415
FXUS63 KLMK 260004
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
804 PM EDT SAT JUL 25 2026
KEY MESSAGES
* SPOTTY SHOWERS CONTINUE THROUGH TONIGHT, BUT SEVERE WEATHER IS NOT
EXPECTED.
* HEAT AND HUMIDITY BEGIN TO INCREASE TOMORROW, WITH TEMPERATURES
NEAR 90F AND HEAT INDEX VALUES CLOSE TO 100F.
* MAX AFTERNOON HEAT INDICES COULD BE IN THE TRIPLE DIGITS FOR SOME
BY EARLY NEXT WEEK, BUT THIS REMAIN CONDITIONAL ON ANY
THUNDERSTORM CHANCES.
* A ROUND OR TWO OF STRONGER THUNDERSTORMS IS POSSIBLE SUNDAY NIGHT
AND AGAIN MONDAY AND/OR TUESDAY, HOWEVER CONFIDENCE REMAINS LOW ON
THE FINER DETAILS.
UPDATE
ISSUED AT 804 PM EDT SAT JUL 25 2026
RECENT OBSERVATIONS OF VISIBILITY REDUCTIONS, LIGHT (MOSTLY LESS
THAN 25 DBZ) REFLECTIVITIES FROM KLVX, AND THE LIGHT PRECIPITATION
(GENERALLY 0.01" OR LESS) OBSERVED AT ASOS/AWOS SITES ACROSS THE
AREA SUGGESTS THE PRESENCE OF DRIZZLE. THE LATEST RAP GUIDANCE
ADVERTISES >90% RH IN THE 0-1KM LAYER, LOW (<10%) CHANCES FOR CLOUD
ICE, AND POCKETS OF LIGHT PRECIP/DIMINISHED VISIBILITY - SUGGESTING
THIS DRIZZLE COULD CONTINUE INTO THE OVERNIGHT PERIOD. DURING THE
SECOND HALF OF THE OVERNIGHT, HOWEVER, ISENTROPIC UPGLIDE WEAKENS
AND SUBSIDENCE BECOMES MORE FAVORED AS THE AXIS OF A SHORTWAVE
TROUGH CROSSES THE AREA. EVEN SO, TIME-HEIGHTS SUGGEST AT LEAST
PATCHY FOG COULD LINGER INTO SUNDAY MORNING, WHILE HREF GUIDANCE
WOULD SAY LOW STRATUS MAY NOT (50% CHANCE) BREAK UP TO GIVE US A
VIEW OF THE SUN UNTIL AROUND MIDDAY. WE ELECTED NOT TO ADJUST
TEMPERATURES MUCH AT THIS JUNCTURE, BUT HIGH TEMPERATURES TOMORROW
MAY NEED TO BE KNOCKED DOWNWARD IF THESE CLOUDS DO, INDEED, STICK
AROUND FOR AS LONG AS SOME OF THE MORE PESSIMISTIC GUIDANCE SUGGESTS.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 351 PM EDT SAT JUL 25 2026
ISOLATED LIGHT SHOWERS CONTINUE TO PASS OVER THE AREA THIS AFTERNOON
DUE TO WEAK ISENTROPIC LIFT OVER A STATIONARY BOUNDARY TO OUR
SOUTHWEST AND A SUBTLE UPPER LEVEL DISTURBANCE RIDING THROUGH THE
FLOW. AN ISOLATED TO SCATTERED SHOWER CHANCES WILL LINGER THROUGH
THE REST OF THE AFTERNOON AND INTO THE EVENING HOURS, AND PERHAPS A
LOW END RISK FOR A THUNDERSTORM TOO. HOWEVER, MOSTLY CLOUDY SKYCOVER
AND THE RAINY CONDITIONS SO FAR TODAY HAS LIMITED OUR HEATING AND
DESTABILIZATION, SO CONFIDENCE IN ANY THUNDERSTORMS FOR THE REST OF
TODAY REMAINS LOW. TEMPS HAVE BEEN LIMITED TO THE LOW 70S FOR A
LARGE PORTION OF THE AREA, THOUGH SOUTH-CENTRAL KY HAS SLIGHTLY
BETTER HEATING WITH UPPER 70S SO FAR. REGARDLESS, FORECAST TEMPS
HAVE BEEN KNOCKED DOWN A FEW DEGREES FOR THE REST OF TODAY TO MATCH
UP WITH THE CURRENT OBS. A FEW ISOLATED SHOWERS OR A STORM REMAIN
POSSIBLE OVERNIGHT AS WELL, BUT CERTAINLY NOT A WASHOUT BY ANY
MEANS. THERE WILL BE LINGERING LOWER LEVEL MOISTURE, RESULTING IN A
DECENT SIGNAL FOR LOW STRATUS AND PATCHY DENSE FOG ACROSS THE AREA
FOR THE EARLY MORNING HOURS.
