671  
FXUS63 KDVN 172309  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
609 PM CDT FRI AUG 17 2018  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 329 PM CDT FRI AUG 17 2018  
 
UPPER LEVEL TROF AXIS WAS MIGRATING EASTWARD ACRS NORTHERN IL ATTM,  
WITH IT'S SIGHTS SET ON LOWER MI INTO NORTHWEST IN BY THIS EVENING.  
VORT SPOKES ROTATING AROUND THIS FEATURE COMBINING WITH AFTERNOON  
HEATING TO PRODUCE ANOTHER AFTERNOON OF SCTRD SHOWERS AND A FEW  
THUNDERSTORMS. AFTER THIS TROF GETS OUT OF THE WAY, A BOUT OF  
RIDGING TO MAKE FOR A FAIR AND SEASONABLY WARM WEEKEND, BEFORE THE  
NEXT WAVE(NOW OVER THE PACIFIC NW) ROLLS INLAND AND ACRS THE MID  
CONUS FOR ANOTHER ROUND OF RAIN FOR THE LOCAL AREA STARTING LATER  
SUNDAY NIGHT AND LASTING INTO EARLY NEXT WEEK.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SATURDAY)  
ISSUED AT 329 PM CDT FRI AUG 17 2018  
 
TONIGHT...WILL DECREASE POPS AND COVERAGE OF SCTRD SHOWERS AND A FEW  
STORMS AS THE EVENING PROGRESSES THROUGH SUNSET AND BEYOND. UNTIL  
THEN, THE MORE VIGOROUS SHOWERS WILL UTILIZE ONGOING HIGH PRECIPITAL  
WATER(PWATS) OF 1.6 TO 1.7+ INCHES TO PRODUCE LOCALLY HEAVY  
DOWNPOURS AND RAINFALL. THE SHOWER AND STORM CLUSTER NOW ACRS  
CENTRAL INTO SOUTHWESTERN WI MAY GET INTO THE NORTHWESTERN CWA LATE  
THIS AFTERNOON AND EARLY EVENING BEFORE DECREASING. ONGOING UPPER  
LEVEL LOW DYNAMICS AS WELL AS LLVL VORTICITY , LOW LCL'S AND  
INSTABILITY WILL ALSO KEEP THE CHANCE OF NON-SUPERCELL FUNNEL CLOUDS  
GOING THROUGH EARLY EVENING, ALTHOUGH AREAS MORE PRIME FOR THAT  
PHENOMENA APPEAR TO BE TO THE EAST OF THE AREA CLOSER TO THE UPPER  
LOW CENTER. THEN CLOUD COVER WILL LOOK TO DECAY DIURNALLY OVERNIGHT,  
AND WITH ONGOING RATHER MOIST SFC LAYER/ LINGERING HIGH SFC DPTS  
WITH LIGHT NORTHEAST WINDS, ANOTHER ROUND OF PATCHY TO AREAS OF  
DENSE FOG POSSIBLE LATE TONIGHT INTO EARLY SAT MORNING. WILL GO WITH  
WIDESPREAD LOWS IN THE MID TO UPPER 60S, OR SIMILAR LOWS TO WHAT  
OCCURRED THIS MORNING IN MOST AREAS.  
 
SATURDAY...ANOTHER MORNING OF WHATEVER FOG AND LOW STRATUS/STRATOCU  
LIFTING INTO A LOW CLOUD DECK FOR PART OF THE MORNING, BUT THEN MORE  
SUBSIDENCE WITH UPPER RIDGING TAKING OVER TO CLEAR THINGS OUT BY  
LATE MORNING. STILL SOME SUPPORT(CU RULE ALSO AGREES)FOR AMBIENT  
DIURNAL CU FORMATION(OR MAINTENANCE FROM THE MORNING) OF AT LEAST  
SCTRD CU COVERAGE DURING THE AFTERNOON. BUT THIS SHOULD STILL MEAN  
MOSTLY SUNNY SKIES FOR MOST OF THE AREA. A FEW MODELS LIKE THE 12Z  
RUN NAMNEST AND GFS BREAK OUT ISOLATED SHOWERS IN A CONVERGENT ZONE  
SOUTHWEST OF DUBUQUE OR ACRS THE NORTHWESTERN THIRD OF THE CWA BY  
SAT AFTERNOON, BUT LOW CONFIDENCE IN THIS AND WILL KEEP THE FCST DRY  
FOR NOW. ..12..  
   
