623
FXUS63 KLMK 270647
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
147 AM EST SAT FEB 27 2021
FORECAST UPDATE
ISSUED AT 147 AM EST SAT FEB 27 2021
REALLY IMPRESSIVE 925-850 MB MOISTURE TRANSPORT CURRENTLY OCCURRING
FROM MIDDLE TN INTO SOUTHERN KY. PW VALUES HAVE PUSHED ABOVE 1.2
INCHES ACROSS SOUTHERN KY. KOHX 0621Z VAD WIND PROFILE CONFIRMED A
50 KT SOUTHWESTERLY LLJ AT 3 KFT, WHICH IS HELPING PRODUCE ROBUST
WAA AND ISENTROPIC LIFT. IR CLOUD TOP TEMPERATURES HAVE BEEN
STEADILY COOLING OVER THE PAST COUPLE OF HOURS OVER THE LAKE
CUMBERLAND REGION, AND SCATTERED LIGHTNING STRIKES HAVE BEEN NOTED
ON BOTH SIDES OF THE TN BORDER.
GIVEN THE ENVIRONMENT AND THE CURRENT POSITION OF THE HEAVY RAIN
BAND, HAVE INCREASED QPF BETWEEN 06-12Z THIS MORNING A FAIR AMOUNT.
THE FORCING AND MOISTURE TRANSPORT WILL LIKELY KEEP MODERATE TO
HEAVY RAIN OVER THE LAKE CUMBERLAND REGION THROUGH 11-12Z. 6-HOURLY
RAINFALL AMOUNTS OF 1-1.5 INCHES ARE LIKELY IN MONROE, CUMBERLAND,
CLINTON, AND RUSSELL COUNTIES. QPF HAS BEEN INCREASED IN OTHER
ADJACENT COUNTIES AS WELL, SUCH AS ALLEN, BARREN, METCALFE, AND
ADAIR. RAINFALL TOTALS WILL LIKELY COME UP SHY OF 3-HR FFG VALUES,
BUT WILL NEED TO CONTINUE TO MONITOR CLOSELY FOR POTENTIAL MINOR
FLOODING THIS MORNING.
ISSUED AT 940 PM EST FRI FEB 26 2021
EARLIER COVERAGE OF RAIN SHOWERS ACROSS NORTHERN KENTUCKY AND
SOUTHERN INDIANA HAS MOVED ON OFF TO THE NORTHEAST. HOWEVER, NEXT
BATCH OF PRECIPITATION IS CURRENTLY DEVELOPING TO THE SOUTHWEST OF
THE REGION WITH LIGHT RETURNS ALREADY MOVING INTO SOUTHERN KY.
CURRENT TEMPERATURES WERE GENERALLY AROUND 40 ACROSS SOUTHERN IN AND
NORTHERN KY. A BIT OF A TEMPERATURE GRADIENT WAS SEEN ACROSS
SOUTHERN KY (MAINLY SOUTH OF THE CUMBERLAND PARKWAY) WHERE
TEMPERATURES INCREASE FROM THE LOWER 40S ALONG THE CUMBERLAND
PARKWAY BUT INCREASE TO NEAR 50 ALONG THE KY/TN BORDER.
CURRENT FORECAST FOR THE OVERNIGHT PERIOD LOOKS GOOD. UPPER LEVEL
SHORT WAVE TROUGH AXIS OVER WESTERN TX IS FORECAST TO MOVE EASTWARD
WITH A LOW-LEVEL JET AXIS DEVELOPING OVERNIGHT FROM THE MS DELTA
REGION UP THROUGH THE TN AND LOWER OH VALLEYS. BEST CHANCES OF
RAINFALL LOOK TO BE ACROSS SOUTHERN KY OVERNIGHT WITH A DECREASING
COVERAGE OF RAINFALL AS ONE HEADS NORTH OF THE WK/BG PARKWAYS.
RAINFALL AMOUNTS OF A QUARTER TO HALF INCH STILL LOOK GOOD ACROSS
THE SOUTHERN THIRD OF KY OVERNIGHT WITH LESSER AMOUNTS NORTH OF THE
PARKWAYS.
