942  
FXUS64 KJAN 301750  
AFDJAN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JACKSON MS  
1250 PM CDT SUN APR 30 2017  
 
...SEVERE WEATHER AND FLOODING TODAY AND POTENTIALLY AGAIN MID  
WEEK...  
   
UPDATE
 
 
UPDATED FOR 18Z AVIATION DISCUSSION  
 

 
   
AVIATION
 
 
18Z TAF DISCUSSION:  
A MIX OF VFR/MVFR/IFR CONDITIONS PREVAIL ACROSS THE ARKLAMISS THIS  
AFTERNOON AS SHOWERS AND THUNDERSTORMS MOVE ACROSS THE AREA. MOST  
OF THE THUNDERSTORMS ARE EFFECTING SITES ALONG AND EAST OF THE  
I-55 CORRIDOR AND THESE STORMS WILL CONTINUE TO MOVE EAST. THERE  
COULD BE SOME RE-DEVELOPMENT OF SHOWERS AND THUNDERSTORMS THIS  
AFTERNOON THAT MAY BRING ANOTHER ROUND OF MVFR/IFR TO  
JAN/HKS/MEI/HBG. EXPECT A COLD FRONT TO MOVE ACROSS THE AREA LATER  
THIS AFTERNOON INTO THE EVENING THAT WILL USHER IN DRIER AIR WITH  
MOST SITES BECOMING VFR. EXPECT VFR CONDITIONS TO PREVAIL THROUGH  
THE REMAINDER OF THE PERIOD. THE WINDS WILL BY GUSTY OUT OF THE SE  
BECOMING MORE SW AFTER FRONTAL PASSAGE./15/  
 

 
   
DISCUSSION
 
 
A COLD FRONT CURRENTLY EXTENDS GENERALLY JUST TO THE WEST OF THE  
MISSISSIPPI RIVER THIS MORNING WITH LINE OF QLCS THUNDERSTORMS  
MOVING ACROSS THE AREA. THERE HAVE BEEN MULTIPLE REPORTS OF  
TORNADOES ACROSS THE AREA THIS MORNING ALONG WITH NUMEROUS TORNADO  
DEBRIS SIGNATURES ON RADAR. THIS LINE OF STORMS WILL CONTINUE TO  
MOVE EAST ACROSS THE AREA THIS MORNING INTO THE AFTERNOON HOURS  
AND WITH PLENTY OF INSTABILITY/SHEAR EXPECT THERE TO BE THE  
POSSIBILITY OF MORE TORNADOES. THESE INITIAL LINE OF STORMS WILL  
MOVE EAST OF THE AREA BY EARLY AFTERNOON, BUT THERE COULD BE SOME  
RE-DEVELOPMENT THIS AFTERNOON. THE GLOBAL AND HI-RES MODELS DO TRY  
AND RE-DEVELOP SOME CONVECTION DURING THE AFTERNOON ALONG AND  
AHEAD OF THE COLD FRONT MAINLY OVER AREAS EAST OF I-55. THERE WILL  
BE A CONTINUED CHANCE FOR SEVERE THIS AFTERNOON FOR THOSE AREAS,  
AS THE MODELS SUGGEST GOOD INSTABILITY WITH H700-H500 LAPSE RATES  
OF 6.5 TO 7.5 C/KM, 1500-2000 J/KG OF MU CAPE AND 45-50KTS OF  
DEEP LAYER SHEAR. WILL CONTINUE TO MONITOR FOR THIS AS WE PROGRESS  
THROUGH THE LATE MORNING/EARLY AFTERNOON. ALL OF THE CONVECTION  
SHOULD EXIT EAST OF THE AREA BY EARLY EVENING./15/  
 
PRIOR DISCUSSION BELOW:  
 
TODAY THROUGH TONIGHT,  
 
TODAY'S FOCUS REMAINS ON THE POTENTIAL FOR SEVERE WEATHER AND HEAVY  
RAINFALL, AS A DEEP LOW PRESSURE SYSTEM SWEEPS THROUGH THE CENTRAL  
CONUS. THE DEEPENING LOW HAS INCREASED SOUTHERLY FLOW OVER THE  
SOUTHERN MISSISSIPPI VALLEY AT ALL HEIGHTS, CAUSING A SURGE OF  
ANOMALOUS MOISTURE INTO OUR REGION. BLENDED TOTAL PRECIPITABLE WATER  
IMAGERY SHOWS A BROAD SWATH OF 1.5 TO 2 INCH PWAT VALUES EXTENDING  
FROM SOUTH CENTRAL LOUISIANA THROUGH SOUTHERN MISSOURI. A LINE OF  
THUNDERSTORMS - FOCUSED MAINLY ALONG AN ADVANCING COLD FRONT - WILL  
CONTINUE MARCHING EASTWARD THROUGHOUT THE DAY TODAY. THE HEAVIEST  
AND MOST INTENSE RAINFALL LOOKS TO BE ASSOCIATED WITH AND MCS  
CENTERED IN CENTRAL LOUISIANA AND ANOTHER MOVING THROUGH NORTHERN  
MISSISSIPPI AND WESTERN TENNESSEE. BOWING SEGMENTS ALONG THE LINE OF  
STORMS WILL HAVE TO BE MONITORED FOR WIND AND BRIEF TORNADO  
POTENTIAL. RAINFALL AMOUNTS OF 2 TO 3 INCHES WILL BE COMMON ACROSS  
THE AREA TODAY, WITH ISOLATED HIGHER AMOUNTS. FLASH FLOODING AND  
AREAS OF RIVER FLOODING WILL BE POSSIBLE WITH THIS HEAVY RAIN.  
/NF/  
 
