Flash Flood Warning 18, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
714 AM EDT Tue Jun 9 2026

...Updated Aviation Discussion...

.KEY MESSAGES...

* Unsettled weather with localized area of heavy rainfall and flash
  flooding are possible across KY and southern IN now through
  Wednesday morning. While basin average rainfall of 0.75-2 inches
  are expected, localized amounts of 3-6 inches will be possible in
  heavier swaths, mainly across central KY.

* Despite some morning showers and weak storms on Wednesday, hot
  temperatures and mugginess are expected Wednesday and Thursday,
  with peak afternoon heat index values between 90-100.

* An approaching cold front later in the week provide more
  opportunity for rain and some storms Thursday evening through
  Friday, though timing is still uncertain.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 401 AM EDT Tue Jun 9 2026

A complex of showers and storms continues overnight along our
western CWA gradually moving NE. Though daytime heating has waned,
there is plenty of moisture in the vertical throughout our CWA,
which has produced some torrential downpours along our western
border counties. Some of these areas have already picked up 1-1.5"
of rain in the past few hours and will continue to see on and off
moderate rain showers through the morning. This type of periods of
heavy rain will be the theme for the short term, at least through
Wednesday morning. The synoptic setup features very weak low to mid
level flow over the next 24 hours. As a result, as waves of rain and
storms roll through, localized heavier rainfall totals creating
flooding concerns will continue through this afternoon and into
overnight Wednesday. The current rounds of rain was part of a series
of shortwaves moving through the Plains, and as the first of a
couple moves off to our north, it leaves behind moisture-rich air,
high dewpoints and warm temperatures for the morning. Another
shortwave moving NE through the central plains will maintain surface
SW flow for the remainder of Tuesday - Wednesday.

From general lift induced by the central plains shortwave,
additional rounds of MCVs will move in along an axis of enhanced
PWATs oriented along a NW-SE line from roughly the Kansas City area
towards Richmond, KY. The initial MCV moving SE from Kansas City
will generally break up as it approaches, though rainfall rates will
remain high within embedded storms from what will likely become a
messy scattered complex of convection. Short range model guidance
has a general drying trend later in the evening on Tuesday, before
more storms and/or additional MCVs fire off again within a pool of
increased PWATs that will linger right over KY overnight through
Wednesday morning.

This general pool of increased stationary PWATs of 1.8-2.0"
lingering through the overnight is the cause of greatest concern for
flooding. Latest 00Z HREF guidance suggests a series of back-
building and training storms over far southern IN moving SE through
the heart of KY towards the Somerset-Richmond, KY area. HREF 6hr
LPMM data through overnight Wednesday features some areas of
receiving 4-6". Other signals of significant rainfall within short
bursts of time exist in HREF guidance, with 3hr QPF probability of
exceeding 1" is above 50% early Wednesday morning, with a 10%
hatched area of exceeding 3" in 3hr QPF. Altogether, there is a
strong signal of localized flooding, mainly through central KY going
through a lull of flooding probability Tuesday afternoon and
increasing in action from training storms overnight Tuesday into
Wednesday. As a result, the current Flood Watch will be extended
through 12Z Wednesday morning, and will be monitored for any further
expansion or time extensions.

With regard to any severe risk, as storms approach from the WNW,
there may be enough mid-level shear to sustain a severe wind threat
over our western CWA. The severe risk is low and is only for gusty
winds and this will be monitored throughout the day. The main
concern is for localized flooding concerns that ramp up later in the
night on Tuesday. Area wide rainfall totals through Wednesday
morning should range 0.75 - 2", though localized areas of 3-6" are
still possible in training storms in central KY.

Despite the rounds of rain today, muggy conditions with dew points
in the low to mid 70s will make the air feel thick and oppressive
between showers. Highs will be in the low to mid 80s with breaks in
cloud cover later on Tuesday.

By Wednesday morning, the main concern will be continued training
showers and storms. Surface moisture will remain high giving plenty
of moisture for storms to work with despite the lack of daytime
heating. As the day progresses, an axis of high pressure to our SW
will build into the lower Ohio Valley, expected to act as a lid for
any continued convection and generally sweep storms out towards the
east by lunchtime. Latest HREF guidance wants to slow this process
down with continued convection. For now, we are forecasted skies to
gradually clear SW to NE during the day. Without a significant
change in air masses though, dew points will remain high in the low
to mid 70s. A heat advisory may need to be issued for Wednesday as
highs will reach the low 90s by afternoon, with heat indices maxing
out in the low 100s at times.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 401 AM EDT Tue Jun 9 2026

      Wednesday - Sunday ...

Heading into Thursday, the surface to mid level ridge will remain
overhead locking in hot temperatures and high dew points. Heat
indices will raise into the upper 90s and isolated low 100s again,
meaning another heat advisory may be needed. One note of difference
is a building LLJ from the SW in response to a tightening pressure
gradient on Thursday. A larger mid to upper level trough will be
swinging through the Northern Plains meaning gusty winds on Thursday
afternoon from daytime mixing is possible, gusting 20-25 MPH. This
could serve as a way to cool off during the day if nothing else.

This trough over the northern plains will kick off a trailing cold
front that should sweep through the Ohio Valley. The timing of this
cold front is key to any severe weather potential Thursday evening-
Friday morning. Current trend is to sweep through during the
overnight limiting the severe potential and serving as another rain
chance with some gusty winds. Beyond this, relief from the heat at
least temporarily is expected. Temperatures will remain near or just
above normal as a return of warm moist air looks to return beyond
Saturday.

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 714 AM EDT Tue Jun 9 2026

VFR to MVFR conditions will continue through the morning hours with
storms rolling through KY airports over the next several hours.
Southerly flow will slowly shift out of the southwest this afternoon
gusting near 20kts. Beyond this initial round of storms this
morning, spotty storms are possible in the afternoon. More
widespread coverage of storms returns later this evening from the NW
that will linger overnight into Wednesday morning. Prolonged rounds
of storms and rain are possible at times Tuesday evening temporarily
dropping ceilings to MVFR conditions. Otherwise, passing -SHRA with
winds becoming lighter overnight is expected with VFR-MVFR
conditions remaining Wednesday morning.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flood Watch through this evening for KYZ023>031-034-038-045-
     046-053-054-061>065-070>078-081-082.
IN...Flood Watch through this evening for INZ076>078-083-084-
     089>092.

&&

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