613
FXUS63 KLMK 051041
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
641 AM EDT Tue May 5 2026

...Updated Aviation Discussion...

.KEY MESSAGES...

* Waves of showers and thunderstorms are expected today into
  Wednesday, bringing widespread beneficial rainfall to the area.
  Widespread rain totals of 1-2" are likely, with localized heavier
  totals possibly leading to a few instances of high water or minor
  flooding.

* High temperatures look to warm back into the 70s this weekend,
  with isolated to scattered rain showers.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 259 AM EDT Tue May 5 2026

A slow moving frontal boundary will approach our region later today
into tonight, with clusters of showers and storms along and ahead of
this boundary. As the frontal boundary enters our CWA tonight, a
strong mid to upper level impulse will eject out of the southern
Plains into the mid Mississippi River Valley and Ohio River Valley.
Strong low level jetting on the order of 40-50 knots will respond
beneath this mid level impulse in addition to surface low pressure
developing along the boundary, likely across our CWA. The end result
will be clusters and waves of showers and storms later this
afternoon into tonight given increasing forcing and deeper moisture
transport.

Things are quiet across the CWA at this hour with mild temperatures
mostly in the low and mid 60s under steady winds and scattered upper
sky cover. We will be keeping an eye on an upstream convective
complex as we move into the pre-dawn hours, however expect this line
of storms to diminish and gust out as it encounters our more stable
and overall drier antecedent airmass. Could get some gusty
convective outflow and perhaps some decaying showers along and north
of I-64 between 5 and 10 AM. That being said, don`t expect much
else out of it.

We`ll also be keeping an eye on another convective complex moving
steadily across MO/AR early this morning that will be set to slide
across our region by around midday into the afternoon. 05/00z HREF
probabilities for any ML CAPE values over 500 J/KG are 0%, so do
expect this cluster of showers, or perhaps a storm, to be somewhat
elevated. One thing worth noting, however, is that there will be a
pretty dry 1000-850 mb layer that creates an inverted V look to the
sounding near the surface. Given that low level jetting will be
increasing through the afternoon and evening/overnight, it does seem
plausible that some stronger gusts could be realized the deeper into
the afternoon and evening we get as the column saturates with any
shower/storm. SPC did add a Marginal Risk for an isolated severe
wind gust across the west central part of our CWA. It should be
noted that the overall shear profile is very impressive, with plenty
of speed and directional shear. The good news is that most of the
low level shear should be mitigated thanks to the elevated nature of
storms. The best evidence to support this is seen with 0-3km SRH
values around 650 m2/s2 tonight at 06z, however effective SRH values
are less than 200 m2/s2 with forecast soundings showing more stable
low levels.

The other thing we will have to keep an eye on through tonight will
be potential for some locally heavy swaths of rain. Overall QPF is
currently forecast in the 1 to 2" rain on average across the region
through Wednesday. That being said, HREF 48hr Max QPF values do have
some swaths of 3-4" rainfall amounts focused across western to west-
central KY. 24 hr PMM values also show these higher localized swaths
as a possibility. Given that PWATs surge to 1.5"+ just ahead of the
front, and you could have some training of locally heavy showers and
storms, do think these pockets of higher amounts could occur.
Therefore, like the WPC Marginal Risk of Excessive Rainfall for
today and tonight. Don`t think we are to the level of concern for a
Flood Watch given the spread out nature of rounds of convective
clusters, however will monitor trends and latest hi-res guidance
through the day.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 259 AM EDT Tue May 5 2026

Wednesday - Wednesday Night...

Broad troughing will continue to envelop the eastern two-thirds of
the CONUS through mid week, with several individual shortwaves
embedded within. A surface cold front will be sinking slowly
southeastward across our CWA by sunrise Wednesday, and will likely
clear our SE boundary by early to mid afternoon. We`ll keep some
lingering shower and storm chances down there through the day on
Wednesday closer to the boundary and still ahead of the upper trough
axis where deeper SW flow will still be providing some moisture
transport over the area. However, expect a drying trend across
southern Indiana and northern Kentucky by afternoon. Overall, pretty
cool temperatures expected behind the front on Wednesday with highs
only in the lower 60s across our N, and mid to upper 60s across our
southern CWA. This would be about 10-15 degrees below normal for
this time of year.

The drying trend should continue from NW to SE through Wednesday
night as the front pushes farther SE and surface high pressure
begins to build into the area. Looking for chilly overnight lows in
the 40s.

Thursday - Friday...

Broad troughing and surface high pressure should control our area
through the late week portion of the forecast, bringing continued
below normal temperatures and mostly dry conditions. Tending to lean
toward a fully dry forecast given the overall pattern, however there
is some data that suggests another shortwave ejecting out of the
southern Plains into the mid Mississippi River Valley on Thursday
that could bring a few showers. Low confidence as other data keeps
this energy more suppressed to the south. Either way, Thursday night
and Friday have higher confidence in a fully dry forecast.

Cool temperatures continue with highs only expected in the low and
mid 60s on Thursday. The coldest night of the forecast period looks
to be on Thursday night where some upper 30s and low 40s will be
possible. Can`t completely take frost off the table for Thursday
night across our eastern CWA, however NBM probabilities of
temperatures less than 37 degrees are only in the 5-10% range along
the I-75 corridor. Temperatures recover a little by Friday back into
the upper 60s and low 70s, however still a good bit below normal.

Friday Night - Sunday..

Broad troughing continues across our area through the weekend. By
later Friday night into Saturday morning, another shortwave will dig
from the central Plains into the mid Mississippi River Valley.
Expect more showers, and perhaps a rumble of thunder, to develop
ahead of this feature. We should be in the subsident wake of this
feature by Saturday afternoon, so do expect a dry forecast for the
afternoon. As a result, temperatures should still be able to recover
to the low and mid 70s, just a touch below normal.

Yet another shortwave trough axis and an associated cold front
rotates through our region for Sunday. This feature looks a bit
stronger, and will have the potential for more widespread chances
for showers and storms along it. Could be a setup for a few stronger
storms, however more precise timing and fine details will have to be
worked out in the coming days, and much of that will depend on just
how much strong storm potential there will be.

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 641 AM EDT Tue May 5 2026

The line of thunderstorms has diminished to scattered showers at the
HNB/SDF TAF sites, and the outflow has pushed south of these sites.
Gradient winds will quickly find their way back to a SSW to NNE
component by the time this TAF cycle begins. There will likely be a
brief dry period before the next round of showers and storms arrives
from W to E midday through early afternoon. VFR prevails until this
time.

Otherwise, look for gusty SSW winds to pick up again today, peaking
in the 20-25 mph range this afternoon. Scattered showers and storms
this afternoon are expected to give way to more widespread showers
and storm this evening. Could see gusty winds, brief visibility
reductions, and ceilings sinking into the MVFR range at times. A
cold front slowly passes from NW to SE later tonight, where some low
MVFR or IFR ceilings may settle in after Midnight. Watch for more
LLWS threat later tonight again, but not yet mentioning in TAF.

&&

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

&&

$$

SHORT TERM...BJS
LONG TERM...BJS
AVIATION...BJS