Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 221638 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1238 PM EDT TUE JUL 22 2014 .SYNOPSIS... A STATIONARY FRONT ALONG THE COAST WILL SLOWLY MOVE INLAND TODAY AND DISSIPATE TONIGHT. BERMUDA HIGH PRESSURE WILL BUILD INTO THE AREA WEDNESDAY AND THURSDAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE THURSDAY...STALLING NEAR THE COAST FOR THE WEEKEND. ANOTHER COLD FRONT WILL APPROACH FROM THE NORTHWEST MONDAY OR TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1230 PM TUESDAY...CONVECTIVE COVERAGE IS A LITTLE LESS THAN I HAD ANTICIPATED AT NOON BUT RAINFALL RATES WHERE STORMS ARE OCCURRING ARE QUITE LARGE. RADAR IS ESTIMATING UP TO 1.75 INCHES PER HOUR WITH THE ACTIVITY NEAR CASTLE HAYNE IN NORTHERN NEW HANOVER COUNTY. NO CHANGES ARE PLANNED AT THIS TIME TO THE FLOOD WATCH... ALTHOUGH THE NEW 12Z NAM AND GFS ARE SUGGESTING LESS CONVECTIVE COVERAGE MAY OCCUR INLAND...AND THE WATCH COULD BE DROPPED WEST OF I-95 WITH THE 3 PM UPDATE. PREVIOUS DISCUSSION FROM 1000 AM FOLLOWS... THE SYNOPTIC PATTERN FEATURES AN UPPER LOW OVER COASTAL ALABAMA AND AN UPPER RIDGE OFF THE SOUTHEAST COAST. IN BETWEEN THESE TWO FEATURES A STREAM OF DEEP TROPICAL MOISTURE BEING LIFTED FROM THE CARIBBEAN ACROSS FLORIDA AND OVER THE CAROLINAS. AT THE SURFACE AN OLD STATIONARY FRONT STILL LIES FROM NEAR CAPE FEAR TO EAST OF GEORGETOWN SC. WIDESPREAD LOW STRATUS AND FOG LAST NIGHT IS TAKING ITS TIME BURNING OFF INLAND. THE STATIONARY FRONT OFFSHORE WILL PROBABLY REDEVELOP IN THE NEXT 1-2 HOURS ALONG THE EASTERN EDGE OF THE LOW CLOUDS...WITH THIS BOUNDARY BECOMING THE PREFERENTIAL DEVELOPMENT REGION FOR NEW SHOWERS AND THUNDERSTORMS. PRECIPITABLE WATER VALUES ARE EXCEPTIONAL: 2.1 TO 2.3 INCHES ON MODEL SOUNDINGS. THIS COUPLED WITH SLOW STORM MOVEMENT SHOULD LEAD TO MORE HEAVY RAINFALL AND FLOODING THIS AFTERNOON. A FLOOD WATCH WAS ISSUED EARLIER TODAY AND STILL APPEARS WARRANTED...ESPECIALLY FOR REGIONS EAST OF INTERSTATE 95. FLASH FLOOD GUIDANCE VALUES FROM THE NWS SOUTHEAST RIVER FORECAST CENTER ARE 1.5 TO 2.5 INCHES IN 1 HOUR...AND 2.2 TO 3.2 INCHES IN 3 HOURS. THESE VALUES WILL NOT BE HARD TO REACH GIVEN THE ANTICIPATED SETUP THIS AFTERNOON. FREEZING LEVELS HAVE RISEN FROM YESTERDAY AND WILL APPROACH 16000 FEET THIS EVENING. THIS WILL CREATE A VERY DEEP REGION FOR EFFICIENT WARM-CLOUD COALESCENCE RAINFALL PROCESSES. RAINFALL AMOUNT FORECASTS ON THE BROAD SCALE ARE 0.5 TO 1.0 INCH EAST OF INTERSTATE 95 WITH ISOLATED AREAS PROBABLY PICKING UP ANOTHER 4-5 INCHES. WEST OF I-95 STORM COVERAGE MAY BE A LITTLE MORE SPARSE WITH RAINFALL RATES WILL BE JUST AS HEAVY. HIGHS TODAY SHOULD RANGE FROM 83 ON THE BEACHES TO THE MID 80S INLAND. SOME UPPER 80S MAY STILL OCCUR ACROSS THE PEE DEE REGION ASSUMING LOW STRATUS BURNS OFF ON SCHEDULE. