539  
FXUS63 KDVN 150456  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
1156 PM CDT SAT SEP 14 2019  
   
..AVIATION UPDATE
 
 
   
UPDATE
 
 
ISSUED AT 614 PM CDT SAT SEP 14 2019  
 
ALL OUR FOCUS WILL BE ON THE ONSET OF THE STORMS FROM CENTRAL IOWA  
LATER THIS EVENING IN THE WEST/NORTHWEST. ON THE LATEST RAP DATA  
ON SPC'S MESOPAGE, WE STILL SEE A CUT OFF MUCAPE TO NIL OVER  
EASTERN IOWA, THUS, DESPITE THE STORMS CLOSE PROXIMITY TO EASTERN  
IOWA, I DON'T EXPECT A RAPID INTENSIFICATION, NOR WIDESPREAD  
DEVELOPMENT OF STORMS INTO OUR AREA QUITE YET. LATER TONIGHT, THE  
STORMS SHOULD EXPAND INTO AN MCS WITH HEAVY RAIN OVER OUR AREA,  
WHICH STILL IN SOMEWHAT IN QUESTION ON HOW FAR NORTH OR SOUTH THIS  
TRACKS.  
 

 
   
SYNOPSIS
 
 
ISSUED AT 312 PM CDT SAT SEP 14 2019  
 
18Z SURFACE DATA HAS A WEAK WARM FRONT RUNNING FROM EASTERN IOWA  
BACK INTO THE EASTERN DAKOTAS. DEW POINTS WERE IN THE 50S ACROSS  
THE GREAT LAKES WITH 60S AND 70S FROM THE MISSISSIPPI VALLEY INTO  
THE PLAINS.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SUNDAY)  
ISSUED AT 312 PM CDT SAT SEP 14 2019  
 
HEADLINE CHANGES...THE FLASH FLOOD WATCH FOR JO DAVIESS,  
STEPHENSON AND CARROLL COUNTIES HAS BEEN EXTENDED UNTIL 10 AM  
SUNDAY MORNING.  
 
THROUGH LATE THIS AFTERNOON...  
 
A PERSISTENT DECAYING STORM COMPLEX ACROSS IOWA WILL LIKELY PUSH  
SPRINKLES OR SOME ISOLATED SHOWERS SOUTH OF I-80 AND NORTH OF  
HIGHWAY 34 THROUGH LATE AFTERNOON IN EASTERN IOWA.  
 
TONIGHT AND SUNDAY...  
 
THE PERSISTENT COMPLEX ACROSS IOWA TODAY RAISES QUESTIONS AS TO HOW  
STORMS WILL DEVELOP AND EVOLVE TONIGHT.  
 
TWO SCENARIOS ARE POSSIBLE TONIGHT. WHAT IS COMMON BETWEEN EITHER  
SCENARIO IS HIGH MOISTURE LEVELS, UNSTABLE AIR ALOFT AND FORCING  
FROM A PASSING UPPER LEVEL DISTURBANCE THAT WILL RESULT IN HEAVY  
RAINFALL.  
 
SCENARIO 1 INVOLVES NEW STORM INITIATION ALONG THE IA/MN BORDER  
DURING THE EVENING THAT MOVES SOUTHEAST OVERNIGHT AND EXITS THE AREA  
LATE SUNDAY MORNING.  
 
IF THIS SCENARIO OCCURS THEN THE INTERNAL SIGNAL POINTS TO THE  
HEAVIEST RAINFALL OCCURRING BETWEEN HIGHWAY 20 AND HIGHWAY 30  
GENERALLY NORTH OF AN INDEPENDENCE, IA TO STERLING, IL LINE.  
 
SCENARIO 1 IS WHAT THE CURRENT FORECAST IS BASED UPON.  
 
SCENARIO 2 WOULD HAVE NEW CONVECTION DEVELOP WITH THE REMNANTS OF  
THE CURRENT SYSTEM ACROSS IOWA. IF THIS OCCURS THEN THE HEAVIER  
RAINFALL WOULD OCCUR ACROSS SOUTHEAST IOWA INTO WEST CENTRAL  
ILLINOIS.  
 
