Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 160221 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1021 PM EDT MON SEP 15 2014 .SYNOPSIS... A COLD FRONT WILL PUSH OFFSHORE EARLY TUESDAY MORNING. HIGH PRESSURE WILL RIDGE DOWN INTO THE CAROLINAS FROM THE NORTH BEHIND THIS FRONT...PROVIDING FALL-LIKE WEATHER FOR THE REMAINDER OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1030 PM MONDAY...THE NCEP PARALLEL VERSION OF THE HRRR HAS AN EXCELLENT HANDLE ON OBSERVED RADAR ECHOES AND EVEN HAS PICKED UP ON THE MESOSCALE LANDBREEZE WINDS OBSERVED NEAR THE BEACHES THIS EVENING. BASED ON ITS EXCELLENT HANDLING OF ACTIVITY SO FAR I HAVE BLENDED ITS 23Z RUN INTO MOST SENSIBLE FORECAST GRIDS OVERNIGHT. THE BEST POTENTIAL FOR MEASURABLE RAIN OVERNIGHT WILL EXIST FOR THE NEXT FEW HOURS NEAR THE SANTEE RIVER AND ALONG THE SOUTH CAROLINA COAST. THIS ACTIVITY WILL PROBABLY THIN OUT AFTER MIDNIGHT...BUT AS THE 500 MB TROUGH APPROACHES OUR LONGITUDE LATE TONIGHT SHOWER COVERAGE MAY INCREASE AGAIN ACROSS SOUTHEAST NORTH CAROLINA AND THE SC COAST. NO CHANGES ARE NEEDED TO FORECAST LOWS WHICH RANGE FROM THE UPPER 60S INLAND TO AROUND 70 AT THE BEACHES. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... ONLY TWO CHANGES HAVE BEEN MADE TO THE FORECAST WITH THIS EARLY EVENING UPDATE. FORECAST LOW TEMPERATURES HAVE BEEN RAISED BY SEVERAL DEGREES BASED ON THE EXPECTATION CLOUD COVER WILL IMPEDE RADIATIONAL COOLING OVERNIGHT. INCREASING LOW-LEVEL WINDS WILL ALSO HELP TO KEEP THE BOUNDARY LAYER MIXED WITH ONLY A WEAK NOCTURNAL INVERSION EXPECTED. RADAR SHOWS AN AREA OF RAIN WITH EMBEDDED THUNDERSTORMS CROSSING THE SANTEE RIVER HEADING TOWARD GEORGETOWN. POPS HAVE BEEN RAISED SUBSTANTIALLY ACROSS GEORGETOWN COUNTY FOR THE NEXT COUPLE OF HOURS...BUT LATEST MODELS SHOW PRECIP CHANCES FOR THE REMAINDER OF THE FORECAST AREA ARE QUITE LOW OVERNIGHT. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS... THICK CLOUDS HAVE KEPT AFTERNOON TEMPS BELOW NORMAL. THESE CLOUDS ARE EXPECTED TO HANG ON THROUGH THE NIGHT GIVEN PLENTIFUL LOW LEVEL MOISTURE WITH CEILINGS LOWERING AS THE COLUMN COOLS AND STABILIZES. A WEAK MID-LEVEL SHORTWAVE AND SURFACE REFLECTION WILL REACH THE EASTERN CAROLINAS FROM THE WEST OVERNIGHT. THESE FEATURES MAY PROVIDE JUST ENOUGH CONVERGENCE TO GENERATE ISOLATED TO SCATTERED SHOWERS AND THUS WILL HAVE TO KEEP SMALL POPS IN THE FORECAST THROUGH SUNRISE TUE. WE DO NOT EXPECT ANY OF THE PRECIPITATION TO BE HEAVY GIVEN THE DIMINISHING DEPTH OF DEEPER MOISTURE AND THE LACK OF INSTABILITY. A RATHER FLAT DIURNAL CURVE IS EXPECTED WITH NIGHTTIME VALUES ONLY ABOUT 10 DEGREES BELOW THE HIGHS ACHIEVED THIS AFTERNOON. DESPITE THE CLOUDS...WE ARE GENERALLY FORECASTING MINIMUMS TO BE NEAR OR JUST BELOW THE COOLEST OF GUIDANCE.