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 330 AM TUESDAY...SHOULD SEE A LULL IN WIDESPREAD CONVECTION WED AS UPPER RIDGE BUILDS IN BRIEFLY AND A DEEP SW FLOW WILL VEER BECOMING MORE WESTERLY ALLOWING FOR SOME MID LEVEL DRYING. THE DEEPEST MOISTURE WILL REMAIN TO OUR EAST OVER THE WATERS WHERE PCP WATER VALUES WILL BE MAXED OUT AROUND 2.3 INCHES WED AFTN. EXPECT MORE LOCALIZED CONVECTION ON WED ESPECIALLY ALONG THE SEA BREEZE IN THE AFTN AND THE WESTERLY COMPONENT TO THE WINDS SHOULD HELP TO KEEP SEA BREEZE PINNED CLOSER TO THE COAST AND HELP STORMS MOVE OFF TO THE EAST OVER THE WATERS. BY THURS FLOW WILL INCREASE OUT OF THE SOUTHWEST AS GRADIENT TIGHTENS AS COLD FRONT MOVES IN FROM THE NORTHWEST. MODELS LOOK FASTER WITH THE DIGGING MID TO UPPER TROUGH PUSHING THE COLD FRONT INTO THE COASTAL CAROLINAS BY THURS NIGHT. THE DAY SHOULD START OUT DRIER WITH PCP WATER VALUES DOWN CLOSER TO 1.5 INCHES. NAM AND ECMWF ARE A LITTLE MORE AGGRESSIVE WITH SOUTHWARD PROGRESSION OF FRONT SHIFTING IT SOUTH OF AREA BY FRI MORNING WHILE THE GFS HANGS IT UP RIGHT ALONG THE COAST AS THE H5 TROUGH LIFTS NORTH. EITHER WAY...SHOULD SEE STRONGER AND MORE NUMEROUS SHWRS/TSTMS ON THURS AHEAD OF FRONT INLAND INITIALLY AND THEN SHIFTING CLOSER TO THE COAST. WILL NEED TO KEEP A CLOSE EYE ON HOW FAST THIS SYSTEM MOVES. TEMPS WILL RISE THROUGH THE PERIOD REACHING NORMAL OR SLIGHTLY ABOVE NORMAL AS HEIGHTS RISE THROUGH MID WEEK AS RIDGE BUILDS IN ON WED. TEMPS MAY LOWER THURS AS TROUGH DIGS DOWN LOWERING H5 HEIGHTS AND PRODUCING MORE IN THE WAY OF CLOUDS AND PCP AHEAD OF COLD FRONT. OVERNIGHT LOWS SHOULD REMAIN ABOVE NORMAL...IN THE MID 70S...IN A CLOUDIER AND MORE HUMID AIR MASS. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 330 AM TUESDAY...COLD FRONT MAY BE HUNG UP RIGHT ALONG THE COAST FRI MORNING BUT NAM WANTS TO PUSH IT SOUTH AND EAST OF AREA LEAVING HIGH PRESSURE IN CONTROL. NOT CONFIDENT THAT THE BOUNDARY WILL GET TOO FAR SOUTH AS H5 TROUGH LIFTS NORTH LEAVING A VERY BROAD MID TO UPPER TROUGH ANCHORED OVER THE GREAT LAKES MAINTAINING MORE OF A SW FLOW ALOFT AND NOT GIVING MUCH OF PUSH TO THE COLD FRONT. THEREFORE WILL KEEP FRONT JUST TO OUR NORTHWEST ON FRI. DEEP SW FLOW WILL KEEP A WARMER AND MORE HUMID AIR MASS OVER THE AREA LEAVING POTENTIAL FOR LOCALIZED CONVECTION THROUGH THE WEEKEND. MID TO UPPER TROUGH WILL DIG DOWN FROM