IF SCENARIO 2 OCCURS THEN THE OVERALL FORECAST MESSAGE WOULD NEED TO  
BE CHANGED CONSIDERABLY.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH SATURDAY)  
ISSUED AT 312 PM CDT SAT SEP 14 2019  
 
TARTING THE PERIOD OFF WITH ADDING SOME PRECIPITATION CHANCES TO  
THE SOUTHERN AREAS FOR SUNDAY EVENING. THE FRONT WILL BE SITUATED  
ACROSS THE FAR SOUTHERN PART OF THE FORECAST AREA AND WITH SOME  
CONVERGENCE AND MOISTURE POOLING ALONG THE FRONT, FELT THERE IS  
ENOUGH OF A CHANCE FOR SHOWERS AND THUNDERSTORMS TO ADD A SLIGHT  
CHANCE IN FOR THE EVENING HOURS.  
 
HIGH PRESSURE BUILDS IN AT THE SURFACE THROUGH THE DAY MONDAY WITH  
RETURN FLOE BEING SEEN OVER THE PLAINS INTO WESTERN IOWA AS THE  
UPPER LEVEL RIDGE IS CENTERED UP AND DOWN THE MISSISSIPPI RIVER  
VALLEY. THE SETUP LOOKS GOOD FOR PATCHY TO EVEN AREAS OF FOG WITH  
GOOD MOISTURE AT THE SURFACE UNDER THE INVERSION AND MOSTLY CLEAR  
SKIES SUNDAY NIGHT INTO MONDAY. THE AREAS WITH THE WEAKEST LOW LEVEL  
FLOW TO SUPPORT FOG DEVELOPMENT WILL BE ACROSS THE NORTHEAST  
QUADRANT OF THE FORECAST AREA SO HAVE LIMITED THE MENTION OF FOG DO  
THOSE AREAS.  
 
TEMPERATURES ON MONDAY WILL BE A BIT WARMER THAN ON SUNDAY AND WILL  
BE WELL ABOVE NORMAL IN THE 80S. THINK THAT EVEN IF FOG DOES FORM  
AND HOLDS ON LONGER INTO THE MORNING, TEMPERATURES SHOULD RECOVER  
RATHER QUICKLY TO GET THOSE AREAS INTO THE 80S.  
 
THE BIG STORY FOR THE WEEK WILL BE HOT AND HUMID. THE UPPER LEVEL  
RIDGE SITS IN PLACE THROUGH THE WEEK. TEMPERATURES MONDAY THROUGH  
WEDNESDAY WILL BE WARMEST WITH HIGHS IN THE MID TO UPPER 80S AND  
WITH DEWPOINTS IN THE UPPER 60S TO LOW 70S, IT WILL BE QUITE  
UNCOMFORTABLE FOR THIS TIME OF YEAR.  
 
A FEW SHORTWAVE TROUGHS WILL MOVE THROUGH THE FLOW TO PROVIDE  
CHANCES FOR THUNDERSTORMS BEGINNING ON WEDNESDAY AND CONTINUING  
THROUGH THE WEEK. THE CHANCES FOR WIDESPREAD THUNDERSTORMS IS  
HIGHEST WEDNESDAY NIGHT AS THE PRIMARY WAVE OF SHORTWAVE ENERGY  
MOVES ACROSS THE AREA. TIMING COULD CHANGE THIS TO EARLIER OR  
LATER, WHICH WILL NEED TO BE WATCHED FOR ANY STRONGER STORM  
POTENTIAL OR HEAVY RAIN/FLOODING POTENTIAL. MOVING THROUGH THE  
REMAINDER OF THE WEEK, THERE WILL BE MINOR WEAK SHORTWAVE ENERGY  
MOVING THROUGH THE SOUTHWEST FLOW ACROSS OUR AREA PERIODICALLY,  
BUT TIMING THOSE PIECES OF ENERGY IS NOT ANYTHING THAT CAN BE DONE  
AT THIS POINT WITH HIGH CONFIDENCE. ALSO, WITH HIGH DEWPOINTS  
PROVIDING DECENT INSTABILITY WILL LIKELY LEAD TO AT LEAST SOME  
DAILY DIURNAL CONVECTION. THEREFORE THUNDERSTORM CHANCES ARE IN  
THE FORECAST THROUGH ALL PERIODS.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)  
ISSUED AT 1153 PM CDT SAT SEP 14 2019  
 