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...A LINGERING FRONT THAT WAS SOUTH OF AREA WILL MOVE BACK INTO THE AREA. A MINOR PERTURBATION IN THE MID TO UPPER LEVELS WILL MOVE THROUGH EARLY TUES HELPING TO ENHANCE CONVECTION ALONG THE FRONT. LOOKS LIKE THE FRONT WILL CONTINUE TO MOVE SLOWLY NORTHWARD THROUGH TUES AS A COLD FRONT MOVES DOWN FROM THE NORTHWEST. A PRE FRONTAL TROUGH SHOULD MERGE WITH THIS SYSTEM AND MODELS CONTINUE TO SHOW WEAK LOW PRESSURE DEVELOPING ALONG THIS SYSTEM ALONG THE SC COAST THROUGH TUES NIGHT INTO WED BEFORE AMPLIFYING MID TO UPPER TROUGH FINALLY PUSHES THE WHOLE SYSTEM OFF SHORE. THE HIGHEST PCP WATER VALUES WILL CREEP BACK NORTH THROUGH TUES MORNING REMAINING OVER EASTERN CAROLINAS BEFORE GETTING PUSHED OFF SHORE. THEREFORE SHOULD SEE DECENT CONVECTIVE ACTIVITY THROUGH AT LEAST EARLY TUES AS WAVE OF LOW PRESSURE DEVELOPS ALONG LINGERING FRONT WHILE ANOTHER COLD FRONT MOVES IN FROM THE NORTHWEST. PCP WATER VALUES UP ABOVE 2 INCHES ON TUES WILL DECREASE SLOWLY TO 1.5 INCHES BY WED AND DOWN TO 1.3 INCHES BY EARLY THURS MORNING AS MID TO UPPER TROUGH SHIFTS EAST WITH DEEPER DRIER NW FLOW DEVELOPING. LOW LEVEL MOISTURE BELOW 5K FT WILL PERSIST AND THEREFORE EXPECT PLENTY OF CLOUDS THROUGH MOST OF THE PERIOD. SOME DRIER AIR DOES MAKE IT INTO AREA IN W-NW LOW LEVEL FLOW IN THE LOW TO MID LEVELS BY TUES AFTN AND THEREFORE MAY SEE SOME SUNSHINE ACROSS INLAND AREAS THROUGH THE DAY ON TUES. THE BEST CHC OF HEAVIER SHWRS/TSTMS WILL EXIST ON TUES...BUT LINGERING MOISTURE WILL KEEP CLOUDS AND SOME PCP IN THE AREA THROUGH WED. TEMPERATURES MAY BE A BIT TRICKY ON TUES. SHOULD REACH INTO THE MID 80S AS WINDS SHIFT SOUTH OVER PORTIONS OF THE AREA AND IN PLACES THAT SEE SOME BRIGHTENING OF SKIES TUES AFTN. TEMPS WILL BE LOWER ON WED AS COOLER AIR MAKES ITS WAY IN BEHIND FRONT. OVERNIGHT LOWS WILL RUN ABOVE NORMAL WITH CLOUDS BLANKETING THE AREA MOST OF THE TIME. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 300 PM MONDAY...MID LEVEL TROUGH OVER THE EAST COAST AT THE START OF THE PERIOD WILL SHIFT NORTHEAST AS MID LEVEL RIDGE OVER THE WESTERN GULF COAST EXPANDS EAST. DEVELOPMENT OF PROGRESSIVE FLOW OVER NEW ENGLAND FRI WILL HELP PUSH SURFACE HIGH RIDGING DOWN THE COAST THU/FRI OFF THE COAST FOR THE WEEKEND. THIS WILL BRING AN END TO LOW CLOUDS...BELOW CLIMO TEMPERATURES...AND THE THREAT OF PRECIP FOR SAT AND SUN. WEAK MID LEVEL RIDGING OVER THE REGION COMBINED WITH ELONGATED SURFACE HIGH OVER THE CENTRAL CAROLINAS