406  
FXUS63 KJKL 270549  
AFDJKL  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JACKSON KY  
1249 AM EST SAT FEB 27 2021  
   
UPDATE
 
 
ISSUED AT 1249 AM EST SAT FEB 27 2021  
 
LATEST MODEL GUIDANCE IS VERY SUPPORTIVE OF A BAND OF 1+ INCHES OF  
RAINFALL SETTING UP FROM WAYNE COUNTY NORTHWEST THROUGH LONDON,  
TOWARDS JACKSON OVERNIGHT. IR SATELLITE HAS SHOWN SOME VERY GOOD  
COOLING ON THE CLOUD TOPS OVER THE PAST SEVERAL HOURS COINCIDING  
WITH FANTASTIC 925-850MB MOISTURE TRANSPORT INTO SOUTHERN  
KENTUCKY. EVEN SEEING SOME CONVECTION BEING REPORTED ACROSS NORTH  
CENTRAL TN. ALL THIS POINTS TO SOME LOCALLY HEAVY RAINFALL  
POTENTIAL THROUGH DAWN. WENT AHEAD AND SHIFTED THE AXIS OF  
HEAVIER RAIN A BIT NORTH AND INCREASED AMOUNTS CLOSER TO THE 1  
INCH MARK, BUT MAY NEED TO GO HIGHER IF THE TRENDS CONTINUE. WE  
WILL PROBABLY COME UP SHORT OF THE 3 HOUR FLASH FLOOD GUIDANCE OF  
1.50-2.00 INCHES, BUT CERTAINLY SOME LOCAL HIGH WATER ISSUES SEEMS  
REASONABLE BY DAWN. EITHER WAY, THIS RAIN WILL HELP TO PRIME THE  
AREA FOR ANY ADDITIONAL RAINFALL LATER THIS WEEKEND.  
 
UPDATE ISSUED AT 1005 PM EST FRI FEB 26 2021  
 
DID A QUICK UPDATE TO THE GRIDS TO REFLECT THE TEMPORARY PCPN LULL  
OVER THE AREA AND INCLUDE THE LATEST OBS AND TRENDS FOR THE T/TD  
GRIDS. THESE UPDATES HAVE BEEN SENT TO THE NDFD AND WEB SERVERS.  
HAVE ALSO SENT A CONTINUATION STATEMENTS FOR THE FLOOD WATCH. A  
FRESHENED SET OF ZONES WILL FOLLOW BY 11 PM MAINLY TO REMOVE THE  
EVENING WORDING.  
 
UPDATE ISSUED AT 745 PM EST FRI FEB 26 2021  
 
00Z SFC ANALYSIS SHOWS A BROAD AREA OF LOW PRESSURE MOVING INTO  
KENTUCKY FROM THE SOUTHWEST. THIS IS THE START OF A SERIES OF  
SFC WAVES MOVING THROUGH THE AREA WITH BOUTS OF MODERATE TO HEAVY  
RAINS. OUR PRELIMINARY ROUND LOOKS TO BE DEPARTING TO THE  
NORTHEAST AFTER AFFECTING MAINLY THE NORTHERN PORTION OF THE CWA.  
WE WILL SEE A LULL IN THE ACTIVITY FOR THE LATTER PART OF THE  
EVENING BEFORE THE NEXT ROUND MOVES IN FROM THE SOUTH. CURRENTLY,  
TEMPERATURES ARE RUNNING IN THE LOW TO MID 40S MOST PLACES WITH  
SOME UPPER 30S IN THE NORTHWEST ALONG WITH THE LINGERING CHILLY  
RAIN SHOWERS. DEWPOINTS, MEANWHILE, ARE SIMILAR TO TEMPERATURES  
VARYING FROM THE UPPER 30S NORTHWEST TO THE MID 40S IN THE SOUTH.  
WINDS ARE GENERALLY BLOWING FROM THE SOUTHEAST AT 5 TO 10 MPH THIS  
EVENING. HAVE UPDATED THE FORECAST TO FINE TUNE THE POPS AND  
WEATHER GRIDS WHILE ALSO ADDING IN THE LATEST OBS AND TRENDS FOR  
THE T/TD GRIDS. THESE UPDATES HAVE BEEN SENT TO THE NDFD AND WEB  
SERVERS.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SATURDAY NIGHT)  
ISSUED AT 520 PM EST FRI FEB 26 2021  
 
