845  
FXUS62 KILM 131437  
AFDILM  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON NC  
1037 AM EDT THU AUG 13 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE ACROSS THE WESTERN ATLANTIC WILL MAINTAIN SOUTHERLY  
WINDS, ALONG WITH SEASONABLY WARM AND HUMID CONDITIONS. WEAK LOW  
PRESSURE WILL PRODUCE GREATER COVERAGE OF STORMS INTO THE  
WEEKEND.  
 

 
   
UPDATE
 
 
FORECAST ON TRACK AS WEAK LOW JUST EAST AND LOW LEVEL TROUGH,  
EVIDENT RUNNING FROM SW TO NE JUST INLAND OF THE COAST, DRIFTS  
NORTHEAST THROUGH TODAY ALONG WITH UPPER LEVEL LOW. FOCUS WILL  
REMAIN ON LOCALIZED FLOODING IN STORM DEVELOPMENT TODAY WITH  
WEAK STEERING FLOW AND VERY HIGH PCP WATER VALUES.  
 

 
   
NEAR TERM /THROUGH FRIDAY/
 
 
GOES-EAST IN GEOSTATIONARY ORBIT, PRESENTLY SAMPLING A STREAM OF  
PRECIPITABLE WATER VALUES IN EXCESS OF 2 INCHES STREWN ABOUT THE  
AREA, AND LIFTED INDICES OF -1 TO -2. AN UPPER WEAKNESS WITH EQUALLY  
FAINT CYCLONIC CIRCULATION WAS SUPPORTING DEEP CONVECTION OFFSHORE.  
THIS FEATURE IS EXPECTED TO DRIFT NE TO OFFSHORE OF NC OUTER BANKS  
BY FRIDAY, AS AN UPPER TROUGH WEST OF THE AREA SLOWLY MIGRATES EAST.  
 
MARINE OUTFLOWS INTO UNSTABLE AIR WITH LIGHT STEERING CURRENTS WILL  
LEAD TO ISOLATED WATERSPOUTS BENEATH RAPIDLY DEVELOPING CONVECTION,  
SOME OF WHICH COULD MOVE ASHORE LATER THIS MORNING. THIS MAY ENHANCE  
COASTAL CONVERGENCE, LEADING TO DECENT SHOWERS CHANCES FOR COASTAL  
ZONES, ESPECIALLY CAPE FEAR REGION THIS MORNING.  
 
NEW CONVECTION INLAND, ASIDE FROM THE COASTAL ACTIVITY, SHOULD BEGAN  
TO FLARE UP AROUND 1 PM, SCATTERING THE LANDSCAPE THROUGH EARLY  
EVENING WITH SHOWERS AND TSTMS, RAIN BRIEFLY HEAVY IN SPOTS. THERE  
IS NO DISCERNIBLE MOTION TO STORMS TODAY, AND PERIPHERAL  
OUTFLOWS WITH NEWLY SPAWNED CONVECTION WILL OUTPACE ANY SINGLE  
STORM MOVEMENT. THE STORM STAGNANCY AND HIGH PWAT INDICES MAY  
LEAD TO EXCESS WATER IN SPOTS, AND PONDING ON HIGHWAYS.  
 
FRIDAY SIMILAR, EXCEPT THE UPPER WEAKNESS OFFSHORE MAY HAVE LESS  
IMPACT OVER THE COASTAL INTERIOR, AS IT BECOMES POSITIONED SOUTH OF  
CAPE LOOKOUT, BUT STILL CLOSE ENOUGH FOR COASTAL SHOWERS FRIDAY  
MORNING. BECAUSE OF CLOUDS AND RAIN, MAX-T NEAR TO A COUPLE DEGREES  
BELOW NORMAL THIS PERIOD.  
 

 
   
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/
 
 
WEAK UPPER LOW WILL PUSH OFF TO THE NE ON FRIDAY EVENING AS A DEEPER  
UPPER-TROUGH APPROACHES THE AREA FROM THE WEST. THUNDERSTORM  
COVERAGE WILL BE SCATTERED TO WIDESPREAD ON SATURDAY AS THE APEX OF  
THE TROUGH AND AN ASSOCIATED FRONTAL BOUNDARY APPROACH THE SOUTHERN  
APPALACHIANS. LOCALLY, WIND FIELD THROUGHOUT THE SOUNDING SHOWS VERY  
LITTLE SPEED OR DIRECTIONAL SHEAR AND STORM MOTION WILL BE ON THE  
ORDER OF 10-20 KNOTS. WITH THESE PARAMETERS, IT IS LIKELY THAT  
SEVERE WEATHER WILL BE LIMITED TO ONE OR TWO EXCEPTIONAL PERFORMERS  
WITH A RELATIVELY LOW FLOODING THREAT. WITH THE UPPER-LEVEL ENERGY  
AVAILABLE AND THE MOISTURE-LADEN ATMOSPHERE AHEAD OF THE FRONT,  
EXPECT WIDESPREAD THUNDERSTORM COVERAGE TO LINGER INTO THE OVERNIGHT  
HOURS.  
 

