937  
FXUS63 KDVN 231620  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
1120 AM CDT SAT OCT 23 2021  
   
..HYDROLOGY UPDATE
 
 
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 225 AM CDT SAT OCT 23 2021  
 
EARLY MORNING SATELLITE IMAGERY SHOWS MID LEVEL CLOUDS SOUTH OF  
I-80 KEEPING TEMPERATURES SLIGHTLY WARMER THERE IN THE UPPER 30S  
AND LOWER 40S. ELSEWHERE, TEMPERATURES WERE IN THE LOW TO MID 30S  
IN THE COUNTIES WHERE A FROST/FREEZE HEADLINE IS IN EFFECT.  
 
MSAS SURFACE ANALYSIS SHOWS SURFACE RIDGE EXTENDING FROM CENTRAL  
MN TOWARDS EASTERN IA, WITH MANY SURFACE OBS REPORTING CALM WINDS  
EARLY THIS MORNING. THE WARM FRONT THAT WILL BRING WIDESPREAD  
PRECIPITATION ON SUNDAY, IS CURRENTLY DRAPED ACROSS NORTHERN KS  
THROUGH SOUTH CENTRAL MO.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 225 AM CDT SAT OCT 23 2021  
 
NO CHANGES TO CURRENT FROST/FREEZE HEADLINES. QUIET AND DRY  
CONDITIONS ARE EXPECTED TODAY, WITH SLIGHTLY BELOW NORMAL  
HIGH TEMPERATURES.  
 
AFTER A COLD FROSTY START, MUCH OF THE AREA WILL SEE MOSTLY SUNNY  
SKIES THROUGH THE DAY WITH WINDS TURNING EASTERLY. WENT WITH THE  
NBM FOR HIGHS TODAY, WHICH HAS READINGS MAINLY IN THE MIDDLE TO  
UPPER 50S. ATTENTION THEN TURNS TO THE STRONG EASTERN CO LOW AND  
ASSOCIATED WARM FRONT THAT WILL LIFT NORTH OVER MO OVERNIGHT. MID  
AND HIGH LEVEL CLOUDS WILL INCREASE THIS EVENING KEEPING  
TEMPERATURES WARMER OVERNIGHT THAN THIS MORNING. HOWEVER, SOME  
PATCHY FROST IS STILL NOT OUT OF THE QUESTION OVER NORTHERN IL  
EARLY SUNDAY.  
 
AFTER LOOKING AT MODEL TRENDS, MOISTURE PROFILES, AND WARM FRONT  
PLACEMENT, HAVE SLOWED THE ARRIVAL OF RAIN CHANCES SLIGHTLY EARLY  
SUNDAY. STRONG LIFT, RICH 850MB THETA-E AIR, AND NEGATIVE  
700-500MB THETA-E LAPSE RATES WILL RESULT IN WIDESPREAD STRATIFORM  
RAIN, WITH EMBEDDED THUNDER ENTERING OUR NORTHEAST MO, SOUTHEAST  
IA, AND WEST CENTRAL IL COUNTIES JUST PRIOR TO 12Z SUNDAY. A QUICK  
HALF INCH OF RAIN IS POSSIBLE PRIOR TO SUNRISE.  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 255 AM CDT SAT OCT 23 2021  
 
KEY MESSAGES:  
 
1. WIDESPREAD RAIN AND THUNDERSTORMS SUNDAY INTO MONDAY.  
2. MIDWEEK SYSTEM TO BRING MORE RAIN AND EVEN SOME THUNDER TO THE  
AREA.  
3. MAY SEE SOME STRONG TO SEVERE STORMS AND FLOODING SUNDAY  
AFTERNOON.  
 
