576
FXUS63 KLMK 080021
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
821 PM EDT WED OCT 7 2026
..UPDATE AVIATION DISCUSSION
KEY MESSAGES
* AFTERNOON RELATIVE HUMIDITY VALUES WILL DROP INTO THE 20 TO 35
PERCENT RANGE EACH DAY THROUGH FRIDAY, BUT LIGHT WINDS (GENERALLY
LESS THAN 15 MPH) SHOULD LIMIT FIRE WEATHER CONCERNS.
* REMNANTS OF TROPICAL STORM ISAIAS WILL BRING WIDESPREAD
RAINFALL TO THE REGION OVER THE WEEKEND. WHILE MOST AREAS WILL
BENEFIT FROM THIS RAIN GIVEN THE ONGOING DROUGHT, THERE IS A
LOW CHANCE THAT LOCALIZED RAIN AMOUNTS EXCEED 3 INCHES TO
RESULT IN FLASH FLOODING.
DISCUSSION
ISSUED AT 123 PM EDT WED OCT 7 2026
*** WARM AND DRY INTO SATURDAY ***
EARLY WEDNESDAY AFTERNOON, WEST-NORTHWEST FLOW ALOFT WAS PRESENT
OVER THE LOCAL AREA BETWEEN A RIDGE ACROSS THE GREAT PLAINS AND
UPPER LEVEL TROUGH OVER THE GREAT LAKES. LIKE YESTERDAY, DEEP MIXING
WILL ADD A COUPLE MORE DEGREES TO SURFACE TEMPERATURES FOR HIGHS IN
THE UPPER 70S (EAST) TO LOW 80S (WEST), THOUGH IT'LL STILL FEEL MILD
FOR MOST - ESPECIALLY IN THE SHADE - AS LOW RELATIVE HUMIDITY KEEPS
APPARENT, OR "FEELS LIKE," TEMPERATURES A COUPLE DEGREES BELOW
ACTUAL AIR TEMPERATURES.
A DECAYING COOL FRONT WILL SINK SOUTH AND WASH OUT OVER SOUTHERN
INDIANA TONIGHT, WHILE IN ITS WAKE SURFACE HIGH PRESSURE WILL SHIFT
EAST FROM THE MIDWEST TO THE APPALACHIANS TOMORROW INTO FRIDAY. THIS
WILL RESULT IN GENTLE NORTHEAST WINDS WHICH WILL KEEP THE AIRMASS
DRY AND PERHAPS 1-2 DEGREES LESS WARM DURING THE DAY TOMORROW. IN
ADDITION, IF WE LOSE THE WIND OVERNIGHT INTO FRIDAY MORNING, RURAL
LOW-LYING AREAS MAY ONCE AGAIN DIP INTO THE UPPER 30S OR AT LEAST
LOW 40S - THOUGH THE PROBABILITY OF WIDESPREAD FROST IS VERY LOW
(LESS THAN 2%).
MEANWHILE, TROPICAL STORM ISAIAS WILL BE BREWING OVER THE GULF,
AND ON FRIDAY IT SHOULD START TO LIFT NORTHWARDS TOWARDS THE
COAST AS IT MERGES WITH A CUTOFF LOW OVER TEXAS/LOUISIANA. IN
RESPONSE, THE LOCAL AREA WILL SEE STRENGTHENING EASTERLY FLOW
FRIDAY INTO SATURDAY, BY WHICH TIME SOME GUIDANCE SHOWS A
NOTABLE DOWNSLOPING EFFECT IN THE PRESSURE GRADIENT FIELD OFF OF
THE APPALACHIANS. WHILE THIS WOULD HAVE A DRYING EFFECT, THE
ABUNDANT TROPICAL MOISTURE ACCOMPANYING ISAIAS' REMNANTS MAY
OFFSET THIS - THOUGH PERHAPS NOT UNTIL LATE SATURDAY, SPARKING
AT LEAST LOW CONCERNS OVER FIRE WEATHER EARLY IN THE DAY. WHILE
CONFIDENCE IS MUCH HIGHER IN DAYTIME RH VALUES OF 20-30%
(LOCALLY LOWER) ON FRIDAY, WINDS SHOULD BE LIGHT ENOUGH (GUSTS
GENERALLY LESS THAN 15 MPH) TO MINIMIZE ANY FIRE WEATHER
CONCERNS DESPITE MINIMUM AFTERNOON 10-HOUR FUEL MOISTURES OF
7-9%. ALL THE WHILE, THE CONTINUED DRY AND SEASONABLY WARM
WEATHER WILL RESULT IN EXPANDING AND WORSENING DROUGHT
CONDITIONS.
