312  
FXUS64 KMEG 262015  
AFDMEG  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MEMPHIS TN  
315 PM CDT WED APR 26 2017  
   
DISCUSSION
 
 
WIDESPREAD SHOWERS AND THUNDERSTORMS CONTINUE FROM THE ARKLATEX  
AREA INTO SOUTHEAST MO. THIS LINE OF STORMS APPEARS TO BE LOCATED  
ALONG A PRE-FRONTAL TROUGH AHEAD OF A WEAK COLD FRONT THAT WILL  
MOVE EAST ACROSS THE MID-SOUTH OVERNIGHT. INSTABILITY IS MODEST IN  
THE WARM SECTOR, WITH MLCAPE VALUES ON THE ORDER OF 1000 J/KG  
WITH EFFECTIVE LAYER SHEAR OF 45-55 KTS. HOWEVER, A STRONG CAPPING  
INVERSION OVER THE AREA HAS PREVENTED CONVECTION FROM DEVELOPING  
DOWNSTREAM OF THE CURRENT CONVECTIVE ACTIVITY. THIS CAP WILL  
WEAKEN THIS EVENING AND, COMBINED WITH STRONG FRONTAL FORCING,  
WILL AID IN SUSTAINING THE QLCS AS IT MOVES ACROSS THE MISSISSIPPI  
RIVER BEFORE STORMS GRADUALLY WEAKEN DURING THE THE MID/LATE  
EVENING HOURS AS THEY CONTINUE EAST. A FEW EMBEDDED SUPERCELLS  
WILL POSE THE MOST SIGNIFICANT SEVERE WEATHER RISK, WITH LARGE  
HAIL AND DAMAGING WINDS BEING THE PRIMARY HAZARDS. THE LINEAR MODE  
OF THIS CONVECTION WILL LIMIT THE TORNADO POTENTIAL, BUT THE  
POSSIBILITY STILL WARRANTS MENTION.  
 
AVERAGE QPF AMOUNTS FOR TONIGHT ARE NEAR 1 INCH ACROSS MUCH OF  
THE MID-SOUTH, BUT HIGHER AMOUNTS WILL BE POSSIBLE IN NORTHEAST  
AR WHERE THE DEEP-LAYER SHEAR VECTOR WILL BE NEARLY PARALLEL TO  
THE SURFACE BOUNDARY, PROMOTING STRONG, TRAINING CELLS. RAIN WILL  
MOVE EAST OF THE AREA LATE TONIGHT, WITH GENERALLY DRY WEATHER  
ANTICIPATED THURSDAY AND THURSDAY NIGHT ACROSS MUCH OF THE CWA.  
 
THUNDERSTORMS WILL BE POSSIBLE ACROSS PORTIONS OF THE MID-SOUTH ON  
FRIDAY, MAINLY DURING THE EVENING AND OVERNIGHT PERIOD. A SURFACE  
LOW IS PROGGED TO DEVELOP OVER MO, WITH A WARM FRONT EXTENDING  
EAST INTO THE TENNESSEE VALLEY. SURFACE TEMPERATURES IN THE 80S  
WILL RESULT IN STRONG INSTABILITY BUT A STRONG CAP WILL LIMIT THE  
THUNDERSTORM POTENTIAL THROUGH THE AFTERNOON HOURS. HOWEVER, A FEW  
STORMS COULD BREAK THROUGH THE CAP, SO LOW POPS WERE CONTINUED.  
RAIN CHANCES INCREASE FRIDAY NIGHT AS THE CAP WEAKENS AND STORMS  
DEVELOP ALONG THE WARM FRONT. STRONG SHEAR PROFILES MAY RESULT IN  
STRONG TO SEVERE THUNDERSTORMS FRIDAY NIGHT. IN ADDITION, LOCALLY  
HEAVY RAINFALL WILL BE POSSIBLE, MAINLY NORTH OF I-40.  
 
