293
FXUS63 KLMK 141727
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
127 PM EDT Fri Aug 14 2026

...Updated Aviation Discussion...

.KEY MESSAGES...

* A few storms are possible (20-40% chance) today, mainly north of I-
  64 during the late morning. There is a low risk for severe weather
  with any storms this afternoon.

* Additional storms are possible (20-30% chance) across areas mainly
  east of a Salem, Indiana to Richmond, Kentucky line tomorrow
  afternoon and evening. Any storms that form could be severe with
  damaging winds and large hail.

* Outside of storms, heat indices are likely (60-80% chance) to
  surpass 100 degrees west of I-75 this afternoon. The heat and
  humidity peaks Saturday and Sunday, when HeatRisk is forecast to
  reach the Major category area-wide.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 226 AM EDT Fri Aug 14 2026

***** WARM AND MUGGY WITH STORM CHANCES TODAY *****

Early Friday morning, ridging was present over the Deep South and
Tennessee River Valley, while a shortwave disturbance was diving
southeast across the Lower Great Lakes. At the juncture of these two
features, optimal overlap of elevated instability and deep layer
shear is sustaining robust and likely gravity-wave associated
convection (GWAC) across portions of central/northern Illinois into
central Indiana. Meanwhile, tranquil conditions persist over the
local area, which remains largely stable in the wake of evening
convection. A > 13 kft warm cloud layer, PWATs over 2 inches, and
moisture transport into the activity to our north via a
strengthening west-southwesterly LLJ suggests training, efficient
rain producers which will carry and attendant flash flooding risk
through sunrise. Fortunately, high resolution ensemble guidance from
the HREF exhibits high confidence in the worst of this activity
remaining just to the north of the local area. Though these
ensembles are underdispersive, it`s reassuring that the probability
of more than 2 inches of rainfall, maximized (60-90%) near and just
north of the I-74 corridor in Illinois and Indiana, drops off to
less than 20% in Jefferson and Scott (Indiana) Counties. Still,
several convective allowing models (CAMs) drop this activity into
our local area after around 8am EDT, by which time it will be both
weakening (due to a waning LLJ) and perhaps more progressive,
particularly if a notable outflow can develop and push south. We
increased rain chances in the forecast to 30-50% north of I-74
during the mid to late morning timeframe to account for this
possibility.

The question then is whether a few storms may re-fire along any
residual outflow boundary during the afternoon. The NAMNest, ARW,
and a couple iterations of the HRRR fire a couple storms
near/southeast of E-town between noon and 3 pm EDT, so we held on to
15-20% precip chances there, but those may need to be increased
further if an outflow boundary does indeed push that far south
across our area later this morning.

The prospect of early day storms and cloud cover, particularly
across the northern half of the CWA, complicates the temperature
forecast and has made it challenging to place a Heat Advisory for
today. 14.00z HREF probabilities for afternoon heat indices greater
than or equal to 105 degF (our Advisory threshold) are generally
50+% from Hancock to Marion to Cumberland Counties in Kentucky and
points southwest; however, these "probabilities" as only as reliable
as the models comprising them, and they`ve proven mercurial in this
weakly forced environment so far this week. We`re going to hold off
until a bit later in the shift to reassess with some of the 06z
guidance, but this is the area most likely to wind up with a Heat
Advisory today.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 226 AM EDT Fri Aug 14 2026

***** HEAT SPREADS EAST INTO THE WEEKEND *****

In theory, our resident quasi-stationary front, which has served as
a focus for convection in and northeast of the area all week, should
lift far enough north to keep storms away both tomorrow and Sunday.
However, I have trust issues with the more optimistic models at this
point, having seen convective outflows sink further south and fuel
more thunderstorms than guidance has suggested on multiple
occasions. Consequently, I added some slight (15-24%) precipitation
chances to the forecast tomorrow afternoon-evening northeast of a
roughly Salem, IN to Richmond, KY line where the HRRR and FV3 fire a
couple storms along an outflow boundary in an environment
characterized by 3000+ J/kg MLCAPE and 20-30 kt 0-6km bulk shear. If
we have storms, these parameters suggest they will be capable of
producing severe weather, with both damaging winds and large hail
concerns. Strong clockwise-curved hodographs suggest we`ll need to
keep one eye on the tornado potential with individual cells, but
LCLs (1000-1400m) appear to be on the high side for tornadoes and
the better shear is between 1 and 3km (vs 0-1km); in addition, the
hodograph bends back in on itself throughout the rest of the cloud
layer (up to around 13kft), suggesting poor ventilation may limit
updraft strength and longevity.

The bigger story this weekend will be heat and humidity, which
outside of storms will become oppressive at times. Uncertainty in
the extent of potential convective activity has precluded a Heat
Advisory for Saturday and Sunday at this time, but one will almost
certainly be needed for most, if not all, of the county warning area
both days as afternoon temperatures reach the mid 90s and dewpoints
hover in the mid to locally upper 70s - pushing heat indices to 105-
110. In addition, warm overnight low temperatures in the mid to
upper 70s will offer little relief to those without proper cooling,
which pushes HeatRisk into the Major Category for most of the area
both Saturday and Sunday.

***** LESS HOT, MORE STORMY TO KICK OFF NEXt WORK WEEK *****

A shortwave trough looks to flatten the ridge late Sunday into
Monday, bringing better (40-70%) chances for storms as early as
Sunday night, and perhaps offering at least limited relief from the
oppressive heat and humidity Monday into Tuesday. WPC Cluster
analysis suggests that, by midweek, the highest source of
uncertainty among long range ensembles (given by PC1 for EOF1) is in
the east-west placement of h5 ridging building over the central US
and hence: whether our area sees (outcome 1) oppressive heat return
or (outcome 2) remains far enough northeast of the ridge to instead
see more seasonable temperatures and waves of "ridge-riding"
thunderstorms. About 50% of models favor each scenario.

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 126 PM EDT Fri Aug 14 2026

VFR conditions will continue across the region this evening, with a
lower confidence precip chance through the afternoon. LEX and RGA
have the best chance for an isolated shower or storm, so have
utilized PROB30 groups there. SDF could see a shower too, but
chances were less, so decided to keep their TAF dry for now.
Otherwise, VFR continues tomorrow with light winds from the south.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory from 11 AM EDT /10 AM CDT/ Saturday to 9 PM EDT
     /8 PM CDT/ Sunday for KYZ023>031-034-038-039-045-046-053-
     054-061>065-070>077-081.
     Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for
     KYZ023-024-026>028-053-054-061>065-070>077-081.
IN...Heat Advisory from 11 AM EDT /10 AM CDT/ Saturday to 9 PM EDT
     /8 PM CDT/ Sunday for INZ076>078-083-084-089>092.

&&

$$

SHORT TERM...JRB
LONG TERM...JRB
AVIATION...CJP