Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 310745 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 345 AM EDT THU JUL 31 2014 .SYNOPSIS...
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COOL HIGH PRESSURE WILL PERSIST ONE MORE DAY ACROSS THE AREA TODAY. A COASTAL TROUGH WILL LIFT NORTH ON FRIDAY...AND STALL OVER THE AREA DURING THE WEEKEND. THIS WILL BRING GOOD RAIN CHANCES...WITH PERIODS OF HEAVY RAINFALL POSSIBLE...FRIDAY THROUGH MONDAY. MORE SEASONABLE WEATHER WILL DEVELOP THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 330 AM THURSDAY...AN UNSEASONABLY DEEP LONGWAVE TROUGH WILL MAINTAIN ITS POSITION OVER EASTERN CONUS THROUGH THE NEAR TERM. A SERIES OF WEAK SHORT WAVE DISTURBANCES WILL ROUND THE BASE OF THE TROUGH THROUGH THE PERIOD. LOW CONFIDENCE TIMING OF THESE DISTURBANCES DUE TO WIDE VARIATION IN THE GUIDANCE AND WEAKNESS OF THE FEATURES. CLOSER TO THE SURFACE A STALLED FRONT WELL OFFSHORE WILL START TO BEND BACK TOWARDS THE FORECAST AREA...LINING UP AS A NASCENT WARM FRONT ALONG THE COAST BY DAYBREAK ON FRIDAY. MOISTURE PROFILES CONTINUE TO SHOW DRY MID LEVELS...HOWEVER...MORE ABUNDANT MOISTURE HIGHER UP IN THE COLUMN WILL ACT TO KEEP IN A SUBSTANTIAL AMOUNT CIRRUS TODAY AND TONIGHT. INCREASINGLY STRONG LIFT OF THE ISENTROPIC VARIETY WILL ALLOW A GRADUAL RAMPING UP OF POPS THROUGH THE NEAR TERM...ESPECIALLY OVERNIGHT AS THE WARM FRONT WORKS BACK TOWARDS THE COAST. EVEN SO...DRY MID LEVELS AND NOT OVERLY GENEROUS LOW LEVEL MOISTURE WILL LIMIT ANY CONVECTIVE COVERAGE...WHICH I WILL CAP AT SLIGHT CHANCE FOR THE NEAR TERM. TEMPERATURES WILL REMAIN ON THE RELATIVELY COOL SIDE...WITH DAYTIME HIGHS NOT TOO MUCH DIFFERENT THAN THE OCEAN SURFACE...WHICH THE LOCAL AIRMASS IS CURRENTLY BEING ADVECTED OVER. EXPECT HIGHS IN THE MID TO UPPER 80S...WITH LOWS OF RIGHT AROUND 70. GUIDANCE IN CLOSE AGREEMENT ON THESE NUMBERS.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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AS OF 330 AM THURSDAY...THE BEGINNING OF AN UNSETTLED...POSSIBLY EXCEEDINGLY WET...PERIOD BEGINS FRIDAY. SEVERAL FEATURES WORK TOGETHER TO MAKE THE SHORT TERM COOL AND WET...AS THE LARGE UPPER TROUGH WHICH HAS BEEN PLAGUING THE AREA THE LAST WEEK OR SO WILL BEGIN TO WEAKEN. THIS TROUGH BEGINS TO ERODE THANKS TO THE PARENT VORTEX FILLING AND LIFTING OFF TO THE NORTHEAST INTO EASTERN CANADA...AND THE STRONG RIDGE ACROSS THE ATLANTIC BEGINNING TO EXPAND BACK TO THE WEST. THIS DRIVES THE TROUGH AXIS WEST OF THE