Franklin, Kentucky 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

392
FXUS63 KLMK 191102
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
702 AM EDT Sat Jul 19 2025

.KEY MESSAGES...

* Scattered to numerous showers and thunderstorms are likely
  today, which could result in some instances of flash flooding and
  strong straight-line winds.

* Active weather pattern will continue Sunday through Tuesday, with
  episodic bouts of showers and storms. Excessive rainfall and
  flooding will be possible in areas that see repeated rounds of
  storms.

* Hot and very humid mid to late next week, with prolonged
  significant impacts from excessive heat possible.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 403 AM EDT Sat Jul 19 2025

Conditions are mostly dry across central KY and southern IN early
this morning as nighttime microphysics satellite imagery shows
scattered mid-level convective debris clouds moving across the area.
Regional obs show patchy fog, with more widespread fog noted over
southwest OH. From now through sunrise, would expect mostly dry
conditions to continue, with only very isolated showers expected.
Have added patchy fog to the forecast in areas which received good
amounts of rainfall today, though confidence is fairly low given
lingering cloud cover. Temperatures should remain fairly steady in
the low-to-mid 70s.

Today, upper level ridging over the southeast US will expand
westward, with the Ohio Valley remaining on the northern edge of the
ridge. Later this morning, daytime heating should lead to the
development of a stratocu layer as low-level moisture mixes upward.
By late morning, convective temperatures should be reached, with
isolated convection gradually increasing in coverage through the
early afternoon hours. Before showers and storms develop,
temperatures should warm into the mid-to-upper 80s and lower 90s,
with heat index values reaching the upper 90s and lower 100s.

While the air mass showers and storms which develop over the area
are expected to be mainly garden-variety given weak deep layer
shear, we will have to watch ongoing convective complexes over IA/MN
associated with a mid-level shortwave. This MCS is expected to
follow a gradient in SBCAPE from NW to SE, descending toward the
Ohio Valley this afternoon. As it does so, it should encounter a
gradually less supportive environment, but it is possible that it
holds together into at least southern IN. If it does maintain its
strength, strong, possibly damaging winds along the leading gust
front would be possible. Locally heavy rainfall amounts would be
expected given high PWAT values and potential training of storms,
and flash flooding will remain a threat this afternoon and evening.
Admittedly, this is a low confidence forecast, especially given
recent poor performance of high resolution guidance. As a result,
will hold off on a new flood watch given uncertainty in the location
of the heaviest rainfall. Regardless, will advertise likely to
categorical (60-80%) PoPs for this afternoon and evening, with PoPs
decreasing after sunset.

Tonight, we will have to watch for additional convective development
after midnight as high res guidance does show additional waves of
showers and storms, particularly over the northeastern CWA. However,
this will largely be controlled by what happens this afternoon and
evening, as a strong complex of storms could eliminate the
availability instability for storms later tonight. Otherwise, mild
and muggy conditions are expected, with temperatures in areas not
cooled by rain likely remaining in the mid-to-upper 70s, while rain-
cooled areas should fall into the low 70s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 403 AM EDT Sat Jul 19 2025

Sunday through Tuesday Night...

For the second half of the weekend into early next week, the upper
level pattern will shift as height falls occur across the
northeastern US while heights rise over the southern and central
Plains. This will lead to a transition to NW flow across the Ohio
Valley, with central KY and southern IN being on the northeast edge
of the upper-level ridge. Waves of showers and thunderstorms are
expected to ride along an instability gradient extending from the
mid-MS valley toward the central Appalachians from Sunday through
Tuesday. Stronger mid-level flow will support slightly higher
amounts of deep layer shear, especially to the north and east of the
area. This type of pattern typically supports mesoscale convective
systems which can produce damaging winds and heavy rainfall.

While the entire period will feature active weather, of particular
concern is the Sunday night into Monday morning period, when current
medium-range guidance shows the "train tracks" of the 500 mb flow
pattern setting up over the northeastern two-thirds of the CWA. A NW-
SE oriented sfc boundary is also expected to set up over the area,
which could help to focus convection and lead to backbuilding and
training of showers and storms. With an abnormally humid environment
(PWATs 2-2.2", or around the 99th percentile of EPS Climo) and deep
warm cloud depths in place, efficient, torrential rainfall rates
would be likely in thunderstorms. The ECMWF Extreme Forecast Index
does feature a stripe of 0.6-0.7 for QPF, which indicates medium-to-
high confidence in unusually heavy rainfall. Given this setup, would
not be surprised if increased messaging (e.g., a Flood Watch) may be
needed, though we`ll hold off for now given variability in
positioning of the heaviest rain swath.

During the Sunday through Tuesday period, temperatures will be
dependent on the presence of waves of convection, but should
generally be in the upper 80s and lower 90s. Monday could be
slightly cooler, especially across southern IN and the KY Bluegrass
region where showers and storms are more likely. Lows should be in
the upper 60s and low-to-mid 70s.

Wednesday through Friday Night...

For the second half of next week, the main weather story will shift
from showers/storms and heavy rainfall to hot temperatures as 597 dm
ridging sets up over the lower Ohio and mid-MS valleys. As height
rises take place over the region, the axis of organized waves of
showers and storms will shift to the northeast. While showers and
storms will still be possible during the middle of next week,
coverage will become much more isolated.

The ridge which builds over the region mid-to-late next week will be
anomalously strong, with EPS mean 500 mb heights approaching the
99th percentile of model climatology. Given the greater thicknesses
and less coverage of clouds/storms, temperatures will surge for the
second half of the week. However, would expect the recent rainfall
and resulting elevated soil moisture to help keep temps in check,
with NBM indicating fairly low probabilities (<30%) of exceeding 95
degrees for highs outside of the urban heat islands. While the temps
may not be all that unusually high, as the adage goes, "it`s not the
heat, it`s the humidity", and that will certainly be the case next
week as dewpoints should be in the mid-to-upper 70s. The HeatRisk
tool is already identifying next Wednesday-Friday as an impactful
period, with widespread major heat impacts predicted.

By the end of next week, the upper ridge is expected to weaken
somewhat, allowing shower/storm chances to increase. This should
also lead to somewhat-reduced temps, but forecast confidence is
lower at this lead time.

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 701 AM EDT Sat Jul 19 2025

The first few hours of the current forecast period are challenging
as lower ceilings and visibilities are concentrated near terminals
which received heavier rainfall yesterday. As this moisture begins
to mix out later this morning, it is uncertain how widespread the
resulting stratocu field will be, though this could bring a few
hours of MVFR/IFR ceilings before lifting to VFR.

Later today, SW winds on the order of 5-10 kt are expected. Latest
runs of model guidance have decreased coverage of TSRA, and TAFs may
need to be amended to remove PROB30 if the trend continues. If there
are storms, the main time window looks to be between 19-01Z. Outside
of any storms, VFR conditions are expected to continue through this
evening. Winds will be around 5 kt out of the S/SW tonight. Another
wave of TSRA may try to approach SDF/LEX/RGA late tonight; however,
confidence is too low to mention in the current forecast.

&&

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

&&

$$

SHORT TERM...CSG
LONG TERM...CSG
AVIATION...CSG