LMK issues Area Forecast Discussion (AFD) at Jul 20, 2:55 PM EDT129
FXUS63 KLMK 201855
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
255 PM EDT Sun Jul 20 2025
.KEY MESSAGES...
* Waves of showers and thunderstorms will continue this afternoon
through Monday. Gusty winds, torrential rainfall, and lightning
are expected with storms. A Slight Risk (level 2/5) for severe
weather remains in effect for the damaging wind potential today.
* Swaths of heavy rainfall amounts are expected over the next few
days, which may lead to flash flooding. A Flood Watch remains in
effect through Monday.
* Outside of showers and storms, temperatures are in the upper 80s
to low 90s this afternoon, with heat index values peaking in the
low to mid 100s.
* Hot and very humid mid to late next week, with prolonged
significant impacts from excessive heat possible.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 255 PM EDT Sun Jul 20 2025
A MCV is spinning east across northern Indiana this afternoon, with
an effective boundary modulated by convective outflow pushing south
through central Indiana and SW Ohio. Deep convection has now pushed
southeast into SW Ohio ahead of the MCV and mid-level speed max. We
are now starting to see some congested cumulus back to the SW along
the outflow boundary, which will continue to sink into southern
Indiana this afternoon.
To the south of the approaching outflow boundary, strong
destabilization has taken place today in southern Indiana and
central Kentucky (MLCAPE exceeding 2000-2500 J/kg). The effective
boundary will continue to sink south into southern IN and northern
KY into the evening hours. Enhanced low-level convergence will allow
for new convective development across southern IN, SW OH, and
northern KY. This activity will propagate ESE along the instability
gradient. Thus, scattered storms are most likely in the northeastern
CWA through this evening, most notably southern IN into the KY
Bluegrass.
This effective boundary/axis of convection this evening will be
positioned along the southern edge of the stronger mid-level flow
aloft associated with the MCV. Effective deep shear increases to 30-
35 kts, which may allow for more organized clusters and line
segments through the evening hours. This could locally enhance the
isolated damaging wind threat in any convective clusters.
The primary hazards will still be excessive rainfall and flooding.
Deep atmospheric moisture remains in place, and PW values will again
surge to 2+ inches this evening and overnight. The modified sfc
boundary will sink into the Ohio Valley tonight into Monday.
Mid/upper level flow will gradually veer more northwesterly with
time. At least one or two upstream convective complexes appear
likely to dive southeast along the boundary, especially through
portions of southern IN and north-central KY, overnight into early
Monday. The potential for training convection along the NW to SE
oriented boundary may result in localized swaths of excessive
rainfall - perhaps 2-4 inches, with locally higher amounts. The
flash flooding could be significant or life threatening in isolated
areas. The current Flood Watch looks well placed for the greatest
risk area, so no headline changes are planned at this time.
Otherwise, while thunderstorm chances begin to increase this
afternoon across northern portions of the forecast area, much of
central KY will continue to see sweltering conditions this afternoon
with heat indices exceeding 100. The Heat Index may touch 105+ at
times, especially in the Heat Advisory area - so will let that
headline ride through the evening. Temperatures will drop back into
the low to mid 70s early Monday morning.
Beyond Monday morning, thunderstorm chances will depend on how
activity evolves overnight into early morning. There is a signal
that we may see scattered storms concentrate a little further south
across central and southern KY Monday afternoon and evening. This
would make sense as that effective boundary continues to sink
further south, allowing additional southward propagation as diurnal
heating/destabilization takes place.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 255 PM EDT Sun Jul 20 2025
Monday Night through Tuesday Night...
Scattered storms should diminish/shift southwest of the area
relatively quickly Monday night. Mid and upper level ridging
continues to build northeast over the Plains, Midwest, and Lower
Ohio Valley.
By Tuesday, the upper ridge to our southwest continues to build
northward. As it does so, sfc high pressure will sink into southern
Ontario and upstate NY. This should cause the sfc front over the
area to weaken and shift farther SW. At the same time, drier mid-
level air is expected to work in from the NE, reducing PWAT values,
although near-sfc moisture will still be high. This is expected to
lead to somewhat less coverage of showers and storms on Tuesday,
though isolated to widely scattered storms are still possible. High
temperatures are expected to reach the upper 80s and lower 90s, with
the core of the hottest temperatures still SW of the area.
Wednesday through Saturday Night...
Temperatures will increase Tuesday into Wednesday as the upper ridge
builds across the Ohio and Tennessee valleys. For Wednesday through
Friday, there is fairly high confidence that the ridge will remain
in place, with no significant changes to the synoptic pattern.
Current elevated soil moisture values should keep temperatures from
getting too high; however, low-to-mid 90s looks like a pretty good
bet during this period. With dewpoints remaining in the 70s, this
should get afternoon heat indices up between 100-110. At the same
time, there won't be much relief at night, with temperatures only
falling into the 70s. Although details will still be worked out over
coming days, impactful excessive heat looks likely for Wednesday
through at least Friday.
For Wednesday and Thursday, shower and storm coverage should be
greatly suppressed with broad subsidence in the vicinity of the
upper ridge. However, ample low-level moisture may lead to one or
two garden-variety showers/storms in the afternoon and evening.
By the end of the week and the first part of next weekend, there is
some model divergence on how much the upper ridge begins to break
down. The GFS remains fairly quick to break down the ridge and bring
back the idea of at least scattered diurnal convection by Friday.
Look for hot and humid conditions, with the potential for scattered
afternoon and evening storms Friday and Saturday.
&&
.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 147 PM EDT Sun Jul 20 2025
Convection is pushing into SW Ohio this afternoon ahead of a
convectively induced wave of low pressure. Trailing stratiform
showers extend back to the west across central and northern IN along
a frontal boundary. Only isolated SHRA are noted across portions of
eastern KY at this time.
The last of the MVFR stratus is becoming SCT and lifting toward the
VFR threshold at LEX and RGA. Hot and humid conditions to the south
of the effective boundary in central IN will help lead to additional
TSRA development across southern IN, southern OH, and eventually
northern KY from mid-afternoon through the evening hours. TSRA
impacts will be possible mainly at SDF and LEX after 21-22Z. An
additional wave of SHRA/TSRA will be possible across southern IN and
central KY overnight into early Monday. Torrential rainfall, gusty
winds, and frequent lightning will be possible with any TSRA
activity.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
KYZ023>030-038-045-046-053-054-061>065-070>076.
Flood Watch through Monday evening for KYZ025-029>043-045>049-
054>057-066-067.
IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
INZ076>078-083-084-089>092.
Flood Watch through Monday evening for INZ076>079-083-084-
089>092.
&&
$$
SHORT TERM...EBW
LONG TERM...EBW/CSG
AVIATION...EBW
Source:
LMK issues Area Forecast Discussion (AFD) at Jul 20, 2:55 PM EDT---------------
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