HEAT AND HUMIDITY INCREASE TOMORROW AS THE UPPER RIDGE CONTINUES TO
BUILD ACROSS THE WESTERN US. DRY WEATHER IS EXPECTED TOMORROW AS WE
LACK A TRIGGER, WITH HIGHS CLIMBING INTO THE UPPER 80S AND LOWER
90S. DEWPOINTS START CREEPING BACK INTO THE 70S, WHICH WILL YIELD
HEAT INDICES NEAR 100 TOMORROW AFTERNOON. BY SUNDAY NIGHT, THERE
COULD BE A CONVECTIVE CLUSTER THAT DEVELOPS OVER THE MIDWEST, THEN
DIVES SOUTHEAST DUE TO THE NW STEERING FLOW AND COULD IMPACT OUR
AREA SUNDAY NIGHT OR EARLY MONDAY MORNING. THE 18Z HRRR WEAKENS THIS
CLUSTER SUNDAY NIGHT AS LOW LEVEL STABILITY ELEVATES ANY OVERNIGHT
THUNDERSTORMS. HOWEVER, ADDITIONAL WAVES MAY BE POSSIBLE INTO
MONDAY.
LONG TERM /MONDAY THROUGH SATURDAY/
ISSUED AT 351 PM EDT SAT JUL 25 2026
===== MONDAY - TUESDAY ======
FORECAST UNCERTAINTY IS A CONCERN FOR THE FIRST HALF OF THE UPCOMING
WEEK DUE TO WEAK FORCING AND POTENTIAL MCS ACTIVITY, WHICH IS OFTEN
HANDLED POORLY BY DETERMINISTIC GUIDANCE. ADDITIONALLY, THE
TEMPERATURE FORECAST FOR THE TIME FRAME COULD BE DERAILED IF WE DO
SEE THUNDERSTORM ACTIVITY, SO THERE ARE MULTIPLE CONDITIONAL
FORECAST PARAMETERS AT PLAY FOR THE BEGINNING OF THE LONG TERM
PERIOD.
STRONG UPPER RIDGING WILL CONTINUE TO HAVE A TIGHT HOLD OVER THE
WESTERN US, WITH DOWNSTREAM TROUGHING ACROSS THE EASTERN US, WHICH
PLACES THE OHIO VALLEY IN DEEP NW FLOW ALOFT. A MORE AMPLIFIED
SHORTWAVE LOOKS TO PIVOT THROUGH THE NW FLOW MONDAY AND TUESDAY,
WHICH WILL LIKELY TRIGGER SOME THUNDERSTORM DEVELOPMENT ACROSS THE
GREAT LAKES AND UPPER MIDWEST REGION. HOWEVER, DUE TO THE
ORIENTATION OF THE STEERING FLOW ALOFT, WILL EXPECT ANY THUNDERSTORM
COMPLEXES THAT DEVELOP WILL TAKE A SOUTHEAST DIVE INTO THE LOWER
OHIO VALLEY. THERE REMAINS CONSIDERABLE UNCERTAINTY REGARDING IF THE
FORECAST AREAS WOULD EVEN BE IMPACTED BY THESE PASSING COMPLEXES,
BUT SPC DOES INCLUDE A MARGINAL AND SLIGHT RISK FOR MONDAY ACROSS
MAJORITY OF THE AREA. BOTH THE GFS AND ECMWF INDICATE A SECOND MCS
CLUSTER MOVING IN FROM THE NORTH LATE MONDAY MORNING, WHICH WOULD
ULTIMATELY ARRIVE BEFORE THE PEAK OF DAYTIME HEATING AND GREATEST
DESTABILIZATION. IF THAT WOULD HAPPEN TO PLAY OUT, IT WOULD MOST
LIKELY DERAIL THE TEMPERATURE FORECAST FOR MONDAY AFTERNOON, WHICH
CURRENTLY HAS HIGHS IN THE MID 90S AND HEAT INDICES OVER 100F. IF
THAT MCS DOES NOT OCCUR IN OUR AREA, THEN THERE IS HIGH CONFIDENCE
THAT A HEAT ADVISORY WOULD BE NEEDED AS WE SHOULD SEE HEAT INDICES
REACH THE 103-110F RANGE.
