499  
FXUS63 KDVN 281202  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
702 AM CDT THU JUL 28 2016  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 340 AM CDT THU JUL 28 2016  
 
MSAS SURFACE ANALYSIS AT 07Z SUGGESTED A WEAK SURFACE BOUNDARY OR  
INVERTED TROUGH, REACHING FROM NEAR ST LOUIS NORTH THROUGH EASTERN  
IOWA TO NEAR LA CROSSE. ISOLATED SHOWERS AND THUNDERSTORMS WERE  
OCCURRING ALONG AND EAST OF THIS FEATURE, MAINLY IN TWO AREAS; ONE  
SOUTH OF QUINCY AND THE OTHER JUST EAST AND SOUTHEAST OF THE QUAD  
CITIES. WEAK LOW LEVEL CONVERGENCE AND DEWPOINTS POOLING IN THE  
UPPER 60S TO AROUND 70 WERE RESULTING IN A FEW AREAS OF MAINLY  
AVIATION/MVFR TYPE FOG. ALOFT, A SERIES OF SHORTWAVES WAS EMBEDDED  
IN THE NW FLOW FROM IL TO THE ROCKIES.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 340 AM CDT THU JUL 28 2016  
 
MAIN CHALLENGE IS CENTERED ON CHANCES FOR THUNDERSTORMS THROUGHOUT  
AS CONVECTION CONTINUES TO FIRE ALONG AND EAST OF THE WEAK SURFACE  
TROUGH OVER THE AREA. THE BULK OF SHORT RANGE MODELS DEVELOP THE  
INVERTED TROUGH INTO A NW TO SE ORIENTATION ACROSS THE FORECAST AREA  
TODAY, THEN SHIFT IT SOUTHWARD TO FOCUS CONVERGENCE TO MAINLY OVER  
WEST CENTRAL IL TONIGHT. BUILDING DAYTIME INSTABILITY, WITH PERHAPS  
SOME ASSISTANCE FROM THE NEXT UPSTREAM SHORTWAVE ADVANCING OUT OF  
SOUTHERN SD, SHOULD TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS FROM  
LATE MORNING THROUGH AFTERNOON, ESPECIALLY ALONG AND EAST OF THE MS  
RIVER, WHERE HIGHER CHANCE POPS ARE PLACED. CONDITIONS DO NOT APPEAR  
FAVORABLE FOR SEVERE STORMS DUE TO THE WEAK FORCING AND LACKING  
SHEAR. HOWEVER, AS SEEN THE PAST COUPLE DAYS, THE WEAK SHEAR,  
CONVERGENCE ALONG LOW LEVEL BOUNDARIES AND SUFFICIENTLY STEEP LOW  
LEVEL LAPSE, MAY LEAD TO ISOLATED FUNNEL CLOUDS. THE LAYER NON-  
SUPERCELL TORNADO PARAMETER TOOL IN BOTH WRF/NAM AND RAP MODELS  
SUGGEST THE HIGHEST POTENTIAL OF OCCURRENCE WOULD BE OVER NW IL OR N  
CENTRAL IL AROUND MIDDAY, THEN SHIFTING EASTWARD THROUGH THE  
AFTERNOON.  
 
WITH A LACK OF SIGNIFICANT CLOUD COVER IN PLACE, AND LITTLE  
CONTRIBUTION FROM UPSTREAM CONVECTION EARLY THIS MORNING, SKIES  
SHOULD BE AT LEAST PARTLY SUNNY, HAVE BOOSTED HIGHS TO THE UPPER 70S  
NORTH TO MID 80S IN THE SOUTH.  
 
