337  
FGUS73 KLOT 201343  
ESFLOT  
ILC031-037-043-063-089-091-093-099-103-141-197-201-INC089-202200-  
 
HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE CHICAGO IL  
843 AM CDT TUE AUG 20 2019  
 
...FLOODING POSSIBLE DUE TO HEAVY RAINFALL MOVING INTO AREA LATER  
THIS MORNING INTO EARLY AFTERNOON...  
 
A WEATHER SYSTEM MOVING TOWARD THE AREA IS THE FOCUS FOR HEAVY  
THUNDERSTORMS AND HAS A HISTORY OF PRODUCING HEAVY RAINFALL AND  
ISOLATED FLASH FLOOD REPORTS IN A FEW AREAS ACROSS IOWA. THESE  
THUNDERSTORMS ARE EXPECTED TO MOVE TOWARD NORTH CENTRAL AND  
NORTHEAST ILLINOIS OVER THE NEXT SEVERAL HOURS BRINGING THE  
POSSIBILITY OF ISOLATED FLASH FLOODING.  
 
THIS FLOOD POTENTIAL EXISTS FROM THIS MORNING THROUGH AT LEAST  
LATE THIS AFTERNOON.  
 
RAINFALL OVER THE LAST SEVEN DAYS HAS BEEN GENERALLY LESS THAN  
ONE INCH EXCEPT FOR AREAS CLOSE TO THE CHICAGO METRO WHERE AMOUNTS  
HAVE BEEN AS HIGH AS TWO INCHES. THIS GENERALLY DRY WEATHER HAS  
BEEN A CONTINUATION OF A MULTI-WEEK PERIOD OF MAINLY DRY  
CONDITIONS LEADING TO A SUBSTANTIAL DROP IN SOIL MOISTURE TOWARD  
MORE NORMAL VALUES FOR AUGUST. RIVER LEVELS HAVE ALSO BEEN  
GENERALLY FALLING AND ARE NEAR NORMAL TO SLIGHTLY ABOVE NORMAL FOR  
THIS TIME OF YEAR.  
 
DESPITE THESE CONDITIONS WHICH WOULD TYPICALLY REDUCE A FLOOD THREAT,  
HEAVY THUNDERSTORMS ARE EXPECTED LATER THIS MORNING THROUGH THIS  
AFTERNOON. THESE STORMS HAVE A HISTORY OF ISOLATED RAINFALL RATES  
OF 1-2 INCHES PER HOUR AND MORE THAN THREE INCHES OVER A THREE  
HOUR PERIOD. FOR AREAS THAT EXPERIENCE RAINFALL RATES OF THIS  
MAGNITUDE, FLASH FLOODING MAY OCCUR. FLOOD IMPACTS WOULD MOST  
LIKELY BE CONFINED TO QUICK-RESPONSE AREAS SUCH AS UNDERPASSES,  
URBAN AREAS, AND SMALL STREAMS.  
 
THIS OUTLOOK MEANS THAT ELEVATED WATER LEVELS AND POTENTIAL  
IMPACTS ARE POSSIBLE, BUT NOT YET CERTAIN. PERSONS SHOULD CLOSELY  
MONITOR FORECASTS INCLUDING THE POSSIBILITY OF FLOOD WATCHES,  
WARNINGS, AND ADVISORIES.  
 

 
 
WSL  
 
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