724
FXUS63 KLMK 040727
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
327 AM EDT Fri Sep 4 2026

.KEY MESSAGES...

* Heat Advisory has been extended into Saturday.

* Friday afternoon temperatures in the mid to upper 90s with heat
  index values  over 100 and up to 107. Saturday will see daytime
  highs in the mid to lower 90s and heat index values near or
  slightly above 100 to around 106.

* Warm overnight temps in the mid to upper 70s will provide little
  relief during the nighttime hours. Practice heat safety by
  remaining hydrated and limit time outdoors if possible.

* A weak cold front will increase the chance of isolated to
  scattered showers and storms  late Friday into Saturday, ending
  our stretch of hot conditions across the region by the end of the
  weekend.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 327 AM EDT Fri Sep 4 2026

***HEAT CONTINUES - HEAT ADVISORY EXTENDED***

Heat Advisory continues through the end of the week and has been
extended into Saturday. The upper-level ridging responsible for our
ongoing heat wave will continue to keep things hot through today and
into the start of the weekend, even as it starts to weaken and
slowly shift westward. Confidence is high that afternoon
temperatures will once again be in the upper 90s today with another
shot of some locations seeing temperatures reach the 100 degree
mark. Dew points are currently in the low 70s and will be there as
we go into the start of the day, While some afternoon mixing is
likely, this will lower dew points just a couple of degrees (68-70)
but not enough to keep heat index values from getting back to around
102 to 107 later this afternoon.

Confidence has also increased that the ongoing heat will continue
into the start of the weekend. The weak sfc boundary that is
expected to bring to bring a brief period of relief from our on
going heat wave is currently stretched across the Great Lakes from
central WI across central MI, over Lake Erie into northwest PA and
into western NY. This boundary is currently stalled and forecast
guidance seems to be in general agreement that this boundary doesn`t
work into our area until late Saturday afternoon/evening. Giving the
hot air mass currently in place a little extra time to linger over
southern IN and central KY. That is why the decision was made to
extend the current Heat Advisory through the day on Saturday.

Confidence is generally high that most locations across the CWA will
see afternoon temperatures into the mid 90s for another consecutive
day to start the weekend with heat index values over 100-105. Most
notably for locations across southern KY and along and west of I-65.
Confidence is a little lower (near or slightly above 50%) as you
work further east and northeast towards Lexington and the Bluegrass.
The potential limiting factors for the heat here is the approaching
cold front from the northeast. Clouds from approaching convection
and the development of pre-frontal convection Saturday afternoon
would keep temperatures cooler than current guidance. It was the
professional opinion of this forecaster that given the uncertainty
of boundary arrival later Saturday as well as timing of prefrontal
convective activity, it would be a lot easier to scale back and
remove counties late Friday or early Saturday once we had higher
confidence than to expire it too early.

***STORM CHANCES AND SEVERE THREAT***

While the current thinking is today will be mostly dry, hi-res CAMS
continue to hint at isolated development later this afternoon,
similar to what we saw yesterday. While forecast soundings show
SBCAPE values between2000-2500 J/kg we continue to lack shear <
20kts as well as any strong forcing. After placing portions of our
northern CWA in a Marginal Risk for severe weather today, SPC in
their latest Day 1 outlook has removed most of our CWA from the
Marginal with exception of our furthest east counties. Given the
delay in frontal boundary arrival as well as the lack of forcing I
agree with this as the though the last 24 hours was the threat of
severe was very low.

In the SPC Day 2 convective outlook, they have put most of the CWA
in a Marginal Risk (Level 1 of 5) with our far eastern counties,
mainly those east of the I-75 corridor, in a Slight Risk (Level 2 of
5). As was mentioned in the previous discussion, while the boundary
does represent better forcing for convective development, wind shear
remains weak and limited. Main threat could be hail and gusty winds
given the steeper lapse rates.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 327 AM EDT Fri Sep 4 2026

Cold front will have departed south by Sunday morning allowing for
sfc high pressure to our northeast to build in over the region. This
will give us a needed respite from the high heat we saw over the
last week. This will cool temperatures into the upper 80s to near 90
with dew points in the low/mid 60s as the second half of the holiday
weekend looks to be dry. Overnight lows will also be cooler with
morning lows in the low/mid 60s by Monday morning.

This break from the heat is only brief as the upper ridge that
retreated over the weekend builds back over the Ohio Valley by the
middle of next week. While not as hot as the past week, highs will
return to the low/mid 90s Tuesday through Thursday as well as
increase moisture advection from the south. Could see heat index
values near 100 by Wednesday but not for a prolonged length of time.

The end of the forecast period on Thursday becomes more uncertain as
another pattern shift looks to take shape. Most deterministic and
ensemble guidance picks up on a robust upper level low moving from
central Canada towards the NE CONUS while a surface cold front
passes over the Ohio Valley. The uncertainty lies in the timing and
progression of these features, but it does appear that this could be
the next chance for more appreciable precipitation across the region.

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 110 AM EDT Fri Sep 4 2026

Ridging aloft and sfc high pressure continue to influence our
forecast through the 06z TAF forecast period. Overall we remain VFR
but here are the potential impacts during this forecast:

Through the rest of the overnight and morning we will remain quiet
with light winds and clear skies. Some patchy fog is possible in
spots but I think terminal sites remain unaffected.

As has been the trend the last couple of days, with the heat and
humidity we have the chance of isolated showers or storms with a
scattered Cu field in the afternoon. The chance of showers is under
20 percent so no mention of a Prob30 but it is possible an isolated
storm could hit a site tomorrow afternoon/evening but confidence is
generally low.

Mixing winds are again possible as we go late afternoon and evening
with some isolated gusts of 10-15kts.

Once the sun sets, skies clear and winds become light but a sfc cold
front to our northeast will start to track into the region late
tomorrow and Saturday. Think this is slow to arrive but as it gets
closer we could see more increased clouds and PoP chances late
Friday into Saturday.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for
     KYZ023>043-045>049-053>057-061>067-070>078-081-082.
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for
     INZ076>079-083-084-089>092.

&&

$$

SHORT TERM...BTN
LONG TERM...BTN
AVIATION...BTN