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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