748  
FXUS64 KHUN 242341  
AFDHUN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
641 PM CDT MON SEP 24 2018  
   
UPDATE
 
 
FOR 00Z TAFS.  
 

 
   
NEAR TERM
 
(THIS EVENING AND TONIGHT)  
ISSUED AT 325 PM CDT MON SEP 24 2018  
 
A SLIGHTLY BUSIER DAY ACROSS THE REGION, WITH NUMEROUS SHOWERS AND  
SOME ISOLATED THUNDERSTORMS DEVELOPING ACROSS THE REGION THIS  
AFTERNOON. AS HAS BEEN THE CASE THE PAST SEVERAL DAYS, MOST OF THE  
APPRECIABLE RAINFALL HAS OCCURRED OUTSIDE THE REGION ACROSS NORTH  
GEORGIA AND SOUTHEAST TENNESSEE. HOWEVER, WITHIN THE LAST HOUR, A  
DEEP PLUME OF CONVECTION WAS NOTED ACROSS CENTRAL AND SOUTH ALABAMA  
WHICH WILL CONTINUE TO WORK IT'S WAY NORTH INTO THE AREA OVER THE  
NEXT FEW HOURS. PER THE LATEST CAMS, A WINDOW FOR MORE WIDESPREAD,  
LOCALLY HEAVIER CONVECTION WILL BE POSSIBLE FROM 21-03Z THIS EVENING,  
ASSOCIATED WITH THIS DEEP PLUME OF MOISTURE AND WEAK LOW-LEVEL  
CONVERGENCE. AREAS MOST LIKELY TO BE IMPACTED BY THIS ACTIVITY WILL  
BE ALONG AND EAST OF INTERSTATE 65. A SILVER-LINING TO ALL THIS IS  
THAT SOIL MOISTURE IS EXCEEDINGLY LOW IN THIS AREA AND THAT FLOODING  
CONCERNS, AT LEAST AT THE MOMENT, ARE STILL QUITE LOW. STILL, WITH  
PWATS AROUND 2", LOCALLY HEAVY DOWNPOURS WILL BE LIKELY WITH THIS  
ACTIVITY, AND WE'LL HAVE TO WATCH RAINFALL OBS/ESTIMATES AND  
STREAMFLOW TRENDS TO ASSESS ANY LOCALIZED FLOOD POTENTIAL.  
 
ADDITIONALLY, SOME BREAKS IN THE CLOUDS HAVE ALLOWED FOR SOME HEATING  
AND DESTABILIZATION (MAINLY ACROSS NORTHEAST ALABAMA), SO WE MAY  
NEED TO WATCH FOR A LOCALLY STRONG STORM HERE. LATEST SPC  
MESOANALYSIS IS SHOWING AROUND 2500 J/KG OF SBCAPE AND 1500 J/KG OF  
MLCAPE, A LITTLE HIGHER THAN EXPECTED. THIS ACTIVITY WILL WANE IN  
INTENSITY AND COVERAGE AFTER SUNSET, BUT AM EXPECTING AT LEAST WIDELY  
SCATTERED SHOWERS TO LINGER THROUGH THE NIGHT GIVEN THE DEEP  
MOISTURE IN PLACE. GIVEN THE LACK OF FOG LAST NIGHT AND THE LOWER  
CLOUDS EXPECTED TO DEVELOP OVERNIGHT, WILL KEEP A MENTION OF PATCHY  
FOG OUT OF THE FORECAST FOR NOW -- THOUGH THE BOUNDARY LAYER WOULD  
SUPPORT IT IF SOME CLEARING WERE TO OCCUR.  
   
SHORT TERM
 
(TUESDAY THROUGH THURSDAY)  
ISSUED AT 325 PM CDT MON SEP 24 2018  
 
MODELS CONTINUE TO KEEP THE COLD FRONT JUST TO OUR NORTH AGAIN ON  
TUESDAY. DUE TO THIS BOUNDARY STILL REMAINING JUST TO OUR NORTH,  
UNCERTAINTIES REMAIN ON STORM COVERAGE AND QPF AGAIN FOR TUESDAY.  
STILL, DEEP SOUTHERLY FLOW WILL HELP TO MAINTAIN THIS VERY MOIST  
AIR MASS IN PLACE -- ONE THAT IS VERY FAVORABLE FOR LOCALLY HEAVY  
RAINFALL. GUIDANCE CONTINUES TO SUGGEST THE POTENTIAL FOR A  
SHORTWAVE OR TWO TO ROTATE THROUGH THE AREA AGAIN TOMORROW, THANKS  
TO A GRADUALLY AMPLIFYING UPPER- TROUGH OVER THE GREAT PLAINS. ALL  
THIS TO SAY, THERE APPEARS TO STILL BE AN OPPORTUNITY FOR SCATTERED  
TO NUMEROUS SHOWERS AND THUNDERSTORMS ON TUESDAY -- VERY SIMILAR TO  
TODAY. CLOUD COVER SHOULD SIGNIFICANTLY LIMIT THE THERMODYNAMIC  
ENVIRONMENT -- AND GENERALLY, STRONG STORMS ARE NOT EXPECTED.  
 