LONG TERM
 
(SATURDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 329 PM CDT FRI AUG 17 2018  
 
MAIN FOCUS IS POTENTIAL FOR WIDESPREAD SOAKING RAINS EARLY NEXT  
WEEK WITH THE LAST AND POTENTIALLY STRONGEST IN A SERIES OF RECENT  
STORM SYSTEMS.  
 
THIS WEEKEND... GENERALLY DRY, AND SEASONABLY WARM AND HUMID WITH WEAK  
GREAT LAKES RIDGING THE DOMINANT WEATHER FEATURE. EACH AFTERNOON WILL  
HARBOR VERY ISOLATED SHOWER/WEAK STORM POTENTIAL WITH CONVECTIVE  
TEMPERATURES BREACHED. LACK OF ANY FORCING OF NOTE MAKES COVERAGE TOO  
LIMITED FOR ANY MENTION. HIGHS MOSTLY MID/UPPER 80S - NEAR TO A LITTLE  
ABOVE NORMAL.  
 
EARLY NEXT WEEK... CONTINUE TO SEE ENCOURAGING SIGNAL FOR WIDESPREAD  
RAINFALL ON MONDAY, AS STRONGER SOUTHERN STREAM SHORTWAVE POTENTIALLY  
PHASES WITH NORTHERN STREAM ENERGY FOR DECENT FORCING WITH ATTENDANT  
DEFORMATION ZONE. MAGNITUDE OF FORCING, AND DECENT MOISTURE ADVECTION  
WITH SOME GULF AND POTENTIAL MONSOONAL FETCH WOULD BE SUPPORTIVE OF  
MODERATE TO AREAS OF HEAVY RAINFALL. HOWEVER, LOCATION OR MOST FAVORED  
AREAS STILL IN QUESTION DUE TO UNCERTAINTIES ON TRACK/STRENGTH OF SYSTEM  
BUT DESPITE THIS BELIEVE MANY AREAS IN LINE FOR A LEAST SOME RAINFALL.  
SEVERE WEATHER POTENTIAL LOOKS RATHER LOW WITH FAIRLY MOIST SOUNDINGS  
AND LIMITED INSTABILITY/SHEAR.  
 
MAY SEE SOME SHOWER CHANCES LINGER TUESDAY WITH ADDITIONAL ENERGY  
DROPPING DOWN ON BACKSIDE OF DEPARTING SYSTEM. THEN, GENERALLY DRY AND  
QUIET FOR MUCH OF THE REST OF THE WEEK WITH THE NEXT RAIN CHANCE  
PERHAPS ARRIVING TOWARD THE WEEKEND. TEMPERATURES LOOK TO DIP NEAR TO  
SLIGHTLY BELOW NORMAL THROUGH MIDWEEK IN NORTHWEST FLOW, WITH HIGHS IN  
THE UPPER 70S TO LOWER 80S AND LOWS IN THE 50S. BY NEXT WEEKEND SHOULD  
SEE MODERATION OF TEMPERATURES NEAR NORMAL IN DEVELOPING ZONAL FLOW.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 603 PM CDT FRI AUG 17 2018  
 
THE REGION WILL REMAIN ON THE EDGE OF AN UPPER LOW PRESSURE SYSTEM  
THIS EVENING, WITH A FEW SHOWERS ROTATING SOUTH OVER THE AREA.  
THESE ARE ISOLATED ENOUGH NOT TO BE INCLUDED IN THE 00Z TAF SET.  
OVERNIGHT, SKIES WILL BE CLEAR INITIALLY THEN GROUND FOG FORMATION  
WILL ONCE AGAIN BE POSSIBLE THROUGH ABOUT 13 OR 14Z SATURDAY.  
SATURDAY WILL BE VFR WITH LIGHT WINDS AND SCATTERED CUMULUS.  
 

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

 
 

 
 
SYNOPSIS...12  
SHORT TERM...12  
LONG TERM...05  
AVIATION...ERVIN  
 
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