471  
FXUS63 KDVN 232312  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
612 PM CDT SUN JUL 23 2017  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 322 PM CDT SUN JUL 23 2017  
 
ISOLATED SHOWERS AND THUNDERSTORMS WERE DEVELOPING ACROSS  
NORTHERN ILLINOIS AS OF 230 PM AS A TROUGH PUSHED ACROSS THE  
MISSISSIPPI RIVER. AHEAD OF THIS TROUGH, DEW POINTS WERE IN THE  
LOWER TO MID 70S WHILE BEHIND IT DEW POINTS WERE IN THE MID TO  
UPPER 60S. TEMPERATURES RANGED FROM THE LOWER 80S NORTHWEST OF A  
LINE FROM CEDAR RAPIDS TO DUBUQUE WITH THE LOWER 90S ACROSS  
NORTHEAST MISSOURI.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY)  
ISSUED AT 322 PM CDT SUN JUL 23 2017  
 
THE MAIN FORECAST CONCERNS IN THE NEAR TERM ARE SCATTERED SHOWERS  
AND THUNDERSTORM CHANCES THEN THE FOCUS IS ON TEMPERATURES AND CLOUD  
COVER.  
 
IN THE NEAR TERM, ISOLATED SHOWERS AND THUNDERSTORMS ARE ASSOCIATED  
WITH THE CONVERGENCE ALONG THE WIND SHIFT BOUNDARY AS WELL AS COLDER  
TEMPERATURES ALOFT. NEAR TERM MODELS HAVE THE SHORTWAVE ENERGY  
ASSOCIATED WITH THIS EXITING THE AREA BY 21 UTC AND EXPECT ANY  
CONVECTION TO DISSIPATE OR MOVE OUT OF THE AREA AS THE MAIN FORCING  
EXITS THE AREA.  
 
DRY AND COOL AIR ADVECTION WILL MOVE INTO THE AREA AS HIGH  
PRESSURE BUILDS FROM THE NORTHERN PLAINS INTO THE UPPER MIDWEST  
SUNDAY NIGHT. SKIES WILL CLEAR THIS EVENING WITH THE LOSS OF PEAK  
HEATING. EXPECT NOTICEABLY COOLER OVERNIGHT LOWS WITH TEMPERATURES  
SLIGHTLY BELOW NORMAL. THE ONLY PROCESS THAT MAY HOLD BACK  
TEMPERATURES WILL BE THE AMOUNT OF WATER AND MOISTURE ACROSS THE  
AREA. THE MOISTURE MAY ALSO LEAD TO THE DEVELOPMENT OF PATCHY FOG  
ACROSS THE AREA NORTH OF INTERSTATE 80 BUT CURRENT THINKING IS THAT  
THE DRY AIR MOVING INTO THE REGION WILL PREVENT ANY FOG DEVELOPMENT.  
 
HIGH PRESSURE WILL REMAIN TO THE NORTHEAST OF OUR AREA ACROSS  
WISCONSIN WITH WINDS TURNING TO THE NORTHEAST AND ADVECTING IN  
COOLER AIR OFF OF LAKE MICHIGAN FOR THE DAY ON MONDAY. THIS MAY TRAP  
SOME LOWER CLOUDS ACROSS OUR NORTHEAST HALF DURING THE DAY ON MONDAY  
AS MODEL CROSS SECTIONS AND SOUNDINGS SHOW ABUNDANT LOW LEVEL MOISTURE  
TOMORROW.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 322 PM CDT SUN JUL 23 2017  
 
NO SIGNIFICANT CHANGES TO THE EXTENDED PERIOD.  
 
DRY AND COMFORTABLE CONDITIONS ARE EXPECTED OVER THE AREA MONDAY  
INTO TUESDAY WITH NORTHWEST FLOW ALOFT AND A LARGE AREA OF SURFACE  
HIGH PRESSURE SETTLING IN OVER THE REGION.  
 
THE WEATHER WILL BECOME ACTIVE AGAIN DURING THE MIDDLE OF THE WEEK  
AS AN UPPER TROUGH TRAVERSES SOUTHERN CANADA, FORCING A COLD FRONT  
INTO THE REGION. AHEAD OF THE FRONT, A QUICK BOUT OF HIGHER HUMIDITY  
(DEWPOINTS IN THE 70S) WITH HEAT INDICES IN THE LOWER 90S NORTH  
TO LOWER 100S ACROSS THE SOUTH, IS FORECAST FOR WEDNESDAY. THE 12Z  
MODEL RUNS ARE STILL SUGGESTING A PROGRESSIVE SYSTEM, THEREBY  
LIMITING THE CHANCES FOR STORMS TO A 12-24 HR WINDOW. HOWEVER,  
PWATS AROUND 2 INCHES ARE FORECAST TO POOL AHEAD OF THE COLD  
FRONT, INCREASING THE RISK FOR HEAVY RAINFALL RATES WITH ANY  
THUNDERSTORMS THAT OCCUR.  
 
THE STORM PREDICTION CENTER HAS A SLIGHT RISK FOR SEVERE STORMS  
NORTH OF I-80 FOR WEDNESDAY AND WEDNESDAY NIGHT. CONFIDENCE ON THE  
TIMING AND COVERAGE OF STRONG TO SEVERE STORMS IS LOW AT THIS LEAD  
TIME.  
 
