168  
FXUS63 KDVN 191132  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
632 AM CDT SUN AUG 19 2018  
   
..AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 311 AM CDT SUN AUG 19 2018  
 
06Z SURFACE DATA HAS HIGH PRESSURE OVER THE GREAT LAKES WITH A WEAK  
LOW OVER SOUTH DAKOTA AND A DEVELOPING STORM SYSTEM OVER THE  
OKLAHOMA PANHANDLE. DEW POINTS WERE IN THE 60S ACROSS THE MIDWEST  
WITH 70S ACROSS THE LOWER MISSISSIPPI VALLEY AND DEEP SOUTH.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 311 AM CDT SUN AUG 19 2018  
 
THROUGH SUNRISE PATCHY FOG WILL AGAIN OCCUR DUE TO LIGHT WINDS AND  
HIGH MOISTURE CONTENT IN THE LOWER ATMOSPHERE. RIVER VALLEYS AND LOW  
LYING AREAS ARE MOST SUSCEPTIBLE FOR FOG THAT MAY BE LOCALLY DENSE.  
 
FROM MID MORNING THROUGH SUNSET, MAINLY DRY AND WARM CONDITIONS WILL  
BE SEEN ACROSS THE AREA TODAY. DIURNAL HEATING MAY GENERATE A COUPLE  
OF ROGUE SHOWERS AND THUNDERSTORMS BUT 99 PERCENT OF THE AREA WILL  
REMAIN DRY.  
 
TONIGHT THE NEXT STORM SYSTEM STARTS MOVING INTO THE AREA. SINCE THE  
SYSTEM IS CLOSED OFF, THE PRECIPITATION WILL LIKELY ARRIVE SLOWER  
THAN FORECAST. SEVERAL MODEL SOLUTIONS KEEP MUCH OF THE AREA DRY  
DURING THE EVENING BEFORE RAIN ARRIVES AFTER MIDNIGHT. REGARDLESS,  
SHOWERS AND SOME THUNDERSTORMS SHOULD BEGIN DEVELOPING BY MID TO  
LATE EVENING AND SLOWLY INCREASE IN AREAL COVERAGE AFTER MIDNIGHT.  
   
LONG TERM
 
(MONDAY THROUGH SATURDAY)  
ISSUED AT 311 AM CDT SUN AUG 19 2018  
 
SEASONABLY STRONG STORM SYSTEM MOVING THROUGH THE REGION THE ONSET  
IS THE PRIMARY FOCUS. THIS IS FOLLOWED BY A QUIET MID WEEK PERIOD  
THAT FEATURES DRY WEATHER WITH LOWER HUMIDITY AND NEAR TO BELOW  
NORMAL TEMPERATURES. THE LATEST MODELS HAVE LATCHED ONTO LATE WEEK  
STORM SYSTEM AND RAIN CHANCES HAVE BEEN INTRODUCED FOR FRIDAY.  
 
MODELS CONTINUE TO TREND WITH A MORE NORTHERLY TRACK OF BOTH THE  
UPPER LEVEL WAVE AND SURFACE LOW THAT PASS THROUGH THE FORECAST AREA  
MONDAY AND MONDAY NIGHT. THE GFS LEADS THE PACK WITH THE MOST  
NORTHERLY SOLUTION, AND SLIGHTLY SLOWER TIMING, ACROSS CENTRAL TO  
NORTHEAST IOWA, WHILE THE ECMWF, NAM AND CANADIAN GENERALLY AGREE ON  
A PATH ACROSS SOUTHEAST IOWA INTO NORTHERN IL MONDAY. EITHER WAY,  
THE HEAVIEST RAINFALL FOR THE EVENT WOULD BE FOCUSED ACROSS THE  
NORTHERN HALF TO THIRD OF THE FORECAST AREA, WHERE TOTALS OF 1 TO 2  
INCHES WILL BE POSSIBLE, CONSIDERING THE AMOUNT OF MOISTURE  
AVAILABLE ACROSS THE SOUTHERN PLAINS AND GULF COAST LIKELY TO FEED  
INTO THE SYSTEM. POPS AND QPF IS KEPT MUCH LOWER ACROSS THE SOUTH,  
ESPECIALLY DURING THE AFTERNOON, WHEN THE SYSTEM'S DRY SLOT COULD  
REDUCE PRECIPITATION TO SCATTERED SHOWERS AND THUNDERSTORMS.  
 
