589  
FXUS63 KDVN 210517  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
1117 PM CST TUE FEB 20 2018  
   
..AVIATION UPDATE
 
 
   
UPDATE
 
 
ISSUED AT 536 PM CST TUE FEB 20 2018  
 
THE RAIN IS NOW SHIFTING EAST OF THE MISSISSIPPI RIVER, AND AS  
TEMPERATURES THERE ARE JUST REACHING FREEZING. THAT WILL LIKELY  
ALLOW US TO CLEAR OUT THE SOUTHEAST IOWA COUNTIES AND NORTHEAST  
MISSOURI COUNTIES EARLY FROM THE ADVISORY.  
ERVIN  
 
UPDATE ISSUED AT 400 PM CST TUE FEB 20 2018  
 
THE REMAINDER OF THE FLOOD WATCH HAS BEEN CANCELLED AS THE BULK OF  
THE RAIN HAS SHIFTED SOUTH AND EAST OF THE DVN CWA.  
 

 
   
SYNOPSIS
 
 
ISSUED AT 325 PM CST TUE FEB 20 2018  
 
LATEST SFC ANALYSIS WAS INDICATING OCCLUDING LOW ACRS THE U.P. OF  
MI, WITH MAIN TRAILING COLD FRONT DROPPING DOWN ACRS NORTH CENTRAL  
IL AND THEN DOWN TOWARD THE ST LOUIS MO AREA. SEASONABLY IMPRESSIVE  
LONG FETCH MOIST CONVEYOR OF SHOWERS WITH SOME EMBEDDED THUNDER  
STRETCHING ALL THE WAY FROM SOUTHERN TX, TO THE HEART OF THE GRT  
LKS. POST-FRONTAL NORTHWEST WINDS INCREASING TO 15 TO 20 KTS ACRS  
THE WESTERN CWA, WITH SOME DRIER SFC DPT INFLUX NOTED. THIS WILL  
EVENTUALLY LEAD TO A WINTRY MIX SCENARIO AGAIN ON THE WESTERN FLANK  
OF LINGERING OVER-RUNNING PRECIP BAND THIS EVENING. THEN ACTIVE  
SOUTHWEST FLOW WILL CONTINUE TO MAKE FOR A CHALLENGING FCST PERIOD  
WITH PRECIP SYSTEM POSSIBLE ALMOST EVERY OTHER DAY INTO THE  
WEEKEND.  
 

 
   
SHORT TERM
 
(THIS EVENING AND TONIGHT)  
ISSUED AT 325 PM CST TUE FEB 20 2018  
 
TONIGHT...WITH POST FRONTAL COOLING AND DRYING LLVL FETCH FEEDING  
INTO THE BACKSIDE OF THE RATHER SLOW MOVING PRECIP CONVEYOR, FEEL  
THERE WILL BE ANOTHER TRANSITION TO FREEZING RAIN PROFILES AS THE  
LATE AFTERNOON AND ESPECIALLY EVENING PROGRESS...ESPECIALLY ALONG  
AND EAST OF THE MS RVR GENERALLY FROM FAR NORTHEASTERN MO,  
NORTHEASTWARD TO THE PRINCETON AND STERLING IL AREAS. TOWARD THE END  
OF THE PERIOD, COLD AIR MAY DEEPEN ENOUGH FOR SOME SLEET TO MIX IN,  
BEFORE THE PRECIP TRAIN PUSHES OFF TO THE EAST. WILL ISSUE A NEW  
WINTER WEATHER ADVISORY FOR PRIMARILY THE FREEZING RAIN ACRS THE  
SOUTHEASTERN THIRD OR MORE OF THE DVN CWA, WITH UP TO A TENTH OF AN  
INCH OF GLAZE POSSIBLE. WILL RUN IT TO 09Z WED MORNING FOR A BUFFER  
END TIME , BUT SEVERAL OF THE LATEST HIRES MODELS WIND IT DOWN  
SEVERAL HOURS BEFORE THEN. THE REST OF THE CWA WILL HAVE TO WATCH  
OUT FOR FREEZING UP WET SURFACES AND PUDDLES THIS EVENING, IF THE  
INCREASING NORTHWEST WINDS DON'T DRY UP THE SURFACES BEFORE THEN.  
FLURRIES NOTED IN THE STRATOCU DECK OUT ACRS CENTRAL INTO WESTERN IA  
ATTM, AND SOME OF THESE MAY MAKE IT INTO THE LOCAL AREA LATER THIS  
EVENING. WILL GO WITH LOWS IN THE LOW 20S IN THE EAST, TO THE LOW  
TEENS OR AROUND 10 IN THE NORTHWEST. THESE NORTHWESTERN AREAS WILL  
ALSO HAVE WIND CHILLS AROUND OR BELOW ZERO TOWARD 12Z WED MORNING.  
..12..  
   
