Area Forecast Discussion
Issued by NWS Wilmington, NC

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476 FXUS62 KILM 281402 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1002 AM EDT THU APR 28 2016 .SYNOPSIS... WARM AND HUMID AIR TODAY WILL HELP CREATE SHOWERS AND THUNDERSTORMS. A WEAK COLD FRONT WILL MOVE OFF THE COAST EARLY FRIDAY MORNING... FOLLOWED BY ANOTHER FRONT EARLY SATURDAY MORNING. HIGH PRESSURE WILL MOVE ACROSS THE GREAT LAKES AND NEW ENGLAND THIS WEEKEND BRINGING COOLER AIR TO THE CAROLINAS. LOW PRESSURE FROM THE PLAINS STATES WILL MOVE THROUGH THE MID-ATLANTIC REGION MONDAY... DRAGGING ANOTHER COLD FRONT THROUGH THE CAROLINAS. HIGH PRESSURE WILL BUILD IN FROM THE WEST TUESDAY AND WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM THURSDAY...THIS NEAR TERM UPDATES FOCUS ON THE LINE OF THUNDERSTORMS MOVING QUICKLY EASTWARD ACROSS SOUTH CAROLINA. THIS ACTIVITY IS TIED TO AN UPPER LEVEL DISTURBANCE EASILY PICKED OUT IN WATER VAPOR SATELLITE IMAGERY NOW APPROACHING THE INTERSTATE 95 CORRIDOR. LIFT JUST AHEAD OF THIS DISTURBANCE SHOULD MAINTAIN THESE SHOWERS AND STORMS AS THEY PUSH EASTWARD TO MYRTLE BEACH AND EVENTUALLY WILMINGTON OVER THE NEXT FEW HOURS. SURFACE- BASED PARCELS ARE CAPPED...AND THIS CONVECTION APPEARS TO BE ROOTED IN A LAYER OF ELEVATED INSTABILITY BETWEEN 4000-7000 FEET AGL AS DIAGNOSED ON THE 12Z CHS SOUNDING. THE UPPER DISTURBANCE SHOULD TAKE THIS CONVECTION LARGELY OFF THE COAST BY NOON. DRIER AIR AT AND ABOVE THE 700 MB LAYER WILL BUILD OVER THE AREA FOR THE AFTERNOON HOURS WITH A SHARP REDUCTION IN THE COVERAGE OF STORMS EXPECTED INITIALLY. AS SURFACE TEMPERATURES SOAR THROUGH THE 80S AND SURFACE-BASED INSTABILITY GROWS TO 1500-2000 J/KG I ANTICIPATE 20-30 PERCENT COVERAGE OF SHOWERS AND STORMS TO REDEVELOP MAINLY DUE TO INSTABILITY ALONE. THE DRY AIR ALOFT ENTRAINING INTO THE STORMS SHOULD CAUSE THE RISK FOR GUSTY WINDS TO GROW AS DIAGNOSED BY FORECAST DOWNDRAFT CAPE (DCAPE) VALUES OF 800-1000 J/KG IN FORECAST SOUNDINGS. BULK SHEAR THROUGH THE 0-6 KM LAYER REMAINS TOO WEAK FOR CONCERN...SO THE MARGINAL RISK FROM SPC IS LIKELY TIED TO THIS DRY AIR ALOFT. SEVERAL OF THE HIGH-RES MODELS ARE KEYING ON A WEAK DISTURBANCE LATE THIS AFTERNOON ACROSS NORTHERN NORTH CAROLINA TO DEVELOP A POSSIBLY SIGNIFICANT CONVECTIVE CLUSTER THERE. SHOULD THIS OCCUR...VEERING MID-LEVEL FLOW PLUS THE DRY AIR ALOFT COULD CAUSE THIS CONVECTION TO TURN SOUTHEASTWARD AND RACE TOWARD OUR PORTION OF THE CAROLINAS THIS EVENING. THIS IS A CONDITIONAL RISK BASED ON CONVECTION DEVELOPING AND BEHAVING AS I AM EXPECTING...BUT THIS FINAL CLUSTER OF STORMS COULD IMPACT THE AREA DURING THE LATE EVENING HOURS. I HAVE BUMPED POPS UP TO 40 PERCENT IN THE WILMINGTON AREA...20-30 PERCENT ELSEWHERE...FOR THIS POTENTIAL. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 400 AM THURSDAY...THE TREND FOR FRIDAY THRU SATURDAY WILL BE FOR A STRENGTHENING MID-LEVEL RIDGE ACROSS THE SE STATES. FOR FRI HOWEVER...THE W TO NW FLOW THRU THE ATM COLUMN...AND THUS A DOWNSLOPE TRAJECTORY OFF THE APPALACHIANS...WILL AID MAX TEMPS ON FRI THAT REACH THE MID TO POSSIBLY UPPER 80S. THE W-NW FLOW ALOFT WILL ALSO SCOUR OUT ANY CLOUDINESS OR MOISTURE ALOFT BY THE TIME IT REACHES THE ILM CWA. THE UPPER RIDGE WILL AID THE SFC HIGH CENTERED OVER THE NE STATES...TO TEMPORARILY RIDGE SOUTHWARD ACROSS THE FA LATE FRI NIGHT THRU SAT. THIS WILL PRODUCE A NE-ENE COOL SURGE PEAKING DURING SAT. NO PCPN EXPECTED WITH THIS SURGE DUE TO A DRY ATM COLUMN UNDER W TO NW FLOW ALOFT. THE UPPER RIDGE AXIS PUSHES OVER THE ILM CWA SAT NIGHT ENDING THE COOL SURGE OF AIR. IN ADDITION... MOISTURE ALOFT WILL INCREASE AS THE UPPER FLOW BACKS TO THE SW AFTER THE UPPER RIDGE AXIS PASSES BY. RETURN SE FLOW AT THE SFC...WILL START PUSHING LOW LEVEL MOISTURE BACK ACROSS THE FA. HAVE HELD POPS AT BAY UNTIL DAYTIME SUN. STAYED CLOSE TO THE GFS MOS GUIDANCE FOR BOTH MAX AND MIN TEMPS THIS PERIOD. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 330 AM THURSDAY...LOW PRESSURE MAKES ITS WAY TOWARD THE CAROLINAS FROM THE WEST AS NORTHERN STREAM SHORTWAVE PUSHES RIDGE OVER THE SOUTHEAST OUT TO SEA. A DEEP SOUTHWESTERLY FLOW AHEAD OF THIS SYSTEM WILL STREAM MOISTURE INTO THE EASTERN CAROLINAS. PCP WATER VALUES WILL REACH UP NEAR 1.5 INCHES SUN AFTN. OVERALL EXPECT INCREASE IN CLOUDS AND SHOWER ACTIVITY SUNDAY AFTN THROUGH EARLY MONDAY. LOOKS LIKE THIS SYSTEM WILL BE MOVING OFF OF THE MID ATLANTIC COAST ON MONDAY DRAGGING A COLD FRONT EAST. OVERALL EXPECT SLIGHTLY COOLER BUT MAINLY DRIER AIR FOR LATE MON INTO TUES AS HIGH PRESSURE BUILDS IN. ECMWF MUCH WETTER FOR MIDWEEK WITH SHORTWAVE DIGGING SOUTH AND CONVECTION FLARING UP OVER THE CAROLINAS WHILE THE GFS KEEPS MUCH BROADER MID TO UPPER TROUGH WITH BEST CHC OF PCP TO THE SOUTH WHERE BEST LIFT WILL BE. EITHER WAY IT LOOKS LIKE IT WILL REMAIN UNSETTLED WITH A INCREASED POTENTIAL FOR CLOUDS AND SHOWERS TUES INTO WED. TEMPS IN THE 80S SUN INTO MON WILL COOL MON NIGHT INTO TUES BEHIND COLD FRONT. OVERALL SHOULD STAY BETWEEN 75 AND 80 MOST PLACES THROUGH THE WEEKEND THEN WARMING AHEAD OF FRONT MONDAY AND RELATIVELY COOLER AGAIN TUES INTO WED. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... AS OF 12Z...AREAS OF BRIEF MVFR/IFR LOW STRATUS THIS MORNING ALONG THE COAST. ELSEWHERE...EXPECT VFR THIS MORNING WITH MVFR/IFR THIS AFTERNOON AS CLOUDS INCREASE ALONG WITH CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS AHEAD OF A COLD FRONT DROPPING FROM THE NORTH. VFR PREVAILS ACROSS THE AREA THIS MORNING WITH THE EXCEPTION OF KCRE WHERE LOW CIGS ARE CREATING IFR ATTM. EXPECT MVFR/IFR AT KCRE/POTENTIALLY KMYR OVER THE NEXT HOUR OR TWO. LATEST RADAR IMAGERY DEPICTS SHOWERS JUST SOUTH AND EAST OF KILM AS WELL AS JUST WEST OF THE FORECAST AREA. WHILE SHOWERS NEAR KILM WILL CONTINUE TO MOVE OFFSHORE...EXPECT SHOWERS JUST WEST OF THE AREA TO CONTINUE MIGRATING EASTWARD TOWARDS THE INLAND TERMINALS. FOR THE REST OF TODAY...EXPECT INCREASING CHANCES FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WITH SOUTHWEST WINDS INCREASING TO AOB 15 KTS AND HIGHER GUSTS NEAR 20 KTS AT TIMES. SLIGHTLY HIGHER GUSTS AND LOWER CIGS ARE POSSIBLE WHICH MAY CREATE MVFR/IFR IN ANY HEAVY DOWNPOURS OR THUNDERSTORMS. TONIGHT...SHRA/TSRA ACTIVITY WILL GRADUALLY TAPER OFF AND WEST-SOUTHWEST WINDS