332  
FXUS63 KPAH 291145  
AFDPAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PADUCAH KY  
645 AM CDT SAT APR 29 2017  
   
UPDATE
 
 
ISSUED AT 522 AM CDT SAT APR 29 2017  
 
UPDATED FORECAST PRODUCTS AND GRIDDED FORECAST TO REFLECT  
EXPIRATION OF SEVERE THUNDERSTORM WATCH 172 AT 5 AM CDT.  
 
KPAH RADAR WIND PROFILES SHOWING MORE UNIDIRECTIONAL FLOW NOW FROM  
SURFACE AND ALOFT. THE 50KT 3-5KFT MSL SOUTHWESTERLY WINDS AIR  
ALSO SHRINKING, SUGGESTING A GRADUAL WEAKENING OF THE LOW LEVEL  
JET NEARING ITS CLIMATOLOGICAL DIURNAL MINIMUM. WINDS ALOFT ARE  
ALSO WEAKENING SLIGHTLY, HOLDING NEAR THE 50-60 KNOTS IN THE  
9-25KFT MSL LAYER. SUSPECT THIS IS AN BAROCLINIC AND AGEOSTROPHIC  
RESPONSE TO THE UPPER LOW IN THE SOUTHWEST U.S. DIGGING AND  
BUILDING IN THE MID-UPPER LEVEL RIDGE FROM SOUTHEAST TO NORTHWEST  
ACROSS THE WFO PAH FORECAST AREA.  
 
KPAH RADAR REFLECTIVITY ALSO SUGGESTS THAT STRONGER UPDRAFTS ARE  
MOVING INTO A MORE ELEVATED AREA OF THE FRONTAL ZONE, AWAY FROM  
THE ADJACENT UPSHEAR ZONE OF THE SURFACE-NEAR SURFACE FRONTAL  
BOUNDARY. THIS TRANSITIONAL CHANGE WILL LIMIT SEVERE POTENTIAL,  
BUT WITH A PERSISTENT MOISTURE INFLUX, THIS WILL STILL MAINTAIN A  
FLOOD POTENTIAL THROUGH THE MORNING, GRADUALLY DIMINISHING FROM  
EAST TO WEST TOWARD SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS.  
 
STILL HAVE TO WORK ON TIMING OF SEVERE THUNDERSTORM POTENTIAL, BUT  
ANTICIPATE IT WILL BE DELAYED UNTIL LATER SATURDAY NIGHT.  
 

 
   
SHORT TERM
 
(TODAY THROUGH MONDAY NIGHT)  
ISSUED AT 358 AM CDT SAT APR 29 2017  
 
FLASH FLOOD WATCH, INCLUDING THE EXTENSION FROM THE FRIDAY  
AFTERNOON PACKAGE INTO SOUTHWEST INDIANA AND THE BORDER COUNTIES  
INTO NORTHWEST KENTUCKY WILL REMAIN IN EFFECT UNTIL SUNDAY  
EVENING.  
 
UNIDIRECTIONAL WIND FIELDS ABOVE 5KFT MSL ON THE KPAH WSR-88D IS  
HELPING TO MAIN SUFFICIENT SHEAR FOR UPDRAFTS ABOVE THE ELEVATED  
WARM FRONT (NOW STALLED FRONTAL BOUNDARY). BELOW 5KFT MSL, THERE  
IS SUFFICIENT DIRECTIONAL SHEAR, WITH W-SWLY 50KT 850 MB WINDS  
RIDING OVER THE FRONTAL ZONE. THE COMBINATION IS SUPPORTING LINEAR  
BANDS WITH UPDRAFTS SUFFICIENT TO SUPPORT HAIL AS WELL AS  
EXCESSIVE AMOUNTS OF RAIN GIVEN THE RICH LOW LEVEL MOISTURE  
TRANSPORT AND TRAINING TAKING PLACE ALONG AND JUST NORTH OF THE  
FRONTAL BOUNDARY. WITH PRISTINE (NOT POLLUTED BY CONVECTION)  
MOISTURE INFLOW UNDER THE EML SOUTH OF THE FRONTAL BOUNDARY,  
EXCESSIVE RAINFALL AMOUNTS WILL CONTINUE THROUGH DAYBREAK.  
 
SHOULD SEE SOME RELAXATION OF INFLOW ALONG THE BOUNDARY AS THE LOW  
LEVEL JET DIMINISHES BY MID-MORNING.  
 
UTILIZED WEATHER PREDICTION CENTER (WPC) QPF (RAINFALL AMOUNT)  
ESTIMATES FOR REMAINDER OF FLASH FLOOD WATCH PERIOD.  
 