WILL CLEAR SKIES AND BRING ABOUT A RETURN TO SEASONABLE CONDITIONS FOR THE WEEKEND. ANOTHER COLD FRONT...PUSHED BY A STRONG MID LEVEL TROUGH...WILL MOVE ACROSS THE AREA ON MON. FROPA TIMING STILL SOMEWHAT UNCERTAIN AS IT COULD BE ANYWHERE FROM MON MORNING TO MON EVENING. LIFT ALONG THE FRONT AND NARROW BAND OF MOISTURE SHOULD KICK OFF SOME SHOWERS REGARDLESS OF TIMING. IF THE FRONT ARRIVES LATER AND DIURNAL INSTABILITY IS ABLE TO DEVELOP COVERAGE WOULD BE INCREASED...AS WOULD THE POTENTIAL FOR THUNDER. FOR NOW FAVOR THE SLOWER SOLUTION GIVEN THE TENDENCY FOR MID LEVEL RIDGING TO HOLD ON LONGER THAN EXPECTED. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS OF 00Z...SATELLITE IMAGERY SHOWS A FEW MORE BREAKS IN THE LOW CLOUDS AS COMPARED TO YESTERDAY...AND CONDITIONS COULD BRIEFLY IMPROVE TO VFR THIS EVENING. BUT CIGS ARE EXPECTED TO FILL BACK IN AND LOWER TO MVFR/IFR OVERNIGHT AS COOL MOIST AIR LINGERS OVER OUR AREA. THE HRRR...SREF PROBS AND MODEL SOUNDINGS AGREE THAT CIGS AT KFLO/KLBT WILL DROP TO IFR/LIFR LEVELS AFTER 08Z AND PERSIST THRU DAYBREAK. COULD ALSO SEE REDUCED VSBYS OVERNIGHT AS WINDS GO CALM. MVFR CIGS WILL LIKELY PREVAIL AT THE COASTAL TERMINALS EARLY TUE... AS ANY IFR THAT DEVELOPS ALONG THE COAST WOULD BE BRIEF AND MORE TEMPO IN NATURE. HAVE ALSO INCLUDED VCSH FOR KILM/KCRE/KMYR EARLY TUE AS DEEP MOISTURE RETURNS WITH A REMNANT FRONT LIFTING NORTHWARD AS WELL AS A WEAK UPPER DISTURBANCE. ANY SHOWERS THAT DEVELOP COULD PRODUCE BRIEF/LOCALIZED PERIODS OF IFR OVER A COASTAL TAF SITE. MVFR CIGS MAY LINGER THROUGH THE MORNING...BUT EXPECT VFR DURING THE AFTN HOURS AS LIGHT N-NW WINDS BECOME SOUTHEAST AOB 10 KT AHEAD OF AN APPROACHING COLD FRONT. EXTENDED OUTLOOK...POST-FRONTAL MVFR CIGS MAY DEVELOP WED AS COOLER AIR WEDGES INTO THE REGION. EARLY MORNING MVFR/IFR CIGS POSSIBLE ON THU. GUSTY NORTHEAST WINDS EXPECTED FRI/SAT AS THE COOL AIR WEDGE STRENGTHENS OVER THE CAROLINAS. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM MONDAY...A LANDBREEZE HAS DEVELOPED OVER THE PAST FEW HOURS AS INLAND AIR TEMPERATURES HAVE FALLEN INTO THE LOWER 70S BUT OFFSHORE AIR TEMPERATURES REMAIN IN THE UPPER 70S. THE LIGHT EASTERLY SYNOPTIC WINDS WERE NOT ENOUGH TO KEEP THIS LANDBREEZE PINNED TO THE BEACHES AND EVEN RADAR SEES THE LEADING EDGE OF THIS COOLER AIR 10 MILES OFF THE COAST AND SPREADING SOUTHWARD. THIS MESOSCALE WIND CIRCULATION IS GOING TO OVERWHELM THE SYNOPTIC WIND FOR AT LEAST THE NEXT SEVERAL HOURS UNTIL THE COLD FRONT APPROACHES LATE TONIGHT. THE 23Z NCEP PARALLEL VERSION OF THE HRRR CAPTURED THIS EFFECT QUITE WELL...AND WAS USED AS THE BASIS FOR THE FORECAST UPDATE THIS EVENING. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... PREVIOUS FORECAST IS IN PRETTY GOOD SHAPE. THE ONLY CHANGES WERE TO BACK WINDS AROUND MORE EAST TO NORTHEASTERLY EARLY THIS EVENING BASED ON CURRENT OBSERVATIONS ALONG THE COAST. WIND DIRECTIONS SHOULD VEER OFFSHORE EARLY TUESDAY MORNING AS PREVIOUSLY EXPECTED. RADAR SHOWS AN AREA OF RAIN AND EMBEDDED T-STORMS JUST WEST OF GEORGETOWN WHICH SHOULD AFFECT THE WATERS MAINLY SOUTH OF MYRTLE BEACH OVER THE NEXT FEW HOURS. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS... EASTERLY WINDS THROUGH THIS EVE WILL VEER AS HIGH PRESSURE REORIENTS AND A TROUGH REACHES THE AREA TUE MORNING. WINDS SHOULD TURN TO SOUTHERLY LATER THIS EVE AND THEN ALL THE WAY AROUND TO A WNW DIRECTION BY MORNING. WIND SPEEDS WILL BE 10 KT OR LESS THROUGH THE NIGHT. SEAS WILL GENERALLY BE 2 FT OR LESS. SEAS WILL BUILD ON TUE AS SWELL FROM DISTANT HURRICANE EDOUARD BEGIN TO REACH THE AREA. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM MONDAY...WINDS WILL BE VARIABLE ON TUES AS A WAVE OF LOW PRESSURE DEVELOPS ALONG LINGERING FRONT TO THE SOUTH AS IT MAKES ITS WAY BACK NORTH. AT THE SAME TIME A COLD FRONT WILL MOVE IN FROM THE NORTHWEST. EVENTUALLY WINDS WILL TAKE ON A MORE NORTHERLY FLOW. OVERALL WINDS WILL REMAIN LIGHT AND VARIABLE WITH SEAS HOLDING BELOW 3 FT TUES. AS WINDS SHIFT TO THE E-NE THROUGH WED EXPECT AN INCREASE UP TO 10 TO 15 KTS. THIS WILL COMBINE WITH A LONG PERIOD UP TO 16 SEC EASTERLY SWELL TO PUSH SEAS UP TO 2 TO 4 FT WITH SOME 5 FTERS IN OUTER WATERS ON WED. THE LONGER PERIOD EASTERLY SWELLS FROM EDOUARD WELL OUT IN THE ATLANTIC WATERS WILL BEGIN TO ENTER THE LOCAL WATERS TUES AFTN PEAKING AROUND 16 SECONDS OVERNIGHT TUES. LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 PM MONDAY...A COMBINATION OF SCEC AND SCA HEADLINES WILL LIKELY BE REQUIRED FOR MUCH IF NOT ALL OF THE PERIOD. HIGH PRESSURE BUILDING DOWN THE COAST THU AND FRI WILL MAINTAIN PINCHED GRADIENT WITH SPEEDS APPROACHING 20 KT AT TIMES. GRADIENT STARTS TO RELAX A LITTLE SAT AS HIGH ELONGATES. HOWEVER...NORTHEAST FLOW WILL REMAIN A SOLID 15 KT THROUGH THE END OF THE PERIOD. SEAS 3 TO 5 FT AT THE START OF THE PERIOD WILL BUILD TO 4 TO 7 FT THU NIGHT OR FRI...MAINLY IN WATERS EXPOSED TO PROLONGED NORTHEAST FLOW. SHELTERED WATERS MAY SEE AS LOW AS 2 FT. SEAS THU WILL BE A COMBINATION OF THE BUILDING WIND WAVE AND SWELL FROM EDOUARD. SEAS FRI AND SAT WILL BE WIND WAVE DOMINATED.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...RJD/TRA SHORT TERM...RGZ LONG TERM...III AVIATION...BJR

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