THE GREAT LAKES COME MONDAY PUSHING ANOTHER COLD FRONT INTO THE CAROLINAS. THIS WILL PRODUCE MORE WIDESPREAD CONVECTION IN INCREASED UPPER LEVEL SUPPORT LATER ON MONDAY. ONCE AGAIN UPPER LEVEL TROUGH WILL REMAIN TO OUR WEST LEAVING A FLOW RUNNING MORE PARALLEL TO FRONT AND NOT GIVING IT TOO STRONG OF A PUSH THROUGH THE AREA. THEREFORE MAY NOT SEE TOO MUCH OF AN AIR MASS CHANGE BEHIND FRONT. OVERALL EXPECT GREATEST POTENTIAL FOR MORE WIDESPREAD CONVECTION EARLY FRI AND AGAIN MON AFTN INTO EARLY TUES...BUT EXPECT MORE TYPICAL DIURNAL TYPE SHWR ACTIVITY MOST DAYS. SOME DRIER AIR SHOULD MAKE IT INTO INLAND AREAS ON FRI AND ON TUES BEHIND FRONTS...BUT WILL MOST LIKELY REMAIN JUST TO THE WEST OF FORECAST AREA. TEMPS WILL BASICALLY BE ABOVE CLIMO WITH OVERNIGHT LOWS IN THE 70S AND DAY TIME HIGHS INTO THE 90S MOST DAYS WITH LOWER TEMPS EXPECTED. AS TROUGH DIGS DOWN THURS INTO FRI AND AGAIN MON INTO TUES MAY SEE BELOW NORMAL TEMPS IN LOWERED H5 HEIGHTS. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 18Z...WIDESPREAD MVFR/IFR IS EXPECTED THROUGH TONIGHT AS SHRA/TSRA COVERAGE INCREASES OVER THE NEXT SEVERAL HOURS. SHRA/TSRA WILL TAPER OFF...BUT DO EXPECT MVFR/IFR/LIFR THROUGH THE OVERNIGHT HOURS DUE TO LOW CIGS AND AREAS OF REDUCED VISIBILITIES. LATEST RADAR IMAGERY DEPICTS SHRA/TSRA CONTINUING TO BECOME MORE WIDESPREAD ACROSS THE AREA...PRODUCING HEAVY DOWNPOURS AT TIMES...AREAS OF FOG AND LOW CIGS. AS A RESULT...EXPECT MVFR/IFR TO PERSIST THROUGH TONIGHT...THOUGH CANNOT RULE OUT BRIEF IMPROVEMENTS TO VFR AT TIMES AS VARYING CIG HEIGHTS ARE MOVING ACROSS THE AREA. EAST-SOUTHEASTERLY WINDS ARE EXPECTED THROUGH THE DAY AOB 10 KTS. SHRA/TSRA WILL TAPER OFF THIS EVENING...BUT WILL STILL SEE WIDESPREAD MVFR/IFR/POSSIBLE LIFR DUE TO LOW CIGS AND AREAS OF FOG...ESPECIALLY INLAND. INTO WEDNESDAY MORNING...EXPECT LIGHT WINDS WITH PERSISTENT LOW CLOUDS AND POSSIBLE VCSH/VCTS THROUGH THE END OF THE PERIOD. EXTENDED OUTLOOK...CHANCE OF SHOWERS/TSTMS WILL PERSIST THROUGH THE EXTENDED PERIOD. EXPECT PREDOMINANTLY VFR CONDITIONS WITH TEMPO PERIODS OF MVFR/IFR CIGS/VSBYS IN STORMS. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1230 AM TUESDAY...WINDS ARE VEERING SOUTHEASTERLY ACROSS THE NC WATERS AS THE OLD FRONT BEGINS TO SHIFT INLAND. WE ARE STILL HOLDING ONTO A NORTH-NORTHEAST WIND OVER COASTAL SOUTH CAROLINA... BUT EVEN HERE WINDS SHOULD BECOME SOUTHERLY BY LATE IN THE DAY. SHOWERS AND THUNDERSTORMS ARE DEVELOPING ON A LINE FROM WILMINGTON TO OAK ISLAND WITH RATHER CHAOTIC MOVEMENT NOTED SO FAR. MARINERS ARE NOT IN THE CLEAR AS THIS ACTIVITY MAY DEVELOP