DISCUSSION:  
 
PROGRESSION OF THE LARGESCALE PATTERN HAS NOT CHANGED WITH THIS  
FORECAST ITERATION. A WARM FRONT WILL STALL EITHER JUST SOUTH OR  
JUST INTO THE CWA SUNDAY AS SEASONABLY HIGH PWATS MOVE INTO THE  
AREA. LIFTING OVER THESE BOUNDARIES WILL LEAD TO HEAVY RAIN ACROSS  
THE AREA. THE CLOSED UPPER LEVEL LOW WILL MOVE EAST INTO THE AREA  
ON SUNDAY AND CONTINUE TO PRODUCE ASCENT FOR PRECIP. ONCE THE LOW  
MOVES EAST, THE WRAPAROUND WILL CONTINUE PRECIP INTO MONDAY. WEAK  
RIDGING BUILDS BACK INTO THE AREA BEFORE ANOTHER STRONG WAVE  
MIDWEEK. THIS WAVE HAS SLOWED A LITTLE AND IN SOME GUIDANCE BEGINS  
TO CLOSE OFF AND TRY TO SWING NEGATIVE OVER THE AREA. ADDITIONAL  
HEAVY RAINFALL IS POSSIBLE WITH THIS SYSTEM AS WELL. ANOTHER  
FROST/FREEZE IS POSSIBLE MONDAY NIGHT MAINLY NORTH OF HIGHWAY 34.  
AFTER THIS RIDGING BUILDS IN FOR NEXT WEEKEND ALONG WITH QUIETER  
WEATHER.  
 
MOST ATTENTION IN THIS SHIFT WAS FOCUSED ON THE HEAVY RAIN EVENT  
SUNDAY INTO MONDAY. THERE REMAINS A CONDITIONAL THREAT FOR SEVERE  
WEATHER AS WELL IN THE AFTERNOON. LET'S FIRST DIVE INTO THE  
SYNOPTIC PATTERN. LATEST GUIDANCE WOULD SUGGESTED A NORTHERN SHIFT  
TO THE HEAVIEST RAIN AS THE H92 AND H85 LOWS ARE FURTHER NORTH. THIS  
IS REPRESENTED IN THE 00Z GUIDANCE, EXCEPT FOR THE GEM WHERE THE  
NAM/GFS PULL THE FRONT FURTHER NORTH AND THE ECM IS WHERE THE US  
MODELS WERE 24 HOURS AGO. SO THE QUESTION OF WHERE IS NOT MORE  
CLEAR WITH THIS RUN. TO THROW A LARGER WRENCH INTO THIS, THE CAMS  
ARE SOUTH WITH THE HEAVIER RAINFALL. CAMS ARE GREAT WITH MODE, BUT  
NOT THAT GOOD WITH LOCATION. STILL, THIS DOESN'T ADD MORE  
CONFIDENCE TO WHERE THE HEAVIEST RAINFALL WILL OCCUR. WITH THE  
LATEST GUIDANCE, ANYWHERE SOUTH OF HWY 30 COULD SEE THE BAND WITH  
THE MOST CONSISTENT SIGNAL BEING NEAR THE IA/MO BORDER.  
 
AS FAR AS QPF GOES, STILL THINK 2 TO 4 IN THE BAND IS REASONABLE  
WITH HIGHER AMOUNTS POSSIBLE. PWATS ALONG THE FRONT PUSH 1.5 INCHES  
WHICH IS NEAR RECORD FOR THIS TIME OF YEAR. WITH THE STRONG  
SYNOPTIC LIFT, AIDED BY CONVECTIVE ELEMENTS, WE WILL SEE SOME HEAVY  
RAIN THAT MAY LEAD TO LOCALIZED FLASH FLOODING. A FLASH FLOOD WATCH  
WILL LIKELY BE NEEDED LATER TODAY IF WE CAN NAIL DOWN A BETTER  
THREAT AREA. I DO THINK THE RAIN WILL BE THE MAIN THREAT WITH THIS  
SYSTEM.  
 