WITH SURFACE DEWPOINTS LIKELY TO INCREASE INTO THE LOWER 70S IN THE  
CYCLONE'S WARM SECTOR, AND CAPES POSSIBLY REACHING INTO THE 1500 TO  
2000 J/KG RANGE, CANNOT RULE OUT AT LEAST AN ISOLATED SEVERE STORM  
EAST OF THE MS RIVER MONDAY AFTERNOON, WHERE SPC HAS A MARGINAL RISK  
FOR DAY 2. BULK SHEAR IS LESS SUPPORTIVE AND ANY SEVERE POTENTIAL  
WOULD BE CLOSELY LINKED TO CLOUD COVER TRENDS AND THE LOCATION OF  
THE LOW LEVEL BOUNDARIES. GIVEN THE AMOUNT OF FORCING AND  
SUFFICIENTLY STEEP MID LEVEL LAPSE RATED, WILL HAVE THUNDERSTORMS  
MENTIONED OVER THE ENTIRE FORECAST AREA. MONDAY NIGHT, THE  
ASSOCIATED DEFORMATION AXIS WILL SHIFT THE AREA OF SHOWERS AND  
ISOLATED THUNDERSTORMS TO MAINLY THE NORTHEAST HALF OF THE FORECAST  
AREA. TUESDAY WILL SEE BRISK NORTH TO NORTHEAST WINDS WITH AT LEAST  
ISOLATED SHOWERS AND THUNDERSTORMS POSSIBLE ALONG AND EAST OF THE MS  
RIVER.  
 
WEDNESDAY AND THURSDAY, HIGH PRESSURE AND NORTHWEST FLOW ALOFT WILL  
PROVIDE SUNSHINE AND HIGHS TO THE 70S IN MOST AREAS WITH DEWPOINTS  
IN THE 50S PROVIDING COMFORTABLE HUMIDITY LEVELS.  
 
THE 00Z RUN OF THE GFS, CANADIAN AND ECMWF FEATURE A SHORTWAVE  
PASSING NORTH OF THE AREA WITH A WEAK FRONTAL SYSTEM AND MOISTURE  
RETURN GENERATING WIDESPREAD QPF OVER THE FORECAST AREA. FOR NOW,  
THE BLENDED FORECAST WILL INTRODUCE LOW CONFIDENCE CHANCE TO LIKELY  
WORDING FOR SHOWERS AND THUNDERSTORMS FRIDAY AND FRIDAY NIGHT. THE  
RETURN TO A MORE ZONAL UPPER LEVEL FLOW AND WARMING AT 850 MB WILL  
RETURN HIGHS TO THE 80S WITH LOWS IN THE 60S GOING INTO NEXT  
WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 628 AM CDT SUN AUG 19 2018  
 
PATCHY LIFR/VLIFR CONDITIONS FROM FOG HAVE DEVELOPED AMONG MORE  
GENERAL MVFR/VFR CONDITIONS. CONDITIONS WILL RAPIDLY IMPROVE TO  
VFR AFTER 13Z/19 AND CONTINUE THROUGH 03Z/20. AFTER 03Z/20  
CONDITIONS WILL SLOWLY DETERIORATE BACK TO MVFR AS A STORM SYSTEM  
MOVES INTO IOWA. AFTER 12Z/20 WIDESPREAD MVFR CONDITIONS WITH SOME  
IFR CONDITIONS ARE EXPECTED WITH RAIN AND SOME TSRA.  
 

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

 
 

 
 
SYNOPSIS...08  
SHORT TERM...08  
LONG TERM...SHEETS  
AVIATION...08  
 
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