THE SHORT TERM PERIOD WILL BE CHARACTERIZED BY WEST SOUTHWEST TO  
SOUTHWEST FLOW ALOFT BETWEEN UPPER LEVEL RIDGING OVER THE GULF OF  
MEXICO AND CARIBBEAN AND EXTENDING INTO PORTIONS OF THE ATLANTIC  
AND AN UPPER LEVEL TROUGH EXTENDING FROM CENTRAL CANADA INTO THE  
ROCKIES AND PLAINS. THIS PATTERN TYPE FAVORS A RISK OF HEAVY  
RAINFALL ACROSS EAST KY. THE FIRST IS A SERIES OF SHORTWAVE  
TROUGHS IN SOUTHWEST FLOW IS WORKING ACROSS THE REGION AT THIS  
TIME, WITH THE ASSOCIATED AREA OF SHOWERS STARTING TO DEPART TO  
THE NORTH AND EAST. ANOTHER IS EXPECTED TO MOVE FROM THE CENTRAL  
PLAINS TO THE MID MS VALLEY AND OH VALLEY LATER TONIGHT, BEFORE  
DEPARTING NORTHEAST EARLY ON SATURDAY. A WEAKENING WAVE OF SFC LOW  
PRESSURE WILL TRACK FROM THE LOWER MS VALLEY INTO THE TN VALLEY  
ALONG A FRONTAL ZONE TO THE SOUTH OF THE AREA. ISENTROPIC LIFT  
OVER THIS BOUNDARY SHOULD LEAD TO PW RISING TO THE 1 TO 1.2 INCH  
OR SO RANGE BY LATE TONIGHT. SOME ELEVATED INSTABILITY IS  
ANTICIPATED ACROSS THE SOUTH WITH THIS LATER ON TONIGHT AS WELL  
AND SOME THUNDER. MEASURABLE RAINFALL FROM THIS ROUND OVERNIGHT  
TONIGHT IS PROBABLE ACROSS THE AREA, ESPECIALLY FROM I 64  
SOUTHEAST. THE HEAVIEST RAINFALL SHOULD BE ACROSS THE SOUTHEAST  
WHERE A HALF OF AN INCH TO AN INCH IS POSSIBLE.  
 
A RELATIVE LULL IN THE PRECIPITATION CHANCES WILL OCCUR FOR MUCH  
OF SATURDAY, ESPECIALLY ACROSS THE NORTHWEST AS WORK SFC HIGH  
PRESSURE PASSES BY. DURING THIS TIME, PW ACROSS THE NORTHWEST  
SHOULD FALL BELOW 1 INCH OR A TIME. HOWEVER, THE NEXT SHORTWAVE  
MOVING THROUGH THE MEAN TROUGH AXIS EXTENDING FROM CENTRAL CANADA  
TO THE SOUTHERN ROCKIES WILL APPROACH THE LOWER OH VALLEY ON  
SATURDAY NIGHT FROM THE CENTRAL AND SOUTHERN PLAINS. MEANWHILE, A  
COMPLEX SFC LOW PRESSURE SYSTEM SHOULD APPROACH THE GREAT LAKES  
AND OH VALLEY REGION WITH A WARM FRONT EXTENDING TO THE EAST  
LIFTING ACROSS THE TN VALLEY AND ACROSS MUCH OF THE COMMONWEALTH  
BY LATE SATURDAY NIGHT. MOISTURE TRANSPORT WILL BE RATHER  
SIGNIFICANT WITH GULF OF MEXICO MOISTURE TRANSPORTED INTO EAST KY  
AT THE LOWER LEVELS AND PACIFIC MOISTURE AT A MID AND UPPER  
LEVELS. PW SHOULD RISE INTO THE 1.1 TO 1.3 INCH AREAWIDE DURING  
THIS TIME. IN ADDITION TO ANOTHER ROUND OF ISENTROPIC LIFT, THE  
LEFT EXIT REGION OF A 500 MB JET STREAK MAY LEAD TO SOME ENHANCED  
LIFT ACROSS NORTHWESTERN SECTIONS OF THE AREA LATE SATURDAY NIGHT.  
ELEVATED INSTABILITY IS EXPECTED AGAIN ON SATURDAY EVENING INTO  
SATURDAY NIGHT IN ADVANCE OF THE NORTHWARD LIFTING WARM FRONT SO  
SOME THUNDERSTORMS ARE ALSO POSSIBLE. LOCALLY HEAVIER RAIN IS  
EXPECTED WITH ANY THUNDERSTORMS. THE MODEL CONSENSUS IS FOR THE  
HEAVIER RAIN ON SATURDAY NIGHT TO FALL NORTH OF THE LIFTING WARM  
FRONT NEAR TO THE OH RIVER ACROSS WESTERN AND CENTRAL KY AND THEN  
ALONG AND NORTH OF THE I 64 ACROSS EASTERN PORTIONS OF THE STATE.  
 