MONDAY THROUGH SATURDAY NIGHT,  
 
A LULL IN THE ACTIVE WEATHER PATTERN IS EXPECTED EARLY THIS WEEK  
BEFORE THE NEXT POTENTIAL HEAVY RAIN/SEVERE WEATHER EVENT  
THREATENS THE ARKLAMISS AS WE GO INTO WEDNESDAY/THURSDAY. THAT  
SYSTEM SHOULD BE FOLLOWED BY MUCH COOLER CONDITIONS TO FINISH UP  
THE WEEK.  
 
FOR THE MONDAY THROUGH TUESDAY NIGHT PERIOD, WEAK SURFACE HIGH  
PRESSURE WILL MOVE EAST ACROSS THE FORECAST AREA BRINGING DRY  
CONDITIONS WITH SEASONABLY WARM DAYS AND COOL NIGHTS.  
 
THE NEXT SHORTWAVE TROUGH WILL THEN DIG SOUTHWARD IN ASSOCIATION  
WITH A FAIRLY IMPRESSIVE TROPOSPHERIC UNDULATION (2.0 PVU  
INTRUSION TO NEAR H600) THAT WOULD RESULT IN RAPID CYCLOGENESIS  
OVER THE SOUTHEAST CONUS. GLOBAL MODELS HAVE BEEN QUITE ERRATIC IN  
HOW MUCH DIGGING AND CYCLOGENESIS WILL TAKE PLACE, BUT THEY HAVE  
ALSO BEEN PRETTY CONSISTENT WITH THE GENERAL LARGE SCALE RESPONSE  
INCLUDING IMPRESSIVE WARM ADVECTION FOLLOWED BY STRONG HEIGHT  
FALLS. SO EXPECT THE COMBINATION OF FORCING/MOISTURE/INSTABILITY  
WILL BE SUPPORTIVE OF MULTIPLE CONVECTIVE ROUNDS THAT COULD RESULT  
IN VERY HEAVY RAINFALL IN ADDITION TO SEVERE WEATHER.  
 
OF COURSE, DEPENDING ON WHAT TRANSPIRES TODAY, ANTECEDENT  
CONDITIONS COULD BE AN ISSUE WITH MUCH OF THE AREA UNDER A THREAT  
FOR MORE SIGNIFICANT FLOODING. WE WILL BE FOCUSING MORE ON THIS  
EVENT IMMEDIATELY FOLLOWING TODAY'S SYSTEM. BEYOND THURSDAY, IF  
THE MORE WRAPPED UP SOLUTIONS VERIFY, WOULD EXPECT CYCLONIC FLOW  
TO MAINTAIN SOME WHAT UNSETTLED AND MUCH COOLER CONDITIONS WITH  
CONTINUED LIGHT RAIN CHANCES AS WE GO INTO FRIDAY. IF THE MORE  
PROGRESSIVE SOLUTIONS VERIFY, THEN DRIER/CLEARER AND COOLER  
CONDITIONS WOULD BE THE GENERAL RULE GOING INTO NEXT WEEKEND. /EC/  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
JACKSON 76 52 77 53 / 99 38 0 0  
MERIDIAN 80 54 78 52 / 96 100 0 0  
VICKSBURG 74 51 78 54 / 96 11 0 0  
HATTIESBURG 80 53 80 52 / 98 92 0 0  
NATCHEZ 73 51 78 54 / 96 10 0 0  
GREENVILLE 73 51 75 55 / 90 10 0 0  
GREENWOOD 75 52 74 54 / 99 25 0 0  
 

 
   
JAN WATCHES/WARNINGS/ADVISORIES
 
 
MS...FLASH FLOOD WATCH UNTIL MIDNIGHT CDT TONIGHT FOR MSZ030-031-033-  
038-039-044>046-050>052-056>058-064>066-072>074.  
 
FLASH FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR MSZ025>029-032-  
035>037-042-043-048-049-054-055-062-063.  
 
LA...NONE.  
AR...NONE.  
 

 
 

 
 
15  
 
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