250  
FXUS63 KDVN 262345  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
645 PM CDT FRI AUG 26 2016  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 315 PM CDT FRI AUG 26 2016  
 
18Z SURFACE DATA HAS HIGH PRESSURE OVER THE UPPER MIDWEST WITH A LOW  
IN EASTERN KANSAS WEST OF KEMP. A FRONTAL BOUNDARY RUNS EAST FROM  
THE LOW INTO THE OHIO VALLEY. DEW POINTS WERE IN THE 50S AND 60S  
NORTH OF THE FRONT WITH 70S ALONG AND SOUTH OF THE FRONT.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SATURDAY)  
ISSUED AT 315 PM CDT FRI AUG 26 2016  
 
THROUGH LATE AFTERNOON MAINLY DRY CONDITIONS SHOULD BE SEEN ACROSS  
THE AREA WITH POSSIBLY A FEW LIGHT SHOWERS ACROSS THE SOUTH THIRD OF  
THE AREA.  
 
THERE HAS BEEN A FAIRLY CONSISTENT SIGNAL FROM THE RAP INDICATING  
SHOWERS AND EVENTUALLY THUNDERSTORMS WILL DEVELOP ACROSS THE  
SOUTHEAST HALF OF THE AREA DURING THE EVENING. THIS SCENARIO IS  
SUPPORTED BY THE WEAK RADAR RETURNS ACROSS EASTERN MISSOURI AND AN  
APPROACHING UPPER LEVEL DISTURBANCE IN WATER VAPOR IMAGERY. THE  
NORTHWEST HALF OF THE AREA SHOULD EVENTUALLY SEE SHOWERS AND  
POSSIBLY A FEW THUNDERSTORMS DEVELOP PRIOR TO MIDNIGHT.  
 
BY OR AFTER MIDNIGHT, THE CONVECTION THAT DEVELOPS DURING THE  
EVENING WILL GROW UPSCALE INTO AN ORGANIZED THUNDERSTORM COMPLEX.  
THE SOUTHEAST HALF OF THE AREA SHOULD HAVE THE BETTER AREAL COVERAGE  
ALONG WITH THE POTENTIAL FOR LOCALLY HEAVY RAINFALL.  
 
THE NOCTURNAL THUNDERSTORM COMPLEX THAT DEVELOPS TONIGHT WILL EXIT  
THE AREA SATURDAY MORNING. THUS AREAL COVERAGE OF PRECIPITATION WILL  
DECREASE DURING THE MORNING ROUGHLY FROM WEST TO EAST.  
 
BOUNDARIES LEFT OVER FROM THIS CONVECTION WILL THEN PROVIDE THE  
FOCUS FOR DIURNAL CONVECTION THAT DEVELOPS SATURDAY AFTERNOON.  
POTENTIAL CLOUD COVER FROM THE MORNING DOES RAISE QUESTIONS ABOUT  
HOW MUCH CONVECTION WILL DEVELOP DURING THE AFTERNOON.  
   
LONG TERM
 
(SATURDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 315 PM CDT FRI AUG 26 2016  
 
THE EXTENDED FORECAST BEGINS WITH THE SOMEWHAT POORLY ORGANIZED  
CONVECTIVE POTENTIAL THIS WEEKEND AND EARLY WEEK, FOLLOWED BY AT  
LEAST TWO LIKELY DRY DAYS UNDER A PASSING HIGH PRESSURE SYSTEM AT  
THE SURFACE. THIS DRY PERIOD WILL LIKELY NOT COMPLETELY APPEAR  
OBVIOUS IN OUR FORECAST GRIDS UNTIL TOMORROW WHEN BLENDS HOPEFULLY  
LET GO OF THE VERY LOW POPS REMAINING IN THE MID WEEK PERIODS.  
 
