Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 301636 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1236 PM EDT THU JUL 30 2015 .SYNOPSIS... LOW PRESSURE REMAINS OFF THE SOUTHEAST COAST. A COLD FRONT WILL MOVE INTO THE AREA FRIDAY AND STALL OVER THE WEEKEND BEFORE DISSIPATING MONDAY. BERMUDA HIGH PRESSURE WILL EXPAND WEST TUESDAY AND WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1230 AM THURSDAY...NO SIGNIFICANT CHANGES HAVE BEEN MADE TO FORECAST HIGH TEMPERATURES OR DEWPOINTS...THE COMBINATION OF WHICH YIELD HEAT INDICES RIGHT AT THE DOORSTEP OF HEAT ADVISORY CRITERIA ACROSS PARTS OF SOUTH CAROLINA. SEEING THE DEWPOINT FALL INTO THE 60S ALREADY IN FLORENCE BOLSTERS CONFIDENCE WE WILL REMAIN BELOW 105 DEGREE HEAT INDEX VALUES. DESPITE PLENTY OF DRY AIR ABOVE 850 MB...RICH MOISTURE BELOW THAT LEVEL HAS GENERATED A VERY HEALTHY CUMULUS FIELD FROM SOUTHPORT ACROSS WILMINGTON TO JACKSONVILLE NC. WHILE AN ISOLATED SHOWER/SPRINKLE IS POSSIBLE ACROSS THE SURF CITY/HOLLY SHELTER SWAMP AREA OF PENDER COUNTY I THINK DRY AIR SHOULD PREVENT ANYTHING MORE. I STILL LOOK FOR ISOLATED SHOWERS/STORMS LATE IN THE DAY NEAR/WEST OF I-95 WHERE THE DRY MID- LEVEL AIR SHOULD BE MOISTENING THROUGH THE DAY. DISCUSSION FROM 1030 AM FOLLOWS... LOW PRESSURE CENTERED ROUGHLY 300 MILES EAST OF SAVANNAH HAS A NICE SWIRL IN VISIBLE SATELLITE IMAGERY. BUOY 41002 RECENTLY GUSTED TO 37 KNOTS AS A CONVECTIVE OUTFLOW BOUNDARY PASSED ACROSS IT. ASIDE FROM NORTHERLY FLOW AROUND THE PERIPHERY OF THIS LOW DRAGGING SOME DRIER AIR SOUTHWARD...THIS LOW WILL HAVE ALMOST NO IMPACT ON OUR WEATHER TODAY ACROSS THE EASTERN CAROLINAS. FOR OUR AREA IT SHOULD BE A FAIRLY TYPICAL SUMMER DAY WITH THE EXCEPTION OF 850 MB TEMPS NEAR +20C...A COUPLE DEGREES ABOVE NORMAL. WITH PLENTY OF SUNSHINE THIS SHOULD PUSH HIGHS TO 92-98 DEGREES INLAND FROM THE BEACHES TODAY...3 TO 8 DEGREES ABOVE NORMAL. DEWPOINTS SHOULD MIX DOWN TO 70-72 THIS AFTERNOON AWAY FROM THE COAST...AND THIS COULD PUSH HEAT INDICES VERY CLOSE TO 105 DEGREES. I HAVE UPDATED THE HAZARDOUS WEATHER OUTLOOK FOR HIGHLIGHT NEAR- ADVISORY CRITERIA FOR HEAT INDEX ACROSS INTERIOR SOUTH CAROLINA AND ROBESON COUNTY NC. CONVECTIVE POTENTIAL APPEARS QUITE LIMITED TODAY AS THERE IS A SLUG OF VERY DRY AIR IN THE 850-700 MB LAYER ALONG THE COAST. USING MEAN RH <70% THROUGH THIS LAYER AS A GUIDE I HAVE REMOVED ANY MENTION OF PRECIPITATION TODAY EAST OF I-95...WITH ONLY A 20 POP REMAINING ACROSS THE SANDHILLS/INTERIOR PEE DEE REGION. THE LATEST FEW HRRR RUNS ALSO GENERATE NO PRECIPITATION EAST OF I-95 TODAY. A COLD FRONT CURRENTLY ACROSS WEST VIRGINIA AND EASTERN TENNESSEE WILL MOVE INTO THE CAROLINAS TONIGHT AND WILL REACH I-95 BEFORE DAYBREAK. INCREASING CLOUDS AND MOISTURE POOLING NEAR THE FRONT SHOULD HELP KEEP LOWS QUITE WARM...72-76 MOST AREAS. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 AM THURSDAY...WEAK COLD FRONT MOVING INTO THE AREA AT THE START OF PERIOD WILL STALL NEAR THE COAST...LINGERING IN THE AREA THROUGH THE END OF THE PERIOD. FRONT ARRIVES WITH AN ABUNDANCE OF DEEP MOISTURE AND LOW LEVEL CONVERGENCE BUT TIMING IS RATHER EARLY AS FAR AS SURFACE BASED INSTABILITY IS CONCERNED. FRONT AND DEEP MOISTURE BRIEFLY STALL IN THE AREA FRI AND IT SHOULD ONLY BE A MATTER OF WAITING UNTIL EARLY AFTERNOON BEFORE HEATING CAN GENERATE LOW LEVEL INSTABILITY...LEADING TO CONVECTION. PREVIOUSLY IT APPEARED THE DEEPER MOISTURE WOULD LINGER OVER THE AREA INTO SAT BUT WITH THE 00Z GUIDANCE THERE HAS BEEN AN INCREASE IN THE RATE AT WHICH DRY AIR TO THE NORTHWEST MOVES INTO THE AREA. FORECAST SOUNDINGS NOW SHOW DRY AIR MOVING OVER WESTERN COUNTIES BY EARLY TO MID AFTERNOON FRI AND TO THE COAST BY SAT MORNING. THE DROP IN PRECIPITABLE WATER IS RATHER SIGNIFICANT WITH VALUES DROPPING FROM OVER 2 INCHES FRI MORNING TO AROUND 1.5 INCH LATE FRI NIGHT OR EARLY SAT. IF THE LATEST GUIDANCE IS CORRECT THERE MAY BE LITTLE IN THE WAY OF PRECIP ALONG AND WEST OF I-95 WITH A RAPID INCREASE IN PRECIP CHANCES EAST OF I-95. THE PRESENCE OF DRY AIR SAT ALONG WITH A LACK OF ANY MID LEVEL DYNAMICS AND ONLY A WEAKENING SURFACE BOUNDARY IN PLACE ALSO PUTS HEFTY PRECIP CHANCES SAT IN DOUBT. WILL MAINTAIN INHERITED CHC POP BUT DID TREND VALUES DOWN A LITTLE BIT. TEMPERATURES WILL BE NEAR TO SLIGHTLY ABOVE CLIMO THROUGH THE PERIOD. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 300 AM THURSDAY...DISSIPATING FRONT WILL LINGER IN THE AREA INTO THE MIDDLE OF NEXT WEEK...SLOWLY BECOMING A WASHED OUT SURFACE TROUGH BY TUE/WED. THE EVOLUTION OF THE MID LEVEL PATTERN WILL DETERMINE HOW UNSETTLED NEXT WEEKS WEATHER IS. BY SUN MORNING FAIRLY BROAD 5H TROUGH WILL BE OVER THE EAST COAST. THE BIG QUESTION REMAINS HOW CLOSE WILL THE TROUGH AXIS BE TO THE COAST. THIS WILL DETERMINE IF THE DEEP MOISTURE WILL LINGER OVER THE AREA OR OFF THE COAST. ALTHOUGH THE MEDIUM RANGE GUIDANCE AND THE ENSEMBLES DO NOT PROVIDE A CLEAR PICTURE IT SEEMS THE TRENDS ARE TO SHIFT THE DEEP MOISTURE OFF THE COAST DURING THE SECOND HALF OF THE WEEKEND. THIS WOULD LEAD TO SOME DRYING FOR NEXT WEEK AND A REDUCTION IN PRECIP CHANCES. GIVEN THE AMOUNT OF UNCERTAINTY AND THE POTENTIAL FOR MOISTURE TO LINGER CLOSER TO THE COAST WILL MAINTAIN INHERITED CHC POP DURING THE FIRST HALF OF THE PERIOD. TROUGH LIFTS OUT EARLY TUE...ALLOWING THE 5H RIDGE TO THE WEST AN OPPORTUNITY TO EXPAND EAST. THIS WILL HAPPEN GRADUALLY AND THE FLOW ALOFT WILL BE ON THE WEAK SIDE WITH LITTLE FORCING. WILL CARRY SLIGHT CHC TO CHC POP FOR THE END OF THE PERIOD...MAINLY FOR DIURNAL CONVECTION ON THE SEA BREEZE AND PIEDMONT TROUGH BUT INCREASING SUBSIDENCE WILL LEAD TO DECREASING PRECIP CHANCES AS THE PERIOD ENDS. TEMPERATURES NEAR TO SLIGHTLY ABOVE CLIMO EARLY IN THE PERIOD WILL CLIMB ABOVE CLIMO TUE/WED AS SURFACE AND MID LEVEL RIDGING EXPAND AND SUBSIDENCE STARTS TO DEVELOP. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AS OF 18Z...LFC`S COMING DOWN NORTH OF THE REGION. MAY SEE CONVECTION IN PENDER AND NEW HANOVER COUNTIES THIS AFTERNOON...BUT WILL STICK WITH VCSH DUE TO COVERAGE AND INTENSITY. MAINLY AN EAST NORTHEAST WIND THIS AFTERNOON ALONG THE COAST...LIGHT INLAND. TONIGHT...THE NAM WANTS TO KEEP CONVECTION GOING AS THE FRONT LAYS OVER THE CWA. DUE TO LACK OF FORCING...SHOULD SEE CONVECTION ENDING FOR DIURNAL REASONS AFTER 02Z WITH ONLY ISOLATED ACTIVITY OVERNIGHT. FRIDAY...EXPECT CONVECTION TO FIRE FAIRLY EARLY...MAINLY OVER THE EASTERN HALF OF THE REGION. POST FRONTAL LIGHT NORTHERLY FLOW IS FORECAST. EXTENDED OUTLOOK...PREDOMINANTLY VFR THROUGH THE PERIOD WITH A SLIGHT CHANCE AFTERNOON SHRA/TSRA. BEST CHANCE SHRA/TSRA FRIDAY AND SATURDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1230 AM THURSDAY...LOW PRESSURE CENTERED ROUGHLY 300 MILES EAST OF SAVANNAH HAS A NICE SWIRL IN VISIBLE SATELLITE IMAGERY. BUOY 41002 RECENTLY GUSTED TO 37 KNOTS AS A CONVECTIVE OUTFLOW BOUNDARY PASSED ACROSS IT. ASIDE FROM TWO ENHANCED SWELL SETS (7 SECONDS FROM THE SOUTH AND 10 SECONDS FROM THE SOUTHEAST) THIS LOW WILL HAVE ALMOST NO IMPACT ON OUR WEATHER TODAY OR TONIGHT ACROSS THE EASTERN CAROLINAS. LIGHT NORTHEAST WIND THIS MORNING WILL SHIFT ONSHORE THIS AFTERNOON WITH THE SEABREEZE...WITH NEARSHORE WINDS INCREASING TO 10- 12 KNOTS. SEAS CURRENTLY 2-3 FEET MAINLY IN SWELL WILL DEVELOP AN INCREASING WIND CHOP COMPONENT ON TOP THIS AFTERNOON. BY TONIGHT A COLD FRONT CURRENTLY ACROSS WEST VIRGINIA AND EASTERN TENNESSEE WILL APPROACH THE AREA. SOUTH WINDS THIS EVENING WILL VEER WESTERLY BY DAYBREAK FRIDAY AS THE FRONT APPROACHES THE BEACHES. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 300 AM THURSDAY...WEAK COLD FRONT IN THE AREA AT THE START OF THE PERIOD WILL LINGER ALONG THE COAST FRI THEN PUSH INLAND SAT AS IT STARTS TO DISSIPATE. BRIEF PERIOD OF OFFSHORE FLOW FRI MORNING WILL BE REPLACED BY LIGHT ONSHORE FLOW AS WEAK SEA BREEZE DEVELOPS IN THE AFTERNOON. BY SAT BERMUDA HIGH WILL BE ON ITS WAY TO REESTABLISHING ITSELF...RESULTING IN SOUTHWEST FLOW IN THE 10 TO 15 KT RANGE LATER SAT AND SAT NIGHT. SEAS 2 TO 3 FT FRI INTO SAT BUILD TO 2 TO 4 FT LATER SAT AND SAT NIGHT. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 300 AM THURSDAY...BERMUDA HIGH WILL MAINTAIN 10 TO 15 KT SOUTHWEST FLOW THROUGH THE PERIOD. NEARSHORE SEA BREEZE DEVELOPMENT WILL ENHANCE ONSHORE FLOW EACH AFTERNOON. SEAS WILL RUN 3 TO 4 FT. && .TIDES/COASTAL FLOODING... AS OF 300 AM THURSDAY...MINOR COASTAL FLOODING IS POSSIBLE DURING THE NIGHTTIME HIGH TIDE OVER THE NEXT SEVERAL DAYS. THESE HIGHER THAN NORMAL TIDES ARE THE RESULT OF THE PERIGEAN SPRING TIDE AND FULL MOON WHICH OCCURS ON JULY 31. DEPARTURES OF PLUS 1/2 TO 1 FOOT MLLW WILL BE ENOUGH TO PRODUCE A BRIEF PERIOD OF MINOR COASTAL FLOODING. THE RISK IS HIGHEST FOR PORTIONS OF THE LOWER CAPE FEAR RIVER TO INCLUDE DOWNTOWN WILMINGTON. HOWEVER...THIS CYCLE...EVEN THE BEACHES HAVE A SMALL RISK. HIGH TIDE TONIGHT IS ABOUT 730 PM AT THE BEACHES AND ABOUT 10 PM IN DOWNTOWN WILMINGTON. A COASTAL FLOOD ADVISORY WILL BE ISSUED BY THE NATIONAL WEATHER SERVICE IF COASTAL FLOODING IS EXPECTED. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...III LONG TERM...III AVIATION...DL TIDES/COASTAL FLOODING...RJD

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