889  
FXUS62 KILM 151507  
AFDILM  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON NC  
1107 AM EDT WED AUG 15 2018  
   
SYNOPSIS
 
 
BERMUDA HIGH PRESSURE OFF THE COAST WILL MAINTAIN HOT AND HUMID  
WEATHER THIS AFTERNOON THROUGH FRIDAY. THUNDERSTORMS WILL  
INCREASE IN COVERAGE LATE IN THE WEEK AND CONTINUE THROUGH THE  
WEEKEND AS AN APPROACHING UPPER TROUGH BRINGS INCREASING  
MOISTURE TO THE CAROLINAS.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
AS OF 1030 AM WEDNESDAY...BASICALLY LOOKING AT SUMMERTIME  
CONVECTION, WITH THE FA IN GENERAL THUNDER VIA SPC, FOR THIS  
AFTN INTO THE EVENING. THE SEA BREEZE AND WHAT'S LEFT OF THE  
STALLED FRONTAL BOUNDARY WILL PROVIDE LIFT TO HELP INITIATE  
CONVECTION ONCE CONVECTIVE TEMPS ARE REACHED. THE UPPER CLOSED  
LOW OVER THE NE STATES IS ON THE MOVE AND WILL BE OPENING UP  
INTO A S/W TROF AS IT LIFTS OFF TO THE NE LATER TODAY THRU THU.  
THUS DO NOT EXPECT ANY INFLUENCE FROM THIS FEATURE, IN FACT  
S/W RIDGING ALOFT WILL BECOME THE PLAYER ACROSS THE FA LATER  
TODAY THRU THU AND INTO FRI. WITH NOT NEARLY AS WIDESPREAD  
FOG/LOW STRATUS COMPARED TO THE PREVIOUS 2 MORNINGS, THOSE  
CONVECTIVE TEMPS SHOULD BE MET BY MIDDAY OR EARLY AFTN. POPS  
WILL GENERALLY BE IN THE LOW CHANCE CATEGORY.  
 
PREVIOUS.......................................................  
AS OF 300 AM WEDNESDAY...PREDAWN FOG EXPECTED AND COULD BECOME  
LOCALLY DENSE INLAND WHERE DEWPOINT DEPRESSIONS ARE MINIMIZED.  
FORECAST SOUNDINGS SHOW THAT THIS MOISTURE IS SHALLOW AND MIXING  
OUT WILL BE RAPID AFTER SUNRISE. WESTERLY FLOW AROUND UPPER LOW  
IN EASTERN NY HAS PROVIDED A DEEP LAYER OF DRY AIR. THIS WILL  
COME TO BEAR WITH THE AFTERNOON'S PROSPECTS FOR CONVECTION. COLD  
FRONT STALLED TO OUR WEST WASHES OUT AND WON'T REALLY BE A  
PLAYER IN WEATHER TODAY LOCALLY. THE SEA BREEZE WILL ONCE AGAIN  
PROVIDE MOISTURE AND LIFT AND COULD CERTAINLY SPAWN A STORM OR  
TWO, BUT LIKELY NOT WITH THE GUSTO PORTRAYED IN THE WRF. THE GFS  
SHOWS SOME SCANT CONVECTION MAINLY OVER SC COASTAL ZONES AND  
THIS SEEMS QUITE PLAUSIBLE. HAVE LEFT THE 20 POPS/SLIGHT CHANCE  
INTO COASTAL NC IN DEFERENCE TO BOTH CONTINUITY AND THE SKILLFUL  
VERIFICATION OF THE WRF AS OF LATE. HIGHS TODAY WILL BE IN THE  
LOW 90S AND LOWS TONIGHT IN THE LOW TO MID 70S. FOG MAY RETURN  
AGAIN TONIGHT ESPECIALLY WHERE HIGHER DEWPOINTS POOL AND/OR  
RAINFALL OCCURS.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/
 