LONG TERM
 
(WEDNESDAY THROUGH NEXT TUESDAY)  
ISSUED AT 325 PM CST TUE FEB 20 2018  
 
FORECAST FOCUS ON ACTIVE PATTERN THROUGH THIS WEEKEND. THIS FORECAST  
BASED HEAVILY ON THE GFS, AS THE ECMWF WAS NOT AVAILABLE AS OF THIS  
WRITING.  
 
WEDNESDAY...MOSTLY SUNNY BUT COLD WITH HIGHS IN THE MID 20S TO LOWER  
30S. CLOUDS SHOULD BE ON THE INCREASE DURING THE AFTERNOON  
ESPECIALLY ACROSS OUR SOUTHERN HALF OF THE CWA. THIS WILL BE AHEAD  
OF THE NEXT UPPER LEVEL DISTURBANCE EJECTING OUT THE MAIN WESTERN  
TROUGH.  
 
WEDNESDAY NIGHT AND THURSDAY: POTENTIAL FOR A WINTER WEATHER  
ADVISORY HEADLINE FOR OUR SOUTHERN AND WESTERN COUNTIES FOR A  
COMBINATION OF LIGHT SNOW AND FREEZING RAIN. FORECAST SOUNDINGS  
SUGGEST THE FREEZING RAIN MAY BE CONFINED TO OUR SOUTHERN CWA WHILE  
THE SNOW WOULD BE IN OUR NORTH. DURING THE AFTERNOON, WARMER AIR  
COMING NORTHWARD WOULD CHANGE EVERYTHING OVER TO RAIN. LOWS WILL BE  
IN THE UPPER TEENS TO MID 20S WITH AFTERNOON HIGHS IN THE 30S. AS OF  
NOW, ICE ACCUMULATIONS ARE EXPECTED TO BE LESS THAN A TENTH OF AN  
INCH WITH SNOW AMOUNTS LESS THAN AN INCH.  
 
THURSDAY NIGHT AND FRIDAY...ANOTHER UPPER LEVEL DISTURBANCE (AND A  
BIT STRONGER) WILL PUSH INTO THE MIDWEST IN THE FAST SOUTHWEST FLOW.  
THIS SYSTEM WILL ALSO HAVE MORE MOISTURE TO WORK WITH. THIS ALSO  
LOOKS TO BE A FREEZING RAIN EVENT, ESPECIALLY IN OUR NORTHERN HALF.  
THIS TOO MAY NEED A WINTER WEATHER ADVISORY HEADLINE WITH ICE  
ACCUMULATIONS BETWEEN ONE AND TWO TENTHS OF AN INCH POSSIBLE. WARMER  
AIR ARRIVING BY AFTERNOON SHOULD CHANGE THE FREEZING RAIN OVER TO  
RAIN. LOWS WILL BE IN THE 20S NORTH TO THE 30S SOUTH WITH HIGHS  
PUSHING INTO THE 40S.  
 
