NWS Forecast Discussion - Louisville, KY

700
FXUS63 KLMK 060122
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
922 PM EDT Sat Jul 5 2025

.KEY MESSAGES...

* Continued hot and mostly dry into Sunday, with isolated to
  scattered storms possible in the afternoon and evening, mainly
  in southern Indiana.

* Humidity and rain chances increasing in earnest Monday through
  most of the upcoming work week.

&&

.UPDATE...
Issued at 922 PM EDT Sat Jul 5 2025

Isolated showers and storms continue at this hour along and west of
the I-65 corridor. While convection likely has or is gradually
becoming elevated above a nocturnal inversion, there is still some
instability aloft thanks to steep lapse rates above the near-sfc
stable layer. As a result, think that isolated showers and storms
could continue for into the early overnight hours, especially where
outflow/cold pools from existing convection can lift parcels above
the stable boundary layer. For most, dry conditions and mostly clear
skies will continue tonight. Where dewpoints remained in the upper
60s and low-to-mid 70s this afternoon, patchy fog may try to develop
before dawn Sunday morning. Additionally, places which saw rain this
afternoon would also have an increased chance for patchy fog.

The main change to the previous forecast was prolonging shower/storm
slight chance PoPs this evening, as well as adding patchy fog
mention Sunday morning. Lows tonight should generally fall into the
upper 60s and lower 70s, with mid-70s likely in the urban heat
centers.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 301 PM EDT Sat Jul 5 2025

Upper ridge axis draped across the Ohio Valley will start to
get pinched in between a shortwave trof moving into the Great Lakes
and Tropical Storm Chantal making landfall in the Carolinas. As the
sfc high continues to pull off to the east, thicknesses will remain
the same even as heights aloft fall slightly, so temps will be very
close to persistence, perhaps a degree warmer at night and a degree
cooler by day. Slight increase in humidity will push heat index
values up just a bit but still not enough to approach advisory
levels. The experimental HeatRisk tool suggests a Moderate risk of
heat-related impacts, especially for heat sensitive groups without
adequate cooling/hydration.

A select few will get at least temporary relief from the heat as
isolated to scattered storms will pop in the afternoon. The best
chances for a pop-up storm will be in southern Indiana, but can`t
rule out convection in central Kentucky west of I-65. Most locations
will still remain dry. Shear is too weak for organized storms.
However, any storms that do develop in this tropical air mass will
be capable of producing locally gusty winds as updrafts collapse,
along with briefly torrential rainfall.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 301 PM EDT Sat Jul 5 2025

Typical midsummer weather for most of the upcoming week as a weak
cold front drops into Indiana, only to get hung up and linger nearby
for several days. Modest height falls aloft will allow the band of
stronger westerlies to settle closer to us, allowing multiple
opportunities for showers and storms as these disturbances aloft
interact with the quasi-stationary front. Too difficult to time
these impulses, but in this air mass convection is a good enough bet
that we will carry high-end scattered POPs, keying on the afternoons
as the most likely opportunity for storms.

Given the moist air mass, temps will be slightly above normal by day
and solidly above climo at night. While precip chances will be in
the forecast for multiple days at a time, none of the days actually
looks like a washout, but any location could pick up a shower or
storm on any day. Shear is too weak to support any organized SVR
threat but pulse storm hazards are in play, including localized
gusty winds and briefly torrential rainfall.

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 717 PM EDT Sat Jul 5 2025

Diurnal cu field across the region and isolated SHRA/TSRA southwest
of BWG should dissipate by 06/03Z, with VFR conditions expected
through the evening hours. Crossover temperatures would suggest BWG
and HNB as the most likely locations for fog development Sunday
morning, with RGA looking less likely given dewpoints falling into
the low 60s this afternoon. Would expect 06/07-12Z to be the main
window for any mist/fog development, with TEMPO MVFR/IFR
visibilities possible in any areas of fog. After sunrise Sunday, VFR
conditions are expected at all sites through the end of the forecast
period, with SW winds expected to pick up to around 6-12 kt Sunday
afternoon. Isolated TSRA may approach HNB toward the end of the
forecast period, though forecast confidence is low.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

UPDATE...CSG
SHORT TERM...RAS
LONG TERM...RAS
AVIATION...CSG

NWS LMK Office Area Forecast Discussion