BECOMING LIGHT AND VARIABLE OVERNIGHT. IN ADDITION...AS RETURN FLOW OCCURS ANTICIPATE TO SEE AN INCREASE IN LOW LEVEL MOISTURE...ALLOWING FOR A FEW/SCT/BKN 4-5KFT CLOUD LAYER TO DEVELOP THIS AFTERNOON AND PERSIST INTO THE OVERNIGHT HOURS. INTO TUESDAY MORNING...COULD SEE SOME LIGHT -DZ/-RA ALONG THE COAST EARLY ON...BUT OTHERWISE EXPECT LIGHT WEST-NORTHWEST WINDS WILL PREVAIL WITH NEARLY CLEAR SKIES. EXTENDED OUTLOOK...EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM MONDAY...A RAPIDLY EAST-PROGRESSING HIGH MOVES OFFSHORE THIS EVENING. SOUTHERLY FLOW WILL INCREASE SLIGHTLY IN STRENGTH IN RESPONSE AND SEAS WILL BUILD UP TO 3 FT TOWARDS THE OUTER REACHES OF MAINLY NRN LEGS. SOUTHERN ZONES MAY STAY CAPPED AT 2 FT AS THERE IS NOT QUITE SUFFICIENT ONSHORE FLOW COMPONENT TO ALLOW FOR 3 FOOTERS. THE LATE NIGHT PASSAGE OF A STRONG UPPER SYSTEM WILL PUSH A SURFACE TROUGH ACROSS THE WATERS. THIS WILL VEER THE WINDS TO WEST AND HELP TO PUSH THE 3 FT SEAS BACK OUT OF THE AREA CLOSE TO THE END OF THE PERIOD. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...WINDS WILL VEER THROUGH TUES FROM SW EARLY TO MORE WESTERLY THROUGH THE AFTN AS TROUGH OF LOW PRESSURE JUST OFF THE COAST TUES MORNING MOVES EAST THROUGH THE DAY. A COLD FRONT WILL FOLLOW FOR TUES NIGHT. OVERALL EXPECT W-SW WINDS 10 TO 15 KTS THROUGH TUES AHEAD OF MAIN COLD FRONT. ONCE FRONT CROSSES THE WATERS TUES NIGHT A SURGE OF N-NW WINDS WILL DEVELOP AS COOLER AND DRIER AIR FLOWS OVER THE RELATIVELY WARMER WATERS. EXPECT GUSTY WINDS UP TO 20 KTS IN A WELL MIXED MARINE LAYER. SEAS BELOW 2 FT OR LESS ON TUES WILL KICK UP IN CAA BEHIND FRONT EARLY WED THROUGH WED NIGHT...UP TO 3 TO 4 FT MAINLY IN OUTER WATERS. NEAR SHORE WATERS SHOULD REMAIN LESS THAN 2 FT IN AS STRONGER OFF SHORE FLOW WILL KEEP GREATEST SEAS OFF SHORE. LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 PM MONDAY...SOLID 15 KT NORTHWEST FLOW AT THE START OF THE PERIOD WILL DIMINISH TO 10 TO 15 KT THU AND THU NIGHT AS GRADIENT RELAXES SLIGHTLY. GRADIENT REMAINS STATIC FRI AND SAT AS THE CENTER OF THE SURFACE HIGH SLOWLY SHIFTS SOUTH. FLOW WILL REMAIN WEST-NORTHWEST WITH SPEEDS IN THE 10 TO 15 KT RANGE. SEAS WILL RUN 2 TO 3 FT THROUGH THE PERIOD. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...MBB SHORT TERM...RGZ LONG TERM...III AVIATION...MBB/SGL

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