AS FAR AS CONVECTIVE POTENTIAL GOES, MODEL SOUNDINGS SHOW A
RELATIVELY STABLE BOUNDARY LAYER THIS EVENING WITH A BIT GOOD CINH
ACROSS THE REGION. HOWEVER, LOW-LEVEL JET PUSHING INTO THE AREA
OVERNIGHT SHOULD PROVIDED A DECENT AMOUNT OF LIFT RESULTING IN GOOD
PARCEL ASCENT ABOVE THE TOP OF THE MORE STABLE BOUNDARY LAYER. MODEL
SOUNDINGS ILLUSTRATE THAT WELL WITH SOME POTENTIAL FOR ELEVATED
INSTABILITY. SO REALLY CAN'T RULE OUT SOME RUMBLES OF THUNDER OR A
FEW LIGHTNING STRIKES DOWN ALONG THE KY/TN BORDER AREA AND INTO THE
LAKE CUMBERLAND REGION WITH CONVECTION OVERNIGHT.
SHORT TERM
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 228 PM EST FRI FEB 26 2021
AFTER SOME SCATTERED LIGHT RAIN SHOWERS IN THE AREA THIS EVENING,
COVERAGE SHOULD INCREASE OVERNIGHT AS A WAVE OVER WEST TEXAS THIS
AFTERNOON MOVES INTO THE OH VALLEY AND A LOW LEVEL JET DEVELOPS FROM
NORTHERN MISSISSIPPI TO EASTERN KENTUCKY. AN ISOLATED RUMBLE OF
THUNDER WILL BE POSSIBLE NEAR THE TENNESSEE STATE LINE, AND THOUGH
INSTABILITY WILL BE MEAGER, CAN'T COMPLETELY RULE OUT SOME BRIEF
VERY SMALL HAIL NEAR LAKE CUMBERLAND AFTER MIDNIGHT IN THE MOST
ROBUST CONVECTION. RAINFALL TOTALS TONIGHT INTO EARLY SATURDAY
MORNING WILL BE VERY LIGHT IN MOST LOCATIONS, BUT THE LAKE
CUMBERLAND/DALE HOLLOW LAKE AREAS COULD SEE BETWEEN HALF AN INCH AND
AN INCH OF RAIN, MOSTLY BETWEEN MIDNIGHT AND DAWN. TEMPERATURES
TONIGHT WON'T MOVE MUCH, WITH READINGS IN THE 40S.
ON SATURDAY ANY LINGERING SHOWERS SHOULD MOVE OFF TO THE EAST EARLY
IN THE MORNING AND LEAVE US WITH A MOSTLY DRY DAY THANKS TO WEAKLY
RISING PRESSURES AND HEIGHTS, BEFORE MORE SHOWERS MOVE IN FROM THE
WEST TOWARDS EVENING. ATMOSPHERIC MOISTURE PROFILES SHOW LOW CLOUDS
HANGING AROUND THROUGH THE DAY, WITH BETTER CHANCES FOR MORE
CLOUDINESS AS ONE GOES SOUTH TOWARDS SOUTHERN KENTUCKY. MODEL
GUIDANCE IS IN TWO GROUPS FOR MAX TEMPS TOMORROW AFTERNOON -- ONE
WARMER AND ONE COOLER. WILL GO WITH THE COOLER GUIDANCE GIVEN CLOUDS
AND A LACK OF STRONG LOW LEVEL WARM ADVECTION...BUT ON THE WARM SIDE
OF THAT COOLER GROUP WITH INCREASING THICKNESSES. THAT RESULTS IN
HIGHS MOSTLY IN THE 50S, WHICH IS STILL SEVERAL DEGREES ABOVE NORMAL
FOR LATE FEBRUARY.
LONG TERM
(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 300 PM EST FRI FEB 26 2021
..HEAVY RAINFALL LIKELY SATURDAY NIGHT - SUNDAY
SATURDAY NIGHT - SUNDAY NIGHT...
THE NEXT AND LIKELY MOST SIGNIFICANT WAVE OF PRECIPITATION IS
EXPECTED TO MOVE INTO THE AREA LATE SATURDAY NIGHT THROUGH SUNDAY.
SYNOPTIC PATTERN WILL FEATURE A WESTERN TROUGH AND EASTERN RIDGE,
WITH DEEP SOUTHWESTERLY FLOW CONTINUING OVER THE OH VALLEY AS A
SERIES OF SHORTWAVES MOVE THROUGH THE LARGE-SCALE TROUGH. AT THE
SURFACE, EXPECT TO FIND A FRONTAL BOUNDARY DRAPED ACROSS THE DEEP
SOUTH THAT WILL GRADUALLY LIFT NORTHWARD AS A WARM FRONT INTO THE
LOWER OH VALLEY LATE SATURDAY NIGHT AHEAD OF A SYSTEM DEVELOPING TO
THE WEST. AS THE WAVES OF ENERGY INTERACT WITH THIS FRONTAL
BOUNDARY, EXPECT WIDESPREAD RAINFALL TO DEVELOP OVER THE AREA
STARTING LATE SATURDAY NIGHT AND CONTINUING THROUGH THE DAY SUNDAY.