WILL DECREASE TO AROUND 5 KTS OVERNIGHT. VFR WILL PREVAIL THOUGH AREAS OF FOG ARE POSSIBLE TOWARDS EARLY FRIDAY MORNING. EXTENDED OUTLOOK...AREAS OF FOG POSSIBLE FRIDAY MORNING. MVFR POSSIBLY IFR CONDITIONS FROM CONVECTION SUNDAY INTO MONDAY. OTHERWISE EXPECT VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM THURSDAY...AN UPPER LEVEL DISTURBANCE MOVING QUICKLY EASTWARD ACROSS THE EASTERN CAROLINAS SHOULD PUSH SHOWERS AND THUNDERSTORMS ACROSS THE GRAND STRAND COASTAL WATERS OVER THE NEXT HOUR. THESE MAY SPREAD NORTHEASTWARD TO IMPACT THE CAPE FEAR WATERS BEFORE NOON. THIS ACTIVITY SHOULD DELAY THE FORMATION OF TODAY`S SEABREEZE BY SEVERAL HOURS...AND I DON`T EXPECT TO SEE NEARSHORE WIND SPEEDS KICK UP SUBSTANTIALLY UNTIL MID AFTERNOON. BEHIND THIS UPPER LEVEL DISTURBANCE THE COVERAGE OF SHOWERS AND STORMS SHOULD DECREASE FOR THE AFTERNOON HOURS...BUT WE`LL BE WATCHING FOR SOME GUSTY STORMS TO POSSIBLY ARRIVE FROM THE NORTHWEST LATE THIS EVENING. OTHERWISE...HIGH PRESSURE WELL OFFSHORE IS CONTINUING TO PROVIDE A SOUTHWEST WIND ACROSS THE WATERS. A WEAK FRONT SHOULD PUSH THROUGH THE AREA LATE TONIGHT VEERING WIND DIRECTIONS MORE NORTHWESTERLY. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 400 AM THURSDAY...A RELAXED SFC PG ON FRIDAY WILL PRODUCE WINDS AT 10 KT OR LESS. THE PRESSURE PATTERN WILL RESULT IN A WESTERLY DIRECTION. THE SEA BREEZE DEVELOPMENT FRI AFTN WILL RESULT IN SOUTH WINDS UP TO 15 KT ACROSS THE NEAR SHORE WATERS...WITHIN 10 NM FROM THE COAST. SIGNIFICANT SEAS FRI WILL RUN 2 TO 3 FT. THE ENE GROUND SWELL AT 9 SECOND PERIODS WILL OCCASIONALLY DOMINATE THE SIGNIFICANT SEAS DURING FRI. A COOL NE WIND SURGE WILL OCCUR LATER FRI NIGHT THRU SAT AS HIGH PRESSURE TEMPORARILY NOSES DOWN THE EAST COAST TO THE ILM CWA. FROM CAPE FEAR NORTHWARD...LOOK FOR WINDS AT A SOLID 15 TO POSSIBLY 20 KT DEPENDING ON THE AMOUNT OF CAA...AND SOUTH OF THE CAPE...10 TO 15 KT. WINDS WILL QUICKLY VEER TO THE E-SE SAT NIGHT DUE TO THE BREAK FROM THE SFC RIDGING FROM THE NORTH. THE GRADIENT WILL PRODUCE 10 TO 15 KT WIND SPEEDS. SIGNIFICANT SEAS SAT THRU SAT NIGHT WILL ELEVATE TO 3 TO 4 FT CAPE FEAR NORTH...AND HOLD AT 3 FT OR LESS SOUTH OF THE CAPE. WIND DRIVEN 3 TO 5 SECOND PERIODS TO DOMINATE SIGNIFICANT SEAS SAT. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 330 AM THURSDAY...WINDS WILL BECOME MORE SOUTHERLY BY SUN AFTN AS HIGH PRESSURE SHIFTS OFF THE NORTHEAST COAST AND LOW PRESSURE APPROACHES THE CAROLINAS FROM THE WEST. THIS LOW WILL MOVE EAST OFF THE MID ATLANTIC COAST BY MONDAY DRAGGING A COLD FRONT THROUGH THE WATERS. WINDS WILL VEER AROUND TO THE NORTH BEHIND THE FRONT AS HIGH PRESSURE BUILDS IN HEADING INTO TUES. SEAS WILL REMAIN IN THE 2 TO 4 FT RANGE THROUGH SUN BUT WILL BEGIN TO INCREASE OVERNIGHT SUN INTO MON MORNING AS LOW PRESSURE MOVES INTO THE CAROLINAS TIGHTENING THE GRADIENT FLOW OUT OF THE S-SW. WNA SHOWS SEAS REACHING 4 TO 5 FT IN OUTER WATERS MON AFTN BUT THEN DECREASING HEADING INTO TUES. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...TRA NEAR TERM...TRA SHORT TERM...DCH LONG TERM...RGZ AVIATION...SGL

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