AREA AND CAUSES MID-LEVEL FLOW TO BECOME INCREASINGLY SOUTHERLY...A DIRECTION WHICH MOISTENS THE ATMOSPHERIC COLUMN. AT THE SURFACE...THE COLD FRONT WHICH HAS BEEN STALLED OFFSHORE SINCE TUESDAY...WILL LIFT BACK AS A TROUGH/WARM FRONT FRIDAY BEFORE STALLING OVER THE AREA ON SATURDAY...FURTHER ENHANCING MOIST ADVECTION IN THE LOWER LEVELS OF THE COLUMN...AND PWATS CLIMB ABOVE 2 INCHES FRIDAY NIGHT AND REMAIN THERE ON SATURDAY. ALL OF THIS TOGETHER SUGGESTS INCREASINGLY UNSETTLED WEATHER DURING THE SHORT TERM...WITH WIDESPREAD SHOWERS AND THUNDERSTORMS LIKELY. WITH PWATS ABOVE TWO INCHES...SURFACE CONVERGENCE ALONG THE FRONT...AND 300MB DIFFLUENCE WITHIN A NEARLY STATIONARY JET STREAK ON DOWNWIND SIDE OF THE UPPER TROUGH...PERIODS OF HEAVY RAIN ARE LIKELY WITHIN CONVECTION DURING THE PERIOD. WPC IS HIGHLIGHTING THE AREA FOR 1-3" OF QPF...AND THIS LOOKS MORE THAN REASONABLE FOR THE TIMEFRAME. WILL BUMP POP TO LIKELY FRI AND SAT...WITH NO TIME PERIOD FAVORED SPECIFICALLY FOR THE HEAVIEST AND MOST WIDESPREAD RAINFALL. DUE TO CLOUDS AND THE CONTINUED UPPER TROUGH...TEMPS THROUGH THE PERIOD WILL REMAIN BELOW NORMAL...TO WELL BELOW NORMAL...FOR HIGHS. LOW TO MID 80S EXPECTED FRIDAY...WITH HIGHS ONLY SLIGHTLY ABOVE 80 ON SATURDAY. LOWS FRIDAY NIGHT AROUND 70 WILL RISE A FEW DEGREES INTO THE LOW 70S FOR SATURDAY NIGHT.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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AS OF 330 AM THURSDAY...VERY UNSETTLED THE FIRST HALF OF THE PERIOD...BUT A SLOW RETURN TO MORE TYPICALLY SUMMERTIME CAROLINAS WEATHER IS EXPECTED BY THE MIDDLE OF NEXT WEEK. LARGE UPPER TROUGH WILL VERY SLOWLY DAMPEN THROUGH THE EXTENDED WHILE 5H RIDGE RETROGRADES TO WEST AND BECOMES CENTERED OFF THE SE COAST LATE IN THE EXTENDED. AT THE SURFACE...A COASTAL TROUGH STALLED IN THE VICINITY WILL SERVE AS A FOCUS FOR CONVECTION SUN/MON...WHICH COMBINES WITH PWATS OVER 2 INCHES...AND STRONG DIFFLUENCE ALOFT...TO PRODUCE AN EXTENDED PERIOD OF WIDESPREAD SHOWERS/STORMS WITH HEAVY RAINFALL. WPC GRAPHICS SUGGESTS 2-4" OF QPF SUN-TUE...AND WILL CARRY LIKELY POP SUNDAY...HIGH CHC ON MONDAY. SLOW IMPROVEMENT OCCURS THEREAFTER AS THE TROUGH MORE QUICKLY ERODES TO THE NORTH AND THE SURFACE BOUNDARY WASHES OUT...BUT TUESDAY WILL LIKELY FEATURE AGAIN HIGHER-THAN-CLIMO POP...BEFORE IMPROVEMENT OCCURS WEDNESDAY. A WARMING TREND WILL OCCUR THROUGH THE EXTENDED...BUT MUCH OF THE PERIOD WILL REMAIN BELOW NORMAL...WITH SEASONABLE TEMPS DEVELOPING ONLY BY MID-WEEK.
