Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 242333 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 733 PM EDT THU JUL 24 2014 .SYNOPSIS...
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A COLD FRONT WILL APPROACH FROM THE NORTHWEST TODAY...BRINGING A RISK FOR STRONG THUNDERSTORMS THIS EVENING. THIS FRONT WILL STALL ACROSS THE AREA FRIDAY BEFORE DISSIPATING ON SATURDAY. HIGH PRESSURE WILL BRING HOT AND HUMID CONDITIONS SUNDAY. A STRONG COLD FRONT WILL MOVE INTO THE AREA LATE MONDAY...BRINGING COOLER AND DRIER CONDITIONS FOR THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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AS OF 7:30 PM THURSDAY...AREA OF STRONG CONVECTION HAS MOVED OFFSHORE CAPE FEAR WHILE ANOTHER MORE MODERATE AREA OF CONVECTION IS MOVING EAST ACROSS DARLINGTON COUNTY. OTHER THAN THIS LATEST BIT ON ACTIVITY....EXPECT THAT MOST AREAS WILL SEE A LULL IN THE ACTION THROUGH AT LEAST MIDNIGHT. THE DARLINGTON CLUSTER OF STORMS WILL CONTINUE ITS EASTWARD TREK INTO THE EVENING HOURS. HAVE UPDATED FORECAST ACCORDINGLY. RELEVANT PORTION OF PREVIOUS DISCUSSION FOLLOWS: THE SYNOPTIC COLD FRONT IS TOUGH TO FIND ACROSS EASTERN NC DUE TO THUNDERSTORM OUTFLOW...BUT BASED ON SURFACE PRESSURES LIKELY LIES ACROSS THE NC/VA BORDER THEN SOUTHWARD ACROSS THE NC MOUNTAINS. ONE FACTOR THAT APPEARS TO HAVE LIMITED THUNDERSTORM COVERAGE SO FAR TODAY IS A POCKET OF DRY MID-LEVEL AIR DISCERNIBLE IN WATER VAPOR SATELLITE IMAGERY ACROSS EASTERN SOUTH CAROLINA AND EXTREME SOUTHERN NC. OVERLAYING 12Z MODEL 700-400 MB DEWPOINTS ON SATELLITE IMAGERY REVEALS THE MODELS SEE THIS FEATURE TOO...AND THE NAM AND GFS BOTH SCOOT IT OFFSHORE BEFORE 00Z. MOISTENING MID-LEVELS PLUS THE FAVORABLE ALIGNMENT OF AN UPPER LEVEL JET STREAK EXTENDING FROM THE MID-ATLANTIC STATES TO THE NEW ENGLAND COAST SHOULD SUSTAIN AT LEAST SCATTERED THUNDERSTORMS THROUGH THE EVENING AND OVERNIGHT. I HAVE TRIMMED BACK POPS FROM EARLIER PROJECTIONS BASED ON LATEST MODEL DATA AND OBSERVED TRENDS...BUT FORECAST POPS TONIGHT STILL RANGE FROM 40-70 PERCENT...HIGHEST ACROSS SE NORTH CAROLINA AND LOWEST NEAR THE SANTEE RIVER IN SOUTH CAROLINA. WITH THE 500 MB TROUGH NOT MOVING INTO THE AREA UNTIL VERY LATE TONIGHT I CANNOT SAFELY REMOVE POPS FROM THE FORECAST EVEN AFTER MIDNIGHT. 500 MB WIND AS HIGH AS 40 KNOTS IS HELPING PRODUCE 0-6 KM BULK SHEAR AS LARGE AS 25-30 KNOTS. WHILE THIS WOULD BE A LOW VALUE ANY OTHER TIME OF THE YEAR IT SELDOM OCCURS WITH DEWPOINTS IN THE LOW TO MID 70S AND SURFACE-BASED CAPE NEAR 3000 J/KG. RATHER THAN SINGLE CELLS...STORMS SHOULD ORGANIZE INTO MULTICELL CLUSTERS WITH GUSTY WINDS POSSIBLE DUE TO DRY AIR ENTRAINMENT ALOFT. WITH LARGE POTENTIAL INSTABILITY THROUGH THE -10C TO -30C LAYER ALOFT FREQUENT LIGHTNING IS ALSO POSSIBLE. LOW TEMPERATURES SHOULD REACH THE LOWER 70S FOR MOST AREAS...EXCEPT MID 70S NEAR THE COAST.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... AS OF 3 PM THURSDAY...A WEAK COLD FRONT WILL BE STALLED OVER THE EASTERN CAROLINAS AT THE START OF THE PERIOD. THE BOUNDARY WILL LINGER OVER OUR CWA DURING THE DAY AS IT SLOWLY LIFTS NORTHWARD AND EVENTUALLY DISSIPATES. DRIER AIR WILL BEGIN FILTERING INTO THE AREA FRIDAY...BUT THE MAGNITUDE AND TIMING OF THIS DRYING IS WHERE THE GFS/NAM SOLUTIONS DIVERGE. THE 12Z NAM IS MUCH DRIER ABOVE 700 MB THAN THE GFS AS SEEN IN FORECAST SOUNDINGS. WILL TREND POPS DOWNWARD A BIT FOR FRIDAY BUT KEEP AT LEAST SLIGHT CHC IN