866  
FXUS62 KILM 260605 CCA  
AFDILM  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON NC  
205 AM EDT WED JUL 26 2017  
   
SYNOPSIS
 
 
DRIER WEATHER WILL MAKE ITS WAY SOUTH BEHIND A COLD FRONT AS IT  
DRIFTS SLOWLY SOUTH INTO SOUTH CAROLINA TODAY AND THEN DISSIPATES.  
ISOLATED TO SCATTERED STORMS WILL BECOME MORE NUMEROUS FRIDAY AND  
SATURDAY, AS A MODERATELY STRONG FRONTAL SYSTEM ARRIVES AT THE  
COAST. A SLIGHT COOLING AND DRYING TREND MAY OCCUR SUNDAY INTO EARLY  
NEXT WEEK, AS THIS SYSTEM IS KICKED OFFSHORE.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY/
 
 
AS OF 830 PM TUESDAY...MULTIPLE BOUNDARY INTERACTIONS AND AN  
UNSTABLE AIRMASS FUELED ISOLATED STRONG CONVECTION THIS EVENING, BUT  
WITH THE SUNSET ACTIVITY IS NOW ON THE DECLINE. WILL KNOCK POPS BACK  
WITH THE NEXT UPDATE. OTHERWISE FORECAST IS GOOD TO GO. PREVIOUS  
DISCUSSION FOLLOWS:  
 
POTENTIAL FOR WIDELY SCATTERED SHOWERS AND A FEW THUNDERSTORMS  
WITH THE SEA BREEZE THROUGH THE AFTERNOON. ADDITIONAL STORMS ARE  
POSSIBLE TONIGHT AS A COLD FRONT DROPS SOUTHWARD ACROSS THE  
FORECAST AREA. THE FRONT IS EXPECTED TO DRIFT SOUTH OF THE  
FORECAST AREA DURING WEDNESDAY AND BECOME INCREASINGLY DIFFUSE.  
DEWPOINTS WILL LOWER ACROSS THE NORTHERN ZONES WHILE THE BEST CHANCE  
FOR SHOWERS/THUNDERSTORMS WILL BE ACROSS THE SOUTHERN ZONES DURING  
THE DAY. NORTHEAST TO EASTERLY WIND IN THE WAKE OF THE FRONT WILL  
HELP HOLD TEMPERATURES TO THE MID 80S AT THE BEACHES ON WEDNESDAY.  
FOLLOWED A BLEND OF MAV/MET NUMBERS THROUGH THE PERIOD.  
 

 
   
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/
 
 
AS OF 215 PM TUESDAY...VERY INTERESTING SYNOPTIC SETUP THROUGH  
MID- WEEK DESPITE VERY WEAK SURFACE FEATURES AND GRADIENTS. THE  
INTERESTING ASPECT IS FOCUSED MOSTLY AT AND ABOVE 500MB AS A  
NEARLY STATIONARY SHORTWAVE SPINS ACROSS N FL IN RESPONSE TO A  
PERSISTENT RIDGE IN THE WEST, AND JET LEVEL WINDS INCREASE AND  
DIVE SW BETWEEN THE RIDGE AND THE TROUGH. THIS DRIVES A STRONG  
DEFORMATION AXIS ACROSS THE CAROLINAS WHERE NE 250MB WINDS  
CONVERGE WITH MORE TYPICAL WESTERLY 250MB WINDS ALONG A JET AXIS  
OFF THE COAST. AS IS TYPICAL WITH DEFORMATION AXES, MOST OF THE  
PRECIP OCCURS SE OF THIS FEATURE, AS DRIER AIR ADVECTS BEHIND  
IT. THIS IS CLEARLY EVIDENT ON FORECAST PROFILES WITH  
EXCEEDINGLY DRY AIR DEVELOPING ABOVE 600MB, WHICH SHOULD LIMIT  
CONVECTIVE COVERAGE CONSIDERABLY ON THURSDAY. THIS DRY AIR,  
COMBINED WITH WEAK CONFLUENCE INTO THE DEFORMATION AXIS, AND A  
WEAKENING SURFACE FRONT TO THE SOUTH WILL PRECLUDE MUCH IN THE  
WAY OF CONVECTION THURSDAY, AND HAVE OPTED TO REMOVE ANY MENTION  
EVEN ALONG THE SEA BREEZE DESPITE TEMPERATURES AROUND 90.  
WEDNESDAY NIGHT WILL BE DRY AS WELL, MINUS A FEW ISOLATED  
SHOWERS WELL SOUTH, WITH MINS IN THE LOW 70S, WHILE SUBTLY  
INCREASING COLUMN MOISTURE AHEAD OF AN APPROACHING FRONT AND  
DEVELOPING S/SW WINDS WILL KEEP MINS SEVERAL DEGREES WARMER  
THURSDAY NIGHT, FALLING ONLY INTO THE MID TO UPPER 70S.  
 