INITIALLY, MODEL SOUNDINGS INDICATE A DRY LAYER BETWEEN 850-500 MB,
BUT AS A 40-50 KT SOUTHWESTERLY 850 MB JET NOSES INTO THE AREA,
AMPLE MOISTURE WILL BE TRANSPORTED IN AND EXPECT THE COLUMN TO
QUICKLY SATURATE. A STRONG ATMOSPHERIC RIVER WILL BE IN PLACE AS
WELL WITH THE NAEFS AND ECMWF ENS INDICATING IVT VALUES IN THE 99TH
PERCENTILE ADVECTING INTO THE AREA. THIS WILL LEAD TO A SURGE IN
PWATS ACROSS CENTRAL KY AND SOUTHERN IN WITH VALUES INTO THE 1.25 -
1.4 INCH RANGE, WHICH IS ABOVE THE 99TH PERCENTILE FOR THIS TIME OF
YEAR. EXPECT THERE TO BE SOME ELEVATED INSTABILITY AS WELL, WITH
MUCAPE VALUES OF UP TO ~100 -200 J/KG POSSIBLE INTO SUNDAY.
IN GENERAL, MODEL GUIDANCE SEEMS TO BE CONVERGING ON THE IDEA OF A
BAND OF MODERATE TO HEAVY RAINFALL SETTING UP ALONG/IN THE VICINITY
OF THE OHIO RIVER LATE SATURDAY NIGHT INTO SUNDAY MORNING AS THE
FRONT HANGS UP IN THIS VICINITY. RAINFALL IS THEN EXPECTED TO SLOWLY
SHIFT SOUTHEASTWARD THROUGHOUT THE DAY ON SUNDAY AS A COLD FRONT
PRESSES INTO THE AREA IN ASSOCIATION WITH A CLOSED LOW LIFTING
NORTHEAST THROUGH THE UPPER GREAT LAKES REGION. EXPECT THE HEAVIEST
RAINFALL TO OCCUR IN THE 0228/06-12Z TIMEFRAME OVER PORTIONS OF
SOUTHERN IN AND NORTHERN KY WITH 6-HOUR TOTALS AROUND 1 INCH
POSSIBLE. ELSEWHERE ACROSS CENTRAL AND SOUTHERN KY, TOTALS OF AROUND
0.50-0.75 INCHES ARE POSSIBLE. DURING THE MID MORNING HOURS FROM
0228/12-18Z, AN ADDITIONAL INCH OF RAINFALL IS POSSIBLE ACROSS
PORTIONS OF NORTHERN AND CENTRAL KY WITH 0.25 - 0.50 INCHES POSSIBLE
ACROSS SOUTHERN IN AND SOUTHERN KY. BY SUNDAY AFTERNOON FROM 0228/18-
00Z, THE HEAVIEST BAND OF PRECIPITATION WILL HAVE PROGRESSED
SOUTHEAST TOWARDS THE LAKE CUMBERLAND REGION WITH ANOTHER 0.50 -
1.00 INCHES POSSIBLE IN THAT VICINITY AND UP TO A QUARTER INCH FOR
AREAS TO THE NORTH.
OVERALL, THIS BRINGS RAINFALL TOTALS FRIDAY THROUGH SUNDAY INTO THE
1-3 INCH RANGE WITH LOCALLY HIGHER 3+ INCH AMOUNTS POSSIBLE. AT THIS
POINT IN TIME THERE REMAINS SOME UNCERTAINTY IN WHERE EXACTLY THE
BAND OF HEAVIEST PRECIPITATION WILL SET UP, AS SOME OF THE HEAVIEST
RATES AND TOTALS WILL LIKELY BE DRIVEN BY AREAS OF CONVECTION AND
TRAINING STORMS. ADDITIONALLY, EXPECT A SHARP GRADIENT IN QPF NORTH
OF THE OHIO RIVER ON THE NORTH SIDE OF THE HEAVIER PRECIP BAND.