THE MAIN WINDOW FOR LOCALLY HEAVY RAINFALL AND THE HIGHEST CONFIDENCE  
FOR SHOWER/THUNDERSTORM COVERAGE STILL APPEARS TO BE FROM TUESDAY  
NIGHT THROUGH THE DAY ON THURSDAY. A STRONG MID/UPPER-LEVEL TROUGH  
WILL PUSH THROUGH THE OHIO VALLEY, WHICH WILL ASSIST IN FORCING THIS  
COLD FRONT SOUTH AND EAST INTO ALABAMA. ACCOMPANYING THIS BOUNDARY WILL  
BE A 40 KT, 850 MB JET THAT WILL EJECT FROM THE DEEP SOUTH INTO THE  
CENTRAL APPALACHIANS. IN THIS SCENARIO, THE TENNESSEE VALLEY WOULD BE  
PLACED IN THE RIGHT ENTRANCE REGION. THUS, CONFIDENCE IS INCREASING  
FOR THE POTENTIAL FOR NUMEROUS TO WIDESPREAD SHOWERS AND STORMS  
DURING THIS PERIOD.  
 
THE LATEST STORM TOTAL QPF FOR OUR AREA IS STILL RUNNING BETWEEN 2-3  
INCHES THROUGH THURSDAY NIGHT, WITH LOCALLY HIGHER AMOUNTS. THE  
ENVIRONMENT WILL BE FAVORABLE FOR LOCALLY HEAVY RAINFALL AND A  
LOCALIZED FLASH FLOODING THREAT, MAINLY DURING THIS TIME FRAME,  
ESPECIALLY IN AREAS WHERE TRAINING OCCURS. GIVEN THE LACK OF RAINFALL  
THAT HAS OCCURRED SO FAR, DO NOT ANTICIPATE ANY FLOOD PRODUCTS WILL  
BE NEEDED, BUT WILL CONTINUE TO HIGHLIGHT THIS THREAT IN THE HWO.  
WITH THE CLOUD COVER AND RAIN CHANCES, BELOW NORMAL HIGH TEMPERATURES  
WILL CONTINUE TO BE THE RULE -- WITH LOWS IN THE UPPER 60S.  
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 325 PM CDT MON SEP 24 2018  
 
BEYOND THURSDAY NIGHT INTO FRIDAY, THERE CONTINUES TO BE EVIDENCE  
THAT A BROAD SUBTROPICAL RIDGE MAY FORM ALONG THE NORTHERN GULF COAST  
LATE THIS WEEK INTO THE WEEKEND. THIS WOULD FORCE THE REMNANT  
BOUNDARY BACK NORTH AND RESULT IN SOME DRIER WEATHER. UNDERNEATH THIS  
RIDGE, THERE WILL STILL BE PLENTY OF AVAILABLE MOISTURE, SO THINK  
THERE WILL STILL BE AN OPPORTUNITY FOR ISOLATED TO WIDELY SCATTERED  
CONVECTION EACH AFTERNOON ACROSS THE REGION IN THIS STILL WARM, HUMID  
AIR MASS. THERE WILL BE MORE SUNSHINE, HOWEVER, LATE THIS WEEK INTO  
THE WEEKEND, ALLOWING HIGHS TO RETURN TO THE MID TO UPPER 80S DURING  
THE DAY AND 60S AT NIGHT.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)  
ISSUED AT 641 PM CDT MON SEP 24 2018  
 
A PASSING UPPER LEVEL SYSTEM HAS RESULTED IN SCATTERED TO NUMEROUS  
SHOWERS AND THUNDERSTORMS APPROACHING FROM CENTRAL ALABAMA. THIS  
ACTIVITY MOVING TO THE NNE AROUND 30 KTS WILL AFFECT AREAS JUST EAST  
OF THE KHSV AIRPORT, WITH GUSTY WINDS TO 30KT AND CIG/VIS REDUCTION  
FROM HEAVIER SHOWERS. MORE ISOLATED TO SCATTERED ACTIVITY WEST OF  
I-65 COULD BRING SHOWERS TO KMSL/KHSV EARLY THIS EVENING, WITH TEMPO  
CIG/VIS REDUCTIONS IN THE HEAVIER SHOWERS. SHOWER ACTIVITY SHOULD END  
LATER THIS EVENING. MVFR CIGS ARE EXPECTED AROUND DAYBREAK TUE.  
DAYTIME HEATING AND ANOTHER PASSING SYSTEM WILL BRING MORE SHOWER  
CHANCES LATE IN THE TAF.  
 

 
   
HUN WATCHES/WARNINGS/ADVISORIES
 
 
AL...NONE.  
TN...NONE.  

 
 

 
 
NEAR TERM...AMP.24  
SHORT TERM...AMP.24  
LONG TERM...AMP.24  
AVIATION...RSB  
 
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AT WEATHER.GOV/HUNTSVILLE.  
 
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