 
   
LONG TERM /SUNDAY THROUGH WEDNESDAY/
 
 
UPPER TROUGH WILL SHIFT EASTWARD ON SUNDAY AND PUSH A WEAK FRONTAL  
BOUNDARY THROUGH THE AREA. THUNDERSTORM ACTIVITY SHOULD BE LIMITED  
TO THE COAST ON SUNDAY AFTERNOON WITH AFTERNOON STORMS BATTLING MUCH  
DRIER MID- AND UPPER-LEVEL AIR. MOSTLY QUIET ON MONDAY BEFORE THE  
UPPER TROUGH DIGS SOUTHWARD OVER THE CENTRAL PART OF THE CONUS AGAIN  
ON TUESDAY. THIS WILL BRING A PATTERN OF ELEVATED STORM CHANCES EACH  
AFTERNOON THROUGH THE MIDDLE OF NEXT WEEK. TEMPERATURES WILL  
GENERALLY REMAIN IN THE UPPER 80S TO NEAR 90, RIGHT AT THE CLIMO  
MARK FOR MID-AUGUST.  
 

 
   
AVIATION /14Z THURSDAY THROUGH MONDAY/
 
 
VCSH AND VCTS MUCH OF THIS 12Z TAF CYCLE, GENERALLY ISOLATED TO  
SCATTERED IN COVERAGE, BUT IMPACTING MOST TERMINALS TODAY.  
A DISTURBANCE LOCATED OFFSHORE OF THE CAPE FEAR REGION WILL  
SUSTAIN A CHANCE OF SHRA AND TSTM AT COASTAL TERMINALS THROUGH  
THE PERIOD. SOME RESIDUAL MVFR/BRIEF IFR FOG THIS MORNING MAY  
PERSIST THROUGH 13-14Z, THE THICKEST OF IT BEING AT THE MORE  
INLAND TERMINALS. WOULDN'T BE SURPRISED TO SEE BRIEF IFR IN AND  
AROUND STORMS THIS AFTERNOON. CONVECTION SETTLES DOWN AFTER  
SUNSET. THINK KFLO AND KLBT COULD SEE SOME PERSISTENT AREAS OF  
MVFR/IFR FOG BEFORE SUNRISE FRIDAY MORNING. FOG MAY ALSO FORM  
ALONG THE COAST, BUT NOT AS THICK.  
 
EXTENDED OUTLOOK...TSTMS, ISOLATED TO SCATTERED WILL CONTINUE  
THROUGH THE EXTENDED PERIOD. PATCHES OF MORNING FOG GENERALLY  
BETWEEN 8Z-11Z SHOULD BE EXPECTED, OR LOCALIZED MVFR STRATUS.  
WINDS OUTSIDE OF TSTMS SHOULD REMAIN LIGHT, AND SOUTHERLY.  
 

 
   
MARINE
 
 
TSTMS OFFSHORE POSING AN EARLY HAZARD OVER THE 0-20 NM WATERS, AS  
OUTFLOWS ARE APT TO BRING MORE TSTMS CLOSER TO SHORE THIS MORNING.  
ISOLATED WATERSPOUTS AND DANGEROUS CLOUD TO SEA LIGHTNING IS THE  
EXPECTATION THROUGH MOST OF MORNING, AND MARINERS SHOULD OBTAIN  
RADAR UPDATES BEFORE A VENTURE OUT. AWAY FROM TSTMS, LIGHT S WINDS  
IN GENERAL THIS PERIOD. THE SEA SPECTRUM WILL BE COMPOSED OF S-SSW  
WAVES 1 FOOT EVERY 4-5 SECONDS AND SE WAVES 1-2 FEET EVERY 9 SEC.  
ELEVATED TSTM COVERAGE SHOULD BE EXPECTED THROUGH FRIDAY AS AN UPPER  
LOW JUST OFFSHORE DRIFTS SLOWLY TO THE NE, OFFSHORE OF THE OUTER  
BANKS BY FRIDAY. STRONG TSTMS OFFSHORE COULD PRODUCE LOCALLY HIGHER  
SEAS THAN FORECAST, AND MAY BE LOCALIZED. LIGHTNING ACTIVITY TO RUN  
HIGH THIS PERIOD, WITH A HIGHER THAN NORMAL RISK OF A WATER  
SPOUT.  
 
SOUTHERLY BERMUDA-DRIVEN FLOW WILL CONTINUE THROUGH THE WEEKEND AND  
INTO EARLY NEXT WEEK. A WEAK FRONTAL BOUNDARY WILL APPROACH THE AREA  
THIS WEEKEND AND LEAD TO A TIGHTENING OF THE PRESSURE FIELD. SHOWERS  
AND THUNDERSTORMS APPEAR LIKELY THROUGH THE END OF THIS WEEK AND  
INTO THE WEEKEND. THE AFOREMENTIONED FRONT WILL PRODUCE WINDS 10-15  
KNOTS WITH GUSTS TO 20 KNOTS ON FRIDAY AND SATURDAY. THIS BRIEF  
FETCH WILL BE ENOUGH TO PUSH WAVES TO 2-4 FEET THROUGH THE WEEKEND.  
THE BOUNDARY IS EXPECTED TO MOVE THROUGH THE AREA ON SUNDAY AND MAY  
PRODUCE OFFSHORE WINDS FOR A BRIEF PERIOD INTO SUNDAY EVENING.  
THUNDERSTORM CHANCES DIMINISH ON SUNDAY NIGHT AND INTO MONDAY BEFORE  
RAMPING BACK UP AGAIN BY THE MIDDLE OF NEXT WEEK. SEAS WILL  
GENERALLY BE 2 TO 3 FEET WITH NO SIGNIFICANT SWELL NEXT WEEK.  
 

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

 
 

 
SYNOPSIS...ILM  
UPDATE...RGZ  
NEAR TERM...MJC  
SHORT TERM...21  
LONG TERM...21  
AVIATION...IGB  
MARINE...MJC/21  
 
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