032  
FXUS63 KDVN 251108  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
608 AM CDT MON SEP 25 2017  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 222 AM CDT MON SEP 25 2017  
 
ANOTHER SUMMER NIGHT IS GOING ON OUTSIDE, WHILE THE PATTERN THAT HAS  
SUPPORTING IT, IS BEGINNING TO CHANGE. THE SYNOPTIC FRONT, WHICH  
MORE OR LESS REPRESENTS THE DIFFERENCE FROM LATE OCTOBER'S COLD RAIN  
AND BREEZY NORTH WINDS, AND AUGUST'S WARM CLEAR NIGHTS IS FOUND FROM  
NORTH CENTRAL KANSAS, TO SOUTH CENTRAL MINNESOTA. THIS FRONT WILL  
MAKE SLOW PROGRESS TOWARDS THE AREA TODAY.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 222 AM CDT MON SEP 25 2017  
 
IT WILL CERTAINLY BE ANOTHER WARM DAY, AS THE ENTIRE CWA REMAINS  
EAST OF THE FRONT TODAY. THUS, WITH HIGH CONFIDENCE, ANOTHER DAY  
AROUND 90, WITH DEWPOINTS MAINLY IN THE MID 60S ARE FORECAST. THE  
GIVES HEAT INDEX READINGS IN THE LOWER 90S FOR NEARLY ALL OF THE  
AREA, AND WE WILL AGAIN CONSIDER THAT THE MAIN MESSAGE. HOWEVER,  
THE BIGGEST QUESTION TODAY WILL NOW INCLUDE THUNDERSTORM  
COVERAGE. MESOSCALE MODELS TODAY, ARW, NMM, ESRL HRRR, AND TO A  
LESSER DEGREE NAM SHOW ISOLATED, VERY SLOW MOVING THUNDERSTORMS  
FIRING UP DURING PEAK HEATING TODAY. THOSE MODELS ALL HAVE A FEW  
POCKETS OF UPPER 60S DEWPOINTS PRIOR TO CONVECTIVE INITIATION, AND  
NO DOUBT THAT ALLOWS THEM TO BE MORE AGGRESSIVE IN FORMING  
CONVECTION. NORMALLY, I WOULD DISCOUNT THAT POSSIBILITY, BUT  
DEWPOINTS NEAR 68-69 ARE ONLY A FEW DEGREES HIGHER THAN WHAT WE'VE  
BEEN EXPERIENCING THE PAST FEW DAYS, AND SOME MESOSCALE  
CONVERGENCE IN OUR SOUTHEAST WINDS TODAY MAY ALLOW FOR THAT TO  
LOCALLY OCCUR. IN ANY CASE THE STORMS WOULD BE ISOLATED, AND SLOW  
MOVING, SO POPS WILL BE VERY LOW. THE SLOW MOVEMENT WOULD ALLOW  
FOR SPOTTY HEAVY RAIN AMOUNTS PERHAPS. WITH ALL GUIDANCE SHOWING  
THESE CELLS HAVING THEM ALONG AND WEST OF THE MISSISSIPPI RIVER,  
I'LL HAVE THAT LOW POSSIBILITY FORECAST THERE AS WELL, MAINLY  
KEEPING ILLINOIS DRY. TONIGHT, A LOW PROBABILITY SHOWER OR STORM  
IS POSSIBLE IN THE NORTHWEST, WITH DRY CONDITIONS EXPECTED  
ELSEWHERE. SKIES SHOULD BECOME PERSISTENTLY CLOUDY NORTHWEST  
OVERNIGHT, WHILE REMAINING MAINLY CLEAR SOUTHEAST.  
 
ERVIN  
   
LONG TERM
 
(TUESDAY THROUGH SUNDAY)  
ISSUED AT 222 AM CDT MON SEP 25 2017  
 
A CHANCE OF SHOWERS ON TUESDAY WITH A STRONG COLD FRONT THEN  
TEMPERATURES MUCH COOLER IN THE EXTENDED, BASICALLY RETURNING  
TO NORMAL TEMPERATURES FOR THE LAST WEEK OF SEPTEMBER.  
 
TUESDAY AND TUESDAY NIGHT: STRONG COLD FRONT ARRIVES BUT FORCING  
WEAKENS CONSIDERABLY AND IS MAINLY POST-FRONTAL, AS THE MAIN UPPER  
LEVEL TROUGH COMING OUT OF THE ROCKIES LIFTS WELL TO OUR NORTH INTO  
THE UPPER MIDWEST. MODELS REALLY DIMINISH THE QPF AS THE FRONT  
PUSHES ACROSS THE DVN CWA SO WILL KEEP CHANCE POPS FOR SCATTERED  
SHOWERS AND POSSIBLY AN ISOLATED STORM OR TWO. SPC HAS THE CWA IN  
ONLY GENERAL THUNDER AS SHEAR IS WEAK AND INSTABILITY IS MINIMAL, AS  
THERE SHOULD BE EXTENSIVE CLOUD COVER. AHEAD OF THE FRONT  
TEMPERATURES WILL WARM INTO THE 80S FROM EXTREME EASTERN IOWA INTO  
OUR ILLINOIS COUNTIES.  
 
WEDNESDAY THROUGH SUNDAY: A MUCH MORE COMFORTABLE STRETCH OF WEATHER  
AS A PATTERN CHANGE TO A DEEP TROUGH IN THE EASTERN UNITED STATES  
TAKES PLACE. THIS OCCURS AS HURRICANE "MARIA" FINALLY LIFTS NORTH  
AND THEN NORTHEAST OUT INTO THE NORTH ATLANTIC. WHILE THIS WILL BE A  
MUCH COOLER PATTERN COMPARED TO THE PAST WEEK, TEMPERATURES SHOULD  
BE CLOSE TO NORMAL FOR LATE SEPTEMBER. HIGHS WILL BE IN THE MID 60S  
TO LOWER 70S WITH LOWS IN THE 40S TO AROUND 50. RAINFALL DURING THIS  
PERIOD APPEARS TO BE SLIM TO NONE.  
 
HAASE  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)  
ISSUED AT 606 AM CDT MON SEP 25 2017  
 
CLEAR SKIES AND SOUTHEASTERLY FLOW AROUND 5 KTS WILL CONTINUE THIS  
MORNING, WITH WINDS INCREASING FROM THE SOUTH TO JUST UNDER 10 KTS  
FOR THIS AFTERNOON AND TONIGHT. A FEW ISOLATED SHOWERS OR  
THUNDERSTORMS ARE POSSIBLE, BUT COVERAGE IS SO POORLY CONFIDENT  
AND POOR ON WHETHER OR NOT THEY WILL OCCUR THAT I HAVE CHOSEN TO  
NOT INCLUDE MENTION OF RAIN OR THUNDER IN THE 12Z SET OF TAF  
FORECASTS. ANY STORM WOULD BE SLOW MOVING, AND SMALL.  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...NONE.  
IL...NONE.  
MO...NONE.  

 
 

 
 
SYNOPSIS...ERVIN  
SHORT TERM...ERVIN  
LONG TERM...ERVIN  
AVIATION...ERVIN  
 
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