TONIGHT, THE POTENTIAL FOR THUNDERSTORMS ALONG THIS SOUTHWARD  
TRENDING BOUNDARY WILL BE MORE LIMITED AS THE NIGHT PROGRESSED BASED  
ON LOWERING MID LEVEL LAPSE RATES AND MARGINAL MUCAPE VALUES. THUS  
HAVE SLIGHT TO LOW END CHANCE POPS FOR SHOWERS AND THUNDERSTORMS IN  
THE EVENING, SHIFTING SOUTHWARD WITH JUST SHOWERS MENTIONED TOWARD  
MORNING IN THE SOUTHEAST. LOW LEVEL MOISTURE CONVERGENCE AND POOLING  
WILL ALSO AGAIN BE SUPPORTIVE OF AT LEAST PATCHY FOG AND HAVE ADDED  
MENTION OVER MAINLY WEST CENTRAL IL TOWARD MORNING. KEPT MINS A BIT  
COOLER THAN PREVIOUS NIGHTS, FROM THE LOWER 60S NORTH TO MID AND  
POSSIBLY UPPER 60S SOUTH AND SOUTHEAST.  
   
LONG TERM
 
(FRIDAY THROUGH NEXT WEDNESDAY)  
ISSUED AT 340 AM CDT THU JUL 28 2016  
 
FRIDAY...SEVERAL OF THE 00Z RUN MODELS NOW SLOW PROGRESSION OF MID  
AND UPPER LEVEL TROF/LOW ACRS THE REGION THIS DAY. THIS COMBINED  
WITH A SFC WAVE AND/OR INVERTED TROF REFLECTION FEATURE ACRS THE CWA  
AND DIURNAL INSTABILITY, SEEMS THERE WILL BE INCREASING SHOWER AND  
SOME THUNDERSTORM ACTIVITY AS THE DAY PROGRESSES AND ESPECIALLY BY  
AFTERNOON INTO THE EARLY EVENING ACRS THE FCST AREA. BUT NOT ENOUGH  
INSTABILITY OR SHEAR TO PRODUCE STRONG OR SEVERE STORMS. CLOUD COVER  
AND BOUNDARY LAYER NORTH TO NORTHEAST FETCH TO LIMIT HIGHS IN THE MID  
70S TO AROUND 80. AS UPPER LOW MOVES EAST AND LOSS OF DIURNAL  
SUPPORT, SHOWERS SHOULD WANE INTO THE OVERNIGHT. SOME BREAKS IN THE  
CLOUD COVER COULD FOSTER SOME LOW TEMPS IN THE LOWER 60S OR EVEN  
UPPER 50S, AS WELL AS AREAS OF FOG.  
 
SATURDAY AND SUNDAY...LINGERING BROAD UPPER TROF AND DIURNAL  
INSTABILITY MAY ALLOW FOR MORE ISOLATED TO SCTRD SHOWER DEVELOPMENT  
AS SAT PROGRESSES(LESS COVERAGE EXPECTED THAN ON FRIDAY), AND  
DEPENDING ON THE EXTENT OF CLOUD COVER, LLVL THERMAL PROFILES  
SUPPORT ANOTHER SEASONABLY BELOW NORMAL DAY WITH HIGHS IN THE UPPER  
70S TO AROUND 80. CLEARING AND SEASONABLY COOL SAT NIGHT WITH SOME  
UPPER 50S POSSIBLE AGAIN IN SOME LOCATIONS. LATEST 00Z RUN MEDIUM  
RANGE MODELS SUCH AS THE GFS AND ECMWF IN BETTER AGREEMENT OF  
MAINTAINING A DRY SUNDAY WITH SHOWERS AND STORMS TO THE SOUTH OF THE  
AREA ALONG ORGANIZING WARM FRONT ACRS KS INTO MO. WITH MORE  
SUNSHINE, TEMPS WILL MODERATE BACK INTO THE LOW TO MID 80S ON  
SUNDAY. UPSTREAM THERMAL RIDGE WILL CONTINUE TO BUILD ACRS THE  
PLAINS SUNDAY INTO SUNDAY NIGHT. THE MODELS THEN START TO DIVERGE  
SOME ON HOW FAR NORTH OF THE WARM FRONT CAN RETREAT SUNDAY NIGHT AND  
ACT AS A CONVECTIVE FOCUS FOR SOUTHERLY LLJ. THE 00Z ECMWF IS MORE  
BULLISH WITH A FURTHER NORTH PUSH AND BREAKS OUT ELEVATED STORM  
CLUSTERS ACRS AT LEAST THE SOUTH HALF OF THE DVN CWA LATE SUN NIGHT  
INTO MON MORNING. THE 00Z GFS IS FURTHER SOUTH AND JUST CLIPS THE  
SOUTHWESTERN CWA WITH SOME NIGHT TIME STORMS, AND WONDER IF ENOUGH  
DEBRIS AND COOL POOLS LINGER ACRS MO FROM THE EARLIER ACTIVITY THAT  
THE GFS WOULD BE MORE IN LINE.  
 
