231  
FXUS64 KMEG 201129  
AFDMEG  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEMPHIS TN  
629 AM CDT SUN AUG 20 2017  
   
UPDATE
 
 
UPDATED FOR THE 12Z AVIATION DISCUSSION  
 

 
   
PREV DISCUSSION
 
/ISSUED 350 AM CDT SUN AUG 20 2017/  
 
DISCUSSION...  
THE SUBTROPICAL RIDGE CONTINUES TO BUILD OVER THE SOUTHERN CONUS  
THIS MORNING WITH A BROAD RIDGE AXIS EXTENDING FROM WEST TO EAST  
FROM THE SOUTHERN PLAINS TO THE WESTERN ATLANTIC. THERE IS A  
WEAKNESS IN THIS RIDGE OVER THE CENTRAL GULF OF MEXICO WHERE A  
WELL-DEFINED UPPER-LEVEL CYCLONE CONTINUES TO MEANDER IN A GENERAL  
WESTERLY DIRECTION. THE FLOW ALOFT ON THE POLEWARD SIDE OF THE  
RIDGE IS QUASI-ZONAL WITH SEVERAL SHORTWAVE TROUGHS EMBEDDED  
WITHIN THE FLOW. AN MCS IS NOTED OVER THE MIDWEST BUT IT SHOULD  
HAVE NO IMPACT FOR US OTHER THAN SOME CIRRUS BLOWOFF DURING THE  
DAY. OTHERWISE, THE SYNOPTIC PATTERN IS RATHER BENIGN FOR OUR NECK  
OF THE WOODS.  
 
AS THE RIDGE CONTINUES TO BUILD TODAY, MID-LEVEL TEMPERATURES WILL  
WARM SLIGHTLY. THIS WILL BE REFLECTED BY AFTERNOON HIGHS IN THE  
LOW/MID 90S. LOW-LEVEL MOISTURE IS PROGGED TO MIX OUT OVER MUCH  
OF WEST TN AND NORTHEAST MS BUT WILL REMAIN IN PLACE ALONG AND  
WEST OF THE MISSISSIPPI RIVER. THE COMBINATION OF THIS HEAT AND  
HUMIDITY WILL YIELD HEAT INDICES AT OR JUST ABOVE 105 DEGREES  
FROM JONESBORO SOUTH TO CLARKSDALE, EXTENDING AS FAR EAST AS  
MEMPHIS AND BATESVILLE. A HEAT ADVISORY IS IN EFFECT FROM 11A-7P  
TODAY TO ACCOUNT FOR THESE CONDITIONS. ISOLATED DIURNAL CONVECTION  
IS EXPECTED TODAY BUT THE ANTICIPATED COVERAGE DOESN'T WARRANT  
POPS ABOVE 20%. ONCE WE LOSE SURFACE HEATING, ANY ONGOING  
CONVECTION SHOULD QUICKLY DISSIPATE.  
 
HOT AND HUMID CONDITIONS WILL CONTINUE MONDAY AND TUESDAY BUT LOW-  
LEVEL MOISTURE IS EXPECTED TO TREND DOWN SLIGHTLY, KEEPING  
FORECAST HEAT INDICES BETWEEN 100-105 DEGREES BOTH DAYS. WILL  
CONTINUE TO MONITOR THE DEWPOINT TRENDS FOR THE HEAT ADVISORY  
POTENTIAL IN THE COMING DAYS. OTHERWISE, EXPECT HIGHS IN THE  
LOW/MID 90S EACH AFTERNOON.  
 
MONDAY'S SKY COVER FORECAST CONTINUES TO BE THE BIG-TICKET ITEM  
FOR THOSE WISHING TO VIEW THE SOLAR ECLIPSE. DIURNAL CUMULUS  
CLOUDS EXPECTED TO DEVELOP BY MIDDAY, EVENTUALLY GROWING INTO A  
TYPICAL CU FIELD DURING THE AFTERNOON. GIVEN THE ECLIPSE TIMING  
BETWEEN 1-2 PM, THIS CU FIELD WILL LIKELY BE IN PLACE BUT  
SHOULDN'T BE TOO SIGNIFICANT. THAT SAID, THERE MAY BE SOME AREAS  
WHERE VIEWING CONDITIONS ARE LESS THAN OPTIMAL. HOWEVER,  
FORECASTING THESE EXACT LOCATIONS WILL BE DIFFICULT UNTIL MONDAY  
MORNING. A FEW DIURNAL SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE  
ON MONDAY, MAINLY OVER THE WESTERN HALF OF THE CWA. BY TUESDAY,  
RAIN CHANCES BEGIN TO INCREASE AS A SHORTWAVE TROUGH MOVES INTO  
THE OHIO VALLEY AND WEAKENS THE RIDGE ALOFT.  
 
THIS TROUGH WILL PUSH A COLD FRONT INTO THE MID-SOUTH TUESDAY  
NIGHT INTO WEDNESDAY. SHOWERS AND THUNDERSTORMS ARE LIKELY WITH  
THIS COLD FRONT WITH POPS PEAKING WEDNESDAY MORNING. RAIN CHANCES  
WILL QUICKLY TAPER OFF THURSDAY EVENING WITH COOLER AND DRIER  
CONDITIONS ANTICIPATED FOR THURSDAY AND FRIDAY. AFTERNOON HIGHS  
ARE PROGGED TO BE IN THE LOW/MID 80S FOR THE END OF THE WORK WEEK.  
LOW TEMPERATURES WILL BE IN THE LOW/MID 60S FOR MUCH OF THE CWA  
WITH SOME AREAS EXPECTED TO DIP INTO THE UPPER 50S FRIDAY MORNING.  
 
THE SYNOPTIC PATTERN LOOKS TO REMAIN SOMEWHAT PROGRESSIVE LATE IN  
THE FORECAST PERIOD WITH THE NEXT TROUGH PROGGED TO AFFECT THE  
MID-SOUTH OVER THE WEEKEND. POPS OF 20-30% WERE INCLUDED ACROSS  
PORTIONS OF THE CWA DURING THIS PERIOD WITH TEMPERATURES REMAINING  
SEVERAL DEGREES BELOW CLIMATOLOGY.  
 
JOHNSON  
 

 
   
AVIATION
 
 
12Z TAF CYCLE  
 
VFR CONDITIONS SHOULD PERSIST FOR MUCH OF THE FORECAST PERIOD.  
SOME ISOLATED THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON BUT  
COVERAGE WILL BE VERY LIMITED. SOME FOG MAY DEVELOP IN THE KMKL  
AREA OVERNIGHT. WINDS WILL BE LIGHT AND MAINLY FROM THE SOUTH FOR  
MUCH OF THE FORECAST PERIOD.  
 
ARS  
 

 
   
MEG WATCHES/WARNINGS/ADVISORIES
 
 
AR...HEAT ADVISORY FROM 11 AM THIS MORNING TO 7 PM CDT THIS EVENING  
FOR CRAIGHEAD-CRITTENDEN-CROSS-LEE AR-PHILLIPS-POINSETT-ST.  
FRANCIS.  
 
MO...NONE.  
MS...HEAT ADVISORY FROM 11 AM THIS MORNING TO 7 PM CDT THIS EVENING  
FOR COAHOMA-DESOTO-PANOLA-QUITMAN-TALLAHATCHIE-TATE-TUNICA-  
YALOBUSHA.  
 
TN...HEAT ADVISORY FROM 11 AM THIS MORNING TO 7 PM CDT THIS EVENING  
FOR SHELBY.  
 

 
 

 
 
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