738  
FXUS63 KDVN 190835  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
335 AM CDT TUE SEP 19 2017  
   
SYNOPSIS
 
 
ISSUED AT 330 AM CDT TUE SEP 19 2017  
 
UPPER LEVEL SHORTWAVE AND ATTENDANT SHOWERS WILL BE EXITING  
NORTHWEST IL COUNTIES PRIOR TO DAYBREAK. SYSTEM BROUGHT  
SHOWERS TO A FAIR AMOUNT OF THE CWA YESTERDAY AFTERNOON  
THROUGH EVENING, THOUGH RAIN AMOUNTS WERE UNFORTUNATELY  
RATHER LIGHT (LESS THAN 0.1 INCH) BUT SOME ISOLATED MODERATE  
AMOUNTS (0.25-0.6 INCH) ATTENDANT TO STORMS IN PORTIONS OF  
WEST CENTRAL INTO NORTHWEST IL. CLOUDS CONTINUE TO DECREASE  
FROM WEST TO EAST IN THE WAKE OF THE SHORTWAVE, AND  
COMBINED WITH LIGHT WINDS AND LOW LEVEL MOISTURE ENHANCED  
BY RECENT RAIN IS AIDING WIDESPREAD DENSE FOG AND LOW CLOUDS  
MOSTLY SOUTH/WEST OF QUAD CITIES.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 330 AM CDT TUE SEP 19 2017  
 
DENSE FOG LOOKS TO BURN OFF WITHIN AN HOUR OR TWO AFTER SUNRISE  
PER GOES CLOUD THICKNESS TECHNIQUE. STRATUS MAY PERSIST BEYOND  
FOR A WHILE, BUT INCREASING MID/UPPER LEVEL HEIGHTS SHOULD AID IN  
DECREASING CLOUDS THIS AFTERNOON. BANKING ON THIS AMOUNT OF  
SOLAR INSOLATION TO PUSH HIGHS INTO THE UPPER 70S AND LOWER 80S.  
SURFACE WARM FRONT IS SHOWN TO BISECT THE CWA TODAY, BUT  
ABSENCE OF FORCING WITH HEIGHTS BUILDING ALOFT, AND WEAK LOW LEVEL  
CONVERGENCE PRECLUDES FROM ANY PRECIP MENTION TODAY. PRECIP CHCS  
ARE NOT ZERO HOWEVER, AS PRETTY DECENT 850 MB THETA-E ADVECTION  
IS PROGGED TO DEVELOP BY MID AFTERNOON THROUGH THIS EVENING FROM  
SW TO NE WITH STRENGTHENING LLJ, BUT SOUNDINGS SHOW FAIRLY SHALLOW  
MOISTURE DEPTH RESULTING IN CONFIDENCE TOO LOW FOR ANY MENTION.  
DID HANG ON TO SOME SMALL POPS LATE TONIGHT OVER NORTHEAST IA FOR  
POTENTIAL OF SOME ELEVATED CONVECTION DEVELOPING WITH VEERING LLJ  
AND ATTENDANT ADVECTION, AND CAN'T RULE OUT SOME ACTIVITY INTO  
EAST CENTRAL IA NEAR/SW OF QUAD CITIES AS WELL BUT FAR FROM COHERENT  
SIGNAL IN CAMS. LOWS TONIGHT IN STRENGTHENING SOUTHERLY FLOW  
WILL REMAIN MILD AND GENERALLY IN THE 60S, ALTHOUGH A FEW SITES  
COULD ONLY DROP INTO THE LOWER 70S IN WEST/SOUTHWEST CWA.  
   
LONG TERM
 
(WEDNESDAY THROUGH NEXT MONDAY)  
ISSUED AT 330 AM CDT TUE SEP 19 2017  
 
WEDNESDAY...A CHALLENGING FCST DAY WITH MIXED SIGNALS FROM THE  
LATEST AVAILABLE 00Z RUN MODELS. CYCLONIC SOUTHWESTERLY STEERING  
FLOW ADJUSTS ACRS THE MID TO UPPER MS RVR VALLEY, WHILE EMBEDDED  
WAVE SHEARS OUT ACRS MN INTO THE WESTERN LK SUPERIOR BASIN BY  
EVENING. ASSOCIATED SFC FRONT WILL LOOK TO GET SHUNTED ACRS THE  
CENTRAL CWA BY WED EVENING AND THEN STALL AS IT ALIGNS FROM NE-TO-  
SW PARALLEL TO THE STEERING FLOW. JUST A LOW CHANCE FOR SOME  
LINGERING CONVECTIVE DEBRIS OR SHOWERS SAGGING ACRS THE CWA DURING  
THE DAY LEFT OVER FROM STRONGER ACTIVITY EARLIER TO THE  
NORTHWEST, AND FOR NOW WILL KEEP THE SLIGHT CHC POPS LOADED IN THE  
GRIDS. BUT WITH FCST SOUNDINGS SUGGESTING BUILDING CAP/EML AS THE  
DAY PROGRESSES AND LOSS OF CONVERGENT LIFT, FEEL THE DRY 00Z  
ECMWF AND EVEN THE NAM MAY BE MORE ON TARGET THROUGH 00Z ANYWAYS.  
IF PRECIP DOESN'T MATERIALIZE AND DEBRIS DECAYS EARLY, EXTENT OF  
WARM AIR ADVECTION AND MIXING SOUTHWEST WINDS COULD BOOST TEMPS  
INTO THE UPPER 80S TO LOWER 90S ACRS MUCH OF THE AREA AND BE NOT  
ALL THAT FAR OFF RECORD HIGHS FOR SEP 20TH. THE MODELS ARE  
PROBABLY STILL OVERDOING SFC DPTS NEAR 70, AND ONGOING DRY SFC  
LAYER/MIXING MAY TRANSLATE TO VALUES MORE IN THE MID 60S. IF DPTS  
MANAGE TO MAKE IT IN THE UPPER 60S TO AROUND 70, HEAT INDEX  
READINGS WILL RANGE IN THE LOW TO MID 90S WED AFTERNOON.  
 
