LMK issues Area Forecast Discussion (AFD) at Aug 19, 1:53 PM EDT ...Updated Aviation Discussion...598
FXUS63 KLMK 191753
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
153 PM EDT Tue Aug 19 2025
...Updated Aviation Discussion...
.KEY MESSAGES...
* Peak Heat index values around 105 are likely, mainly along and
west of I-65 today. Heat Advisory in effect for those areas.
* Scattered thunderstorms are expected for some later this evening
into the overnight. The strongest storms could produce locally
gusty winds and heavy rainfall.
* Drier and temperatures closer to normal for mid to late week.
* Below normal temperatures expected for the second half of the
weekend into next week.
&&
.UPDATE...
Issued at 1149 AM EDT Tue Aug 19 2025
No significant forecast changes at this time. Skies remain largely
clear/sunny, with just a few clouds in southern Indiana. Earlier
this morning, a weak outflow boundary was able to push south into
southern Indiana. However, this boundary continues to wash out and
any convergence along it is weak at best.
Temperatures continue to warm into the mid 80s to near 90, with heat
indices now approaching 100 in the western forecast area. The Heat
Advisory looks good, and no changes are planned to the headline.
We could see some isolated convective development this afternoon,
perhaps along the weak outflow boundary. However, more favorable low-
level moisture convergence is currently noted from south-central IL
extending northeast into western and central IN ahead of the cold
front. Satellite imagery shows healthier cu development in that
area. This should bring us our best shower and thunderstorm chances
this evening as scattered convection develops across central IN
before dropping south into southern IN and central KY.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 312 AM EDT Tue Aug 19 2025
Things are quiet this morning under clear skies and mild
temperatures in the 70s for most. It should remain that way for the
morning hours before heat and humidity take center stage for the
afternoon, and then showers and storms for the evening into the
overnight.
Currently, a complex of showers and storms is ongoing across north
central IL into northern IN ahead of a cold front trailing from a
weak surface low. This convection should decay through the early
morning hours, but may send some convective outflow down closer to
our northern CWA border around or just after daybreak. Hi-res models
continue to suggest we stay dry through the morning, but can't
completely rule out a stray shower or storm. The more likely
scenario is that we stay mostly sunny with temperatures quickly
warming into the low and mid 90s. This, combined with dew points
pooling into the low and mid 70s ahead of the approaching cold front
should yield another day of hot and humid conditions, especially
along and west of I-65. Other than a low chance that early
convection plays spoiler, don't see a whole lot of limiting factors
to us getting hot during the afternoon, even with a few-sct
afternoon cu field likely to develop. Even with NBM 25th percentile
dew points (pretty good mixing this afternoon) still getting max
heat index values around 105 for several hours I-65 west. Decided to
go with a Heat Advisory for those areas to cover that, and it
matches pretty will with PAH/OHX headlines as well. Farther north,
there is too much uncertainty with convection.
The other concern will be for evening convection, possibly into the
overnight as a cold front sinks into our area. Ahead of this front,
it appears we get moderate to strongly unstable with 2000-3000 J/KG
of ML CAPE pooling ahead of the front across southern Indiana and
north central KY. Surface convergence ahead of the front should be
enough of a trigger in the unstable airmass. No real deep layer
shear to work with so storms will be pulse in nature, however
soundings suggest the atmospheric profile will support isolated
microburst potential (especially with deeper mixing) given steep low
level lapse rates and favorable DCAPE values. SPC Marginal Risk for
damaging wind looks good. The final question is just how long into
the late evening/overnight storms last, and whether we get any
repeated training with slow movement and "chain reaction" type storm
evolution to create a localized heavy rain threat. Something to
watch.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 312 AM EDT Tue Aug 19 2025
Wednesday - Wednesday Night...
Cold front is expected to be across our southern CWA, or already
south of the area by Wednesday morning. Will likely keep some low
chance pops down in that area for Wed, but overall should be a
drying trend from north to south by this time, along with some
slight temperature/humidity relief. Still looking for highs near
normal this day with max values in the upper 80s (north) to the low
90s (south). Wednesday night lows will be similar to the previous
night with most lows around or on either side of 70.
Thursday - Friday Night...
The late week time frame looks to be mostly dry with with
temperatures near normal for this time of year. Highs should mostly
be in the upper 80s to around 90, with lows mostly in the upper 60s
to around 70. Will hold onto a few isolated shower/storm chances
down across southern KY where a bit of a weakness in the upper ridge
will be noted. Slow moving showers or a few efficient thunderstorms
could put down briefly heavy rainfall each afternoon/evening, mainly
south of the Parkways.
Saturday - Monday...
Eastern CONUS troughing will steadily take hold of our area through
the weekend. As this occurs, we'll see a reinforcing cold front drag
through our area Sunday morning. Looks like a notable airmass change
behind this front as Sunday highs should be a touch below normal in
the low to mid 80s. Then, Sunday night lows dip into the upper 50s
and low 60s. Monday highs only top out in the low 80s for most.
Expect to be mostly dry through this stretch as even the cold
frontal passage looks to be mostly moisture starved. Perhaps a few
showers will be possible. Will also have to continue carrying some
slight chances across our SE CWA on Saturday to account for that
weakness in the upper ridge before the trough and cold front arrive.
&&
.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 152 PM EDT Tue Aug 19 2025
VFR conditions continue through the afternoon, along with light
winds generally out of the WSW. FEW-SCT cumulus will continue to
develop early this afternoon at 5-7 kft. Isolated convection has
already developed near IND along a cold front, but further south our
best TSRA chances will be between 21-06Z this evening. Scattered
TSRA appear likely to develop along the front in central IN and sink
south to the Ohio River this evening. Timing at BWG/LEX/RGA will be
relatively later for any TSRA than HNB/SDF. Some terminals may get
gapped due to SCT coverage, so TSRA impacts are not a certainty.
Winds will continue to veer NW and then N tonight into early
Wednesday as the front pushes south through the region. A brief
period of MVFR stratus looks likely Wednesday morning, mainly after
11-12Z at SDF and LEX. Confidence is a bit lower on how far south
and west the MVFR clouds make it, but brief MVFR also possible at
HNB and RGA.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
KYZ023>030-061-062-070>073.
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
INZ076>078-083-084-089>092.
&&
$$
UPDATE...EBW
SHORT TERM...BJS
LONG TERM...BJS
AVIATION...EBW
Source:
LMK issues Area Forecast Discussion (AFD) at Aug 19, 1:53 PM EDT ...Updated Aviation Discussion...---------------
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