THE FORECAST... WITH HIGHEST POPS ALONG THE COAST...AS THE FRONT WAVERS OVER THE AREA. SATURDAY WILL BE WARMER WITH DRY W-NW FLOW ALOFT AS AN UPPER RIDGE OVER THE CENTRAL U.S. EXPANDS EASTWARD. WILL MENTION SLIGHT CHANCE POPS AS GOOD SFC HEATING COULD PRODUCE ISOLATED SEA BREEZE TSTMS IN THE AFTERNOON...BUT OVERALL COVERAGE WILL BE VERY LIMITED IF ANYTHING DEVELOPS. THE NAM PICKS UP ON AN UPPER DISTURBANCE NEAR THE END OF THE PERIOD SPILLING OVER THE TOP OF THE RIDGE...BUT NO SIGNS OF IT IN THE GFS OR ECMWF...SO WILL KEEP SILENT POPS THROUGH SATURDAY NIGHT. EXPECT SEASONABLE HIGHS ON FRIDAY...GENERALLY AROUND 90 DEGREES EVERYWHERE AWAY FROM THE BEACHES. ON SATURDAY HIGHS WILL CLIMB INTO THE LOW TO MID 90S...WARMEST ACROSS THE PEE DEE REGION OF SOUTH CAROLINA. THOUGH DEWPOINTS WILL BE A BIT LOWER ON SATURDAY...COULD STILL SEE HEAT INDICES TOUCH TRIPLE DIGITS ACROSS OUR INLAND ZONES. LOW TEMPS WILL ONLY DROP INTO THE LOW TO MID 70S. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 3 PM THURSDAY...MID LEVEL TROUGH WILL DOMINATE MUCH OF THE PERIOD KEEPING TEMPERATURES ACROSS THE REGION BELOW CLIMO. THE EXCEPTION WILL BE ON SUN WITH MID LEVEL RIDGE TO THE WEST EXTENDING EAST. 850 TEMPS WILL FLIRT WITH 20-22C WHICH SHOULD PRODUCE HIGHS IN THE MID TO UPPER 90S. DESPITE THE HOT TEMPS DO NOT THINK THERE WILL BE MUCH CONVECTION AROUND. WESTERLY MID LEVEL FLOW AND SUBSIDENCE ON THE RIDGES PERIPHERY WILL KEEP MID LEVELS DRY. CANNOT RULE OUT ISOLATED CONVECTION...ESPECIALLY LATER IN THE DAY ASSOCIATED WITH THE PIEDMONT TROUGH BUT SEE NO REASON TO GO ABOVE INHERITED SILENT POP. COLD FRONT MOVES INTO THE AREA LATE MON...PUSHED BY IMPRESSIVE MID LEVEL TROUGH. DOES NOT LOOK LIKE MON WILL BE AS HOT AS SUN GIVEN INCREASED MID LEVEL MOISTURE AND MORE WIDESPREAD CONVECTION LATER IN THE DAY...JUST AHEAD OF THE FRONT. SHOULD THE FRONT BE DELAYED A BIT MON COULD END UP AS HOT AS SUN GIVEN 850 TEMPS HANGING IN THE LOW 20C RANGE FOR MUCH OF THE DAY. LATER MON INTO TUE WILL BE THE MOST ACTIVE PART OF THE PERIOD CONVECTIVELY SPEAKING AND WILL MAINTAIN INHERITED HIGH CHC POP. MID LEVEL TROUGH AXIS WILL REMAIN WEST OF THE AREA THROUGH THE PERIOD WITH THE FRONT STALLING NOT TOO FAR OFF THE COAST. INITIALLY MID LEVELS ARE DRY BUT INCREASING MOISTURE ALOFT WILL RESULT IN A SLOW INCREASE IN POP THROUGH THE MIDDLE OF NEXT WEEK. TEMPS WILL RUN A LITTLE BELOW CLIMO LATE IN THE PERIOD. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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AS OF 00Z...THE SYNOPTIC SITUATION SUPPORTS CONTINUED SHRA/TSRA POTENTIAL THIS EVENING...TAPERING OFF AFTER MIDNIGHT. TEMPO MVFR/IFR AND GUSTY WINDS POSSIBLE IN ANY HEAVY DOWNPOURS...OTHERWISE VFR. A CLUSTER OF SHRA/TSRA IS MOVING E AND WILL LIKELY PRODUCE TEMPO TSRA AT KFLO UNTIL 02-03Z. THIS SHOULD PRODUCE TEMPO TSRA AT KCRE/KMYR 02-04Z AND POSSIBLY A FEW HOURS LONGER. TEMPO TSRA IS POSSIBLE AT KILM 03-05Z BUT CONFIDENCE IS LOWER DUE TO EARLIER TSRA/OUTFLOWS. LATE OVERNIGHT INTO THE EARLY MORNING HOURS...MVFR/IFR IS POSSIBLE DUE TO PATCHY FOG...ESPECIALLY INLAND TERMINALS. VFR EXPECTED ALL TERMINALS 12-13Z WITH LIGHT SW-WNW WINDS AT THE COASTAL TERMINALS AND WNW-N WINDS AT KFLO. WINDS BECOME SE-SW AT THE COASTAL TERMINALS LATE MORNING. SHRA/TSRA POSSIBLE AGAIN BY 18Z WITH BEST CONFIDENCE OF OCCURRENCE AT THE COASTAL TERMINALS. EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE THROUGH FRIDAY...AS WELL AS SUNDAY AND MONDAY.
