473  
FXUS64 KSHV 211217  
AFDSHV  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SHREVEPORT LA  
717 AM CDT SAT APR 21 2018  
   
AVIATION
 
 
FOR THE 21/12Z TAFS, VFR CONDITIONS WILL PREVAIL AT MOST SITES  
INITIALLY, BUT CEILINGS WILL GRADUALLY LOWER INTO THE MVFR RANGE  
FROM WEST TO EAST. CONVECTION CURRENTLY ONGOING ACROSS CENTRAL  
OKLAHOMA AND NORTH TEXAS WILL MOVE INTO THE AREA AFTER 21/18Z. ALL  
TAF SITES WILL BE AFFECTED BEFORE THE END OF THIS PERIOD. FLIGHT  
CONDITIONS WILL DETERIORATE AS THE CONVECTION ARRIVES. ONE OR TWO  
ISOLATED STORMS MAY BECOME SEVERE. A COLD FRONT WILL HELP TO PUSH  
THE STORMS EASTWARD, AND THE STORMS SHOULD END AT MOST OF THE  
EAST TEXAS TERMINALS BY THE END OF THE PERIOD.  
 
/09/  
 

 
   
PREV DISCUSSION
 
/ISSUED 518 AM CDT SAT APR 21 2018/  
 
DISCUSSION...  
THE MORNING SATELLITE IMAGERY REVEALS THAT ELEVATED CLOUD COVER  
HAS RAPIDLY BEGUN TO DEVELOP/SPREAD ENE ACROSS THE REGION THIS  
MORNING, WELL AHEAD OF THE CLOSED LOW OVER CNTRL CO, WITH THE  
TRAILING TROUGH S INTO SRN NM. WEAK SFC RIDGING REMAINS IN PLACE  
ACROSS THE REGION THIS MORNING, BUT THIS WILL CHANGE BY MID TO  
LATE MORNING AS WINDS VEER MORE SERLY AS A SFC LOW OVER NW TX  
BEGINS TO SHIFT E INTO WCNTRL TX ALONG A WEAK INVERTED SFC TROUGH  
THAT WILL DEVELOP ALONG THE RED RIVER. IN FACT, THE LOW LEVEL  
MOISTURE RETURN IS NOT TOO FAR OFF,WITH MVFR CIGS OVER SE TX  
RAPIDLY ENCROACHING ON DEEP E TX ATTM. THE MOSAIC RADAR IMAGERY  
HAS BEEN DEPICTING SOME ELEVATED MID LEVEL RETURNS OVER PORTIONS  
OF EXTREME NE TX/SE OK, ALTHOUGH SFC OBS OVER THESE AREAS HAVE NOT  
RECORDED ANY CIGS AOB 12KFT. HOWEVER, THE LATEST SFC OBS FROM PRX  
HAS JUST RECORDED -RA, MEANING THAT A FEW SPRINKLES ARE INDEED MAKING  
IT TO THE GROUND.  
 
THE AIR MASS SHOULD CONTINUE TO SATURATE TODAY AS MEAN MOISTURE  
CONTINUES TO SPREAD NE AND DEEPEN OVER THE AREA, AS THE CLOSED LOW  
EMERGES OUT OVER OK. THE SHORT TERM PROGS HAVE SLOWED DOWN THE EWD  
PROGRESSION OF THE CONVECTION THIS MORNING THOUGH, REMAINING JUST  
W OF THE CWA THROUGH 18Z (FOR THE MOST PART), BEFORE THE  
CONVECTION RAPIDLY EXPANDS E INTO E TX/SW AR/EXTREME NW LA FOR THE  
AFTERNOON. HAVE SLOWED DOWN THE PROGRESSION OF THE POPS AS WELL  
THIS MORNING, BUT DID BUMP POPS UP A BIT ACROSS SE OK/PORTIONS OF  
EXTREME NE TX AS LARGE SCALE DIFFLUENCE INCREASES LATE IN THE DAY.  
THE HEAVY RAIN THREAT STILL LOOKS ON TRACK FOR TONIGHT ACROSS  
MUCH OF THE REGION, AS A WARM FRONT BEGINS TO LIFT N INTO E TX/N  
LA TO NEAR THE AR/LA BORDER BY MID TO LATE EVENING. THE  
GFS/ECMWF/HRRR ARE IN GOOD AGREEMENT THIS MORNING WITH THE TRACK  
OF THE SFC LOW ROUGHLY ALONG OR JUST S OF THE I-20 CORRIDOR THIS  
AFTERNOON AND EVENING, WITH THE 06Z NAM IN BETTER AGREEMENT NOW,  
BUT MUCAPE BEING LIMITED TO 500 J/KG OR LESS ACROSS THE WARM  
SECTOR THIS EVENING AS DYNAMICAL FORCING INCREASES THIS EVENING  
AHEAD OF AN INCREASINGLY NEGATIVELY TILTED TROUGH AXIS. STILL  
CAN'T RULE OUT ISOLATED STRONG TO SEVERE CONVECTION THIS EVENING  
THROUGH A PORTION OF THE OVERNIGHT HOURS NEAR AND S OF THE WARM  
FRONT GIVEN THE LIMITED INSTABILITY ACCOMPANIED BY 40-50KTS OF  
BULK SHEAR, BUT BELIEVE THE PRIMARY THREAT WILL BE FOR LOCALLY  
HEAVY RAINFALL AS THE CONVECTION DEEPENS WITHIN THE LFQ OF THE  
120KT UPPER JET STREAK, AND GRADUALLY SPREADS E ACROSS THE AREA.  
THE HIGH RES PROGS SUGGEST WIDESPREAD 1-2+ INCHES OF QPF ACROSS  
MUCH OF E TX/SE OK/SW AR/NW LA, WITH ISOLATED HIGHER AMOUNTS OF 3+  
INCHES POSSIBLE GIVEN THE POTENTIAL CELL TRAINING THIS EVENING,  
BEFORE DRY SLOTTING ALOFT BEGINS TO ENTRAIN E BENEATH THE UPPER  
LOW AFTER 06Z SUNDAY. MINOR FLOODING CAN'T BE RULED OUT TONIGHT  
WHERE TRAINING IS OBSERVED, BUT GIVEN THE LOCALIZED INSTANCE OF  
THIS, WILL FOREGO A FLASH FLOOD WATCH ATTM.  
 