 
AS OF 300 AM WEDNESDAY...BERMUDA HIGH PRESSURE WILL REMAIN  
CENTERED ABOUT 500 MILES OFF THE SOUTHEAST COAST. SEVERAL  
INDIVIDUAL SHORTWAVES ACROSS NEBRASKA, MISSISSIPPI, AND THE  
GREAT LAKES WILL PHASE INTO A POSITIVELY TILTED UPPER TROUGH  
JUST WEST OF THE APPALACHIANS BY LATE FRIDAY. THE INCREASING  
DEEP-LAYER SOUTHWESTERLY WIND AHEAD OF THIS TROUGH SHOULD  
ADVECT GULF MOISTURE INTO THE CAROLINAS WITH PRECIPITABLE WATER  
VALUES INCREASING ABOVE 2.0 INCHES.  
 
850 MB TEMPS AROUND +18C BOTH DAYS SHOULD GUARANTEE HIGHS WILL  
REACH OR EXCEED 90 DEGREES FOR ALL BUT THE IMMEDIATE COAST. A  
MODEL BLEND APPEARS REASONABLE FOR BOTH HIGHS AND LOWS, ALTHOUGH  
I'VE NUDGED HIGHS DOWN A DEGREE FOR MOST SPOTS GIVEN RECENT  
VERIFICATION NUMBERS SHOWING MOS HAS BEEN RUNNING WARM IN MOST  
LOCATIONS.  
 
SOME RESIDUAL DRY MID-LEVEL AIR AND A MODEST SUBSIDENCE  
INVERSION WILL HELP KEEP THUNDERSTORM COVERAGE GENERALLY 20  
PERCENT OR LESS ON THURSDAY. BY FRIDAY INCREASING MOISTURE AND  
THE EROSION OF THE INVERSION ALOFT SHOULD ALLOW FOR GREATER  
COVERAGE, WITH POPS AROUND 40 PERCENT IN OUR LATEST FORECAST.  
SHEAR ACROSS THE 0-6 KM LAYER SHOULD REMAIN WEAK, FAVORING  
MAINLY DISORGANIZED SINGLE CELL THUNDERSTORMS.  
 

 
   
LONG TERM /FRIDAY THROUGH TUESDAY/
 
 
AS OF 300 PM TUESDAY...A COLD FRONT STALLING IN THE VICINITY  
THIS WEEKEND WILL BE THE MOST SIGNIFICANT FEATURE OF THE  
EXTENDED. THIS FRONT WILL BE DRIVEN SE BY A SHORTWAVE ROTATING  
THROUGH THE MID- ATLANTIC STATES AND THEN OFF INTO NEW ENGLAND  
BY EARLY NEXT WEEK. AS THIS OCCURS, IT CAUSES HEIGHT FALLS  
LOCALLY AND DRIVES THE SURFACE BOUNDARY INTO THE EASTERN  
CAROLINAS. WITH HIGH PRESSURE BOTH AT THE SURFACE AND ALOFT  
POSITIONED OFFSHORE, IT IS LIKELY THIS BOUNDARY WILL STALL  
BEFORE DISSIPATING, AND A CLEAN FROPA IS NOT EXPECTED. THIS  
SUGGESTS AN UNSETTLED WEEKEND WITH CONVERGENCE ALONG THE FRONT  
AND SOMEWHAT STEEPENED LAPSE RATES FAVORING SCATTERED TO  
WIDESPREAD CONVECTION IN AN AIRMASS CHARACTERIZED BY PWATS  
CLIMBING TOWARDS 2.25 INCHES. NUMERICAL GUIDANCE HAS LKLY POP  
FOR THE WKND AND FEEL THIS IS WARRANTED ACROSS THE ENTIRETY OF  
THE CWA. ALTHOUGH THE FRONT WILL DISSIPATE INTO EARLY NEXT WEEK,  
A VERY MOIST AIRMASS WILL STILL SUPPORT BETTER THAN CLIMO POP  
CHANCES MONDAY BEFORE SUBSIDENCE BEHIND THE DEPARTING SHORTWAVE  
COMBINED WITH BULGING HEIGHTS ALOFT BRING CONVECTIVE CHANCES  
BACK TOWARDS SEASONABLE NORMS. THIS SUGGESTS THAT FRIDAY MAY BE  
THE LEAST ACTIVE OF AN OTHERWISE CONVECTIVELY ROBUST PERIOD.  
 
