Area Forecast Discussion
Issued by NWS Wilmington, NC

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KILM 041439 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1039 AM EDT TUE AUG 4 2015 .SYNOPSIS... AN AREA OF LOW PRESSURE WILL SLOWLY SLIDE UP THE COAST TODAY BRINGING PERIODS OF SHOWERS AND THUNDERSTORMS. THIS MAY LEAD TO PERIODS OF HEAVY RAINFALL ALONG THE COAST. MORE TYPICAL SUMMERTIME CONDITIONS WILL DEVELOP WEDNESDAY THROUGH FRIDAY. A COLD FRONT MOVING CLOSER TO THE AREA WILL INCREASE THE CHANCE OF SHOWERS AND THUNDERSTORMS ONCE AGAIN THIS WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1030 AM TUESDAY...WEAK LOW JUST OFF THE COAST EAST OF GEORGETOWN SOUTH CAROLINA CONTINUES TO CAUSE SHOWERS AND THUNDERSTORMS ACROSS THE AREA THIS MORNING. CONVECTION OVER LAND HAS INCREASED IN THE LAST FEW HOURS DUE TO AN INCREASE IN LOW LEVEL CONVERGENCE AND MOISTURE. DID NOT MAKE WHOLESALE CHANGES TO THE PREVIOUS FORECAST BUT DID TRIM/TWEAK POP GRADIENT AND VALUES BASED ON RECENT RADAR TRENDS. THIS RESULTED IN A SLIGHT LOWERING OF POP/QPF ALONG THE COAST AS WELL AS AN INCREASE IN POP/QPF ACROSS PORTIONS OF INLAND NC. CANNOT RULE OUT SOME LIGHT PRECIP ACROSS PORTIONS OF SC THIS AM AS THE LOW LIFTS NORTHEAST BUT CHANCES ARE RAPIDLY DIMINISHING. THE NORTH TO NORTHWEST FLOW AT THE LOW LEVELS AND WEAK SURFACE DIVERGENCE MAKE SIGNIFICANT CONVECTION DURING THE NEXT FEW HOURS UNLIKELY. CONVECTION MAY REDEVELOP THIS AFTERNOON IF THE LOW DEPARTS QUICKLY AND HEATING RESULTS IN SURFACE BASED INSTABILITY. THERE IS HOWEVER A FAIR AMOUNT OF DRY AIR ALOFT AROUND THE PERIPHERY OF THE MOISTURE PLUM WHICH WILL BE WORKING ITS WAY OVER THE AREA. PREVIOUS DISCUSSION FROM 630 AM FOLLOWS: ANOTHER WET DAY FOR THE COASTAL CAROLINAS AS SFC LOW PRESSURE CREEPS N-NE ALONG THE IMMEDIATE SOUTHEAST U.S. COAST...REACHING THE ILM SC CWA THIS AFTERNOON...AND THE ILM NC CWA THIS EVENING AND OVERNIGHT. THE LOW WILL BE ACCOMPANIED BY UPPER SUPPORT THAT WILL AID IN DRAWING IN THE RICH MOISTURE...PWS IN EXCESS OF 2 INCHES...FROM OFF THE ATLANTIC AS SEEN VIA LATEST KLTX VWP IN THE LOW TO MID LEVELS. AT THIS POINT...MODELS INDICATE THE BULK OF THE HEAVIEST RAIN AND UPPER DYNAMICS TO REMAIN JUST OVER THE ADJACENT ATLANTIC WATERS AS IT PASSES BY THE ILM CWA. POPS WILL BE ORIENTED LOWEST INLAND...ALONG AND WEST OF THE I-95 CORRIDOR...TO HIGHEST ALONG THE IMMEDIATE CAROLINA COASTS. THE GROUNDS HAVE BEEN ABSORBING THE RECENT RAINS LIKE A SPONGE OF LATE...AND WILL CONTINUE TO DO SO TODAY. EVENTHOUGH FFG VALUES ACROSS THE COASTAL COUNTIES HAVE DECREASED SOME...ITS JUST NOT LOW ENOUGH TO WARRANT A FLOOD WATCH AT THIS TIME GIVEN THE CURRENT QPF FORECAST FOR THE COASTAL CAROLINAS AT ONE HALF TO 1 INCH. WITH PWS PROGGED AT 2+ INCH AMOUNTS...THE FA STILL COULD EXPERIENCE ISOLATED HIGHER AMOUNTS FROM THE STRONGER AND MORE EFFICIENT CONVECTION. OVERALL...WILL LIKELY OBSERVE NUISANCE TYPE FLOODING OR PONDING OF WATER ACROSS THOSE NORMALLY PRONE AND VULNERABLE LOCATIONS. HAVE HIGHLIGHTED THIS FLOOD POTENTIAL IN THE HAZARDOUS WEATHER OUTLOOK. MAX TEMPS TO REACH THE 90S WELL INLAND...AND IN THE LOW TO MID 80S ALONG THE COAST. MIN TEMPS TO RANGE AROUND 70 INLAND TO THE UPPER 70S TO NEAR 80 AT THE COAST. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...HOT SUMMER WEATHER FOR THE SHORT TERM AS BERMUDA HIGH PRESSURE COMBINES WITH MID-LEVEL RIDGING...CREATING MORE TYPICAL SUMMERTIME WEATHER. WEDNESDAY LOOKS TO BE A VERY HOT DAY WITH WIDESPREAD MID AND UPR 90S ACROSS THE AREA. THIS IS DUE TO VERY WARM 850MB TEMPS ADVECTING EAST INTO THE CAROLINAS...AND COMBINING WITH A WARM/DRY DOWNSLOPE FLOW...SO EVEN COASTAL SECTIONS WILL RISE WELL INTO THE 90S AS THE SEA BREEZE GETS PINNED. ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY...BUT DRIER AIR BEHIND THE DEPARTING LOW FROM TUESDAY WILL PREVENT ANYTHING BEYOND JUST A FEW STORMS. LOWS WEDNESDAY NIGHT WILL BE QUITE WARM...MID AND UPR 70S...POSSIBLY NEAR 80 ON THE BRUNSWICK COUNTY COAST. SIMILAR WEATHER FOR THURSDAY ALTHOUGH NOT QUITE AS HOT AS THE THICKNESSES BEGIN TO DECREASE AND MID-LEVEL FLOW BECOMES MORE SWLY. TEMPS ARE STILL EXPECTED TO BE ABOVE NORMAL...LOW 90S AT THE COAST AND MID 90S INLAND...BUT LIKE A FEW DEGREES COOLER THAN WEDNESDAY. STORM COVERAGE WILL BE SLIGHTLY HIGHER TOO THANKS TO GREATER INSTABILITY ON HIGHER DEWPOINTS AND STEEPER LAPSE RATES...BUT ONLY LOW-CHC POP IN A TYPICAL SUMMERTIME REGIME IS WARRANTED. ANOTHER WARM NIGHT EXPECTED THURSDAY NIGHT WITH LOWS REMAINING AT LEAST 5 DEGREES ABOVE CLIMO...MID 70S ACROSS THE AREA. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 AM TUESDAY...PATTERN CHANGE BEGINS FRIDAY AS TROUGHING ACROSS THE EASTERN CONUS RE-AMPLIFIES IN RESPONSE TO RIDGING EXPANDING ACROSS THE GREAT PLAINS. THIS WILL BE LED BY A POTENT VORT DRIVING A COLD FRONT INTO THE AREA ON FRIDAY...ALTHOUGH GUIDANCE HAS NOW DIVERGED ON THE TIMING AND PROGRESSION OF THIS SURFACE FEATURE. FOLLOWING WPC PROGS AS A REASONABLE SOLUTION...THE FRONT WILL APPROACH FRIDAY AND THEN LIKELY STALL THROUGH THE WKND...SIMILAR TO WHAT WE JUST EXPERIENCED THIS PAST WKND. HOWEVER...THE LONGWAVE TROUGH SHOULD BE A BIT DEEPER AND THUS THE FRONT HAS A BETTER CHANCE OF MOVING OFFSHORE SATURDAY...SO WILL OPTIMISTICALLY SHOW AT LEAST SOMEWHAT DRIER AIR SUNDAY AND MONDAY WITH TEMPS ACTUALLY BELOW CLIMO...AFTER SEASONABLE BUT WITH GOOD CHANCES FOR SHOWERS/TSTMS FRIDAY AND SATURDAY. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... AS OF 12Z...LOW PRESSURE TRACKING STEADILY UP THE COAST THIS MORNING. THE HRRR MODEL DISPLAYS THIS FEATURE FAIRLY WELL...WITH CONVECTION ALONG THE COAST THROUGH THE MORNING HOURS. WINDS COULD GUST TO NEAR 30 KTS IN THE STRONGEST CONVECTION...WITH INTERMITTENT IFR VISIBILITIES. THE INLAND TERMINALS WILL NOT SEE MUCH IN THE WAY OF CONVECTION...AS MOST OF THE MOISTURE RESIDES ON THE EAST SIDE OF THE LOW. GIVEN ENOUGH HEATING THIS AFTERNOON HOWEVER COULD TRIGGER SOME MAINLY ISOLATED SHOWERS INLAND. MOST OF THE ACTIVITY WILL END BY MID TO LATE AFTERNOON AS THE LOW TRACKS OUT OF THE REGION. EXTENDED OUTLOOK...PREDOMINANTLY VFR THROUGH THE PERIOD WITH DIURNALLY DRIVEN SHRA/TSRA. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1030 AM TUESDAY...SLOW MOVING WEAK LOW IS RESULTING IN SOUTHWEST FLOW AROUND 20 KT ACROSS MUCH OF THE NEAR SHORE WATERS. THIS HAS PUSHED SEAS CLOSE TO 8 FT IN SOME AREAS AND THE SCA CONTINUES FOR ALL ZONES. SURFACE ANALYSIS IS SHOWING PINCHED GRADIENT JUST AHEAD OF THE LOW...RIGHT WHERE BUOYS ARE REPORTING THE HIGHEST WINDS/SEAS. THIS AREA OF ENHANCED WINDS SHOULD SLIDE OFF TO THE NORTHEAST AS THE LOW SLOWLY LIFTS NORTH-NORTHEAST TODAY. ONLY MINOR ADJUSTMENTS NEEDED TO PREVIOUS FORECAST. PREVIOUS DISCUSSION FROM 630 AM FOLLOWS: HAVE POSTED A SMALL CRAFT ADVISORY FOR ALL WATERS FOR TODAY THROUGH THE MAJORITY OF TONIGHT. THIS IN RESPONSE TO A SFC LOW MOVING N BY NE...MOVING ACROSS THE IMMEDIATE SC AND NC COASTS THIS AFTERNOON AND EVENING RESPECTIVELY. ENOUGH OF A TIGHTENED SFC PG DEVELOPS TO PRODUCE S-SW WINDS IN THE 15 TO 25 KT SPEEDS. GUSTS OVER 30 KT REMAINS POSSIBLE ESPECIALLY IF ANY MIXING FROM ALOFT DOWN TO THE OCEAN SFC OCCURS. LATEST MODELS AND THE KLTX VWP INDICATE 25 TO 35 KT WINDS JUST OFF THE OCEAN SFC. THE LOW WILL MOVE AWAY FROM THE AREA WATERS AFTER MIDNIGHT... LEAVING A SW-WSW 10-20 KT WIND IN ITS WAKE. SIGNIFICANT SEAS WILL BUILD TO 4 TO 7 FT..WITH THE 7 FOOTERS RESERVED FOR THE LOCAL WATERS OFF CAPE FEAR. THIS MAY BE A CONSERVATIVE SEAS FORECAST CONSIDERING THE 1 TO 3 FOOT UNDERLYING SE GROUND SWELL AT 10-11 SECOND PERIODS. OVERALL...DOMINANT PERIODS WILL RUN 7 SECONDS...INDICATIVE OF WIND DRIVEN WAVES DOMINATING THE SEAS. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY...BERMUDA HIGH PRESSURE WILL BE THE DOMINANT FEATURE THIS PERIOD CREATING SW WINDS ACROSS THE WATERS. WIND SPEEDS WILL BE 10-15 KTS MOST OF THE PERIOD...BUT A SHARPENING PIEDMONT TROUGH EACH EVENING WILL HELP WINDS ACROSS THE WATERS RISE UP TOWARDS 20 KTS BRIEFLY WED AND THU EVE...BEFORE FALLING BACK AGAIN EACH NIGHT. THESE WINDS WILL BE THE PREDOMINANT DRIVER OF SEAS...WITH A 5 SEC SW WIND CHOP CREATING 3-4 FT SEAS...UP TO 5 FT AT TIMES DURING THE STRONGEST WINDS EACH EVENING. LONG TERM /FRIDAY THROUGH SATURDAY/... AS OF 300 AM TUESDAY...TYPICAL BERMUDA HIGH PRESSURE REMAINS RIDGED ACROSS THE WATERS FRIDAY...AHEAD OF A COLD FRONT WHICH WILL APPROACH FROM THE NW AND THEN DROP ACROSS THE WATERS LATE SATURDAY. THIS COLD FRONTAL PASSAGE WILL DRIVE A WIND SHIFT TO THE NW LATE. SEAS WILL BE DRIVEN PREDOMINANTLY BY THE WINDS...WITH 3-4 FT SEAS EXPECTED FRIDAY...FALLING TO 2-3 FT SATURDAY AS THE SPEEDS EASE WITH THE FRONTAL PASSAGE. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 3 AM EDT WEDNESDAY FOR AMZ254-256. SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR AMZ250-252. && $$ NEAR TERM...III SHORT TERM...JDW LONG TERM...JDW AVIATION...43

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.