949
FXUS63 KLMK 182348
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
748 PM EDT Tue Aug 18 2026

...Updated Aviation Discussion...

.KEY MESSAGES...

* Shower and storm chances (40-60%) return Wednesday night into
  early Thursday. There is a low risk for both severe weather and
  localized flooding across areas west of I-65 in Kentucky.

* Slight (15-24%) shower and storm chances linger through Saturday
  across areas mainly east of the I-75 corridor, but most locations
  look to stay dry.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 314 PM EDT Tue Aug 18 2026

Early Tuesday afternoon, zonal flow aloft was in place across
central Kentucky and southern Indiana, while high pressure was
maintaining dry and mild conditions at the surface with temperatures
in the upper 70s to mid 80s at 3pm EDT. Meanwhile, satellite imagery
reveals increasing mid-high level clouds across the Midwest
associated with an approaching disturbance. Tonight, this first
shortwave will spark upstream convection which will reach our area
in a weakening state tomorrow morning, bringing little (if anything)
in the way of rain but numerous clouds which HREF suggests will
likely (50-70% chance) stick around through at least mid afternoon.
Shower and storm chances look to increase Wednesday night into
Thursday morning as a modest kt LLJ overspreads the area ahead of a
second shortwave trough, giving us 35-45 kt deep layer shear. The
arrival of this better shear during the overnight period when
instability (500-1000 J/kg MUCAPE, per HREF) is at its diurnal
minimum and a stable layer is present below 940mb should limit
severe potential, but marginally severe wind or hail cannot be ruled
out west of I-65 where instability is highest and 20km HREF
neighborhood probs are highest (10-30%) for updraft speeds > 20m/s.
SPC`s day 2 outlook features a level 1 of 5 (marginal) risk for
severe weather west of roughly I-65. Modest moisture transport via
the LLJ and PWATs around 1.7-2 inches (highest southwest) suggest
any showers and storms could be efficient rain producers, and NBM
probabilities for more than 2 inches of rainfall are generally 10-
25% across western portions of the area. However, many of the CAMs
have the main thunderstorm cluster diving southwest of our area
which could limit our supply of Gulf Moisture and mitigate the risk
of any localized hydrological issues. We can`t completely rule out
the prospect of flash flooding, but the risk appears low at this
point given the soils are drier across southwestern Kentucky which
has largely missed out on recent heavy rains.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 311 PM EDT Tue Aug 18 2026

Depending on when the front departs to the southeast, we`ll have to
keep an eye on the potential for redevelopment along it Thursday
afternoon when the National Blend of Models (NBM) gives a 20-35%
chance for more than 2000 J/kg SBCAPE across our far south. In fact,
some guidance suggests the front could lift back north and allow a
few showers and storms along/east of roughly I-75 Friday afternoon
and evening as well. However, for most of our area, we should have a
break Thursday into Friday, with the next system bringing a stronger
front and perhaps some shower and storm chances Saturday into Sunday.

Principle Components (PCs) for Empirical orthogonal functions (EOFs)
applied to the Low Resolution Ensemble Forecast (LREF) system`s
500mb heights suggest the primary source of model spread - and
hence, forecast uncertainty - over the weekend is in the depth of
troughing over the Great Lakes and Northeast. Deeper troughing,
supported by about 40% of LREF membership, suggests a stronger cold
front which would bring the area scattered showers and storms
followed by below normal temperatures; in addition, stronger
kinematics suggest our area could see at least a low (5+%) risk for
severe weather with any storms that develop. A weaker trough to our
east (the remaining 60% of LREF members favor this solution), by
contrast, would favor seasonably warm temperatures through the
weekend and low chances for precipitation. In either case, at least
a couple days of dry weather can be expected to close the weekend
and kick off next work week as northwest flow overspreads the local
area in the wake of that trough.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 747 PM EDT Tue Aug 18 2026

VFR conditions are expected throughout the TAF period. Gradually,
high to mid level clouds will move in from the NW overnight and into
the morning. Winds will remain light and variable or calm until
after sunrise. HNB may see some showers during the mid morning hours
with increasing clouds, but otherwise everyone remains dry. Ceilings
will slowly drop during the day and are expected to remain above 5
kft during the afternoon and evening when a general SW wind
develops. Late in the TAF period for SDF, a PROB30 for overnight
storms Wednesday into Thursday was included. Otherwise, VFR
conditions with OVC skies is expected for Wednesday afternoon.

&&

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

&&

$$

SHORT TERM...JRB
LONG TERM...JRB
AVIATION...BKF