476  
FXUS64 KJAN 211737  
AFDJAN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JACKSON MS  
1237 PM CDT MON AUG 21 2017  
   
UPDATE
 
 
UPDATED FOR 18Z AVIATION DISCUSSION  
 

 
   
AVIATION
 
 
18Z TAF DISCUSSION:  
ASIDE FROM ISOLATED SHRA/TSRA ACTIVITY AND THE POTENTIAL FOR  
PATCHY AREAS OF EARLY MORNING FOG/STRATUS, VFR CONDITIONS WILL  
PREVAIL THROUGH TUESDAY. /EC/  
 

 
   
DISCUSSION
 
 
ANOTHER HOT AND HUMID DAY IS WELL UNDERWAY WITH HEAT INDICES  
ALREADY REACHING 105 IN SOME CASES. EXPECT SHALLOW CONVECTION AND  
CUMULUS DEVELOPMENT TO SLOW DOWN HEATING SOME, AND THERE WILL  
EVEN BE SLIGHT DISRUPTION TO HEATING DUE TO EFFECTS FROM THE  
ECLIPSE, BUT GIVEN CURRENT TRENDS HAVE UPGRADED THE HEAT THREAT  
TO ELEVATED LOCATIONS MAINLY ALONG/NORTH OF I-20. LOCATIONS  
FARTHER SOUTH SHOULD SEE MORE EFFECTS OF CONVECTION HELPING  
MITIGATE THE HEAT DANGER SLIGHTLY COMPARED TO AREAS FARTHER NORTH.  
/EC/  
 
PRIOR DISCUSSION BELOW:  
 
TODAY AND TONIGHT: BETWEEN THE TUTT LOW IN THE GULF OF MEXICO AND  
THE MID LEVEL WAVE DIVING THROUGH THE MID MS VALLEY, THE RIDGE THAT  
HAS BEEN OVER THE FORECAST AREA WILL BEGIN BREAKING DOWN A BIT  
TODAY. WHILE CONVECTION WILL STILL BE HARD TO COME BY OVER CENTRAL  
SECTIONS ALONG THE RIDGE AXIS, AROUND THE PERIPHERY OVER THE SOUTH,  
WEST AND NORTH A SLIGHT INCREASE IN CONVECTIVE COVERAGE WILL BE SEEN  
DURING THE AFTERNOON AND EARLY EVENING.  
 
REGARDLESS OF THE INCREASED CONVECTION, IT WILL STILL BE HOT.  
SIMILAR TO YESTERDAY, MID 90S LOOKS LIKE A GOOD BET AWAY FROM THE  
CONVECTION. HEAT INDICES LOOK TO APPROACH 105 IN THE ARKLAMISS  
DELTA, BUT SLIGHTLY LOWER DEWPOINTS AND SCATTERED CONVECTION SHOULD  
KEEP VALUES FROM GETTING TOO HIGH OR LASTING TOO LONG./26/  
 
TUESDAY THROUGH NEXT MONDAY MORNING: OVERALL EXPECT A HOT & HUMID  
START TO THE EARLY WEEK BEFORE A COLD FRONT MOVES DOWN AROUND  
MID-WEEK THAT WILL HELP BRING INCREASING CONVECTION & LESS  
OPPRESSIVE CONDITIONS AREAWIDE. COOLER THAN NORMAL TEMPERATURES  
ARE EXPECTED IN THE WAKE. ON TUESDAY, ALOFT A STRONG TROUGH WILL  
BE DIGGING THROUGH THE GREAT LAKES & SOUTHERN CANADA & AN TUTT LOW  
DRIFTING WESTWARD OVER THE NORTH-NORTHWESTERN GULF OF MEXICO. AT  
THE SURFACE, A STRONG SURFACE LOW & ATTENDANT COLD FRONT WILL BE  
STRETCHED ACROSS THE GREAT LAKES INTO THE MID TO LOWER MISSISSIPPI  
VALLEY. THIS WILL HELP SPARK INCREASING CONVECTION OFF TO OUR  
NORTHWEST OVER THE EASTERN PLAINS & MID-MISSISSIPPI VALLEY. AS THE  
MID-LEVEL RIDGE BEGINS TO WEAKEN ITS GRIP, TEMPERATURES WILL  
SLOWLY BEGIN TO COOL SOMEWHAT. IT WILL STILL BE A WARM & HUMID  
AFTERNOON WITH HEAT INDICES MAINLY IN THE 100-103 DEGREE RANGE OR  
SO. HOWEVER, THE HIGHER VALUES WOULD LIKELY ONLY BE REACHED VERY  
BRIEFLY DUE TO INCREASING CONVECTION CHANCES, SO NO NEED TO  
MENTION ANYTHING IN THE HWO/GRAPHICS. ANY CONVECTION WILL LIKELY  
BE TIED TO INCREASING MOISTURE TRANSPORT/LIFT FROM ANY SEABREEZE  
INFLUENCE & LESS TIED TO THE TUTT AS IT BEGINS TO WEAKEN & STRETCH  
OUT OVER THE WESTERN GULF. IT COULD PROVIDE SOME LIFT DUE TO SOME  
JET DYNAMICS ALOFT. EXPECT SCATTERED CONVECTION & CLOUDS TO  
SPREAD IN FROM SOUTHEAST TO NORTHWEST INTO THE AFTERNOON.  
 
