LMK issues Area Forecast Discussion (AFD) at Aug 31, 1:34 AM EDT ...Updated Aviation Discussion...038
FXUS63 KLMK 310534
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
134 AM EDT Mon Aug 31 2026
...Updated Aviation Discussion...
.KEY MESSAGES...
* Highs in the upper 80s and low 90s continue Monday with a stray
shower possible.
* Major Heat Risk is expected this week due to the multi-day
duration of hot temperatures with little overnight relief. Anyone
without effective cooling or adequate hydration will be
susceptible to heat illness.
* The upper level pattern may break down toward the end of the week
as the heat ridge moves west and back into the central Plains.
This may bring an increased risk of showers and storms for Friday
and through the weekend.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 312 PM EDT Sun Aug 30 2026
===== Today - Monday Night =====
Cumulus clouds will continue to build and stick around our area
through the rest of the afternoon with highs in the upper 80s and
low 90s. With sufficient mixing, dew points will drop and have done
so a little bit already at SDF where they sit in the mid 60s. Albeit
a small battle, this mixing with dry air above the boundary layer is
making highs feel a little more bearable. Despite some afternoon
isolated showers, everyone will remain dry and partly cloudy. Some
convective cloud debris from storms much further upstream will only
add a few cirrus clouds from time to time.
Winds will calm after sunset or be very light from the south
overnight. Lows should be just a couple degrees warmer than
yesterday's in the upper 60s to low 70s. Overnight cooling should be
aided by the slightly decreased dew points than what NBM had been
suggesting and with mostly clear skies.
Then by Monday morning, isolated valley fog may form but
probabilities remain low for this as well (<20%). The rest of the
day Monday is more of a rinse-and-repeat of today's weather. Cumulus
clouds resembling those in a popular animated movie about toys will
return. The ridge responsible for the increasing temperatures will
nudge a little further into KY, increasing temperatures by a couple
of degrees. Heat indices will climb into the upper 90s and maybe
isolated areas in the SW near Bowling Green of the low 100s. Not
anticipating any heat advisories Monday but this is a concern as the
high keeps building overhead this week. Probabilities of heat
indices exceeding 100 degrees are low Monday (10-30%) but will
increase gradually throughout the week. A stray shower may form but
we're otherwise dry with lows in the upper 60s and low 70s Monday
night.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 312 PM EDT Sun Aug 30 2026
Tuesday through Thursday Night...
The forecast thinking through this time frame is unchanged from 24
hours ago. Latest guidance continues to show a large 594 ridge
building across the Ohio Valley. This will result in mostly sunny
days and mostly clear nights with temperatures gradually increasing
through the period. We'll likely see a gradient of high
temperatures across the region with the hottest air being confined
to areas west of I-65 and slightly lower readings out in the
Bluegrass and I-75 corridors. Dewpoints are still expected to
remain in the 60s through the period. We'll likely see good
atmospheric mixing each day which will result in some dry air
mixdown in the afternoons. This will keep our heat indices each
afternoon in the upper 90s to the very low 100s east of I-65, with
mainly 100-103 in areas west of I-65. LREF heat index guidance
hasn't changed that much with the probability of exceeding 100F on
Tuesday at 20-30% west of I-65. By Wednesday, probabilities
increase to 40-60% west of I-65 and further increase to 50-70% by
Thursday. In the Bluegrass, the highest probs of 40-50% of exceeding
100F on the heat index would be on Thursday. Not much relief will be
found at night as overnight minimums will be in the low-mid 70s with
the dense urban corridors likely only cooling to around 80. With
the expected duration of heat over the coming week, Heat Advisories
will likely be issued for this time range in the next 24 hours or so.
Friday through Sunday...
Moving into the late week and into the weekend, the upper air
pattern will start to change slightly. A large upper trough/closed
low is forecast to plow into the Pacific northwest while the mid-
level ridge over the OV/SE US starts to flatten out and retrograde
slightly to the west. If this were to occur, our flow will become
northwesterly and we'll have to watch for perturbations riding
around the ridge which may bring MCSs back into the forecast. A
fair amount of spread remains in the long range ensembles here
indicating that not all the members are suggesting the ridge
retrograding. The OP Euro trends have been stronger with the ridge
retrograding and bringing some relief to the region. For now, 20-
30% POPs out in the Fri-Sun period look reasonable at this time. The
tropics will become more active in this time period and may end up
influencing the pattern than other synoptic scale features. As such,
the forecast confidence here is lower than average. For now, we'll
likely see low-mid 90s on Friday for highs, but things may cool back
into the upper 80s/lower 90s for Sat/Sun, especially if we get
convection back into the forecast.
&&
.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 131 AM EDT Mon Aug 31 2026
A weak upper level system passing across northern and central IN
could bring some high cloud over HNB to SDF in the pre-dawn hours
but we will remain VFR for the forecast period. As we continue to be
locked under a persistent pattern featuring strong ridging aloft we
will see nearly identical weather setups each day through the middle
of the week. It remains dry with winds generally out of the south to
southwest. As we heat up, air will mix and increase some of the
winds near the surface so occasionally we could see a few gusts
around SDF/LEX of 15-20 kts in the afternoon and the development of
scattered mid-level Cu in the afternoon before we return to mostly
clear skies and light winds overnight and remaining VFR.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...BKF
LONG TERM...MJ
AVIATION...BTN
Source:
LMK issues Area Forecast Discussion (AFD) at Aug 31, 1:34 AM EDT ...Updated Aviation Discussion...---------------
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