HIGHS INITIALLY WILL BE SLIGHTLY ABOVE CLIMO FRIDAY AND SATURDAY,  
BUT ARE FORECAST TO FALL TO BELOW NORMAL SUNDAY AND MONDAY THANKS TO  
INCREASED CLOUDS/SHOWERS AND LOWERED THICKNESSES. A RETURN TO  
SEASONABLE TEMPS MAY DEVELOP BY TUESDAY. MINS THROUGH THE PERIOD  
WILL LIKELY REMAIN ABOVE CLIMO AS DIURNAL RANGES SHRINK.  
 

 
   
AVIATION /15Z WEDNESDAY THROUGH SUNDAY/
 
 
AS OF 12Z...FOG AND LOW CLOUDS ARE NOT NEARLY AS WIDESPREAD  
THIS MORNING AS LAST MORNING. ANY VISIBILITY RESTRICTIONS SHOULD  
BE GONE BEFORE 13Z WITH VFR CONDITIONS EXPECTED THROUGH THE  
MORNING HOURS. DAYTIME CUMULUS CLOUDS WITH BASES GENERALLY  
040-050 MAY GROW DEEP ENOUGH TO PRODUCE ISOLATED SHOWERS ALONG  
THE SEABREEZE FRONT AT THE COAST THIS AFTERNOON. THE LATEST  
HIGH-RES MODELS INDICATE THIS POTENTIAL SHOULD PEAK IN THE  
19-22Z TIMEFRAME.  
 
EXTENDED OUTLOOK...MAINLY VFR CONDITIONS EXPECTED THURSDAY  
EXCEPT FOR AREAS OF PRE-DAWN GROUND FOG. THE POTENTIAL FOR  
THUNDERSTORMS WITH BRIEF IFR CONDITIONS BECOMES MORE LIKELY BY  
FRIDAY THROUGH SUNDAY.  
 

 
   
MARINE
 
 
NEAR TERM /THROUGH TONIGHT/...  
AS OF 1045 AM WEDNESDAY...SOUTHWEST FLOW AROUND 10 KT EXCEPT  
INCREASING TO 10-15 KT ESPECIALLY NEAR SHORE THIS AFTN AND  
EVENING DUE TO THE SEA BREEZE CIRCULATION CYCLE. A LOW-LEVEL  
SOUTHWESTERLY JET OVER THE AREA WATERS IS EXPECTED TONIGHT INTO  
THU MORNING AND SHOULD KEEP SW WINDS IN THE 10 TO 15 KT OR  
POSSIBLY AROUND 15 KT DEPENDING ON IT'S STRENGTH. SIGNIFICANT  
SEAS WILL RUN CLOSE TO A SOLID 3 FT WITH POSSIBLE 4 FOOTERS  
TONIGHT THRU EARLY AM THU.  
 
PREVIOUS......................................................  
AS OF 300 AM WEDNESDAY...FRONT TO OUR WEST WASHES OUT TODAY AND  
LEAVE BEHIND SOME WEAK TROUGHINESS. HIGH PRESSURE WILL STILL BE  
PRESENT IN THE WEST ATLANTIC AND THE TWO TOGETHER WILL MAINTAIN  
A SOUTHWESTERLY FLOW THAT WILL TEND TOWARDS THE 10-15KT RANGE.  
IN THE ABSENCE OF ANY SIGNIFICANT SWELL ENERGY SEAS WILL HOVER  
AROUND 3 FT. LOW LEVEL JETTING STRENGTHENS OFFSHORE TONIGHT AND  
SOME 20KT GUSTS SHOULD BECOME COMMON. THIS COULD SHORTEN WAVE  
PERIOD SLIGHTLY BUT OTHERWISE SEAS ARE NOT EXPECTED TO CHANGE  
SIGNIFICANTLY.  
 