ACTIVE NEXT 6 HOURS FOR THE TAF SITES WITH SHOWERS AND  
THUNDERSTORMS AFFECTING MANY OF THE SITES. EARLY IN THE MORNING,  
WE MAY SEE SOME IFR AND HAVE STARTED TO TREND THAT WAY WITH LOW  
END MVFR. AFTER THE RAIN AND STORMS TONIGHT, EXPECT VFR CONDITIONS  
FOR THE REST OF THE PERIOD.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 1129 AM CDT SAT SEP 14 2019  
 
ROUTED WATER MOVING THROUGH THE RIVER SYSTEMS ALONG WITH  
ADDITIONAL HEAVY RAIN POTENTIAL TONIGHT IS CAUSING FORECAST RISES,  
MANY WITHIN BANK RISES, ACROSS THE AREA.  
 
THE HARDEST HIT LOCAL BASINS HAVE BEEN THE PECATONICA AND ROCK  
RIVER BASINS AND WE ARE GETTING A BETTER HANDLE ON THE FLOWS FROM  
RAINS THAT ALREADY FELL, HOWEVER THERE DOES REMAIN A BIT OF  
UNCERTAINTY ON HOW HIGH THE CRESTS WILL BE. THE PECATONICA IN  
FREEPORT IS CRESTING CURRENTLY AND WILL FALL LESS THAN A FOOT  
BEFORE STARTING TO GO UP AGAIN AS MORE WATER MOVES DOWN FROM  
UPSTREAM.  
 
ON THE ROCK, THE FORECAST FOR THE GAGE AT COMO HAS GONE DOWN THIS  
MORNING AND THE RATE OF RISE HAS SLOWED, GIVING LESS CONFIDENCE  
THAT THE RIVER WILL HIT THE FLOOD STAGE OF 12.5 FT EVEN THOUGH  
IT'S ONLY A HALF FOOT FROM THAT LEVEL CURRENTLY. BECAUSE OF THIS,  
OPTED TO HOLD ONTO THE FLOOD WATCH AND WILL RE-EVALUATE THIS  
AFTERNOON. DOWNSTREAM AT JOSLIN, IT MAY BE NOTICED THAT THE  
HYDROGRAPH IS NOW SHOWING THE RIVER TO RISE TO 14.1 FEET. THINK  
THE RISE IS GOING TO BE VERY NEAR 14 FT, BUT DON'T HAVE ENOUGH  
CONFIDENCE THAT IT WILL REACH OR EXCEED 14 FT TO PUT OUT A NEW  
FLOOD WARNING FOR MODERATE FLOODING YET. WILL CONTINUE TO MONITOR.  
 
THERE IS A CHANCE FOR HEAVY RAINS TONIGHT, IF HEAVIER RAINS FALL  
THAN IS EXPECTED, ADDITIONAL RIVER FLOODING COULD OCCUR.  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...FLASH FLOOD WATCH UNTIL 7 AM CDT SUNDAY FOR BUCHANAN-DELAWARE-  
DUBUQUE-JACKSON-JONES.  
 
IL...FLASH FLOOD WATCH UNTIL 10 AM CDT SUNDAY FOR CARROLL-JO DAVIESS-  
STEPHENSON.  
 
MO...NONE.  

 
 

 
 
UPDATE...ERVIN  
SYNOPSIS...08  
SHORT TERM...08  
LONG TERM...BROOKS  
AVIATION...GIBBS  
 
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