LMK issues Area Forecast Discussion (AFD) at Sep 21, 1:48 PM EDT ...Updated Aviation Discussion...841
FXUS63 KLMK 211748
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
148 PM EDT Mon Sep 21 2026
...Updated Aviation Discussion...
.KEY MESSAGES...
* Scattered thunderstorms (30-50% coverage) are forecast southeast
of the Western Kentucky and Bluegrass Parkways this evening. There
is a level 1 of 5 (Marginal) risk for severe weather, with locally
damaging winds the primary hazard.
* Unseasonably hot weather will continue over southern Kentucky
today with heat indices in the mid to upper 90s.
* Milder weather will gradually overspread the area this week, with
highs likely (70-80% chance) in the 70s north of an Owensboro to
Berea line tomorrow, and area-wide Wednesday through Saturday.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 133 AM EDT Mon Sep 21 2026
*** MILDER NORTH, STILL HOT WITH STORM CHANCES SOUTH TODAY ***
At 130am Monday morning, a quasistationary front, recognizable via a
wind shift, was draped across roughly the Ohio River. Two
perturbations along this front - one near the OH/WV border and
another near the St. Louis Metro - have triggered scattered,
sporadically severe, storms. The latter of these two storm complexes
may threaten our area with convection after around 4am, and given
the 25-35 kt deep layer shear coupled with 500-1000 J/kg MLCAPE
forecast by the RAP there remains a nonzero risk for marginally
severe wind despite a modest nocturnal inversion (25-50 J/kg MLCIN).
CAMs suggest the greatest chances (30-40%) will be over southern
Indiana, on the cool side of the front.
The front is forecast to sink slowly southward today, roughly
bisecting the state from southwest-northeast by mid-afternoon. In
its wake, northern portions of the area will be cloudy and have
milder temperatures with highs in the low-mid 80s; meanwhile,
conditions will stay unseasonably warm and humid south of the
boundary where, despite poor mid level lapse rates around 6-6.5C/km
(HREF mean), MLCAPE will climb to 1500-2500 J/kg. It'll take most of
the day for surface heating to erode the cap, but scattered storms
should fire in the warm sector by late afternoon or early evening,
perhaps peaking in coverage right around sunset. HREF neighborhood
probabilities for > 40 dBZ reflectivities (a proxy for moderate-
heavy showers and thunderstorms) peak in the 30-50% range along and
southeast of the Western Kentucky and Bluegrass Parkways during the
6-10pm timeframe. Given the aforementioned instability and modest
shear (25-35 kt in the 0-6km layer), a few updrafts may become
sufficiently organized to produce severe weather, with localized wet
downburst-induced damaging winds the primary hazard given the high
PWAT environment and steep low level lapse rates.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 133 AM EDT Mon Sep 21 2026
*** MILDER WEATHER ARRIVES TUESDAY INTO WEDNESDAY ***
Global model guidance suggests our resident boundary will stall over
the Lake Cumberland area tomorrow, perhaps allowing a rogue shower
or two to graze our easternmost CWA. Elsewhere, conditions will
likely (90% chance) remain dry, while northerly flow advects a
cooler and less humid airmass into the region. Forecast highs range
from the mid 70s over southern Indiana to the low-mid 80s across
southern Kentucky. As the cold core of the upper level low swings
overhead on Wednesday to bring weak synoptic-scale lift, we may wind
up with a few diurnally-driven showers. In addition, Bufkit time-
heights from the NAM depict a nearly saturated PBL and reduced
visibilities, with a plan view also showing spotty QPF and 0% prob
ice present both Tuesday and Wednesday nights - suggesting we could
see some patchy drizzle, or at least a stratus deck.
Once this pesky low meanders off to the east on Thursday and ridging
over the central US expands into our neck of the woods, we should
see sunshine return, though the continued cool northerly flow will
likely (60-80% chance) maintain highs in the 70s and overnight lows
in the 50s - near normal for late September. Global models and their
respective ensembles remain somewhat split on whether the cut off
low over the Mid-atlantic/Northeast expands back into our area or we
remain under the influence of the aforementioned ridge by the second
half of the weekend, but the latter solution seems to be most
popular at this time, as the NBM brings a 40-60% chance that high
temperatures return to the 80s by Sunday and 70-90% chance by Monday.
&&
.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 148 PM EDT Mon Sep 21 2026
A cool frontal boundary is sinking southward across the area, and
could still be the catalyst for some isolated to widely scattered
thunderstorm development across the BWG/RGA TAF sites late afternoon
into the evening. LEX could also be impacted by a storm, but most of
the activity should be south of that terminal. Outside of that,
conditions are VFR currently however, do expect lowering ceilings
into the low MVFR and/or IFR range (especially LEX/RGA) later
tonight into Tuesday morning. Will also see a notable uptick in
surface winds later this evening as the main frontal boundary gets a
push southward. Perhaps even a few N-S gusts up around 20 mph.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...JRB
LONG TERM...JRB
AVIATION...BJS
Source:
LMK issues Area Forecast Discussion (AFD) at Sep 21, 1:48 PM EDT ...Updated Aviation Discussion...---------------
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