WEDNESDAY NIGHT MAY BE THE MAIN PRECIP WINDOW OPPORTUNITY FOR THE  
REST OF THE WEEK. SOUTHWESTERLY 20-25 KT LLJ FLOW STARTS TO IMPINGE  
ON THE LINGERING LLVL BOUNDARY, AND AS IT TRIES TO RETREAT BACK  
NORTH SOME AS A TYPE OF WARM FRONT, THAT'S WHEN SCTRD SHOWERS AND  
STORMS MAY DEVELOP NOCTURNALLY ALONG AND NORTH/NORTHWEST OF WHERE  
EVEN THE BOUNDARY ADJUSTS. MORE OPTIMUM SHEAR PROFILES, SOUTHERN  
FLANK OF UPPER JET DYNAMICS, AND LLJ CONVERGENCE LOOK TO OCCUR  
FURTHER TO THE NORTH ACRS WI. BUT IF STORMS GET GOING LOCALLY, ENOUGH  
SUPPORT THERE FOR AT LEAST AN ISOLATED STRONG TO SEVERE STORM, EVEN  
IF ELEVATED IN NATURE. RAINFALL AMOUNTS TO BE LOCALIZED AGAIN, WITH  
THOSE THAT MANAGE TO GET UNDER A STORM OR SHOWER CLUSTER POSSIBLY  
GETTING UP TO A HALF INCH BY THU MORNING. MANY OTHER AREAS TO GET  
LITTLE RAIN AT ALL. SEASONABLY MILD OVERNIGHT LOWS IN THE 60S.  
 
THURSDAY AND FRIDAY...AFTER A LOW CHANCE OF SOME LINGERING PRECIP  
THU MORNING OUT OF WHAT EVER WED ACTIVITY CAN OCCUR, THE LATEST SUITE  
OF MEDIUM RANGE MODEL RUNS ALL SUGGEST A HIGH AMPLITUDE-BLOCKED UP  
PATTERN TAKING GRIP ACRS THE CONUS BETWEEN ACTIVE WESTERN ATLANTIC  
TROPICAL SYSTEMS AND WESTERN CONUS L/W TROF. THE NET RESULT LOCALLY  
WOULD BE DRY AND VERY UNSEASONABLY WARM CONDITIONS TO END THE WEEK. A  
LOT OF UPPER 80S TO LOW 90S LOOK TO BE ON TAP, ESPECIALLY WITH A  
SOUTHERLY FLOW RECHARGE AND DEEPER MIX. SUMMER WON'T WANT TO END ON  
FRIDAY.  
 
SATURDAY INTO EARLY NEXT WEEK...LONGER RANGE INDICATIONS/UPPER JET  
TRENDS SUGGEST THE BLOCKED PATTERN TO CONTINUE ACRS THE REGION  
MAINTAINING UNSEASONABLE WARMTH AND DRY CONDITIONS THROUGH AT LEAST  
SUNDAY LOCALLY, COMPOUNDING THE DROUGHT CONDITIONS. INCOMING LEE  
SIDE LONG WAVE TRANSITION ZONE, WHERE WESTERN GULF NORTHWARD  
MOISTURE CONVEYOR SHUTTLES UP ALONG TO FUEL AN ELONGATED PRECIP  
SWATH, NOW LOOKS TO EDGE EAST ACRS THE AREA LATER MON INTO TUE. BUT  
THIS TIMING STILL VERY SUSPECT AT THIS JUNCTURE AND DEPENDS ON  
ONGOING INTERACTION WITH SUBSIDENCE FIELDS OFF/TO THE WEST OF THE  
ATLANTIC TROPICAL SYSTEM/S. ..12..  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 1137 PM CDT MON SEP 18 2017  
 
AREAS OF FOG AND LOW CLOUDS WILL INCREASE OVERNIGHT INTO THE MID  
MORNING HOURS WITH EXTENDED PERIODS OF MVFR TO LIFR CONDITIONS AND  
POSSIBLY VLIFR CONDITIONS AT ALL THE TERMINALS. SKIES WILL CLEAR  
BY LATE MORNING WITH VFR CONDITIONS INTO THE TUESDAY EVENING.  
WINDS WILL BE LIGHT INTO MID MORNING AND THEN BECOME SOUTHERLY AT  
5 TO 10 MPH.  
 

 
   
CLIMATE
 
 
ISSUED AT 317 AM CDT TUE SEP 19 2017  
 
RECORD HIGHS FOR WED SEPTEMBER 20...  
 
MOLINE.........92 IN 1931  
CEDAR RAPIDS...93 IN 1931  
DUBUQUE........92 IN 1895  
BURLINGTON.....93 IN 1940  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR BENTON-CEDAR-  
CLINTON-DES MOINES-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-  
JONES-KEOKUK-LEE-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-  
WASHINGTON.  
 
IL...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR HANCOCK-  
HENDERSON-MCDONOUGH-MERCER-ROCK ISLAND-WARREN.  
 
MO...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR CLARK-  
SCOTLAND.  
 

 
 

 
 
SYNOPSIS...MCCLURE  
SHORT TERM...MCCLURE  
LONG TERM...12  
AVIATION...NICHOLS  
CLIMATE...12  
 
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