MONDAY THROUGH NEXT WEDNESDAY...AS THE ABOVE MENTIONED THERMAL  
RIDGE/HEAT DOME OUT WEST TRIES TO MIGRATE EASTWARD, MON THROUGH TUE  
AND POSSIBLY EVEN INTO WED THE LOCAL FCST AREA MAY LAY UNDER THE  
BATTLE ZONE AND BE SUSCEPTIBLE TO OCCASIONAL STORM CLUSTERS OR MCS'S  
ESPECIALLY AT NIGHT. LLVL SOUTHERLY FLOW REALLY STARTS TO ADVECT  
WARM AND MORE HUMID AIR UP ACRS THE REGION, BUT WARM UP POTENTIAL  
WILL DEPEND ON THE AMOUNT OF LINGERING CONVECTIVE DEBRIS AND COOL  
POOLS FOR ANY STORM EPISODES THIS PERIOD. OTHERWISE, WITHOUT THESE  
POSSIBLE LIMITATIONS HIGHS WILL WARM UP AT LEAST INTO THE UPPER 80S  
TO LOWER 90S BY TUE AND WED AND HEAT INDICES MAY BREACH 100 DEGREES  
AGAIN. ..12..  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)  
ISSUED AT 702 AM CDT THU JUL 28 2016  
 
A WEAK LOW LEVEL TROUGH OVER THE AREA WILL LEAD TO LIGHT  
WINDS, POTENTIAL SHOWERS AND THUNDERSTORMS, AND MVFR CONDITIONS  
AT TIMES DUE TO LOW CLOUDS AND FOG TODAY AND TONIGHT. THIS  
MORNING, AN AREA OF LOW CLOUDS IS EXPECTED TO ADVANCE SOUTHWARD  
INTO EASTERN IOWA, PRODUCING A PERIOD OF IFR CONDITIONS AT CID AND  
POSSIBLY AT DBQ. FOR NOW, WILL ONLY CARRY THIS AT CID, BUT MONITOR  
DBQ CLOSELY AND FORECAST DEVELOPING MVFR CONDITIONS. THE MLI AND  
BRL TERMINALS WILL MOST LIKELY SEE THIS DECK REACH THE AREA AT  
MVFR LEVELS LATER THIS MORNING. DEVELOPING SHOWERS AND ISOLATED  
THUNDERSTORMS THIS AFTERNOON INTO EARLY EVENING WILL MOST LIKELY  
STAY EAST OF THE TERMINALS AND HAVE ONLY MENTIONED SHOWERS AND DBQ  
WHERE FORECAST CONFIDENCE IS SLIGHTLY HIGHER. ALL SITES SHOULD SEE  
A PERIOD OF VFR CONDITIONS FROM AFTERNOON INTO EVENING...THEN  
WIDESPREAD MVFR CONDITIONS ARE EXPECTED, AND HAVE FORECAST IFR  
CONDITIONS AT MLI AND BRL. CONFIDENCE IN THE DETAILS OF THE FINAL  
6 HOURS IS LOW, AND THE TYPICALLY PESSIMISTIC FORECAST GUIDANCE  
SUGGESTING LIFR TO VLIFR CONDITIONS MAY NOT BE TOO FAR OFF.  
 

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

 
 

 
 
SYNOPSIS...SHEETS  
SHORT TERM...SHEETS  
LONG TERM...HLADIK  
AVIATION...SHEETS  
 
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