947  
FXUS63 KDVN 222329  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
629 PM CDT THU JUN 22 2017  
   
UPDATE
 
 
ISSUED AT 629 PM CDT THU JUN 22 2017  
 
AT 6 PM CDT, KDVN RADAR AN ISOLATED POCKET OF SPIRALING LIGHT  
RAIN SHOWERS ASSOCIATED WITH A MCV REMNANT FROM LAST NIGHT'S  
STORMS OVER KS ENTERING SOUTHEAST IOWA. FURTHER NORTH, A BAND OF  
WEAKENING SHOWERS THAT PREVIOUSLY HAD A FEW EMBEDDED WEAK  
THUNDERSTORMS, REACHED FROM THE WATERLOO AREA NORTHEAST INTO FAR  
SOUTHWEST WI. WITH THE MAIN SYNOPTIC COLD FRONT STILL WELL TO THE  
NORTHWEST, AND A CAPPED ENVIRONMENT OVER THE FORECAST AREA, THESE  
FEATURES WILL REMAIN WEAK THROUGH EARLY EVENING AND TONIGHT'S  
ANTICIPATED THUNDERSTORMS HAVE YET TO DEVELOP.  
 
HAVE FINE TUNED THE FORECAST FOR THESE FEATURES IN UPDATES AND  
WILL CONTINUE TO MONITOR TRENDS THIS EVENING FOR ANTICIPATED  
UPSTREAM STORM DEVELOPMENT.  
 

 
   
SYNOPSIS
 
 
ISSUED AT 323 PM CDT THU JUN 22 2017  
 
A FRONTAL BOUNDARY STRETCHES FROM CENTRAL NEBRASKA NORTHEASTWARD  
INTO NORTHERN IOWA AND INTO SOUTHERN WISCONSIN. SCATTERED SHOWERS  
CONTINUE NORTH OF INTERSTATE 80. TEMPERATURES RANGED FROM THE  
UPPER 70S ALONG THE HIGHWAY 20 CORRIDOR TO THE MID 80S IN  
SOUTHEAST IOWA AND NORTHEAST MISSOURI. DEWPOINTS WERE IN THE UPPER  
60S TO LOWER 70S.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 323 PM CDT THU JUN 22 2017  
 
THE MAIN FORECAST CONCERN THIS PERIOD ARE CHANCES OF THUNDERSTORMS  
TONIGHT INTO FRIDAY MORNING. LARGE SCALE MODELS ARE IN GOOD  
OVERALL AGREEMENT AND CAMS ARE RESOLVING THE CURRENT FEATURES A  
LITTLE BETTER.  
 
MODELS DEPICT A COLD FRONT SLIDING SOUTHEASTWARD ACROSS THE REGION  
FROM BASICALLY 06 UTC TO ABOUT 09 UTC FRIDAY. THE BEST LIFT IS  
SLIGHTLY OFFSET FROM THE CONVERGENCE ALONG THE FRONT AND THE BEST  
RH. SURFACE BASE CAPE IS CURRENTLY RANGING FROM 1500 TO 2500 J/KG  
ACROSS THE REGION. THE BETTER 0 TO 6 KM SHEAR IS JUST AHEAD OF THE  
FRONT AND WILL PROBABLY NEED THE ARRIVAL OF THE FRONT TO INITIATE  
STORMS ACROSS THE NORTH AND THEN MOVE SOUTHEASTWARD WITH THE FRONT  
ACROSS THE REGION. THE MAIN THREATS WILL BE HAIL AND WINDS RANGING  
FROM 60 TO 70 MPH. FOR THESE REASONS, THERE IS SLIGHT RISK OF  
SEVERE THUNDERSTORMS ACROSS THE REGION. THE CONVERGENCE OF THE  
FRONT AND SYNOPTIC LIFT WILL BE NEEDED TO OVERCOME THE CAP TO OUR  
NORTH AND DEVELOP THUNDERSTORMS THAT WILL MOVE INTO OUR REGION.  
THERE IS ALSO AN ISOLATED FLASH FLOOD THREAT WITH INCREASING DEEP  
MOISTURE.  
 
