Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 222341 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 641 PM EST SAT NOV 22 2014 .SYNOPSIS... CLOUDS WILL INCREASE OVERNIGHT AHEAD OF A STORM SYSTEM TAKING SHAPE IN THE GULF OF MEXICO. THIS SYSTEM WILL BRING MILD AND WET WEATHER SUNDAY AND MONDAY AS IT LIFTS NORTHEAST. STRONG THUNDERSTORMS WILL BE POSSIBLE LATE SUNDAY THROUGH EARLY MONDAY. A COLD FRONT WILL CROSS THE COAST EARLY TUESDAY...STALLING OFFSHORE. DEEPENING LOW PRESSURE WILL FORM ALONG THIS FRONT...BRINGING A COOL WET CONDITIONS WEDNESDAY. CLEARING WEATHER IS EXPECTED THANKSGIVING DAY WITH BELOW NORMAL TEMPERATURES THROUGH NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 640 PM SATURDAY...TEMPERATURES ARE DROPPING LIKE A ROCK ALONG THE NC COAST WHERE RADIATIONAL COOLING CONDITIONS ARE BEST. TEMPERATURE FALLS ARE MUCH SLOWER ACROSS MOST OF NE SOUTH CAROLINA WHERE HIGH CLOUDS ARE INCREASING AND LOW CLOUDS WILL BE DEVELOPING IN THE NEXT FEW HOURS. A RAPID AIRMASS CHANGE WILL OCCUR THROUGHOUT THE 850-500 MB LAYER BY MIDNIGHT WITH TREMENDOUS WARMING AND MOISTENING BEGINNING VIA DEEP WARM ADVECTION AHEAD OF THE NEXT STORM SYSTEM. CHANGES WITH THIS EARLY-EVENING UPDATE WERE MINOR...MAINLY CENTERED ALONG NEAR-TERM TEMPERATURE TRENDS GIVEN THE NON-DIURNAL TEMPERATURE CURVES EXPECTED. PREVIOUS DISCUSSION FROM 330 PM FOLLOWS... VISIBLE SATELLITE IMAGERY SHOWS CLEAR SKIES ACROSS THE CAROLINAS. FURTHER SOUTH LOW CLOUDS ARE PLENTIFUL AS WARM ADVECTION IS UNDERWAY ACROSS MUCH OF FLORIDA. THE OTHER MAIN DISCERNIBLE FEATURE IS THE MID LEVEL IMPULSE CROSSING TEXAS WHERE WIDESPREAD THUNDERSTORMS HAVE DEVELOPED. AS THESE TWO FEATURES INCREASINGLY ACT OVERNIGHT SOME CLOUD COVER SHOULD INCREASE INTO THE CAROLINAS. FOR MUCH OF THE EVENING AND FIRST PART OF THE OVERNIGHT THIS MAY BE FAIRLY GRADUAL BUT AFTER ABOUT 06Z OR SO IT SHOULD BECOME MUCH MORE RAPID. THE SOUTH TO NORTH INCREASE IN CLOUD COVER MAY HAVE SOME EFFECT ON NIGHTTIME LOWS AS NORTHERN AREAS COOL OFF FOR LONGER BEFORE THE CLOUD COVER RETARDS THE DIURNAL TREND. IN FACT MANY PLACES SHOULD LEVEL OFF OR EVEN RISE BY A DEGREE OR TWO ONCE THE CLOUDS ARRIVE IN EARNEST. RAINFALL FORECAST A BIT MORE PROBLEMATIC. THE WRF SEEMS TO IMPLY RAINFALL KNOCKING AT THE DOOR OF SOUTHERN ZONES BY THE END OF THE PERIOD WHILE OTHER GUIDANCE IS SLOWER. FEEL IT BEST FOR POPS TO MIRROR BUT LAG POPS...MOST OF THE NIGHT WILL BE DRY BUT THEN RAIN CHANCES RISE PRECIPITOUSLY (PARDON THE PUN) TOWARDS DAYBREAK. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... AS OF 336 PM SATURDAY...PRIMARY HEADLINE THIS PERIOD...STRONG TO SEVERE TSTM POTENTIAL LATE SUNDAY THROUGH EARLY MONDAY. LOW-LEVEL SE WINDS WILL INTENSIFY...TRANSPORTING MOISTURE RICH GULF STREAM AIR INTO THE COASTAL ZONES ELEVATING BOUNDARY LAYER DEWPOINTS. A DEVELOPING AXIS OF POSITIVE MIXED-LAYERED CAPES WILL ORIENT ITSELF ALONG OR JUST OFF THE COAST SUNDAY NIGHT THROUGH MONDAY MORNING. THE HIGHEST HELICITY VALUES FAR PRECEDE THE MAXIMUM OF ML-CAPE BUT SOME OVERLAP OF MODERATE