STRONG TO SEVERE STORMS REMAIN IN THE FORECAST FOR THE MID-SOUTH  
FOR THE WEEKEND, ESPECIALLY SATURDAY NIGHT AND SUNDAY. THERE MAY  
BE A LULL DURING THE MORNING AND EARLY AFTERNOON HOURS ON  
SATURDAY, BUT A STRONG SHORTWAVE TROUGH WILL APPROACH THE AREA AND  
WILL HELP PRECONDITION THE ATMOSPHERE FOR INTENSE CONVECTION LATER  
IN THE DAY. DEEP LAYER SHEAR AND INSTABILITY WILL BE IMPRESSIVE  
DOWNSTREAM OF THIS UPPER-LEVEL CYCLONE, SUPPORTING A POTENTIAL  
FOR ALL MODES OF SEVERE WEATHER. AGAIN, HEAVY RAINFALL WILL BE  
POSSIBLE ACROSS THE AREA. QPF AMOUNTS FROM 7 PM FRIDAY TO 7 PM  
SUNDAY ARE GENERALLY IN THE 2-5" RANGE ACROSS THE MID-SOUTH, WITH  
HIGHER AMOUNTS OF 4-6" OVER NORTHEAST AR AND THE MO BOOTHEEL. OF  
COURSE, HIGHER AMOUNTS WILL BE POSSIBLE IN AREAS WHERE THE  
STRONGER STORMS TRAIN, BUT THAT WILL RELY ON MESOSCALE FEATURES  
THAT AREN'T YET APPARENT. FLASH FLOODING WILL CERTAINLY BE A  
CONCERN OVER THE WEEKEND AND A WATCH MAY BE NEEDED AS EARLY AS  
TOMORROW. IN ADDITION, SOME MID-SOUTH RIVERS ARE LIKELY TO MOVE  
INTO FLOOD.  
 
DRY WEATHER IS ANTICIPATED EARLY NEXT WEEK ON MONDAY AND TUESDAY  
IN THE WAKE OF THE DEPARTING TROUGH. TEMPERATURES WILL TAKE A HIT  
AS WELL BEHIND THE COLD FRONT. RAIN CHANCES RETURN BY THE MIDDLE  
OF NEXT WEEK.  
 
JOHNSON  
 

 
   
AVIATION
 
 
18Z TAFS  
 
INITIALLY A MIX OF MVFR AND IFR CEILINGS TO BEGIN THE PERIOD.  
SHORT TERM MODELS ARE INDICATING THAT A LINE OF THUNDERSTORMS WILL  
MOVE THROUGH ALL SITES THIS EVENING. TEMPO GROUPS WERE ADDED TO  
EACH SITE FOR APPROXIMATE PERIOD OF HEAVIEST RAIN AND THUNDERSTORMS.  
STRONG GUSTY WINDS FROM THE WEST WILL ALSO ACCOMPANY THE LINE OF  
THUNDERSTORMS AS IT MOVES THROUGH. THERE IS SOME CONCERN THAT  
GUSTY NON THUNDERSTORM WINDS WILL DEVELOP BEHIND THE FRONT, BUT  
CONFIDENCE IS LOW AT THIS TIME.  
 
CONFIDENCE IS LOW AT THE MOMENT WITH REGARDS TO CEILINGS BEHIND  
THE FRONTAL PASSAGE. A COUPLE MODELS ARE SHOWING IFR AND POSSIBLY  
LIFR CEILINGS THROUGH 27/12Z, WITH AT LEAST ONE SHOWING VFR. WENT  
AHEAD AND SPLIT THE DIFFERENCE WITH PREVAILING MVFR/IFR CEILINGS  
THROUGH EARLY MORNING. WINDS ARE EXPECTED TO SHIFT TO THE WEST BY  
27/12Z, WITH VFR CONDS RETURNING TO ALL SITES BY 27/18Z TOMORROW.  
 
AC3  
 

 
   
MEG WATCHES/WARNINGS/ADVISORIES
 
 
AR...WIND ADVISORY UNTIL 7 PM CDT THIS EVENING FOR CROSS-LEE AR-  
PHILLIPS-ST. FRANCIS.  
 
MO...NONE.  
MS...WIND ADVISORY UNTIL 7 PM CDT THIS EVENING FOR COAHOMA-QUITMAN-  
TALLAHATCHIE-TUNICA.  
 
TN...NONE.  
 

 
 

 
 
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