527
FXUS63 KLMK 201923
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
323 PM EDT Mon Jul 20 2026

.KEY MESSAGES...

* Severe thunderstorms are likely from midday Tuesday through
  Tuesday evening, with all severe hazards possible. Damaging
  straight-line winds are the main hazard, but a few tornadoes and
  large hail will possible. Localized heavy rainfall may lead to
  flash flooding, especially east of I-65.

* A Heat Advisory has been issued for portions of south central and
  west central KY, as well as southwest IN for heat indices of 100-
  110 Tuesday afternoon.

* Calm weather moves in with cooler than average highs for Wednesday
  through Friday this week.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 323 PM EDT Mon Jul 20 2026

This Afternoon and Tonight...

Across the region this afternoon, scattered clouds continue as the
stratus layer from this morning gradually mixes with drier air
aloft. It is quite humid throughout the low-levels of the
atmosphere, with sfc dewpoints generally in the mid-to-upper 70s
across the area. Temperatures have warmed into the mid 80s, with
heat index values generally in the mid-to-upper 90s at this hour.
There have been a few showers which have developed across southern
IN and north central KY over the past few hours, and a few pockets
of agitated cu may lead to additional isolated showers and possibly
a storm through early this evening. However, convective potential
will be limited today by weak forcing and warm mid-level
temperatures, with an upper-level ridge spreading from west to east
across the Ohio Valley. Temperatures should reach the upper 80s
to around 90 this afternoon before cooling this evening.

Tonight, an upper level shortwave is expected to swing around the
edge of the mean trough, descending from the Dakotas toward Lake
Erie by Tuesday morning. In association with this upper wave, a sfc
low and cold front are expected to drop into the upper Midwest
tonight, with pressure falling to the north of the Ohio Valley.
While showers and storms will be ongoing to the north of our area
tonight, the main impacts expected for central KY and southern IN
through mid-morning Tuesday should be increasing southerly winds and
increasing mid- and high clouds. There should be enough boundary
layer mixing overnight to limit fog development, especially as
clouds increase from the north.

Heat and Humidity Tuesday...

Ahead of the cold front and the storm potential tomorrow, one more
day of hot and humid conditions are expected. The main uncertainty
with the temperature forecast Tuesday will be with how quickly and
how far to the southwest the first rounds of convection make it. In
areas that remain storm-free, temperatures should warm into the
upper 80s and low 90s, with heat indices surging above 100 degrees.
In collaboration with offices to the south/west, a heat advisory was
issued along and west of a line from Jasper, IN down to Burkesville,
KY. Depending on how storm chances evolve in later guidance, this
area may need to be expanded to the east.

Severe Storms Likely Tuesday and Tuesday Evening...

Tomorrow morning, a couple clusters of strong to severe storms are
expected to approach the region from the northwest ahead of a cold
front. Across our area, temperatures rising into the 80s with
dewpoints in the upper 70s will support a highly unstable
environment, with around 3500-4500 J/kg MLCAPE expected by peak
heating Tuesday afternoon. Height falls with the descending upper
trough over the Great Lakes should support a belt of strong west-
northwest flow, especially by mid-Summer standards, with around 45-
50 kt expected by midday Tuesday. Model soundings show a decent
amount of shear in the lowest few km early Tuesday, with winds
gradually veering through the afternoon and evening as the sfc cold
front approaches from the north. Additionally, if any discrete cells
were able to develop, 0-1km SRH values exceeding 100 m2/s2 east of I-
65 would support an enhanced tornado potential, in line with the
higher SPC tornado probabilities.

All in all, tomorrow still looks like a straight-line wind dominated
severe risk. With model soundings showing limited capping in place,
expect that storms may become fairly widespread and evolve into one
or several bowing segments as deep-layer shear orients parallel to
the cold front. While somewhat meager low-level lapse rates and
ample boundary layer moisture will likely hamper the strength of any
cold pools which can develop, would still expect stronger cores to
produce instances of 60-70 mph winds. The tornado threat tomorrow
should be maximized where (if) any discrete cells can develop, as
well as along residual boundaries from antecedent waves of
convection. Not to be discounted is the severe hail risk, which like
the tornado potential, will exist primarily in any discrete cells or
convective clusters and should decrease if updrafts begin to
interfere as storms line out.

