930  
FXUS63 KPAH 210917  
AFDPAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PADUCAH KY  
317 AM CST WED FEB 21 2018  
   
SHORT TERM
 
(TODAY THROUGH THURSDAY NIGHT)  
ISSUED AT 317 AM CST WED FEB 21 2018  
 
COLD FRONT AT 09Z IS THROUGH ALL BUT THE KHOP AREA. INITIAL BATCH OF  
RAIN PRODUCED 1 TO 2 INCHES OVER THE PAST 12 HOURS ACROSS SEMO,  
INTO SOUTHERN IL. RAINFALL RATES IN THIS AREA HAVE BEEN KEPT IN  
CHECK, AND ARE LOWERING, NOT TO MENTION ANTECEDENT CONDITIONS WERE  
SUCH THAT, WELL, THE RAIN WAS WELCOME. NO ISSUES SO FAR TONIGHT  
ANYWHERE, OTHER THAN MAYBE SOME PUDDLING ON ROADS. EXPECT SIMILAR  
TO SLIGHTLY LOWER AMOUNTS INTO SW INDIANA AND WEST KY FOR THE REST  
OF THE NIGHT. RAP AND NAMNEST DATA HAVE HANDLED THE WINDS AND  
TEMPERATURE TRENDS THE BEST, AND WILL CONTINUE WITH THOSE  
FORECASTS THROUGH TODAY. TODAY, TEMPS DO GET CLOSE TO 32F FROM SAY  
MARBLE HILL NORTHEAST TO PINCKNEYVILLE. SO SOME PATCHY ICING,  
MAINLY ELEVATED CANNOT BE RULED OUT COMPLETELY IN THIS CORRIDOR.  
NOT SURE THAT IT WILL BE ALL THAT IMPACTFUL. WILL MONITOR.  
 
EXTENDED THE FLOOD WATCH THROUGH 12Z SUNDAY. HIGHER CONFIDENCE FOR  
APPRECIABLE AREAL FLOODING WILL BE FROM LATER THURSDAY ON THROUGH  
SATURDAY NIGHT WHICH HAS BEEN MESSAGED FOR A FEW DAYS. THE LONG TERM  
DISCUSSION WILL HAVE MORE ON THE FRIDAY THROUGH SATURDAY PERIOD.  
MUCH LOWER CONFIDENCE ON THE FRONT END THROUGH TONIGHT, IN  
PARTICULAR FOR SEMO, SOUTHERN IL AND SOUTHWEST IN, GIVEN LOWERING  
RATES, AND AN AXIS SHIFT TO WEST KY. ISOLATED LOW IMPACT ISSUES  
CANNOT BE RULED OUT I SUPPOSE. WILL KEEP A CLOSE EYE ON WEST KY  
THROUGH 12Z THURSDAY. EXPECT A BIT OF A LULL ON THURSDAY BEFORE  
ANOTHER SURGE THURSDAY NIGHT AS THE BOUNDARY PUSHES BACK INTO THE  
AREA ALONG WITH ANOTHER MID LEVEL WAVE MOVING ACROSS THE REGION.  
SELECT RIVER FLOOD WARNINGS HAVE ALREADY BEEN OUT FOR SEVERAL DAYS.  
THE EXTENDED WATCH EXPANDS UPON THAT, ONCE THE RAINFALL REALLY  
TALLIES UP.  
   
LONG TERM
 
(FRIDAY THROUGH TUESDAY)  
ISSUED AT 317 AM CST WED FEB 21 2018  
 
THE PRIMARY CONCERN IN THE LONG TERM CONTINUES TO BE THE POTENTIAL  
FOR HEAVY RAINFALL AND FLOODING FRIDAY INTO SATURDAY NIGHT. WHILE  
FINER DETAILS SUCH AS PRECIPITATION AMOUNTS AND THE AXIS OF HEAVIEST  
RAIN STILL REQUIRE SOME FINE TUNING, OVERALL FORECAST CONFIDENCE IS  
HIGHER THAN AVERAGE GIVEN GENERALLY GOOD AGREEMENT AMONG FORECAST  
MODELS.  
 
AN ANOMALOUSLY MOIST SOUTHWEST FLOW PATTERN WILL PERSIST INTO THE  
FIRST HALF OF THE LONG TERM PERIOD. PERTURBATIONS IN THE STRONG  
SOUTHWEST FLOW ALOFT WILL PROVIDE THE NECESSARY LIFT TO GENERATE NO  
FEWER THAN THREE PRECIPITATION EVENTS DURING THE PERIOD. THE FIRST  
ROUND OF RAIN IS EXPECTED TO CARRY OVER FROM THURSDAY NIGHT INTO  
FRIDAY AS ENERGY RIPPLES ALONG A STALLED OUT FRONTAL BOUNDARY DRAPED  
SOUTHWEST TO NORTHEAST ACROSS THE AREA. THE SECOND ROUND OF RAIN  
ARRIVES FRIDAY NIGHT INTO EARLY SATURDAY AS A WARM FRONT LIFTS NORTH  
ACROSS THE AREA. THE THIRD AND FINAL ROUND OF ACTIVITY ACCOMPANIES  
THE APPROACH AND PASSAGE OF A COLD FRONT LATE SATURDAY AFTERNOON  
INTO SATURDAY NIGHT.  
 