FRIDAY NIGHT THROUGH SUNDAY: A POTENT STORM SYSTEM WILL ARRIVE AS A  
NEGATIVELY-TILTED TROUGH PUSHES OUT OF THE SOUTHERN ROCKIES AND INTO  
THE MIDWEST DURING THIS TIME FRAME. THE GFS TAKES A DEEPENING  
CYCLONE FROM THE OK PANHANDLE 12Z SAT (1006 MB) TO EASTERN IA 06Z  
SUN (991 MB) TO THE EASTERN GREAT LAKES (980MB) LATER ON SUNDAY.  
THIS MAY START OUT AS LIGHT SNOW BUT CHANGE TO LIGHT MODERATE RAIN  
(POSSIBLY HEAVY RAIN) AND THEN BACK TO SNOW AS THE SYSTEM PUSHES OFF  
TO THE NORTHEAST. THIS SYSTEM BEARS WATCHING ESPECIALLY IF THE ECMWF  
IS ON BOARD. ANY ADDITIONAL RAIN WOULD AGGRAVATE ANY EXISTING  
FLOODING AT THAT TIME. CAUTION: THIS IS LOW CONFIDENCE AT THIS TIME  
WITHOUT SEEING WHAT THE 12Z/20 ECMWF SHOWED.  
 
HAASE  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)  
ISSUED AT 1116 PM CST TUE FEB 20 2018  
 
MVFR CIGS ARE NOW CLEARING OUR OF ALL OF EASTERN IOWA AND  
NORTHWEST ILLINOIS. NORTHWEST WINDS OF 12 TO 20 KTS WILL CONTINUE  
TO PUMP COLD DRY AIR INTO THE REGION, WITH VFR CONDITIONS THROUGH  
THE NEXT 24 HOURS.  
ERVIN  
 

 
   
HYDROLOGY
 
 
ISSUED AT 400 PM CST TUE FEB 20 2018  
 
RAINFALL SINCE YESTERDAY WAS 1 TO 3 INCHES ACROSS MUCH OF THE CWA.  
THIS AMOUNT OF RAIN, FALLING ON FROZEN GROUND, HAS RESULTED IN RAPID  
RISES ON MANY RIVERS AND STREAMS WITH SEVERAL IN FLOOD. WHILE THERE  
IS HIGH CONFIDENCE IN THESE RIVER FORECASTS AT THIS TIME, THESE  
FORECASTS MAY STILL CHANGE DUE TO CONTINUED RUNOFF AND ICE JAMS ON  
SOME RIVERS.  
 
DETAILS:  
 
ROCK RIVER:  
 
MAJOR FLOODING IS FORECAST AT MOLINE, WITH MODERATE AT JOSLIN AND  
MINOR AT COMO. THE RIVER WILL RISE ABOVE FLOOD STAGE  
TONIGHT INTO WEDNESDAY MORNING.  
 
LA MOINE/GREEN/WAPSIPINICON RIVER:  
 
MODERATE FLOODING IS FORECAST AT COLMAR, GENESEO, AND DE WITT.  
 
MAQUOKETA/ENGLISH RIVER:  
 
MODERATE FLOODING IS FORECAST AT MAQUOKETA AND KALONA.  
 
PECATONICA RIVER:  
 
MINOR FLOODING IS EXPECTED AT FREEPORT.  
 
IOWA RIVER:  
 
MINOR FLOODING IS EXPECTED AT MARENGO, WAPELLO AND LONE TREE.  
 
OTHER FORECAST POINTS MAY ALSO GO INTO FLOOD AND WE WILL  
CONTINUE TO MONITOR THE SITUATION.  
 
IN ADDITION, AN AREAL FLOOD WARNING IS IN EFFECT FOR PORTIONS OF  
NORTHWEST IL AND EXTREME EASTERN IA UNTIL 1015 AM ON WEDNESDAY. THIS  
IS BECAUSE OF NUMEROUS CLOSED ROADS DUE TO FLOODING. ADDITIONAL  
FLOODING IS POSSIBLE.  
 
PLEASE SEE THE FLOOD WARNINGS AND FLOOD STATEMENTS PRODUCTS FOR  
UPDATED FORECASTS.  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...NONE.  
IL...WINTER WEATHER ADVISORY UNTIL 3 AM CST WEDNESDAY FOR BUREAU-  
HANCOCK-MCDONOUGH-PUTNAM-WARREN.  
 
MO...NONE.  

 
 

 
 
UPDATE...ERVIN  
SYNOPSIS...12  
SHORT TERM...12  
LONG TERM...HAASE  
AVIATION...ERVIN  
HYDROLOGY...HAASE  
 
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