*** TROPICAL REMNANTS TO BRING BENEFICIAL RAIN(?) BY SUNDAY ***
AS WHAT'S LEFT OF ISAIAS LIFTS TOWARD THE LOCAL AREA, STRONG
DIFFLUENCE AND SYNOPTIC LIFT IN THE RIGHT ENTRANCE REGION OF THE
TROUGH SHOULD LEAD TO AN EXPANSIVE RAIN SHIELD WHICH MODELS SUGGEST
WILL LIKELY (80% CHANCE) ENTER THE LOCAL AREA SOMETIME BETWEEN EARLY
SATURDAY AFTERNOON (LREF 10TH PERCENTILE ONSET TIME) AND AROUND DAWN
SUNDAY MORNING (LREF 90TH PERCENTILE ONSET TIME). THE OVERNIGHT
SATURDAY NIGHT INTO SUNDAY MORNING TIMING (GIVEN BY THE LREF MEAN)
OF THE HEAVIEST BANDS OF PRECIPITATION ASSOCIATED WITH THE TROPICAL
REMNANTS SUGGESTS DIURNALLY-DRIVEN INSTABILITY WILL BE VERY LOW -
LIMITING THE RISK FOR TORNADOES. HOWEVER, THE SCREAMING WIND FIELDS
ACCOMPANYING THIS SYSTEM RAISE CONCERNS ABOUT LOCALLY STRONG WINDS
SHOULD ANY HEAVIER SHOWERS/STORMS MIX THEM DOWN TO THE SURFACE. IN
ADDITION, THE STRONG DIRECTIONAL WIND SHEAR ON THE EAST SIDE OF THE
SURFACE LOW - WHICH THE NATIONAL HURRICANE CENTER (NCH) SUGGESTS
WILL TRACK NEAR OR WEST OF THE LOCAL AREA - SUGGESTS THAT SHOULD ITS
NORTHWARD TREK SPEED UP, WE'LL HAVE TO WATCH SOUTHERN KENTUCKY FOR
BRIEF SPIN UPS AS GFS SOUNDINGS SHOW STRONGLY CURVED HODOGRAPHS
FEATURING 500-1000 M^2/S^2 0-3KM SRH SATURDAY EVENING. FORTUNATELY,
THE GLOBAL MODELS, WHOSE RESOLUTION IS TOO COARSE TO CAPTURE
CONVECTIVE FEATURES, SUGGEST GRADIENT WINDS ASSOCIATED WITH THIS
SYSTEM ARE UNLIKELY TO BE PROBLEMATIC WITH EPS (EUROPEAN ENSEMBLE)
MEAN PEAK GUSTS AROUND 20-30 MPH SATURDAY NIGHT INTO SUNDAY; IT
WOULDN'T BE SURPRISING TO SEE THIS INCREASE, KNOWING HOW MODELS
STRUGGLE TO RESOLVE TROPICAL SYSTEMS, SO WE'LL KEEP A CLOSE EYE ON
IT AS WE GET CLOSER TO THE WEEKEND.
THE MAIN STORY WITH THIS SYSTEM WILL BE THE RAINFALL, THOUGH AMOUNTS
REMAIN A SOURCE OF CONSIDERABLE UNCERTAINTY WITH NATIONAL BLEND OF
MODELS (NBM) 25TH-75TH PERCENTILE 48-HOUR RAINFALL TOTALS THROUGH
8AM MONDAY MORNING RANGING FROM ROUGHLY 0.75 TO 2.25 INCHES ACROSS
THE LOCAL AREA. THIS MEANS THAT, AT ANY GIVEN LOCATION, THE CHANCE
OF TOTAL RAIN AMOUNTS FALLING EITHER INSIDE OR OUTSIDE OF THIS RANGE
IS 50% - THAT'S A LOT OF SPREAD. GIVEN THE ANTECEDENT DRY
CONDITIONS, RFC 6-HOUR FLASH FLOOD GUIDANCE (FFG) - OR THE MINIMUM
AMOUNT OF RAINFALL REQUIRED TO INDUCE FLOODING - IS RUNNING 3.5-4.5
INCHES, WHICH IS AROUND NBM'S ENSEMBLE MAX FOR THE WHOLE EVENT. THIS
WOULD INDICATE OUR FLOODING RISK IS LOW, THOUGH NOT NEGLIGIBLE,
SINCE THE GLOBAL MODELS COMPRISING NBM WON'T RESOLVE CONVECTIVE
PROCESSES WHICH COULD ENHANCE RAINFALL RATES; ANY FLOODING WOULD
LIKELY BE CONFINED TO A LOCALIZED BAND OF HEAVIER RAIN - FUELED BY A
60-75 KT 850MB LLJ SATURDAY NIGHT.
AVIATION /00Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 821 PM EDT WED OCT 7 2026
THE ONLY MAIN CHANGE IN THE FORECAST PERIOD WILL BE WINDS
DIMINISHING OVERNIGHT AND DURING THE EARLY MORNING PERIOD WE WILL
SEE WINDS BECOME MORE NORTHERLY. VFR FLIGHT CATEGORIES REMAIN UNDER
MAINLY CLEAR SKIES.
LMK WATCHES/WARNINGS/ADVISORIES
KY...NONE.
IN...NONE.
DISCUSSION...JRB
AVIATION...BTN
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