WHILE 3- AND 6-HR FFG VALUES ARE GENERALLY BETWEEN 1.5 - 3.0 INCHES,
ANY AREAS THAT SEE CONVECTIVE RAIN RATES OR TRAINING OF STORMS COULD
SEE SOME MINOR FLOODING ISSUES DEVELOP. IN COORDINATION WITH
NEIGHBORS, WILL THEREFORE GO AHEAD AND ISSUE A FLOOD WATCH FOR
POINTS GENERALLY ALONG AND SOUTH OF THE OHIO RIVER STARTING 11 PM
EST SATURDAY NIGHT AND CONTINUING INTO EARLY MONDAY MORNING AS
RAIN MOVES OUT OF THE CUMBERLAND REGION. LOOKING AT RIVERS, AT
THIS TIME AREAS MOST LIKELY TO SEE SOME MINOR RIVER FLOODING
DEVELOP WOULD BE POINTS ALONG THE GREEN, LICKING AND KENTUCKY
RIVERS.
MONDAY AND BEYOND...
BY MONDAY, EXPECT TO BEGIN DRYING OUT ACROSS THE REGION AS SURFACE
HIGH PRESSURE BUILDS IN FROM THE NORTHWEST WITH MOSTLY DRY WEATHER
EXPECTED TO CONTINUE INTO TUESDAY. BY TUESDAY AFTERNOON, BEGIN TO
SEE SIGNIFICANT DIFFERENCES BETWEEN MODEL GUIDANCE. LOOKING AT WPC
CLUSTER ANALYSIS, THREE OF THE FOUR CLUSTERS SUGGEST DRY WEATHER FOR
TUESDAY NIGHT WHILE THE FOURTH CLUSTER (CONSISTING OF 1/3 OF THE
TOTAL ENSEMBLE MEMBERS) SUGGESTS WIDESPREAD PRECIPITATION.
SIMILARLY, FOR THURSDAY INTO FRIDAY WE SEE TWO DRY CLUSTERS AND TWO
WET CLUSTERS, WITH THE TOTAL ENSEMBLE MEMBERS BEING SPLIT ABOUT
50/50. AS A RESULT, WILL CARRY SOME SLIGHT CHANCE POPS DURING THESE
TWO TIMEFRAMES UNTIL WE CAN BEGIN TO SEE SOME BETTER AGREEMENT AMONG
MODEL GUIDANCE.
AVIATION
(06Z TAF ISSUANCE)
ISSUED AT 1256 AM EST SAT FEB 27 2021
WIDESPREAD SHOWERS ALONG WITH A FEW THUNDERSTORMS ARE SPREADING
NORTHEAST ACROSS SOUTH-CENTRAL KY, MAINLY FROM BWG EASTWARD. LEX
WILL BEGIN THE PERIOD WITH PREVAILING -RA AS WELL, BUT ONLY
ISOLATED/BRIEF LIGHT RAIN IS POSSIBLE AT HNB AND SDF. RAIN SHOWERS
ARE LIKELY AT BWG AND LEX THROUGH 10-11Z OR SO BEFORE THE BAND
SHIFTS SOUTHEAST OF THOSE TERMINALS. BETWEEN 06-09Z, EXPECT THE
LOWER CEILINGS OVER WEST-CENTRAL KY AND HNB TO GRADUALLY FILL IN
FURTHER EAST. THINK MVFR WILL RETURN AT LEX VERY SOON WITH IFR
LIKELY BY 09Z. BWG SHOULD SEE CEILINGS DROP QUICKER.
AFTER 11Z, A LULL IN RAINFALL IS EXPECTED THROUGH MUCH OF THE DAY AT
THE FOUR TAF SITES. LATE THIS EVENING, AFTER 02Z OR SO, A BAND OF
MODERATE TO HEAVY RAINFALL WILL LIFT NORTH ACROSS CENTRAL KY. THE
HEAVIEST RAIN IS EXPECTED GENERALLY ON EITHER SIDE OF THE OHIO RIVER
BETWEEN 06-12Z SUN. SOME SCATTERED THUNDERSTORMS WILL ALSO BE
POSSIBLE ALONG WITH BRIEF IFR/LIFR VSBYS IN HEAVIER RAIN/STORMS.
LMK WATCHES/WARNINGS/ADVISORIES
IN...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR INZ084-
089>092.
KY...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR
KYZ023>031-033>043-045>049-053>057-061>067-070>078-081-082.
UPDATE...MJ/EBW
SHORT TERM...13
LONG TERM....JML
AVIATION...EBW
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