Flash Flood Warning 94, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
755 PM EDT Thu Jul 9 2026

...Updated Aviation Discussion...

.KEY MESSAGES...

* There is a level 2 of 5 (slight) risk for severe thunderstorms
  west of roughly I-65, with a level 1 of 5 (marginal) risk
  elsewhere. The primary hazard would be damaging wind gusts between
  8pm and 1am tonight.

* Thunderstorms tonight will also bring a level 2 of 4 (slight) risk
  for excessive rainfall, with pockets of over 4 inches potentially
  resulting in flash flooding. Additional waves of storms will
  prolong the flooding risk through at least Saturday.

* Decreasing chances for afternoon showers and storms and seasonable
  temperatures are expected Sunday through the middle of next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 212 PM EDT Thu Jul 9 2026

At 2pm EDT, central KY and southern IN was situated between two
disturbances: a shortwave mid-level trough over the
Appalachians and a more potent disturbance along the MS River -
the latter will bring storms into our area mid-late this
evening. SPC's mesoanalysis reveals anywhere from 500-2000 J/kg
MLCAPE (highest values to the west) across the area, which,
despite only 15-25 kt effective shear, may support a couple
strong to marginally severe thunderstorms. The CAMs generally
advertise a multicell/linear storm mode which would suggest wind
is the primary hazard, though there is a nonzero tornado risk
across the west where there could be a couple hours' overlap
between waning diurnally-driven instability and 20-25 kt 0- 3km
line normal shear during the 8pm-1am EDT timeframe tonight.

The evening storms should weaken as they move east across the area
with the loss of instability, especially if the outflow surges out
ahead of them as several CAMs suggest. This outflow should serve as
a focus for additional thunderstorms overnight, though the primary
concern with those will be heavy rainfall rather than wind, hail, or
tornadoes. Recent model trends have been further south with the
evening wave of storms and associated outflow - possibly far enough
south to confine the best flash flooding risk across Tennessee where
the NAM/RAP depict a 30-40 kt LLJ beginning around 4am EDT Friday.
Nonetheless, there are still a few models that keep that moisture
transport axis - and hence maximum rainfall totals - further north
with the HREF ensemble max giving localized pockets of 5+ inches
(sufficient for substantial flash flooding) as far north as the
IN/KY state line. Needless to say, the WPC level 2 of 4 (slight)
risk for excessive rainfall across our area seems reasonable.

As the shortwave trough responsible for all of the showers and storms
tonight into tomorrow morning shifts off towards the east, we should
see a break in convective activity, though a couple isolated storms
remain possible (20-30% chance) during the afternoon. By evening,
however, additional waves of storms are slated to fire upstream and
propagate east-southeastward along the boundary left in the wake of
morning storms. Given the environment - characterized by PWATs of
1.9-2.0 inches, a deep (>12 kft) warm cloud layer, and weak (10-20
kt) deep layer shear - storms will be efficient rainfall producers
and rather slow moving, which suggests heavy rainfall is again a
concern, particularly Friday night into Saturday. By Saturday
morning, HREF/REFS ensemble max 24-hour rainfall depicts pockets of
4+ inches once again; any areas that received heavy rainfall
Thursday night-Friday will be particularly vulnerable for additional
flash flooding if they receive training storms again with this
second wave Friday night into Saturday. Still, there remains
potential for the heaviest rainfall amounts to once again occur
south of the local area if the effective boundary pushes south as
some of the CAMs suggest. At this time, the National Blend of Models
(NBM) advertises a 40-70% chance (highest across southern KY) for
rainfall totals over 2 inches by 12z/8am EDT Saturday across the
local area.

Once again, additional heavy thunderstorms are forecast Saturday
afternoon and evening as another shortwave trough and attendant
surface low drifts towards the area from the northwest. The Low
Resolution Ensemble Forecast (LREF) system mean brings 25-30 kt 0-
6km shear with this system, which combined with 1500-2500 J/kg
MLCAPE would favor a severe weather risk during the afternoon,
mainly from locally damaging winds in water-laden downbursts. Given
the deep moisture in place (PWATs 1.9-2.1 inches), we'll still have
to watch for locally heavy rainfall in these storms which could once
again trigger flooding, especially if it falls on areas that already
received heavy rainfall between tonight and Saturday morning.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 212 PM EDT Thu Jul 9 2026

As we head into the second half of the weekend, upper-level ridging
will continue to build across the western and central CONUS as an
upper level low becomes cutoff over the Tennessee Valley. At the
surface, a quasi-stationary boundary is expected to lay out over the
Tennessee Valley, though the exact positioning of this boundary will
likely be modified by convective episodes Friday and Saturday. To
the north of the Ohio Valley, high pressure will try to sink south,
along with drier air. There should be a fairly strong north-south
gradient in moisture/PW values on Sunday, though the rich (1.75+"
PW) moisture which will be over our area the next few days should
settle to our south by Sunday. There should still be enough moisture
and instability in the area for scattered storms to develop Sunday
afternoon, with the greatest coverage expected in southern KY.
Weakening flow aloft should limit the severe weather potential, with
more of a pulse/typical summer time storm setup expected. The slower
storm motions will support a continued threat for flash flooding,
though it may be more isolated depending on storm coverage.

For the first half of next week, 600+ dm upper ridging will spread
into the northern Plains, controlling much of the weather across the
CONUS. The pattern over our region will be a bit more complex. An
increasing proportion of the medium-range ensembles keeps an upper-
level low meandering across the TN Valley through much of the early
week, and while moisture won't be particularly rich (PW 1.25-1.5"),
there could be enough combined forcing and moisture for isolated to
scattered afternoon and evening convection Monday and Tuesday.
Temperatures are expected to be fairly seasonable through the middle
of next week, with highs ranging from the mid 80s to around 90
Sunday through Wednesday. With less moisture content in the air,
nighttime temperatures should be able to cool into the upper 60s and
low 70s each night.

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 754 PM EDT Thu Jul 9 2026

Currently isolated rain showers and thunderstorms are moving in from
the west. A more widespread signal for heavy rain and storms looks
to move into the western part of the area around 05z, and work its
way east. MVFR ceilings and vis will accompany these storms as
they produce heavy rain rates and gusty winds. Precip is
expected to mostly clear by 22z aside from a few lingering
showers in the Bluegrass region. Winds will continue out of the
SW through tomorrow ahead of a surface low pressure.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flood Watch through late Saturday night for KYZ023>043-045>049-
     053>057-061>067-070>078-081-082.
IN...Flood Watch through late Saturday night for INZ076>079-083-084-
     089>092.

&&

SHORT TERM...JRB
LONG TERM...CSG
AVIATION...CAL

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