Forecast discussion (LMK)
000
FXUS63 KLMK 142322
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
722 PM EDT Mon Sep 14 2026
...Updated Aviation Discussion...
.KEY MESSAGES...
* An extended period of unseasonably hot and mostly dry weather is
expected over the next 3-5 days. Take necessary heat precautions,
including limiting time outdoors and remaining hydrated.
* Low (10-30%) rain chances return late in the week into the
weekend, with a significant cooldown unlikely through Sunday.
&&
.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 342 PM EDT Mon Sep 14 2026
This afternoon, 1026 mb sfc high pressure over southern Ontario is
beginning to pull away from the Midwest and Ohio Valley as upper
level ridging begins to amplify over the south central and southeast
US. Low-level northeast flow has advected cooler and drier air
across most of the area, though a notable N-S temperature/dewpoint
gradient exists between the Ohio Valley and the TN Valley. For the
rest of this afternoon into tonight, comfortable temperatures and
mostly clear skies will continue, with light winds veering from the
east to the southeast by Tuesday morning. Good radiational cooling
conditions overnight should allow temperatures to fall into the mid-
to-upper 50s across the KY Bluegrass, with stronger warm advection
west of US 127 keeping temperatures milder in the low-to-mid 60s.
Amplification of the upper ridge tonight into tomorrow will support
a significant warm-up for the day on Tuesday as the low-level flow
veers from southeasterly to southwesterly. 1000-850 mb thicknesses
will support high temperatures in the low-to-mid 90s, with the area
of higher humidity also advecting back into the area. While heat
index values should range from 95-105 across the area tomorrow,
given that this is the start of an extended period of unusually hot
weather for mid-September, folks should take appropriate precautions
including remaining hydrated and limiting time outdoors.
A trough ejecting across the upper Midwest and into Canada tomorrow
will bring a sfc cold front into the mid-Mississippi Valley by
tomorrow evening. Ahead of this front, a plume of low-level theta-E
advection will surge from the lower Miss. Valley up into IL/central
IN, with our area on the southeastern edge of this higher moisture
surge. While the best moisture and instability should remain to the
northwest of the area, this forcing could be sufficient for the
development of a stray shower or two west of I-65 and across
southern IN. Poor mid-level lapse rates and broad subsidence should
limit convective potential, so not expecting any thunderstorms
tomorrow afternoon or evening.
Tuesday night into Wednesday morning, the sfc front north of the
region will begin to stall as it encounters an increasingly
unfavorable upper flow pattern. Convection along the front across
central IL/IN will try to regenerate farther to the south along
outflow, with some hi-res progs showing showers and possibly a storm
reaching our southern IN counties early Wednesday morning. While
confidence is low given convection diving headlong into a
strengthening upper ridge, have added a slight chance (20%) PoP to
the forecast north of the OH River Wednesday morning. Temperatures
should be much milder, with lows remaining in the low-to-mid 70s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 342 PM EDT Mon Sep 14 2026
On Wednesday, upper level ridging over the southeast US is expected
to intensify, with ensemble mean 500 mb height progs showing values
around 600 dm over the TN Valley Wednesday afternoon. The subsidence
associated with the growing heat dome should cause the sfc cold
front to the north of the Ohio Valley to dissipate and lift back to
the north, suppressing precipitation chances and reinforcing the
unseasonably hot conditions. There is high confidence in unusually
hot temperatures continuing into Thursday, as ECMWF Extreme Forecast
Index values for high temperatures exceed 0.95, with a Shift of
Tails around 1. Highs are expected to range from 93-97 across the
area Wednesday and Thursday, with peak afternoon heat indices in the
upper 90s and low 100s. Limited nighttime relief will exacerbate the
effects of this late season heat surge, with lows only expected in
the low-to-mid 70s through the week. As confidence in sustained hot
temperatures continues later into the week, the heat advisory may
need to be extended in time.
As we head into Friday and the weekend, the upper height anomalies
over the southeast US will gradually break down from a combination
of shortwave troughs riding across the northern US and a tropical
wave slowly moving across the Gulf. However, recent runs of model
guidance have trended toward persistence of the -PNA pattern with
split flow across the western CONUS, which will limit the ability
for troughing to dig across the eastern US. While the breakdown of
the ridge should allow for a low (10-30%) chance of afternoon
showers and storms to return, a substantial cooldown appears less
likely through the weekend. With that being said, there is a notable
uptick in spread in high temperatures over the weekend, possibly due
to increased potential for clouds and precipitation to limit
warming. A drier solution over the weekend would support continued
highs in the mid-90s, potentially extending this heat wave.
&&
.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 722 PM EDT Mon Sep 14 2026
VFR conditions will prevail through the TAF period. Light winds
tonight will shift from the E to the SSW by midday Tuesday,
increasing to around 7-10 kt during the afternoon hours. A light mid-
level cu field is also expected to develop Tuesday afternoon,
clearing out by the end of the TAF period.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory from noon EDT /11 AM CDT/ Tuesday to 8 PM EDT /7
PM CDT/ Wednesday for KYZ023>034-038-045-046-053-054-
061>065-070>077