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&& .AVIATION /08Z THURSDAY THROUGH MONDAY/... AS OF 06Z...VFR THIS TAF VALID PERIOD...EXCEPT FOR A SHORT PERIOD OF SUB-VFR VSBYS IN THE PRE-DAWN HOURS AT KFLO/KLBT. ONLY LIMITED AMOUNTS OF LOW LEVEL MOISTURE ARE AVAILABLE FOR BR FORMATION. THE BEST MOISTURE IS AT KFLO BUT A BROKEN LAYER OF MID CLOUDS SHOULD PERSIST THROUGH SUNRISE. THUS BELIEVE THE CHANCE OF IFR IS LOW AT KFLO AND LOW AT KLBT DUE TO LESS AVAILABLE MOISTURE. MID LEVEL CLOUDS SCT DURING THE MORNING BUT COULD PERSIST INTO THE AFTERNOON AT KLBT. SCT LOW/MID CLOUDS WITH THIN BKN HIGH CLOUDS EXPECTED FOR MOST OF THE DAY AT THE REMAINING TERMINALS. WINDS WILL BECOME E-ESE WITH STRONGEST SPEEDS AT THE COASTAL TERMINALS. AFTER SUNSET THERE WILL BE SCT MVFR LEVEL LOW CLOUDS ADVECTING INTO THE COASTAL TERMINALS...THEN EVENTUALLY THE INLAND TERMINALS LATE IN THE TAF VALID PERIOD. MVFR CIGS ARE NOT ANTICIPATED AT THIS TIME. EXTENDED OUTLOOK...INCREASING CHANCES FOR SHRA/TSRA AND PERIODS OF MVFR CONDITIONS FRIDAY THROUGH MONDAY AS A FRONT STALLS OVER THE EASTERN CAROLINAS. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 330 AM THURSDAY...EXPECT LITTLE CHANGE IN CONDITIONS OVER THE COASTAL WATERS THROUGH THE NEAR TERM. CURRENTLY...OBS SHOW EASTERLY WINDS IN THE 10 TO 15 KT RANGE...WITH SEAS OF 3 TO 4 FT. THESE CONDITIONS WILL PERSIST THROUGH TONIGHT. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM THURSDAY...COASTAL TROUGH WILL SHARPEN AND MOVE ACROSS THE WATERS AND THEN ONSHORE DURING FRIDAY...AND THEN PUSH FURTHER INLAND SATURDAY AS A RIDGE OF HIGH PRESSURE EXPANDS BACK TO THE WEST FROM THE ATLANTIC. THIS CREATES A TIGHTENING GRADIENT FRIDAY...SO AS WINDS VEER FROM E TO SE THROUGH THE DAY...THEY WILL INCREASE TO AROUND 15 KTS FRIDAY NIGHT...BEFORE EASING TO 10-15 KTS DURING SATURDAY WITH SLIGHTLY MORE DIRECTIONAL CHANGE TO THE SOUTH. ALTHOUGH A 1 FT SE GROUND SWELL WILL EXIST DURING THE PERIOD...WAVE HEIGHTS OF 2-3 FT WILL BE FORMED PRIMARILY BY A 5-6 SEC WIND WAVE VEERING FROM EAST TO SOUTH. LONG TERM /SUNDAY THROUGH MONDAY/... AS OF 330 AM THURSDAY...WEAKENING COASTAL TROUGH INLAND WILL WASH OUT OVER THE LAND THROUGH EARLY IN THE WEEK...LEAVING EXPANDING AREA OF HIGH PRESSURE AS THE DOMINANT FEATURE. AS THIS HIGH PRESSURE STRENGTHENS AND PUSHES WEST...S/SW WINDS WILL DEVELOP EARLY IN THE PERIOD...AND PERSIST INTO THE UPCOMING WEEK...WITH SPEEDS RISING FROM 10 KTS SUNDAY...TO 15 KTS ON MONDAY WHEN RETURN FLOW BECOMES MORE SIGNIFICANT. SEAS WILL BE 2-3 FT SUNDAY...RISING TO 3-4 FT MONDAY ON THE LONGER AND MORE SIGNIFICANT FETCH.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...REK SHORT TERM...JDW LONG TERM...JDW AVIATION...REK MARINE...REK/JDW

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