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&& .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 7:30 PM THURSDAY...NO CHANGES TO THE FORECAST WITH THE LATEST UPDATE. RELEVANT PORTION OF PREVIOUS DISCUSSION FOLLOWS: AN EXERCISE CAUTION HEADLINE REMAINS ON THE FORECAST FOR THE NC WATERS FOR THESE WINDS. A COLD FRONT ACROSS THE NC/VA BORDER WILL DROP SOUTHWARD BUT SHOULD REMAIN INLAND EVEN LATE TONIGHT. THIS FRONT WILL HELP ENHANCE THUNDERSTORM CHANCES THIS EVENING...WITH THE BEST POTENTIAL FOR STORMS ACROSS THE NORTH CAROLINA WATERS THROUGH MIDNIGHT. SEAS CONSIST OF A MIXTURE OF 9-SECOND SOUTHEAST SWELL PLUS A ROUGH 4-5 SECOND CHOP DUE TO THE BREEZY SOUTHWEST WINDS. COMBINED SEAS ARE AVERAGING AROUND 4 FEET...WITH SEAS EXPECTED TO BEGIN SUBSIDING OVERNIGHT AS WIND SPEEDS DIE DOWN. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 3 PM THURSDAY...LIGHT WEST WINDS AOB 10 KT EARLY FRIDAY WILL BECOME S-SW AROUND 10 KT IN THE AFTERNOON AS THE DISSIPATING FRONT LIFTS BACK NORTHWARD. SOUTHWEST WINDS STRENGTHEN TO AROUND 15 KT DURING SATURDAY AS THE GRADIENT TIGHTENS AROUND HIGH PRESSURE WELL OFFSHORE. SEAS WILL REMAIN AROUND 3 FT THROUGH THE PERIOD...BUILDING TO 3-4 FT ACROSS AMZ250/252 AFTER 00Z SUNDAY WITH AN INCREASING SOUTHERLY WIND CHOP. .LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 3 PM THURSDAY...MODEST SW FLOW ON SUN WILL INCREASE INTO MON AS GRADIENT TIGHTENS AHEAD OF ADVANCING COLD FRONT. SPEEDS LATER SUN MAY APPROACH SCEC THRESHOLDS AS PIEDMONT TROUGH STRENGTHENS. SCA HEADLINES SEEM CERTAIN FOR AT LEAST MON AND POSSIBLY SUN NIGHT AS PROLONGED STRONG SOUTHWEST FLOW BUILDS SEAS TO 4 TO 6 FT. FRONT MOVES ACROSS THE WATERS MON NIGHT WITH NORTHERLY FLOW DEVELOPING. GRADIENT RELAXES BEHIND THE FRONT AND SPEEDS WILL DROP UNDER 10 KT BY MIDDAY TUE. FRONT ENDS UP STALLED JUST EAST OF THE WATERS WITH THE PROXIMITY TO THE FRONTAL ZONE KEEPING GRADIENT WEAK AND WINDS LIGHT AND VARIABLE. SEAS WILL DROP TO 3 TO 4 FT BEHIND THE FRONT AND BELOW 3 FT BY THE END OF THE PERIOD.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MBB/BJR NEAR TERM...REK/TRA SHORT TERM...MBB/BJR LONG TERM...III AVIATION...MRR MARINE...REK/TRA/III/MBB/BJR

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