CAPE/HELICITY EXISTS TO WARRANT A CHANCE OF SEVERE STORMS...ALTHOUGH DIURNAL COOLING WILL AND SLIGHT CHILLED INSHORE SST VALUES COULD OFFSET INCREASING CONVECTIVE INTENSITY TRENDS. NEXT NOTEWORTHY ITEM...PRECEDING THIS SEVERE POTENTIAL PLENTY STRATIFORM RAIN APPEARS LIKELY...AND THE LATEST WPC QPF FORECAST FOR SUNDAY AND MONDAY PAINTS 1.5-2.5 INCHES OF RAIN FOR OUR AREA FOR THE 2-DAY PERIOD. STRATIFORM WILL TRANSITIONS TO CONVECTION AS THE WARM FRONT LIFTS NORTH OF THE AREA INTO EARLY MONDAY. EXCEPTIONALLY MILD MONDAY WITH MAXIMUM TEMPERATURES WELL INTO THE 70S IN A DEEP AND MOIST SW WIND FLOW ATOP THE AREA...AND FROPA NEAR END OF THE PERIOD PRIOR TO DAYBREAK TUESDAY. COOLEST PORTION OF PERIOD DAYBREAK SUNDAY WITH CLOUDS AND MIDDLE 40S. HIGHEST POP VALUES SUNDAY NIGHT. && .LONG TERM /MONDAY THROUGH SATURDAY/... AS OF 336 PM SATURDAY...LINGERING FRONT STALLED OFF THE EAST COAST TUE INTO WED AND SHORTWAVE DROPPING INTO THE WESTERN GULF WILL BRING RAIN TO THE AREA DURING THE MIDDLE OF NEXT WEEK. WEAK SURFACE WAVE DEVELOPING ON THE BOUNDARY OVER SOUTHERN FL EARLY TUE WILL BE ENHANCED BY THE AFOREMENTIONED SHORTWAVE. AS THE LOW TRACKS NORTHEAST ALONG THE FRONT...JUST OFF THE SE COAST...RAIN WILL SPREAD OVER MUCH OF THE CAROLINAS. WED LOOKS AS THOUGH IT COULD BE A MISERABLE DAY WITH THE FORECAST AREA ON THE COOL SIDE OF THE LOW AND PERIODS OF HEAVY RAIN POSSIBLE. HIGHS WED MAY STAY IN THE MID 40S WITH AROUND 50 ALONG THE COAST AND HAVE TRENDED HIGHS DOWN. RAPID DRYING WILL COMMENCE LATE WED INTO WED NIGHT AS 5H TROUGH AXIS LIFTS NORTHEAST AND DEEP DRY AIR ARRIVES. BY THU AM PRECIPITABLE WATER VALUES WILL BE AROUND 0.40 INCH AND SOUNDINGS SHOW STRONG DOWNWARD MOTION. LATER HALF OF THE PERIOD REMAINS A QUESTION WITH LATEST GFS/ECMWF DISAGREEING ON THE STRENGTH/AMPLITUDE OF THE NEXT MID LEVEL TROUGH. GFS DEVELOPS ZONAL FLOW ALOFT FRI/SAT WHILE THE ECMWF MAINTAINS 5H TROUGHING INTO THE START OF THE WEEKEND. BOTH SOLUTIONS WOULD RESULT IN A DRY FORECAST BUT WITH DIFFERENCES IN TEMPERATURES AND POSSIBLY AFTERNOON CLOUD COVER. GFS ENSEMBLES ARE NOT VERY HELPFUL WITH ROUGHLY AN EQUAL SPLIT BETWEEN THE 2 SOLUTIONS. INHERITED FORECAST IS BASICALLY A BLEND OF THE GFS/ECMWF AND WILL CONTINUE WITH THIS THINKING UNTIL THERE IS BETTER AGREEMENT. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 00Z...EXPECT VFR OVERNIGHT INTO THE MORNING HOURS ON SUNDAY...WITH CONDITIONS GRADUALLY DETERIORATING TO MVFR AND THEN IFR TOWARDS THE END OF THE PERIOD AS LOW CIGS AND SHRA/ISOLATED TSRA ACCOMPANY THE NEXT APPROACHING WEATHER SYSTEM. LIGHT WINDS WITH INCREASING HIGH CLOUDS WILL BE ON TAP FOR TONIGHT AND THROUGH THE MORNING HOURS AHEAD OF THE NEXT APPROACHING WEATHER SYSTEM. AS A RESULT...EXPECT VFR TO PREVAIL. ON SUNDAY...LOW TO MID CLOUDS WILL SLOWLY INFILTRATE INTO THE AREA BY LATE MORNING...WITH INCREASING CHANCES FOR RAIN THROUGHOUT THE DAY. HEAVY RAIN AT TIMES AND LOWER CIGS WILL CREATE DETERIORATING CONDITIONS TO MVFR AND EVENTUALLY IFR TOWARDS SUNDAY EVENING. THERE IS A POSSIBILITY OF