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...  
AS OF 300 AM WEDNESDAY...BERMUDA HIGH PRESSURE WILL REMAIN  
PERFECTLY STATIONARY ABOUT 500 MILES OFF THE SOUTHEAST COAST.  
LOW PRESSURE ACROSS THE GREAT LAKES AND A WEAK LEE-SIDE TROUGH  
IN THE NC/VA FOOTHILLS WILL MAINTAIN A SOUTHWESTERLY WIND  
THROUGH THE PERIOD. AS THE LOW MOVES INTO THE EASTERN GREAT  
LAKES FRIDAY AND FRIDAY NIGHT, OUR PRESSURE GRADIENT WILL  
TIGHTEN AND SUPPORT STRONGER WIND SPEEDS OVER 15 KNOTS. THIS IS  
ALSO WHEN THE TYPICAL 2-3 FOOT SEAS SHOULD BUILD TOWARD 4 FEET.  
 
ISOLATED SHOWERS AND THUNDERSTORMS ON THURSDAY SHOULD BECOME A  
LITTLE MORE WIDESPREAD ON FRIDAY AS MOISTURE DEEPENS ACROSS THE  
AREA.  
 
LONG TERM /SATURDAY THROUGH SUNDAY/...  
AS OF 300 PM TUESDAY...HIGH PRESSURE OFFSHORE AND A SLOWLY  
APPROACHING COLD FRONT FROM THE NW WILL SUBTLY PINCH THE  
GRADIENT THROUGH THE WEEKEND CREATING PERSISTENT AND GRADUALLY  
INCREASING SW WINDS. WIND SPEEDS WILL INCREASE TO 15-20 KTS  
SATURDAY AND SUNDAY. AS THE FRONT STALLS JUST INLAND FROM THE  
WATERS LATE SUNDAY, A SHIFT IN DIRECTION TO THE WSW IS LIKELY,  
ALONG WITH A WEAKENING IN WIND SPEEDS. ALTHOUGH A SE SWELL WILL  
EXIST IN THE SPECTRUM EACH DAY, WIND WAVES WILL INCREASINGLY  
BECOME DOMINANT FROM THE SW. SIGNIFICANT SEAS WILL BUILD TO AS  
HIGH AS 3-5 FT SUNDAY.  
 

 
   
CLIMATE
 
 
AS OF 300 AM WEDNESDAY...ALTHOUGH RAINFALL IN WILMINGTON OVER  
THE PAST 10 DAYS HAS NOT BEEN SUBSTANTIAL, EXCEPTIONALLY WET  
WEATHER IN MAY AND JULY IS STILL MAINTAINING 2018 AS THE WETTEST  
YEAR IN HISTORY. IN FACT THROUGH YESTERDAY WE'RE STILL RUNNING  
OVER 10 INCHES AHEAD OF THE NEXT WETTEST YEAR! ANNUAL AVERAGE  
RAINFALL FOR WILMINGTON IS 57.61 INCHES.  
 
WETTEST YEARS IN WILMINGTON'S HISTORY (JAN 1 THROUGH AUGUST 14TH)  
 
RANK RAINFALL & YEAR  
1 60.78" IN 2018  
2 49.99" IN 1966  
3 48.86" IN 1886  
4 48.11" IN 1969  
5 46.23" IN 1973  
 
ASSUMING AVERAGE RAINFALL FOR THE REMAINDER OF THE YEAR WE  
SHOULD APPROACH THE ALL-TIME WETTEST COMPLETE YEAR IN  
WILMINGTON'S HISTORY, 1877, WHEN 83.65 INCHES OF RAIN FELL.  
 

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

 
 

 
SYNOPSIS...TRA  
NEAR TERM...DCH/MBB  
SHORT TERM...TRA  
LONG TERM...JDW  
AVIATION...TRA  
CLIMATE...TRA  
 
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