THE VAST MAJORITY OF THE HIGHEST QPF WILL BE RETRACTED BACK TO  
THE SOUTHEAST MISSOURI FOOTHILLS THIS MORNING AS UPPER LOW DEEPENS  
OVER THE FOUR CORNERS AREA AND SHARPENS THE FRONTAL ZONE IN  
ARKANSAS AND SOUTHERN MISSOURI. AS THE UPPER LOW EJECTS OUT THIS  
EVENING AND OVERNIGHT INTO SUNDAY MORNING, THE BOUNDARY WILL LIFT,  
BUT CONVECTIVE LINE SEGMENTS WILL MOVE LIKELY REGENERATE INTO  
SOUTHEAST MISSOURI, SUPPORTING ADDITIONAL STRONG TO SEVERE  
THUNDERSTORM ACTIVITY. GIVEN THE SLOW EASTWARD PROGRESSION OF THIS  
SYSTEM, EXCESSIVE RAINFALL WILL STILL BE A MAJOR CONCERN AND  
THREAT.  
 
BY SUNDAY, THE WFO PAH FORECAST AREA WILL BE WELL INTO THE WARM  
SECTOR. THERE WILL BE THE POTENTIAL OF SOME PRE-FRONTAL CONVECTIVE  
ACTIVITY IN THE 15-21Z (10 AM - 4 PM) TIME FRAME ON SUNDAY, WHICH  
MAY MUDDLE SEVERE POTENTIAL ACROSS PARTS OF WEST KENTUCKY.  
HOWEVER, GIVEN THE WIND FIELDS EXPECTED ACROSS THE COLD FRONT AS  
IT MOVES SLOWLY EAST THROUGH THE DAYTIME HOURS ON SUNDAY, THERE  
WILL STILL BE THE POTENTIAL FOR DAMAGING WINDS ALONG THE FRONT AND  
POSSIBLY SOME EMBEDDED TORNADOES ALONG THE FRONTAL BOUNDARY.  
 
ONCE THE COLD FRONT MOVES THROUGH SUNDAY NIGHT, COOLER AND DRIER  
AIR SHOULD DOMINATE MONDAY THROUGH MONDAY NIGHT.  
   
LONG TERM
 
(TUESDAY THROUGH FRIDAY)  
ISSUED AT 358 AM CDT SAT APR 29 2017  
 
THE SIGNAL STILL REMAINS CONSISTENT FOR A MIDWEEK SYSTEM TO  
FOLLOW IN BEHIND THE EXITING CLOSED LOW AS IT MOVES INTO THE GREAT  
LAKES AND EASTERN CANADA. THE MEDIUM RANGE GUIDANCE HAS BEEN  
SUGGESTING A STRONGER SHORTWAVE WILL DEEPEN IN THE NORTHWEST FLOW  
AND IMPACTING THE WFO PAH FORECAST AREA BEGINNING LATE TUESDAY AND  
PERSISTING INTO WEDNESDAY, BEFORE THE TROUGH AXIS MOVES THROUGH ON  
THURSDAY. DRY WEATHER IS THEN EXPECTED FOR THE REMAINDER OF  
EXTENDED FORECAST PERIOD AS RIDGING BUILDS INTO THE AREA.  
 
THERE STILL APPEARS TO BE THE POTENTIAL FOR A BAND OF SOUTHWEST TO  
NORTHEAST ORIENTED OF HEAVY RAINFALL. THE PLACEMENT OF THIS BAND  
IS STILL VARIABLE GIVEN THE VARIABILITY OF MEDIUM RANGE MODEL  
SOLUTIONS, SO WILL JUST HIGHLIGHT IN THE HAZARDOUS WEATHER OUTLOOK  
FOR NOW.  
 

 
   
AVIATION
 
 
ISSUED AT 645 AM CDT SAT APR 29 2017  
 
GRADUAL IMPROVEMENT IN CEILINGS AND VISIBILITIES EXPECTED FOR WFO  
PAH TAF LOCATIONS AS RIDGING BUILDS IN FROM THE SOUTHEAST TO CAP  
CONVECTIVE ACTIVITY AND SHIFT WINDS TO THE SOUTH AS THE EFFECTIVE  
FRONTAL BOUNDARY MOVES NORTH OF EACH OF THE LOCATIONS THIS  
MORNING.  
 
REDUCED CEILINGS AGAIN AFTER MIDNIGHT SUNDAY (05Z SUNDAY) AS  
CONVECTION MOVES BACK TOWARD KCGI SATURDAY NIGHT.  
 

 
   
PAH WATCHES/WARNINGS/ADVISORIES
 
 
IL...FLASH FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR ILZ075>078-  
080>094.  
 
MO...FLASH FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR MOZ076-086-087-  
100-107>112-114.  
 
IN...FLASH FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR INZ081-082-  
085>088.  
 
KY...FLASH FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR KYZ001>005-014-  
018-019.  
 

 
 

 
 
UPDATE...SMITH  
SHORT TERM...SMITH  
LONG TERM...SMITH  
AVIATION...SMITH  
 
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