586  
FXUS63 KDVN 231114  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
614 AM CDT TUE OCT 23 2018  
   
..12Z AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 223 AM CDT TUE OCT 23 2018  
 
A WEAK COLD FRONT PASSED LAST EVENING ATTENDANT TO LOW PRESSURE  
TRAVERSING SOUTHERN ONTARIO. NORTHERLY WINDS IN THE WAKE ARE  
USHERING IN COOLER AIR, WITH HIGH PRESSURE BUILDING SOUTHWARD  
FROM CANADA. THIS HIGH PRESSURE WILL PROVIDE DRY AND SEASONABLY  
COOL CONDITIONS FOR THE NEXT SEVERAL DAYS. LATE WEEK AND THIS  
WEEKEND WILL BRING INTERMITTENT LIGHT RAIN CHANCES, AS A LARGE  
UPPER RIDGE BREAKS DOWN ALLOWING WEST/NORTHWEST FLOW TO SHUTTLE  
IN A SERIES OF DISTURBANCES.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 223 AM CDT TUE OCT 23 2018  
 
BENIGN WX AS HIGH PRESSURE CONTINUES BUILDING SOUTH INTO THE  
MIDWEST PROVIDING GENERALLY CLEAR SKIES. HIGHS TODAY WILL BE  
NOTICEABLY COOLER THAN THOSE OF MONDAY, WITH COOL AIR DEEPENING  
IN THE LOWER TROPOSPHERE. HAVING SAID THAT, DRY AIR AND DRYING  
GROUND ALONG WITH FULL SOLAR INSOLATION AND MIXING DRY  
ADIABATICALLY TO AROUND 900 MB ALL SUPPORTIVE OF SIDING CLOSER  
TO WARMER SIDE OF GUIDANCE FOR HIGHS, WITH WIDESPREAD 50S.  
HIGH PRESSURE RIDGE CENTERED OVER THE AREA TONIGHT WILL PROVIDE  
AN IDEAL RADIATIONAL COOLING SETUP, AND ALLOW FOR LOWS NEAR TO  
JUST BELOW THE COOLER SIDE OF GUIDANCE AND MAINLY IN THE UPPER 20S  
TO LOWER 30S.  
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 223 AM CDT TUE OCT 23 2018  
 
BELOW NORMAL TEMPERATURES WITH PRECIPITATION CHANCES FOR THE  
WEEKEND.  
 
WEDNESDAY THROUGH THURSDAY  
ASSESSMENT...HIGH CONFIDENCE  
 
DRY AND COOL CONDITIONS WILL CONTINUE WEDNESDAY THROUGH THURSDAY AS  
HIGH PRESSURE REMAINS OVER THE GREAT LAKES. THE MODELS CONTINUE TO  
BACK OFF ON RAIN CHANCES FOR THURSDAY.  
 
THURSDAY NIGHT  
ASSESSMENT...LOW CONFIDENCE  
 
THE GLOBAL MODELS OFFER DIFFERING OPINIONS ON WHAT WILL OCCUR WITH  
THE UPPER LEVEL DISTURBANCE MOVING THROUGH THE AREA. THE OVERALL  
TREND (PER DPROG/DT) IS TO GO LIGHTER WITH ANY PRECIPITATION  
AMOUNTS. THIS TREND SUGGESTS THAT THERE IS MORE DRY AIR OVER THE  
AREA THAN WHAT THE MODELS THOUGHT A FEW DAYS AGO.  
 
THE GFS IS DRY THURSDAY NIGHT WHILE THE CMC GLOBAL HAS LIGHT  
PRECIPITATION OVERSPREADING MUCH OF THE AREA. THE ECMWF IS LIGHTER  
THAN THE CMC GLOBAL ON PRECIPITATION, HAS LESS AREAL COVERAGE, AND  
DELAYS THE ARRIVAL OF ANY PRECIPITATION UNTIL LATE THURSDAY NIGHT.  
 
GIVEN THE MODEL DIFFERENCES, THE MODEL CONSENSUS HAS SLIGHT CHANCE  
POPS ACROSS PARTS OF THE AREA.  
 
FRIDAY ON...  
 
FRIDAY  
ASSESSMENT...MEDIUM TO HIGH CONFIDENCE  
 
DPROG/DT TRENDS THE PAST SEVERAL RUNS HAS BEEN TO BACK OFF ON  
PRECIPITATION CHANCES FOR FRIDAY AND THUS INCREASING THE PROBABILITY  
OF DRY CONDITIONS. RIGHT NOW THE MODEL CONSENSUS HAS MAINLY DRY  
CONDITIONS FOR THE DAYLIGHT HOURS ON FRIDAY.  
 
FRIDAY NIGHT THROUGH SUNDAY  
ASSESSMENT...MEDIUM CONFIDENCE  
 
OVER THE WEEKEND THE GLOBAL MODELS HAVE BEEN PERSISTENT IN  
INDICATING TWO SEPARATE UPPER AIR DISTURBANCES MOVING THROUGH THE  
MIDWEST GENERATING PRECIPITATION. HOWEVER, THE GLOBAL MODELS  
CONTINUE TO DIFFER SOMEWHAT ON TIMING AND TRACK OF THE SYSTEMS. THUS  
WHILE THERE WILL BE A RISK A RAIN, THERE WILL ALSO BE PERIODS OF DRY  
WEATHER OVER THE WEEKEND.  
 
THE ECMWF BRINGS THE FIRST DISTURBANCE THROUGH THE AREA FRIDAY NIGHT  
AND SATURDAY. AFTER A BRIEF BREAK SATURDAY NIGHT THE SECOND  
DISTURBANCE ARRIVES FOR SUNDAY.  
 
THE GFS HAS A WEAK SYSTEM WITH VERY LITTLE PRECIPITATION FRIDAY  
NIGHT AND SATURDAY SUGGESTING MAINLY DRY CONDITIONS, FOLLOWED BY A  
BREAK SATURDAY NIGHT. THE SECOND AND MORE POTENT SYSTEM ARRIVES ON  
SUNDAY BRINGING A BETTER RISK OF RAIN FOR THE ENTIRE AREA.  
 
THE CMC GLOBAL HAS THE FIRST DISTURBANCE SLOWLY MOVE THROUGH FRIDAY  
NIGHT AND SATURDAY BUT IN A WEAKENING FASHION AND THUS GENERATING  
VERY LITTLE PRECIPITATION. AFTER A QUIET SATURDAY EVENING, THE  
SECOND AND MORE POTENT DISTURBANCE ARRIVES LATE SATURDAY NIGHT INTO  
SUNDAY WITH WIDESPREAD PRECIPITATION FOR THE AREA.  
 
GIVEN THE DIFFERENCES BETWEEN THE MODELS THE MODEL CONSENSUS HAS  
SLIGHT CHANCE TO CHANCE POPS FOR THE ENTIRE AREA FRIDAY NIGHT AND  
SATURDAY, SLIGHT CHANCE POPS SATURDAY NIGHT, AND CHANCE POPS ON  
SUNDAY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)  
ISSUED AT 614 AM CDT TUE OCT 23 2018  
 
VFR CONDITIONS ARE EXPECTED ACROSS THE REGION OVER THE NEXT 24  
HOURS. NORTHWEST WINDS AROUND 5-10 KTS WILL BECOME LIGHT AND  
VARIABLE THIS EVENING AS A RIDGE OF HIGH PRESSURE MOVES OVERHEAD.  
 

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

 
 

 
 
SYNOPSIS...MCCLURE  
SHORT TERM...MCCLURE  
LONG TERM...08  
AVIATION...SPECK  
 
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