MAJORITY OF THE THUNDERSTORM ACTIVITY IS EXPECTED REMAIN TO OUR
NORTH THROUGH THIS TIME FRAME DUE TO THE MEAN 700-300MB FLOW, THOUGH
OUR NORTH AND NORTHEAST SECTIONS OF THE FORECAST AREA WILL BE THE
MOST SUSCEPTIBLE TO BEING CLIPPED BY PASSING COMPLEXES. AS MENTIONED
IN THE PREVIOUS DISCUSSION, WE TYPICALLY STILL LIKE WHERE SPC DREW
THE OUTLOOK FOR MONDAY, BUT CONTINUE TO ADVERTISE THIS BEING A
CONDITIONAL THREAT.
IF WE END UP STAYING MOSTLY DRY FOR MONDAY AND TUESDAY, FORECAST
TEMPS COULD BE IN THE MID 90S AGAIN FOR TUESDAY, AND POSSIBLY
ANOTHER DAY OF HEAT ADVISORY APPARENT TEMPS. THIS IS ALSO
CONDITIONAL ON HOW THE THUNDERSTORM CHANCES PLAY OUT.
===== LATE NEXT WEEK =====
AN UPPER SHORTWAVE LOOKS TO DEEPEN INTO A LOW OVER THE NORTHEAST FOR
WEDNESDAY AND INTO LATE NEXT WEEK, WHICH WILL LIKELY LEAD TO PULLING
ANY SUBSTANTIAL MOISTURE OFF TO THE EAST AND LEAVING US DRY FOR
WEDNESDAY AND THURSDAY. TEMPS ALSO MAY DECREASE SLIGHTLY BACK INTO
THE 80S FOR THIS TIME. THERE ARE SIGNS THAT THE UPPER RIDGE MAY
FINALLY BEGIN TO WEAKEN BY LATE NEXT WEEK, THOUGH WE REMAIN IN
GENERAL NW FLOW ALOFT ALL OF NEXT WEEK.
AVIATION /00Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 804 PM EDT SAT JUL 25 2026
ON AND OFF DRIZZLE SHOWERS WILL PASS OVER THE TERMINALS THIS
EVENING, DIMINISHING EARLY SUNDAY MORNING. FOG AND LOW STRATUS,
HOWEVER, WILL LINGER A BIT LONGER, WITH VISIBILITIES GRADUALLY
IMPROVING AFTER SUNRISE AND MVFR CEILINGS POTENTIALLY (50% CHANCE)
PERSISTING UNTIL 16Z/MIDDAY. WINDS WILL BE LIGHT AND VARIABLE
OVERNIGHT, BECOMING PREDOMINANTLY WESTERLY BY SUNDAY AFTERNOON.
LMK WATCHES/WARNINGS/ADVISORIES
KY...NONE.
IN...NONE.
UPDATE...
SHORT TERM...CJP
LONG TERM...CJP
AVIATION...JRB
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