AN AMPLIFYING RIDGE IN THE WEST AND AN EASTERN U.S. TROUGH WILL  
PUT THE REGION IN NORTHWEST FLOW AGAIN FOR THE END OF THE WEEK AND  
WEEKEND. EXPECT A RETURN TO COOLER TEMPS IN THE UPPER 70S NORTH  
TO LOWER/MIDDLE 80S SOUTH, ALONG WITH LOWER HUMIDITY. UTTECH/DLF  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)  
ISSUED AT 610 PM CDT SUN JUL 23 2017  
 
VFR CONDITIONS EXPECTED OVER AT LEAST THE NEXT 24 HOURS. HIGH PRESSURE  
FROM THE PLAINS WILL BRING MOSTLY CLEAR TO CLEAR SKIES AND GOOD VISIBILITIES.  
WINDS WILL BE NORTHERLY TONIGHT AT 5 TO 10 MPH BECOMING NORTHEAST  
TO EAST ON MONDAY.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 351 PM CDT SUN JUL 23 2017  
 
CONTINUING TO WATCH HIGH RIVER LEVELS AS RUNOFF FROM HEAVY RAINS THE  
PAST FEW DAYS MAKES ITS WAY DOWN THROUGH THE RIVER SYSTEMS. THE  
PECATONICA RIVER AT FREEPORT IS HAS AN ONGOING SLOW CREST JUST UNDER  
MAJOR FLOOD STAGE. LOCAL OFFICIALS INDICATE IMPACTS WILL BE  
MANAGEABLE IF THERE IS NO ADDITIONAL RAINFALL TO PROVIDE  
ADDITIONAL RISES IN THE RIVER. SPOTTY SHOWERS AND STORMS THIS  
AFTERNOON COULD BRING SOME RAIN TO THESE AREAS, BUT HEAVY RAIN IS  
NOT ANTICIPATED SO DON'T BELIEVE THE RIVER LEVEL WILL BE IMPACTED  
TOO MUCH FROM TODAY'S ACTIVITY. HOWEVER, YELLOW CREEK, WHICH IS A  
TRIBUTARY OF THE THE PECATONICA HAS SIGNIFICANT FLOODING ONGOING.  
ON THE ROCK RIVER, COMO IS CRESTING AT LEVELS NOT SEEN SINCE 1929.  
AT JOSLIN AND MOLINE, THE FORECAST HAS BEEN ADJUSTED SLIGHTLY  
DOWNWARD DUE TO REAL-TIME MEASUREMENTS TAKEN BY THE USGS THIS  
AFTERNOON, BUT STILL EXPECT CRESTS VERY NEAR RECORD LEVELS AT BOTH  
OF THESE LOCATIONS IN THE NEXT 48 HOURS. MOVING INTO IOWA, ON THE  
WAPSIPINICON, ALSO FORECASTING MAJOR FLOODING FROM INDEPENDENCE  
TO THE ENTRANCE TO THE MISSISSIPPI. LOCAL OFFICIALS STATED THE  
MAJORITY OF THE FEEDER CREEKS AND STREAMS WERE CONTINUING TO RISE  
THIS MORNING AND AFTER LOOKING AT OBSERVATIONS FROM TRIPOLI, FELT  
THE FORECAST NEEDED TO BE INCREASED A BIT FROM LAST EVENINGS  
FORECAST. THE RIVER AT IDPI4 IS RISING RAPIDLY AND IS EXPECTED TO  
CREST TONIGHT. DOWNSTREAM, IT WILL TAKE TIME FOR THE RIVER TO GO  
UP, WHERE AT DEWITT, IT WILL FALL BELOW FLOOD-STAGE, BEFORE RISING  
AGAIN DUE TO THE ROUTED FLOWS.  
 
FOR THE MISSISSIPPI, WITH LESSER FLOWS COMING FROM SOME OF THE  
TRIBUTARIES, INCLUDING THE MAQUOKETA RIVER, FORECASTS WERE ADJUSTED  
DOWNWARD THIS MORNING. AT CAMANCHE, THE RIVER IS NO LONGER  
EXPECTED TO REACH FLOOD STAGE AND THE FLOOD WATCH WAS CANCELLED.  
EVEN WITH THE FORECASTS DROPPING 0.5 TO 1.0 FEET FROM THE PREVIOUS  
FORECAST, THE EXPECTED CRESTS WILL STILL BE WELL ABOVE FLOOD  
STAGE FOR LOCATIONS FROM ILLINOIS CITY THROUGH BURLINGTON, SO  
FLOOD WATCHES WERE UPGRADED TO WARNINGS. DO ANTICIPATE FORECASTS  
COULD DROP A LITTLE BIT YET AS WE GET A BETTER HANDLE ON THE  
AMOUNTS AND TIMING OF THE WATER COMING OUT OF THE TRIBUTARIES, SO  
MANY AREAS MAY CREST IN MINOR FLOOD STAGE LEVELS RATHER THAN  
MODERATE.  
 
LUCKILY, WITH THE EXCEPTION OF SOME RAIN YET TODAY, THE NEXT WEEK  
LOOKS DRY SO LEVELS WILL LIKELY HAVE A CHANCE TO FALL BEFORE  
ADDITIONAL RAIN FALLS ACROSS THE AREA.  
 

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

 
 

 
 
SYNOPSIS...COUSINS  
SHORT TERM...COUSINS  
LONG TERM...UTTECH/DLF  
AVIATION...NICHOLS  
HYDROLOGY...BROOKS  
 
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