THE INITIAL ROUNDS OF RAIN TODAY, TONIGHT, AND WHAT FALLS ON  
SATURDAY EVENING WILL HELP TO SATURATE OR PRIME THE SOIL FOR THE  
ANTICIPATED HEAVY ROUNDS OF MODERATE TO HEAVY RAIN SATURDAY NIGHT  
INTO THE START OF THE LONG TERM PERIOD. A FLOOD WATCH HAS BEEN  
ISSUED FOR THE WEST AND NORTHWEST PORTIONS OF THE AREA STARTING AT  
6Z (1 AM) SUNDAY THROUGH 12Z (7 AM) ON MONDAY AND STARTING AT 12Z  
(7 AM) SUNDAY AND ENDING AT 12Z (7 AM) MONDAY FOR LOCATIONS  
FURTHER SOUTHEAST TO INCLUDE THE HEADWATERS OF THE KENTUCKY AND  
CUMBERLAND.  
 
TEMPERATURES WILL BE SOMEWHAT DIURNALLY LIMITED BY EXTENSIVE CLOUD  
COVER AND PRECIPITATION ACROSS THE AREA DURING THE SHORT TERM  
PERIOD. TEMPERATURES WILL MODERATE TO ABOVE NORMAL LEVELS,  
HOWEVER.  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 540 PM EST FRI FEB 26 2021  
 
THE EXTENDED BEGINS SUNDAY WITH THE REGION UNDER AN AREA OF DEEP  
SOUTHWESTERLY FLOW WITH A RIDGE OVER THE GULF AND A DEEPENING TROUGH  
IN THE SOUTHWEST US. THE ANOMALOUSLY HIGH AMOUNT OF MOISTURE  
COMBINES WITH FAVORABLE JET DYNAMICS TO PRODUCE WIDESPREAD MODERATE  
TO HEAVY RAIN ACROSS THE AREA. A FRONTAL BOUNDARY THAT HAD  
PREVIOUSLY LIFTED NORTH WILL HELP TO KEEP THE HEAVIEST PRECIP  
FOCUSED IN THE NORTHERN TIERS OF THE CWA. MOVING THROUGH SUNDAY AND  
SUNDAY NIGHT, A SURFACE LOW MOVING OVER THE GREAT LAKES WILL PUSH A  
FRONTAL BOUNDARY SOUTH, DRAGGING THE HEAVIEST PRECIP SOUTH THROUGH  
THE AREA WITH IT. SOME SLIGHT UNCERTAINTY REMAINS, BUT THE TOTAL  
RAINFALL CURRENTLY EXPECTED FROM TONIGHT TO SUNDAY NIGHT IS BETWEEN  
2 AND 4 INCHES. SOME INSTABILITY LINGERS THROUGH SUNDAY AND POSSIBLE  
THUNDERSTORMS COULD LEAD TO LOCALLY HIGHER TOTALS. THE PRECURSOR  
RAIN THAT WILL HAVE FALLEN THROUGH THE SHORT TERM ON SATURDAY WILL  
LEAVE THINGS SATURATED AND WILL ALLOW FOR MUCH OF WHAT FALLS SUNDAY  
AND SUNDAY NIGHT TO BECOME RUN OFF. THIS WILL LEAD TO A THREAT FOR  
FLOODING OF AREA STREAMS AND RIVERS AND A FLOOD WATCH HAS BEEN  
ISSUED ACCORDINGLY. ON MONDAY AFTERNOON/EVENING, THE FRONTAL  
BOUNDARY CONTINUES TO SAG SOUTH, QUICKLY TAKING REMAINING PRECIP  
ALONG WITH IT. HIGH PRESSURE THEN MOVES IN OVER THE AREA TO TAKE ITS  
PLACE.  
 