AS THE TROUGH SWINGS THROUGH THE GREAT LAKES & SOUTHERN CANADA, THE  
SURFACE LOW & ASSOCIATED COLD FRONT WILL BEGIN TO MOVE SOUTHEAST AS  
HEIGHTS BEGIN TO FALL ALOFT OVER THE AREA. THIS WILL HELP INCREASE  
CHANCES FOR MORE WIDESPREAD CONVECTION ON WEDNESDAY. THE TUTT OVER  
THE WESTERN GULF WILL BECOME MORE DIFFUSE & STRETCHED BUT THIS WILL  
HELP SOME INCREASING LIFT DUE TO JET DYNAMICS ALOFT. WITH NEARLY 2  
INCH PWS, EXPECT WIDESPREAD SHOWERS & THUNDERSTORMS ACROSS THE  
REGION. BEST CHANCES LOOK TO REMAIN IN THE TO OUR NORTH-NORTHEAST AS  
THAT'S WHERE THE BEST MOISTURE TRANSPORT & CONVERGENCE WILL REMAIN.  
RIGHT NOW NOT EXPECTING MUCH IN THE WAY OF MORE ORGANIZED  
CONVECTION, BUT THERE COULD BE SOME DECENT MID-LEVEL LAPSE RATES &  
VERTICAL TOTALS FOR SOME STRONG STORMS & ANY STORMS THAT ORIENT  
TOWARDS THE SOUTHEAST. HEAVY DOWNPOURS ARE POSSIBLE, BUT STORMS  
SHOULD BE MOVING ENOUGH TO LIMIT HEAVY RAINFALL POTENTIAL. OVERALL,  
DUE TO INCREASED CLOUDS & WIDESPREAD CONVECTION, THIS WILL HELP OUR  
AREA COOL CLOSER TO NORMALS, POSSIBLY A LITTLE COOLER THAN NORMAL IN  
THE HIGHWAY 82 CORRIDOR.  
 
AS A 1028MB SURFACE HIGH BUILDS INTO THE GREAT LAKES, STRONG RIDGING  
WILL BUILD IN OUR AREA. SOME DRIER AIR WILL FILTER IN, WITH  
DEWPOINTS IN THE MID-UPPER 60S & POSSIBLY INTO THE LOWER 60S IN THE  
NORTH, EXPECT MUCH NICER CONDITIONS GOING INTO LATE WEEK. AS THE  
COLD FRONT PUSHES THROUGH THURSDAY, THERE COULD BE SOME SCATTERED  
CONVECTION BUT THIS WILL MOVE THROUGH BY THURSDAY INTO FRIDAY.  
EXPECT COOLER THAN NORMAL HIGHS IN THE MID-UPPER 80S AREAWIDE, WITH  
LESS CONVECTION CHANCES. THESE CONVECTION CHANCES WILL SLOWLY RISE  
INTO THE WEEKEND. AS THAT COLD FRONT STALLS OUT & SLOWLY LIFTS NORTH  
& MORE MOISTURE ADVECTS IN (POSSIBLY 2-2.25 INCHES BY LATE WEEKEND  
INTO EARLY NEXT WEEK) SOME MORE WIDESPREAD RAIN & STORM CHANCES AND  
MUCH COOLER THAN NORMAL HIGHS ARE POSSIBLE. HIGHS COULD POTENTIALLY  
BE AS MUCH AS 5+ DEGREES BELOW NORMAL. IN ADDITION, REMNANTS OF  
HARVEY LOOK TO CONTINUE TO BE SHUNTED TO OUR SOUTHWEST TOWARDS THE  
TEXAS & MEXICO COASTLINE BUT THIS WILL HAVE TO BE MONITORED. /DC/  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
JACKSON 94 74 93 75 / 9 9 26 14  
MERIDIAN 94 74 92 75 / 9 11 28 19  
VICKSBURG 94 74 93 74 / 10 8 20 12  
HATTIESBURG 92 74 92 74 / 39 15 43 22  
NATCHEZ 91 73 91 74 / 14 10 27 12  
GREENVILLE 95 75 93 75 / 10 8 16 23  
GREENWOOD 95 75 93 75 / 10 8 20 18  
 

 
   
JAN WATCHES/WARNINGS/ADVISORIES
 
 
MS...NONE.  
LA...NONE.  
AR...NONE.  
 

 
 

 
 
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