For the timing of the severe threat, there has been a shift with
upstream convection potentially making it into the northeastern CWA
as early as 9-10 AM EDT. From late morning through early evening
Tuesday, would expect several waves of storms to move from north-
northwest to south-southeast across the area, with storms expected
to push into southern KY by 5-8 PM EDT/4-7 PM CDT. Although faster
storm motions should limit residence time of any one round of
storms, torrential rainfall rates and the potential for multiple
waves of storms will support an increased threat for flash flooding.
Along and east of I-65, widespread swaths of 1-2" of rain are
likely, with isolated 3-5+" totals possible. If confidence increase
in the location of heavier rainfall swaths, a short-fused flash
flood watch may need to be issued subsequently. Storms should begin
to push entirely out of the area by late evening Tuesday, or between
9 PM-12 AM EDT/8-11 PM CDT. A few lingering showers and storms may
continue across southern KY into the early hours of Tuesday morning,
but the severe threat should diminish significantly by midnight
Wednesday.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 323 PM EDT Mon Jul 20 2026

Wednesday through Friday...

The current model consensus has the surface cold front pushing
through south central and southeastern KY during the morning hours
on Wednesday, which may leave just enough forcing and low-level
moisture in place for an isolated shower or two south of the WK/BG
Parkways. Otherwise, the mid-to-late week period is expected to
feature dry weather and pleasant temperatures across the Ohio Valley
and into the mid South. Upper-level troughing continuing to dig
across the eastern CONUS should help the sfc cold front push well to
the south of the area as 1020+ mb sfc high pressure settles into the
region from the north. The post-frontal air mass is expected to be
quite refreshing given the recent prevalence of muggy weather, with
ECMWF ensemble mean PW values falling below 1" (< 10th percentile of
climo) Wednesday night into Thursday. Temperatures are also expected
to be below normal Wednesday through Friday, with highs in the upper
70s and low-to-mid 80s with lows in the upper 50s and 60s.

Friday Night into the Weekend...

By the end of the week, the upper level pattern will become more
zonal, though broad NW flow should continue across the Ohio Valley.
A subtle upper shortwave is expected to eject across the northern US
Rockies and into the Plains Thursday night into Friday before
tracking toward our area Friday night. Ahead of this system, model
guidance shows modest moisture return primarily into southern KY,
with PW values creeping back above 1.50" later Friday into Saturday.
While confidence is still low this far out, this could bring a
return to isolated/scattered rain chances for the first part of the
weekend. Behind this system, the broad upper ridge/heat dome across
the western US is expected to nudge slightly to the east, with
temperatures expected to trend back toward normal Sunday into early
next week. Mostly dry conditions are expected late weekend as
seasonable moisture and weak forcing are favored at this time.

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 129 PM EDT Mon Jul 20 2026

Latest surface analysis reveals a warm front extending across
central Kentucky, while current satellite continues to show slowly
dissipating MVFR stratocumulus across much of the region. Expect any
MVFR CIGs to scatter out to VFR conditions quickly. Winds will
continue out of the SW today.

A cold front will push through the region Tuesday, bringing a couple
lines of showers and thunderstorms, some of which could be strong to
severe. Expect gusty SW winds and MVFR to IFR conditions in stronger
storms. Arrival times for storms appear to be around 21/16Z for SDF
and 21/17Z for LEX/RGA.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Air Quality Alert until midnight EDT tonight for KYZ029>031.
     Heat Advisory from 10 AM to 7 PM CDT Tuesday for KYZ023-024-
     026-027-061>063-070>076-081.
IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
     INZ076>079-083-084-089>092.
     Heat Advisory from 11 AM EDT /10 AM CDT/ to 8 PM EDT /7 PM
     CDT/ Tuesday for INZ083-089.

&&

$$

SHORT TERM...CSG
LONG TERM...CSG
AVIATION...CG