NOW TO THE SEVERE THREAT. SPC HAS A MARGINAL RISK FOR MOST OF THE  
AREA, A SLIGHT FOR SOME OF THE SOUTH AND AN ENHANCED FOR THE FAR  
SOUTHERN COUNTIES. THE SLIGHT AND ENHANCED ARE FOR A HAIL THREAT. I  
AM NOT CONFIDENT WE WILL SEE MUCH FROM A SEVERE THREAT. THERE IS NO  
DOUBT SUFFICIENT SHEAR FOR LLVL ROTATION. NOT SURE THE REPEATED  
BOUTS OF CONVECTION WILL ALLOW FOR ENOUGH LLVL CAPE TO BUILD FOR A  
TORNADO THREAT. NONETHELESS WITH THE SHEAR, THE 2% MAKES SENSE. AS  
FAR AS THE HAIL AND ENHANCED GOES, THINK THAT THE HAIL THREAT IS  
ACTUALLY NOT THAT HIGH. WHILE WE HAVE SHEAR AND COULD SEE ELEVATED  
HAILERS, THE OVERALL ENVIRONMENT FOR LARGE HAIL IS NOT THAT GOOD FOR  
US. THINK THERE WILL BE AN OVER ABUNDANCE OF HAIL EMBRYOS AND THUS  
WILL COMPETE WITH EACH OTHER TO GET LARGE. WE WILL LIKELY SEE A  
LOT OF PEA SIZED HAIL STORMS AND MAYBE A QUARTER HERE OR THERE.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)  
ISSUED AT 1107 AM CDT SAT OCT 23 2021  
 
STARTING THE TAF PERIOD OUT CALM, WITH LIGHT EASTERLY WINDS AND  
RELATIVELY CLEAR SKIES. THROUGH THE DAY, CLOUDS WILL BE ON THE  
RISE. THIS EVENING AND TONIGHT, LOW CLOUDS AND RAIN WILL BEGIN TO  
PUSH IN FROM THE SOUTH, QUICKLY DROPPING CIGS TO 500-1000 FT, AND  
VISIBILITIES WILL ALSO BE REDUCED TO 2-4 SM. THESE CONDITIONS WILL  
LAST THROUGH THE DAY TOMORROW, AS THE SYSTEM WILL BE SLOW TO MOVE  
OUT. RAINFALL CAN BE HEAVY AT TIMES AND EMBEDDED THUNDERSTORMS  
WILL ALSO BE POSSIBLE, ESPECIALLY AT BRL. RIGHT NOW, WILL STICK  
WITH FORECAST FOR IFR CONDITIONS MOVING IN FROM THE SOUTH AROUND  
06Z AND FILLING MUCH OF THE AREA BY 15Z. SOME LIFR CONDITIONS  
CANNOT BE RULED OUT TOMORROW MORNING AT BRL AND MLI, BUT WILL  
FURTHER EVALUATE THIS POTENTIAL IN THE NEXT FORECAST RUN.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 1107 AM CDT SAT OCT 23 2021  
 
GIVEN THE CHANCE FOR HEAVY RAIN, WITH SOME SEEING 2 TO 4 INCHES  
OR MORE, THERE IS POTENTIAL FOR RIVER RISES SUNDAY. HEAVIEST  
RAINFALL IS CURRENTLY FORECAST TO FALL ALONG AND SOUTH OF  
INTERSTATE 80, LEADING TO POTENTIAL IMPACTS ALONG THE ROCK, SKUNK,  
LA MOINE AND FOX RIVERS. BASED ON MOST OF THE ENSEMBLE GUIDANCE,  
A HIGH END EVENT WOULD PUT THESE RIVERS INTO FLOOD WITH THE LA  
MOINE HAVING THE BEST CHANCE. RIVER FORECASTS ARE NOT REFLECTING  
THIS HEAVY RAINFALL YET, BUT THESE RIVERS WILL LIKELY SEE RISES IF  
THIS HEAVY RAIN DOES FALL FOR AN EXTENDED PERIOD. STAY TUNED FOR  
FUTURE UPDATES, AS HEADLINES MAY BE NECESSARY.  
 

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

 
 

 
 
SYNOPSIS...GROSS  
SHORT TERM...GROSS  
LONG TERM...GIBBS  
AVIATION...GUNKEL  
HYDROLOGY...GUNKEL  
 
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