THE AIR MASS IN PLACE IN THE MIDWEST CONTINUES TO SUPPORT HIGHS  
MAINLY IN THE 80S, AND LOWS IN THE MID 60S TO LOWER 70S. THIS WILL  
BE ACCOMPANIED BY RATHER HIGH HUMIDITY, ESPECIALLY FOR EARLY  
SEPTEMBER, AT LEAST UNDER THE HIGH PRESSURE MOVES IN FOR WED-THU.  
LOOKING BEYOND, THE GFS AMPLIFIES A HUGE UPPER HIGH, WHILE THE ECMWF  
BUILDS A BROAD TROF INTO THE ROCKIES. CLIMATOLOGY COULD SUPPORT  
EITHER ONE THIS TIME OF YEAR, AND CONFIDENCE IS LOW.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 640 PM CDT FRI AUG 26 2016  
 
VFR CONDITIONS WILL GIVE WAY TO EPISODES OF MVFR CONDITIONS BETWEEN  
27/03Z AND 27/08Z AT ALL OR MOST OF THE TERMINALS AS AN AREA OF SHOWERS  
AND THUNDERSTORMS PASSES. AFTER 27/08Z LOW END VFR TO MVFR CONDITIONS  
DUE TO 1-4K AGL CEILINGS WILL PERSIST WITH RISK OF LIGHT PRECIPITATION  
INTO MID MORNING ON SATURDAY AS A WARM FRONT PASSES. SKIES WILL BECOME  
PARTLY CLOUDY TO MOSTLY SUNNY AFTER 27/15Z AFTER THE WARM FRONT PASSES.  
LIGHT EASTERLY WINDS WILL SHIFT TO THE SOUTH AND SOUTHWEST BY SATURDAY  
MORNING.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 1017 AM CDT FRI AUG 26 2016  
 
AREA RIVERS ARE STILL RISING FOR THE MOST PART, INCLUDING THE  
MISSISSIPPI RIVER. TODAYS FORECASTS SHOW THE IOWA RIVER NEAR  
CONESVILLE AND WAPSIPINICON RIVER NEAR DEWITT APPROACHING OR  
EXCEEDING FLOOD STAGE IN A WEEK MAINLY DUE TO ROUTED FLOW FROM  
UPSTREAM. WE HAVE CHOSEN NOT TO ISSUE A WARNING OR WATCH, AS THIS  
IS STILL A WAYS OUT, AND THE FLOOD PEAK FLOWS UPSTREAM ARE LIKELY  
TO ATTENUATE SOME MORE THAT WE FEEL ARE MODELED CURRENTLY IN THE  
FORECAST, RESULTING IN POSSIBLY LOWER RIVER LEVELS A WEEK FROM NOW  
THAT WHAT IS CURRENTLY FORECAST. THIS IS ALSO TRUE FOR THE  
MISSISSIPPI RIVER, WHEN YOU LOOK AT TODAY'S FORECAST COMPARED TO  
YESTERDAY. THE TURKEY RIVER INPUT UPSTREAM HAS BEEN DROPPED  
SEVERAL THOUSAND CFS, ON TODAY'S RUN, THUS THE FLOOD FORECAST FOR  
BURLINGTON (WELL DOWNSTREAM) HAS BEEN LOWERED A BIT BELOW FLOOD  
STAGE. ALL THAT SAID, THIS IS OFTEN THE CASE OF ROUTED FLOOD WATER  
FROM A HEAVY RAIN EVENT, BUT DOES NOT ACCOUNT FOR ADDITIONAL  
RAINFALL BEYOND TODAY. RIVERS ARE RUNNING HIGHER THAN NORMAL, AND  
SOILS ARE GENERALLY SATURATED. ADDITIONAL HEAVY RAINS COULD RESULT  
IN INCREASED RIVER FORECASTS.  
ERVIN  
 

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

 
 

 
 
SYNOPSIS...08  
SHORT TERM...08  
LONG TERM...ERVIN  
AVIATION...NICHOLS  
HYDROLOGY...ERVIN  
 
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