OR SPREAD OFFSHORE THIS AFTERNOON. PREVIOUS DISCUSSION FROM 1000 AM FOLLOWS... THE OLD STATIONARY FRONT IS STILL HERE..AND AT 10 AM EXTENDS ROUGHLY FROM CAPE FEAR SOUTHWESTWARD ACROSS THE COASTAL WATERS EAST OF GEORGETOWN. THE OVERALL WEATHER PATTERN IS RETROGRADING TODAY...MEANING IT IS SHIFTING WESTWARD RATHER THAN THE TYPICAL EASTWARD PROGRESSION WE SEE. THE FRONT SHOULD SHIFT INLAND BY MID TO LATE AFTERNOON...WITH WINDS VEERING FROM THE NORTHEAST AROUND TO THE SOUTH BY LATE IN THE DAY. SPEEDS WILL ALSO INCREASE WITH THE TIGHTER PRESSURE GRADIENT ON THE EAST SIDE OF THE FRONT BETWEEN IT AND BERMUDA HIGH PRESSURE WELL OFFSHORE. THIS WILL INCREASE WIND SPEEDS TO NEAR 15 KNOTS BY EVENING...WITH GUSTS EXCEEDING 20 KNOTS AT TIMES LATE THIS EVENING. WIDESPREAD THUNDERSTORM ACTIVITY OFFSHORE THIS MORNING WILL SHIFT LARGELY ONSHORE BY THIS AFTERNOON. WHILE THIS WILL DECREASE THE NUMBER OF STORMS OCCURRING OVER THE COASTAL WATERS THERE SHOULD STILL BE A FEW STORMS OFFSHORE EVEN THIS AFTERNOON. COVERAGE OF STORMS MAY ACTUALLY INCREASE OVERNIGHT. SEAS CURRENTLY AROUND 3 FEET WILL BUILD TOWARD 4 FEET AWAY FROM SHORE TONIGHT IN RESPONSE TO THE INCREASING SOUTH WINDS. WAVE SPECTRA WILL BE EVENLY SPLIT BETWEEN 7 SECOND SOUTHEAST SWELL AND SHORTER PERIOD WIND WAVES. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 330 AM TUESDAY...ATLANTIC HIGH PRESSURE WILL BUILD WESTWARD THROUGH MID WEEK WITH A S-SW RETURN FLOW UP TO 15 KTS. A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE THURS WITH WINDS POSSIBLY MAKING IT UP TO 20 KTS IN TIGHTENED GRADIENT FLOW. SEAS 2 TO 4 FT ON WED INTO THURS WILL INCREASE UP TO 3 TO 5 FT BY LATE THURS AHEAD OF COLD FRONT BUT WNA MODEL REMAINS CONSISTENT KEEPING SEAS BELOW SCA THRESHOLDS...ALTHOUGH A PRECAUTIONARY STATEMENT MAY BE NEEDED. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 330 AM TUESDAY...COLD FRONT REACHES INTO THE CAROLINAS EARLY FRI BUT WILL MOST LIKELY STALL AND DISSIPATE OVER INLAND CAROLINAS OVER THE WEEKEND. EXPECT TO MAINTAIN A SW FLOW AROUND BERMUDA HIGH WEAKENING AS GRADIENT RELAXES THROUGH FRIDAY INTO SATURDAY AS FRONT DISSIPATES OVER THE CAROLINAS. SEAS UP TO 3 TO 5 FT EARLY FRI WILL FALL BACK DOWN TO 2 TO 4 FT THROUGH LATE FRI INTO SATURDAY. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...FLOOD WATCH UNTIL 6 PM EDT THIS EVENING FOR SCZ017-023-024-032- 033-039-053>056. NC...FLOOD WATCH UNTIL 6 PM EDT THIS EVENING FOR NCZ087-096-099- 105>110. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...RGZ LONG TERM...RGZ AVIATION...SGL

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