THUNDERSTORMS INTO THE EVENING HOURS...BUT GIVEN LOWER CONFIDENCE OF TIMING AND WHILE CONTINUING TO MONITOR LATEST GUIDANCE INFORMATION...HAVE OPTED TO NOT INTRODUCE ATTM. AS FOR WINDS...EXPECT NORTHEAST WINDS TO BECOME SOUTHEAST BY THE AFTERNOON/EVENING HOURS...WITH SUSTAINED WINDS AOB 10 KTS. EXTENDED OUTLOOK...UNSETTLED WEATHER IS EXPECTED POSSIBLY THROUGH TUESDAY...WITH OCCASIONAL SHOWERS AND MVFR/IFR CONDITIONS. VFR TUESDAY AFTERNOON WITH POSSIBLE MVFR CONDITIONS WEDNESDAY. VFR THURSDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 640 PM SATURDAY...WINDS AND SEAS ARE PRETTY CLOSE TO THE PREVIOUS FORECAST AND NO SIGNIFICANT CHANGES ARE NEEDED WITH THIS EARLY EVENING UPDATE. PREVIOUS DISCUSSION FROM 330 PM FOLLOWS... LIGHT VEERING FLOW FOR MOST OF THE PERIOD AS HIGH PRESSURE JUST TO OUR NORTH SLIDES EASTWARD. ACTUALLY RATHER THAN PROGRESSING EASTWARD IT GENERALLY JUST EXTENDS ITS CENTER EASTWARD AND BECOMES QUITE ELONGATED THIS EVENING AND EARLY TONIGHT. LATER TONIGHT THE OCEAN CENTER OF THE RIDGE TAKES OVER AND JUST A WEAK RIDGE AXIS IS MAINTAINED INTO THE CAROLINAS AND A VERY WEAK TROUGH DEVELOPS IN BETWEEN. THE END RESULT WILL BE FLOW THAT CHANGES FROM NE TO E LATER ON AND THEN EVENTUALLY SE. THE SHIFTING OF THE HIGH AND DEVELOPMENT OF THE TROUGH MAY SHAVE ABOUT THE UPPER 5 KNOTS OFF THE RANGE OF WIND SPEEDS MEANING 10 KTS MORE WIDESPREAD THAN 10 TO 15KT. SEAS WILL TEND TO AVERAGE ABOUT 3 FT...WITH THE ONSHORE FLOW MINIMIZING THE WAVE HEIGHT GRADIENT NEARSHORE VS OFFSHORE MUCH AS IN THE CURRENT OBS...41013 NOW JUST BELOW 4 FT. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 336 PM SATURDAY...DETERIORATING MARINE CONDITIONS SUNDAY AS SE WINDS CRANK UP TO 15-25 KT AHEAD OF AN APPROACHING WARM FRONT. S AND SW BLUSTERY FLOW TO FOLLOW FOR MONDAY 15-25 KT...WHILE SEAS PEAK MAINLY SUNDAY NIGHT DURING MAXIMUM IN S-SE WIND OFFSHORE OF 6-10 FEET AND HIGHEST OUTER WATERS. STRONG TO SEVERE THUNDERSTORMS POSSIBLE SUNDAY NIGHT THROUGH MONDAY...GULF STREAM LATE MONDAY. VENTURING OFFSHORE IS DISCOURAGED FOR SMALL CRAFT VESSELS SUNDAY AND MONDAY. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 336 PM SATURDAY...FRONT STALLED OFF THE COAST TUE WILL HELP MAINTAIN LIGHT NORTHERLY FLOW. LOW PRESSURE DEVELOPING ON THE FRONT LATE TUE WILL TRACK NORTHEAST WED...PASSING JUST EAST OF THE WATERS. AS THE LOW DEVELOPS THE GRADIENT WILL TIGHTEN UP WITH SPEEDS INCREASING TO 20 TO 25 KT WED. LOW EXITS NORTHEAST WED NIGHT WITH WINDS BACKING TO WESTERLY AS THE LOW EXITS. GRADIENT DECREASES WITH SPEEDS DROPPING TO 10 TO 15 KT BY THU MORNING. SEAS 2 TO 3 FT ON TUE WILL BUILD TO 4 TO 7 FT LATE WED IN RESPONSE TO INCREASED NORTHERLY FLOW. DEVELOPMENT OF OFFSHORE FLOW BEHIND THE EXITING LOW DROPS SEAS TO 2 TO 4 FT WED NIGHT AND AROUND 2 FT THU. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM SUNDAY TO 6 AM EST TUESDAY FOR AMZ250-252-254-256. && $$ SYNOPSIS...MJC NEAR TERM...MBB/TRA SHORT TERM...MJC LONG TERM...III AVIATION...SGL

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