TUESDAY ONWARD THE FORECAST BECOMES MORE TRICKY AND CONFIDENCE IS  
NOT HIGH. THE TROUGH INITIALLY OUT OVER THE SOUTHWESTERN US WILL  
HAVE MOVED FURTHER EAST AND CLOSER TO OUR AREA, BUT THERE IS NOT  
MUCH AGREEMENT IN ITS EVOLUTION BEYOND THAT. THE GFS DAMPENS THE  
WAVE MORE AGGRESSIVELY AND KEEPS IT SUPPRESSED TO OUR SOUTH. WITH  
THIS SOLUTION, DRY WEATHER CONTINUES THROUGH TUESDAY AND WEDNESDAY.  
THE ECMWF, HOWEVER, KEEPS THE WAVE STRONGER AND PUSHES IT TO OUR  
NORTH. A SURFACE LOW DEVELOPS OVER THE SOUTHEAST, PUSHING MORE  
PRECIP INTO OUR AREA. THE DRIER SOLUTION OF THE GFS WOULD BE MORE  
IDEAL GIVEN THE RAIN FALLING THIS WEEKEND, BUT THE ECMWF HAS BEEN  
CONSISTENT AND HAS ENOUGH ENSEMBLE SUPPORT TO JUSTIFY KEEPING POPS  
IN THE FORECAST. HOWEVER, GIVEN THE UNCERTAINTY, HAVE KEPT THEM  
LIMITED TO THE CHANCE CATEGORY. BY THURSDAY AND FRIDAY, ANOTHER  
UPPER LEVEL LOW LOOKS TO BE PUSHING IN FROM THE SOUTHWEST US. THE  
GFS IS MORE PROGRESSIVE AND INTRODUCES PRECIP FRIDAY WHILE THE ECMWF  
IS SLOWER AND DOESN'T INTRODUCE PRECIP UNTIL BEYOND THE PERIOD. HAVE  
GONE WITH THE NBM POPS FOR THE END OF THE PERIOD DUE TO THE LACK OF  
AGREEMENT.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)  
ISSUED AT 1249 AM EST SAT FEB 27 2021  
 
MVFR CIGS WILL CONTINUE TO LOWER AS PRECIPITATION SPREADS INTO  
THE REGION OVERNIGHT. IFR CONDITIONS WILL BE MORE LIKELY AFTER 08Z  
AREAWIDE AS WE SEE SOME LOWERING VISIBILITIES WITHIN THE AREA OF  
RAIN AND LOWER CIGS. LIGHT SOUTH TO SOUTHWEST WINDS WILL REMAIN  
UNDER 10 KTS THROUGH THE PERIOD, ALTHOUGH WINDS ALOFT WILL  
STRENGTHEN DURING THE 06 TO 15Z PERIOD LEADING TO SOME LLWS  
CONCERNS FROM THE SOUTHWEST AT UP TO 40 KTS.  
 

 
   
JKL WATCHES/WARNINGS/ADVISORIES
 
 
FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR KYZ044-  
050>052-058>060-068-069-079-080-083-084-104-106>109-111-112-114.  
 
FLOOD WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING FOR  
KYZ085>088-110-113-115>120.  
 

 
 

 
 
UPDATE...KAS  
SHORT TERM...JP  
LONG TERM...HAS  
AVIATION...KAS  
 
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