THIS IS EXPECTED TO BE A PROGRESSIVE SYSTEM WITH THE FRONT MOVING  
THROUGH AND HIGH PRESSURE BUILDING INTO THE REGION FOR THE END OF  
THE WORK WEEK. TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL FOR  
FRIDAY.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 323 PM CDT THU JUN 22 2017  
 
.MAINLY DRY, AND EXCEPTIONALLY PLEASANT CONDITIONS WILL BE FOUND  
FROM FRIDAY THROUGH MONDAY, AS A SEASONALLY STRONG UPPER TROF DIGS  
OVER THE EASTERN 1/3 OF THE COUNTRY. THIS UPPER TROF WILL DRAW DOWN  
A SURFACE HIGH FROM CENTRAL CANADA, WITH DRY DEWPOINTS IN THE 40S  
AND 50S, AND HIGHS IN THE MID 60S TO MID 70S OVER THE UPPER MIDWEST.  
THERE SHOULD BE A DAILY INCREASE IN CUMULUS DURING THE AFTERNOON  
HOURS EACH DAY, AND WITH SOME PASSING UPPER ENERGY, SOME ISOLATED TO  
SCATTERED SHOWERS AND WEAK THUNDERSTORMS ARE POSSIBLE. HOWEVER,  
DESPITE THIS RAIN THREAT, THE DAYS SHOULD BE VIEWED AS DRY DAYS FOR  
THE MOST PART. ANY RAIN SHOULD QUICKLY EVAPORATE WITHIN A FEW  
MINUTES OF FALLING IN THE DRY AIR.  
 
MOVING ON TO MID WEEK, AFTER A PERIOD OF MODERATION UNDER THE HIGH,  
MOISTURE IS EXPECTED TO RETURN TO THE MIDWEST FOR TUESDAY THROUGH  
FRIDAY AS A SERIES OF WAVES PASS THROUGH IN ZONAL FLOW ALOFT. THE  
GFS/GEM/AND EC ALL HIT THE AREA WITH A AT LEAST 1 IF NOT MULTIPLE  
MCS DURING THIS PERIOD. WITH A SUSTAINED SOUTHERLY FLOW HEADED INTO  
THE WARM FRONT DURING THAT PERIOD, PWAT VALUES PROBABLY WILL BE  
SEASONALLY HIGH GIVEN THE CONVERGENCE INTO THE UPPER MIDWEST.  
THEREFORE, A SEASONAL RISK FOR BOTH SEVERE WEATHER AND HEAVY RAINS  
IS EXPECTED IN THIS TIME FRAME. AS TO WHAT DAYS THAT OCCUR, AND  
WHETHER IT IS MULTIPLE EVENTS, OR JUST ONE, IS GOING TO HAVE TO WAIT  
UNTIL THE PATTERN EVOLVES.  
ERVIN  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)  
ISSUED AT 629 PM CDT THU JUN 22 2017  
 
A COLD FRONT MOVING THROUGH THE FORECAST AREA TONIGHT IS EXPECTED  
TO DEVELOP AN ORGANIZED LINE OF THUNDERSTORMS, SOME OF WHICH COULD  
PRODUCE LARGE HAIL AND DAMAGING WINDS. AT ANY GIVEN TAF SITE,  
THERE WILL LIKELY BE A LESS THAN 2 HOUR WINDOW OF THUNDERSTORMS,  
BUT CURRENT FORECASTS WILL HAVE LONGER PERIODS OF THUNDERSTORMS  
MENTIONED DUE TO LOW CONFIDENCE IN TIMING. AFTER THE STORMS MOVE  
THROUGH, SOME FORECAST MODELS ARE SUGGESTING MVFR OR EVEN IFR  
CEILINGS. THIS APPEARS TO BE OVERLY PESSIMISTIC AND FOR NOW WILL  
KEEP POST-FRONTAL CLOUDS IN VFR RANGE.  
 

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

 
 

 
 
UPDATE...SHEETS  
SYNOPSIS...COUSINS  
SHORT TERM...COUSINS  
LONG TERM...ERVIN  
AVIATION...SHEETS  
 
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