477  
FXUS63 KDVN 272312  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
612 PM CDT THU JUL 27 2017  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 318 PM CDT THU JUL 27 2017  
 
THE MAIN COLD FRONT EXTENDED FROM CENTRAL MO TO CENTRAL IL AND WAS  
SAGGING SOUTHWARD. A SECONDARY WEAK FRONT OR TROUGH WAS MOVING  
THROUGH NORTHERN IL (SEEN ON VISIBLE SATELLITE IMAGERY) AND WAS  
PRODUCING A FEW SHOWERS ON THIS BOUNDARY, BUT WAS EAST OF THE DVN  
CWA. DESPITE THE HRRR WANTING TO GENERATE SHOWERS IN THE DVN CWA  
THERE HAS BEEN NO EVIDENCE ON RADAR AS OF YET. WILL HANG ONTO THE  
SLIGHT POPS THIS AFTERNOON JUST IN CASE.  
 
NORTHEAST WINDS WERE COMING OFF THE GREAT LAKES WITH MUCH DRIER  
AIR ACROSS MN/WI/MI WHERE DEWPOINTS WERE IN THE 50S AT MANY  
LOCATIONS. ACROSS THE DVN CWA, DEWS RANGED FROM THE MID 60S NORTH  
TO THE LOWER 70S SOUTH.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 318 PM CDT THU JUL 27 2017  
 
FORECAST FOCUS ON DELIGHTFUL WEATHER FOR THE END OF JULY.  
 
TONIGHT: WITH LOSS OF HEATING THE CUMULUS CLOUDS WILL DISSIPATE  
GIVING WAY TO A CLEAR AND COMFORTABLE NIGHT, AS DEWPOINTS CONTINUE  
TO LOWER ON NORTHEAST WINDS. LOWS SHOULD RANGE FROM 60 AT  
FREEPORT, IL TO THE MID 60S IN EXTREME NORTHEAST MO.  
 
FRIDAY: HIGH PRESSURE BUILDING INTO THE GREAT LAKES WILL BRING A  
FANTASTIC DAY WITH COMFORTABLE HUMIDITY AND LIGHT NORTHEAST WINDS.  
OTHER THAN SCATTERED FAIR WEATHER CUMULUS CLOUDS DOTTING THE  
LANDSCAPE, THERE WILL BE PLENTY OF SUNSHINE. AFTERNOON HIGHS WILL  
PUSH INTO THE UPPER 70S TO LOWER 80S AT MOST LOCATIONS. ..HAASE..  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 318 PM CDT THU JUL 27 2017  
 
FRIDAY NIGHT THROUGH THE WEEKEND...LATEST RUN MEDIUM RANGE MODELS IN  
GOOD AGREEMENT OF SUGGESTING LONG WAVE TROF TO CONTINUE TO DIG SOUTH  
AND ESTABLISH ACRS THE APPALACHIANS AND ATLANTIC SEABOARD THIS  
PERIOD, WHILE BROAD UPPER RIDGE ENGULFS THE WEST HALF OF THE CONUS.  
RESULTANT AMPLIFYING NORTHWEST FETCH WILL ALLOW FOR A SEASONABLY  
ROBUST LLVL HIGH PRESSURE SYSTEM TO DUMP DOWN OUT OF CANADA AND  
BACKDOOR IT'S WAY DOWN THE WESTERN GRT LKS THIS PERIOD. LOOKING AT  
EXTENT OF PROJECTED AIR MASS INFLUX, DRIER COLUMN FROM THE SFC ON  
UP, AND THICKNESSES GENERALLY SUGGEST LOWS AT NIGHT WELL DOWN IN THE  
50S, WITH AFTERNOON HIGHS IN THE UPPER 70S TO LOWER 80S. MORE AREAS  
MAY HAVE TROUBLE MAKING IT OUT OF THE 70S ON SATURDAY DEPENDING ON  
MIX OUT DEPTH, WILL HAVE TO GO ABOVE H85 MB TO GET THE 80S. H85 MB  
RIDGE COOL RULE SUPPORTS LOWS DOWN IN THE LOW TO MID 50S FOR MUCH OF  
THE CWA FOR BOTH FRI AND SAT NIGHTS.  
 
MONDAY THROUGH NEXT THURSDAY...PROJECTED UPPER JET TRENDS AND EXTENT  
OF THE WESTERN RIDGE MASS INDICATE THE SYNOPTIC SCALE PATTERN TO  
ADJUST LITTLE AND REMAIN ALMOST BLOCKED UNTIL LATER IN THE WEEK. THE  
AIR MASS ACRS THE REGION WILL LOOK TO MODIFY AND WARM BACK UP TO  
NORMAL LEVELS THIS PERIOD. LOOKING AT LONGER RANGE TRENDS, IT  
APPEARS THAT RIDGE-RIDING WAVE ENERGY WILL TRY TO PROPAGATE  
SOUTHEASTWARD INTO THE GRT LKS AND RE-ENFORCE THE TROFFINESS FROM  
THE GRT LKS ON EASTWARD. IN THE PROCESS, IT WILL TRY AND SHUNT A SFC  
FRONT DOWN ACRS THE LOCAL AREA FROM THE NORTH SOMETIME WED INTO THU,  
WHICH MAY ACT AS A FOCUS FOR SHOWER AND THUNDERSTORM DEVELOPMENT  
DURING THE AFTERNOON AND EVENING. BUT MOST OF THE MEDIUM RANGE  
SOLUTIONS SUGGEST MARGINAL MOISTURE FEED AND CONVERGENCE INTO THIS  
BOUNDARY AND THERE MAY NOT BE MUCH ORGANIZATION TO ANY CONVECTION...  
SCTRD DIURNAL CLUSTERS TO ISOLATED SHOWERS/STORMS BOTH WED AFTERNOON  
AND POSSIBLY THU. THE 12Z ECMWF REALLY WASHES OUT THIS FEATURE TO  
THE SOUTH BY NEXT THU AND SUGGESTS MOST OF THE DAY TO BE DRY. THE  
12Z GFS OF COURSE IS WETTER AND MORE BULLISH, FESTERING ROUNDS OF  
SHOWERS AND STORMS FROM WED INTO THU ACRS PORTIONS OF THE AREA.  
UNLESS THERE CAN BE A MORE ENHANCED LOW TO MID LEVEL DRAW INTO THE  
FRONT FROM THE SOUTHWEST TO UTILIZE SOME MONSOONAL INFLUENCES,  
CURRENTLY SEE THE 12Z ECMWF SOLUTION BECOMING MORE VIABLE FOR THE  
LONG RANGE. ..12..  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)  
ISSUED AT 612 PM CDT THU JUL 27 2017  
 