 
   
LONG TERM /FRIDAY THROUGH TUESDAY/
 
 
AS OF 215 PM TUESDAY...AN UNSEASONABLY AMPLIFIED UPPER TROUGH  
BECOMES THE PRIMARY FEATURE AND KEY PLAYER FOR LATE WEEK AND  
WEEKEND SENSIBLE WEATHER. THIS WILL TRANSLATE TO ELEVATED RAIN  
CHANCES LATE FRIDAY AND SATURDAY AS THIS SYSTEM USHERS A FAIRLY  
STRONG SURFACE TROUGH ACROSS THE COAST. ECMWF AND GFS CLEAR  
THIS BOUNDARY OFF THE COAST INTO EARLY SUNDAY, THE GFS MUCH  
STRONGER. BOTH SUGGEST THEREFORE SOME DRYING AND COOLING, BUT  
OF DIFFERING MAGNITUDE. A BLEND STILL BRINGS SURFACE DEWPOINTS  
INTO THE 60S EARLY NEXT WEEK, HELPING TO TAKE OFF THE BITE OF  
HIGH ABSOLUTE HUMIDITY VALUES. A DRY MID-LEVEL AIR INTRUSION  
WILL CURTAIL DEEP CONVECTION SUNDAY THROUGH EARLY NEXT WEEK. A  
FEW SHOWERS COULD LINGER AND REMAIN FAVORED CLOSER THE COAST IN  
PROXIMITY TO HIGHER MOISTURE AND THE OCEANIC FRONT, BUT THE  
OVERALL COVERAGE SHOULD TREND DOWN SUNDAY ONWARD. TEMPERATURES  
SLIGHTLY ABOVE NORMAL FRIDAY AT THE START OF THE PERIOD, MAY DIP  
BELOW NORMAL FROM SUNDAY FORWARD, AS COOL AIR ADVECTION PUSHES  
INTO THE BALMY SEA AIR.  
 

 
   
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
 
 
AS OF 06Z...COLD FRONT DRAPED FROM W-SW TO E-NE ACROSS THE AREA HAS  
REACHED A LINE BETWEEN FLO TO ILM AND WILL CONTINUE TO DRIFT SLOWLY  
SOUTH THROUGH TODAY. THIS BOUNDARY WILL REMAIN THE FOCUS FOR  
CONVECTION, AS WELL AS, CONVERGENCE ALONG SEA BREEZE FRONT. NORTH OF  
THE FRONT, HAVE INCLUDED SOME STRATUS AND MAY SEE SOME PATCHY LOWER  
CLOUDS OVER COASTAL TERMINALS AROUND DAYBREAK. AS DRIER AIR MAKES  
ITS WAY IN FROM THE NORTH TODAY, EXPECT MAINLY VFR BY LATER THIS  
AFTN INTO TONIGHT ACROSS MOST TERMINALS. LIGHT NE FLOW WILL VEER TO  
THE E-NE THROUGH THIS AFTERNOON AND SLIGHTLY E-SE IN SEA BREEZE THIS  
AFTN.  
 
EXTENDED OUTLOOK...POSSIBLE MVFR CONDITIONS WITH SOME FLIGHT  
RESTRICTIONS WITH CONVECTION FRIDAY THROUGH SATURDAY AS COLD FRONT  
SWEEPS THROUGH.  
 

