954
FXUS63 KLMK 291056
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
656 AM EDT Fri Aug 29 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* Dry weather with below normal temperatures will continue into the
  Labor Day weekend. There is a very low (<15%) chance for a shower
  this afternoon, mainly across central KY.

* Isolated to scattered daytime shower/storm chances will return
  across southern KY for Labor Day, and then all other locations
  through mid to late week. Potential for substantial rainfall
  amounts has increased, but is still relatively low.

* A strong front will bring another shot of cool and dry air to the
  region late next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 350 AM EDT Fri Aug 29 2025

This morning, water vapor imagery shows an upper-level trough
pivoting from the Great Lakes toward the St. Lawrence valley, with
NW flow across the Midwest and down into the Ohio Valley. The sfc
low associated with this disturbance is analyzed over southern
Quebec this morning, with an attendant cold front extending back to
the SW toward the Ohio Valley. Nighttime microphysics satellite
imagery shows scattered clouds where low-to-mid level moisture has
increased along and just ahead of the front, extending from southern
IN across the Bluegrass at this hour. Temperatures in general are
milder this morning, with most locations in the mid-to-upper 50s and
lower 60s thanks to the increasing moisture and cloud cover.

Later today, the front will gradually push south across southern IN
and central KY as high pressure sinks into the Great Lakes behind
the front. While moisture and upper-level support will be meager
with the front, we should at least see a band of cumulus clouds
develop by early this afternoon. Model soundings continue to show a
layer of CAPE between 850 mb and 650 mb this afternoon, potentially
allowing for sufficient development for a few light rain showers.
However, most CAM guidance shows little if any development of
showers aside from the typically wet-biased models. With this
forecast, we`ll tread a middle ground, keeping a technically "dry"
(<15%) PoP, but advertising a chance of sprinkles, primarily along a
band from Huntingburg, IN to Liberty, KY. The best chance for any
sprinkles/light rain showers would be between 17Z-23Z. Otherwise,
high temperatures should range from around 80 across southern IN to
the mid-to-upper 80s across southern KY.

This evening, cumulus should dissipate quickly after sunset, even
along the front, which should be moving across southern KY. Behind
the front, winds should veer from the W to the NW to the N/NE, which
light NE flow continuing into Saturday morning. This will bring
another shot of lower dewpoints and (slightly) cooler air into the
region. Lows Saturday morning should fall into the 50s in most
areas.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 350 AM EDT Fri Aug 29 2025

Saturday - Sunday Night...

Excellent weather will continue into the last weekend in August as
the cold front which will push across the region today is expected
to wash out over the TN valley on Saturday. Behind the front, sfc
high pressure over the Great Lakes will promote low-level NE flow
into the area, reinforcing the anomalously cool and dry air mass
over the Ohio Valley. With that being said, we will be on the edge
of the cooler air mass, and there should be a north-south
temperature gradient across the forecast area. Highs this weekend
should range from the upper 70s to around 80 across southern IN and
northern KY to the low-to-mid 80s across central and southern KY.
Morning lows should fall into the 50s in most areas, though valleys
and rural areas may drop into the upper 40s.

Labor Day - Tuesday Night...

Heading into early next week, an upper-level blocking high over
central Canada will begin to break down and push east. As it does
so, sfc high pressure over the lower peninsula of Michigan will
shift to the east of the Appalachians. This will help to create a
CAD pattern east of the Appalachians, with inverted sfc troughing
setting up from the Tennessee Valley northeastward across our area.
This pattern shift will allow moisture to be drawn up from the south
starting on Monday and continuing through mid-week.

On Labor Day, the pool of higher PWATs is expected to be confined
over TN and southern KY. As a result, most should continue to see
dry weather on Labor Day, though an isolated afternoon shower or
storm will be possible south of the Kentucky Parkways. As southerly
flow continues to converge into the inverted trough as we head into
Tuesday, the area of isolated to scattered PM shower/storm chances
should expand across much of the forecast area, with the possible
exception of southern IN.

Temperatures Labor Day and Tuesday will still be below normal,
though diurnal ranges will be suppressed as moisture increases.
Expect highs in the upper 70s and low-to-mid 80s with lows ranging
from the mid 50s to the low 60s.

Wednesday - Thursday Night...

Another anomalously amplified trough is expected to descend across
the central and eastern portions of North America during the latter
half of next week. This is expected to bring another shot of
anomalously cool and dry air to the region for the end of next week
and into next weekend, which is outlined nicely on the 6-10 day CPC
temperature outlook.

However, before the main trough descends into the region, a more
subtle upper-level shortwave will try to set up over the mid-
Mississippi Valley next Wednesday. Run-to-run trends in the
deterministic ECMWF show the model has trended stronger with this
disturbance, while the GFS has a similar, but weaker signal. The
reason this is important is that better upper-level support combined
with the pool of moisture which is expected to continue to increase
into Wednesday should support widespread rain chances well ahead of
the main upper trough/sfc FROPA on Thursday. Medium-range ensemble
probabilities of greater than 1" of rain have trended higher from
the 12Z to the 00Z guidance. While reasonable high-end precipitation
amounts are still modest (1-1.5"), any rain will be welcome given
expanding drought conditions across the area. While this is a fairly
new trend in guidance, we`ll continue to monitor to see if a more
reliable signal for substantial rainfall develops over coming days.

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 656 AM EDT Fri Aug 29 2025

VFR conditions are expected through the current forecast period. A
cold front will sink across the region from north to south today,
with winds gradually veering from W to NW to N/NE through the
period. Scattered cumulus currently over LEX and RGA should become
more widespread this afternoon along the front, gradually clearing
this evening as drier air moves in from the north. As noted in the
previous discussion, a few 15+ kt gusts will be possible this
afternoon, especially at SDF and LEX. Tonight, light NE winds are
expected with mainly mid- and upper-level clouds expected.

&&

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

&&

$$

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