SOME OF THE RAIN THAT FALLS COULD BE QUITE HEAVY WITH PRECIPITABLE  
WATER VALUES FORECAST TO BE 2 TO 3 STANDARD DEVIATIONS ABOVE NORMAL.  
THE COLLABORATED FORECAST HAS 2 TO 4 INCHES OF RAIN OVER MUCH OF THE  
AREA FROM FRIDAY THROUGH SATURDAY NIGHT. THAT'S IN ADDITION TO WHAT  
FALLS PRIOR TO FRIDAY. THUNDER WILL ALSO BE POSSIBLE THROUGH MUCH OF  
THE PERIOD, WHICH WILL SERVE TO FOCUS EVEN HEAVIER RAINFALL AMOUNTS  
IN SOME BASINS--LEADING TO THE POTENTIAL FOR FLASH FLOODING.  
 
THE POTENTIAL FOR SEVERE WEATHER WILL ALSO NEED TO BE MONITORED--  
MAINLY SATURDAY AFTERNOON INTO SATURDAY NIGHT--AS A DEEPENING  
SURFACE LOW SHIFTS NORTHEAST FROM THE PLAINS INTO THE QUAD CITIES  
AREA BY 00Z SUNDAY. ATMOSPHERIC DYNAMICS INCLUDING DEEP LAYER SHEAR  
APPEAR FAVORABLE FOR THUNDERSTORM ORGANIZATION. HOWEVER, THE QUALITY  
OF SURFACE-BASED INSTABILITY WILL BE THE GREATEST VARIABLE GIVEN THE  
AMOUNT OF SKY COVER AND RAIN FORECAST. THE 21/00Z GFS SUGGESTS THAT  
INSTABILITY WILL NOT BE A PROBLEM, BUT IT IS SOMETHING THAT WE WILL  
MONITOR AS THE PERIOD COMES INTO THE WINDOW OF NEAR TERM CAM MODEL  
GUIDANCE.  
 
THE PRECIPITATION SHOULD TAPER OFF ABRUPTLY FROM WEST TO EAST  
SATURDAY NIGHT AS THE COLD FRONT SWEEPS THROUGH. IN ITS WAKE, DRY  
AND SLIGHTLY COOLER CONDITIONS ARE FORECAST TO START THE NEW WEEK AS  
HIGH PRESSURE BUILDS IN. AFTER UNSEASONABLY WARM CONDITIONS FRIDAY  
AND SATURDAY, A RETURN TO TEMPERATURES STILL SLIGHTLY ABOVE NORMAL  
IS FORECAST SUNDAY THROUGH TUESDAY. IN FACT, EVEN LOW TEMPERATURES  
MAY REMAIN ABOVE FREEZING BEHIND THE FRONT EARLY NEXT WEEK.  
GENERALLY USED A BLEND OF AVAILABLE GUIDANCE FOR TEMPERATURES.  
 

 
   
AVIATION
 
 
ISSUED AT 437 PM CST TUE FEB 20 2018  
 
INCOMING RAINS WILL DROP CIGS INTO FLIGHT RESTRICTED CATS  
OVERNIGHT, WITH IFR POSSIBLE/BEST CHANCE TIME PERIOD LATE  
TONIGHT-EARLY TMRW. THAT IS ALSO WHEN VSBYS MAY ALSO BRIEFLY  
RESTRICT TO IFR IN HEAVIER SHOWERS. AFTER THAT, IFR CIGS LINGER  
INTO THE MORNING, WITH MVFR VSBYS SLOW TO IMPROVE. RAIN CHANCES  
NEVER GO AWAY, BUT THE NEXT BEST TIME PERIOD WILL BE LATE IN THE  
FORECAST, TOWARD THE END OF THE PLANNING PERIOD, LATE TMRW PM.  
 

 
   
PAH WATCHES/WARNINGS/ADVISORIES
 
 
IL...FLOOD WATCH THROUGH LATE SATURDAY NIGHT FOR ILZ075>078-080>094.  
 
MO...FLOOD WATCH THROUGH LATE SATURDAY NIGHT FOR MOZ076-086-087-100-  
107>112-114.  
 
IN...FLOOD WATCH THROUGH LATE SATURDAY NIGHT FOR INZ081-082-085>088.  
 
KY...FLOOD WATCH THROUGH LATE SATURDAY NIGHT FOR KYZ001>022.  
 

 
 

 
 
SHORT TERM...CN  
LONG TERM....RJP  
 
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