THE ATTENDANT COLD FRONT WILL GRADUALLY PROGRESS SE ACROSS THE  
REGION LATE TONIGHT THROUGH SUNDAY MORNING, EXITING THE AREA  
BY/AFTER 18Z. DID MAINTAIN HIGH CHANCE TO LIKELY POPS SUNDAY  
MORNING ACROSS THE ERN ZONES BEFORE THIS DIMINISHES QUICKLY BY  
MID-MORNING, ALTHOUGH THE POTENTIAL FOR SOME WRAP-AROUND -SHRA  
WILL LINGER ACROSS MAINLY SW AR AND NCNTRL LA AS THE CLOSED LOW  
DRIFTS SE ACROSS CNTRL AND SRN AR. THE BIGGEST QUESTION THOUGH  
REMAINS THE MAX TEMPS, AS THE POST-FRONTAL CLOUD COVER OVER DEEP E  
TX/N LA MAY DIMINISH BY AFTERNOON, ALLOWING FOR BETTER INSOLATION  
BEFORE THE WRAP-AROUND STRATOCU FIELD SPREADS SE ALONG THE  
BACKSIDE OF THE LOW. HAVE TRENDED MAX TEMPS A TAD HIGHER THAN THE  
PREVIOUS FORECAST, BEFORE THE DEEPER WEDGE OF COLD AIR IS ABLE TO  
SINK SE.  
 
THE POST-FRONTAL STRATOCU SHOULD HELP KEEP TEMPS A BIT COOLER  
MONDAY, WITH ISOLATED -SHRA POSSIBLE, BEFORE THE CLOUDS GRADUALLY  
DIMINISH FROM W TO E WITH THE DEPARTURE OF THE CLOSED LOW. A  
WARMING TREND WILL COMMENCE TUESDAY, ALTHOUGH THE NEXT COLD FRONT  
REMAINS PROGGED TO SWEEP SE THROUGH THE AREA WEDNESDAY. THERE  
STILL REMAINS QUITE A BIT OF UNCERTAINTY IN REGARDS TO TIMING,  
WITH THE ECMWF THE SLOWER SOLUTION BY ABOUT 12 HRS BEHIND THE  
FASTER AND MORE PROGRESSIVE GFS. HOWEVER, CONVECTION SHOULD  
QUICKLY DEVELOP AHEAD OF THE ASSOCIATED SHORTWAVE TROUGH OVER THE  
CNTRL PLAINS AND MID-MS VALLEY. DID BUMP POPS UP TO HIGH CHANCE  
WEDNESDAY N OF THE I-20 CORRIDOR, BUT KEPT SLIGHT CHANCE POPS  
GOING WEDNESDAY EVENING FOR THE SRN 3/4ERS OF THE AREA GIVEN THE  
POTENTIAL FOR LINGERING CONVECTION AS DRIER AIR DEEPENS IN WAKE OF  
THIS SHORTWAVE TROUGH/COLD FROPA.  
 
THE PROGRESSIVE PATTERN LOOKS TO CONTINUE THROUGH THE END OF THE  
EXTENDED, WITH ANOTHER DEEPER UPPER TROUGH SLIDING SE INTO THE SRN  
PLAINS/LOWER MS VALLEY FRIDAY, RESULTING IN ADDITIONAL CONVECTION  
AND A REINFORCEMENT OF COOLER AND DRIER AIR FOR NEXT WEEKEND.  
 
PRELIMS TO FOLLOW BELOW...  
 
15  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SHV 72 58 71 53 / 50 100 30 10  
MLU 75 60 73 55 / 20 100 60 10  
DEQ 68 52 67 50 / 80 100 30 10  
TXK 70 56 67 53 / 70 100 30 10  
ELD 73 58 69 54 / 30 100 50 10  
TYR 67 54 66 51 / 70 100 10 0  
GGG 69 57 67 51 / 60 100 10 0  
LFK 73 59 73 51 / 40 100 10 0  
 

 
   
SHV WATCHES/WARNINGS/ADVISORIES
 
 
AR...NONE.  
LA...NONE.  
OK...NONE.  
TX...NONE.  

 
 

 
 
09/15  
 
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