 
   
MARINE
 
 
NEAR TERM /THROUGH WEDNESDAY/...  
AS OF 830 PM TUESDAY...LATEST OBS SHOW SEAS OF AROUND 3 FT WITH  
SW WINDS OF AROUND 10 KTS. NO CHANGES NEEDED WITH THE LATEST  
UPDATE. PREVIOUS DISCUSSION FOLLOWS:  
 
A COLD FRONT WILL DROP SOUTH ACROSS THE WATERS DURING TONIGHT.  
SOUTHERLY WINDS AHEAD OF THE FRONT WILL BECOME VARIABLE FOR A  
BRIEF PERIOD TONIGHT PRIOR TO SHIFTING TO A NORTHEAST-EASTERLY  
DIRECTION OVERNIGHT INTO WEDNESDAY MORNING. EASTERLY FLOW WILL  
PREVAIL THROUGH WEDNESDAY AFTERNOON WITH SPEEDS OF 10-15 KNOTS.  
SEAS ARE EXPECTED TO BE 3 FT OR LESS THROUGH THE NEAR TERM  
PERIOD.  
 
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...  
AS OF 215 PM TUESDAY...A COLD FRONT WILL BE DROPPING ACROSS THE  
SOUTHERN WATERS WEDNESDAY NIGHT BEFORE STALLING SOUTH OF THE  
AREA ON THURSDAY. THIS LEAVES E/NE WINDS LESS THAN 10 KTS  
WEDNESDAY NIGHT, GRADUALLY SHIFTING TO E/SE AND EVENTUALLY  
COMING AROUND TO THE SW THURSDAY NIGHT AS THE FRONT DISSIPATES  
AND HIGH PRESSURE BECOMES DOMINANT ONCE AGAIN. SPEEDS THROUGH  
THE PERIOD WILL BE 10 KTS OR LESS, WITH THE EXCEPTION BEING  
WITHIN THE NEAR SHORE SEA BREEZE THURSDAY WHEN GUSTS TO 15 KTS  
ARE POSSIBLE, AND AGAIN VERY LATE THURSDAY NIGHT WHEN 10-15 KT  
WINDS WILL OVERSPREAD THE WATERS. THESE LIGHT WINDS WILL ALLOW  
THE SE SWELL TO BE DOMINANT UNTIL THE WIND WAVE AMPLIFIES  
THURSDAY NIGHT. SEAS WILL BE 2-3 FT THROUGH THE PERIOD BUT THE  
AVERAGE PERIOD WILL BEGIN TO SHORTEN LATE.  
 
LONG TERM /FRIDAY THROUGH SUNDAY/...  
AS OF 215 PM TUESDAY...WIND DIRECTION WILL BECOME CHANGEABLE  
THIS PERIOD, BUT THE GOOD NEWS IS THAT WIND-SPEEDS WILL DECREASE  
INTO THE WEEKEND, AS A FRONT LAYS UP ALONG THE COAST THEN  
OFFSHORE. TSTMS WILL BECOME MORE NUMEROUS ALONG THE FRONT  
HOWEVER FRIDAY NIGHT AND SATURDAY, SO A RADAR UPDATE SHOULD BE  
ON THE CHECKLIST FIRST PART OF THE WEEKEND. GUSTS TO 20 KT FROM  
SW LIKELY FRIDAY OUT AHEAD OF THE FRONT, AND COULD BE STRONGER  
SO AN SCA IS NOT OUT OF THE QUESTION YET FOR FRIDAY. SEAS 2-4  
FEET THIS PERIOD BECAUSE OF INITIALLY GUSTY WINDS, THEN BECAUSE  
OF SWELL OVER THE WEEKEND. TSTMS WILL DECREASE IN COVERAGE  
SUNDAY, ALTHOUGH THE GULF STREAM AND OUTER WATERS MAY REMAIN  
UNSETTLED DUE TO THE OFFSHORE FRONT.  
 

 
   
ILM WATCHES/WARNINGS/ADVISORIES
 
 
SC...NONE.  
NC...NONE.  
MARINE...NONE.  
 

 
 

 
 
NEAR TERM...REK/SRP  
SHORT TERM...JDW  
LONG TERM...MJC  
AVIATION...RGZ  
 
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