VFR CONDITIONS WILL BE THE RULE OVERNIGHT THROUGH FRIDAY AS HIGH  
PRESSURE BUILDS INTO THE WESTERN GREAT LAKES. THERE IS A LOW  
POTENTIAL FOR PATCHY SHALLOW GROUND FOG, WHICH IS NOT MENTIONED IN  
THE FORECASTS.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 318 PM CDT THU JUL 27 2017  
 
ONLY ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL BE POSSIBLE  
THIS AFTERNOON, THUS NO REAL ADDITIONAL IMPACT EXPECTED TO THE  
FLOOD SENSITIVE RIVER BASINS. AN EXTENDED PERIOD OF DRY WEATHER IS  
STILL ON TRACK ACROSS THE ENTIRE AREA FROM TONIGHT THROUGH AT  
LEAST NEXT TUESDAY NIGHT. THIS DRY WEATHER WILL ALLOW AREA  
WATERWAYS TO GO BELOW FLOOD STAGE AND ALLOW THE SATURATED GROUND  
ACROSS NORTHEAST IOWA AND NORTHWEST ILLINOIS TO DRY OUT. BUT  
ELEVATED READINGS ON ALL AREA WATERWAYS ARE STILL EXPECTED INTO  
EARLY AUGUST.  
 
WAPSIPINICON RIVER...  
 
MODERATE FLOODING IS ONGOING AT ANAMOSA SHAW ROAD, BUT THE GAGE THAT  
WAS DETERMINED TO BE READING INCORRECTLY HAS BEEN ADJUSTED TO 18.8  
FEET. STILL FORECAST THERE TO START FALLING TONIGHT AND DROP BELOW  
MODERATE FLOOD STAGE BY LATE FRIDAY MORNING. MAJOR FLOODING STILL ON  
TRACK NEAR DEWITT BY SATURDAY MORNING.  
 
ROCK RIVER...  
 
MAJOR FLOODING CONTINUES ALONG THE ROCK RIVER. JOSLIN IS FALLING  
AFTER A BRIEF JUMP IN THE RIVER LEVEL THERE FROM THE STORMS OVER  
THAT BASIN YESTERDAY EVENING. COMO WILL EXPERIENCE A SECONDARY CREST  
AROUND 13.2 FEET BY FRIDAY AFTERNOON. MOLINE CONTINUES TO SLOWLY  
FALL WITH THE POTENTIAL OF DROPPING BELOW MAJOR FLOOD STAGE THERE BY  
SUNDAY MORNING.  
 
PECATONICA RIVER...  
 
FLOODING CONTINUES ALONG THE PECATONICA RIVER. THE WINSLOW AREA IS  
OBSERVING SIGNIFICANT FLOODING, WITH THE CREST NEAR THAT LOCATION AS  
OF THURSDAY MORNING. DOWNSTREAM AT FREEPORT THE RIVER SHOULD START  
RISING AGAIN AS THE CREST MAKES ITS WAY DOWNSTREAM. HOWEVER, THE  
TIMING OF THE RISE AND HOW MUCH HIGHER THE RIVER WILL GO IS STILL  
UNCERTAIN AS THERE IS SIGNIFICANT SPREADING OF THE WATER ACROSS THE  
RURAL AREAS. THE CURRENT FORECAST IS FOR THE RIVER TO CREST AROUND  
15.6 FEET, BUT IT COULD BE UP TO 0.3 FT HIGHER OR LOWER THAN THAT.  
 
MISSISSIPPI RIVER...  
 
FLOOD WARNINGS REMAIN IN EFFECT FOR MINOR FLOODING FROM MUSCATINE  
DOWN TO BURLINGTON, ALTHOUGH MUSCATINE SHOULD DROP BELOW FLOOD STAGE  
THIS AFTERNOON. THE FLOOD CREST IS AT GLADSTONE L&D 18, AND  
CURRENTLY APPROACHING BURLINGTON. KEITHSBURG APPEARS TO BE SLOWLY  
FALLING AND THUS HAS CRESTED EARLIER THIS MORNING.  
 

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

 
 

 
 
SYNOPSIS...HAASE  
SHORT TERM...HAASE  
LONG TERM...12  
AVIATION...SHEETS  
HYDROLOGY...BROOKS/12  
 
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