406
FXUS63 KLMK 110717
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
317 AM EDT Tue Aug 11 2026

.KEY MESSAGES...

* There is a level 3 of 5 (enhanced) risk for severe weather this
  evening north of a roughly Bedford, Indiana to Richmond, Kentucky
  line, with the risk decreasing further southwest. Damaging winds,
  some significant (> 75 mph), are the primary hazard.

* Repeated rounds of heavy rainfall in thunderstorms tonight and
  again tomorrow could result in localized flash flooding. There is
  a level 2 of 4 (slight) risk for excessive rainfall.

* Additional rounds of storms are possible (40-60% chance) through
  Friday. There is a level 2 of 5 (slight) risk for severe weather
  tomorrow west of I-65, with damaging winds the primary concern.

* Outside of storms, heat indices are likely (50-80% chance) to
  surpass 100 degrees west of I-65 each afternoon through Thursday,
  and area-wide over the weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 316 AM EDT Tue Aug 11 2026

***** SEVERE WEATHER RISK THIS EVENING *****

Early Tuesday morning, upper level ridging was maintaining
seasonably warm and humid conditions across northern Kentucky and
southwest Indiana, with temperatures/dewpoints mainly in the
upper/mid 70s at 3am. Meanwhile, a weak mid level disturbance
on the northeast periphery of the ridge triggered storms over
portions of Ohio into West Virginia. Northwest flow aloft
should continue to carry these southeastward across West
Virginia - keeping them out of our local area; however, the HRRR
and NAMNest - the two models best handling the placement of
current convection - suggest redevelopment upstream over
northern/central Indiana toward daybreak, and this second wave
could affect our local area during the morning into early
afternoon. Convective allowing models (CAMs) disagree on
precisely how much of our area sees early day activity with this
wave, with the HRRR and ARW merely grazing our northeast
counties, the RRFS hitting areas northeast of a roughly
Louisville to Richmond line, and the NAMNest bringing a decaying
line south across virtually the entire CWA. Given the mean wind
is generally out of the west- northwest (around 280-290
degrees), and having seen the NAMNest overdo an MCS`s right turn
into higher theta-e air several times in the past, our forecast
leans towards the HRRR/ARW solution, with just a low (20-30%)
chance of a storm east of Madison, IN to Lexington, KY line mid
morning-early afternoon.

The evolution of this morning activity will be critical in dictating
the trajectory of the next and potentially more impactful wave of
storms this evening into tonight. The large-scale set-up: A
shortwave trough embedded within broad west-northwest flow will
provide lift to trigger storm development across Iowa/southern
Minnesota/southern Wisconsin this morning, with that activity
generally favored to spread southeast along the instability axis
during the afternoon and evening. If early day activity stays to our
northeast, the effective boundary (and hence instability gradient)
should keep the focus for evening storms across central/northern
Indiana and much of Ohio; however, if we have more in the way of
early day storms, evening storms could take a right turn and dive
south along the remnant outflow boundary. In either case, some
guidance - most notably the most recent (04z) HRRR iteration -
suggests these afternoon and evening storms will develop a strong
cold pool, and produce widespread damaging winds (with some
locations seeing gusts > 75 mph) wherever they track. Based on the
best overlap of shear and instability, the most favored corridor
would be just northeast of our local area, but given the uncertainty
and potential for significant impacts the SPC has areas north of a
roughly Bedford, Indiana to Richmond, Kentucky line outlooked in a
level 3 of 5 (enhanced) risk for severe weather; the slight risk
extends southward to a roughly Huntingburg, Indiana to Windsor,
Kentucky line. Wind is in CIG 1 hatching, indicating potential for
75+ mph gusts capable of structural (primarily shingle/siding) and
significant tree (large trees snapped, many limbs downed) damage,
with the latter likely to also result in numerous power outages
(from trees/limbs falling on lines). In addition, there is a 2%
tornado risk, suggesting a low but nonzero chance of a brief spin up
in the line of storms, mainly in the northern portion of any bowing
segments where the line becomes nearly orthogonal to 0-3km shear
vectors (roughly out of 280 degrees). However, we`d like to
reiterate that confidence on storm track is low; there is potential
that most/all of this passes to our north, leaving us unscathed.

Outside of storms, it`ll be a seasonably hot and muggy day with the
HREF/REFS suggesting a medium-high probability (50-80% chance) of
afternoon heat indices in the triple digits west of I-65. The
greatest potential for heat indices topping 105 should be confined
to areas west of a roughly Bedford, IN to Scottsville, KY line,
where a Heat Advisory is in effect.

***** FLOODING POTENTIAL TONIGHT INTO WEDNESDAY MORNING *****

Once the forward-propagating portion of the line pushes through (or
to the northeast of) the local area, a lingering outflow boundary
could serve as a focus for additional storms on the nose of what the
RAP/NAM depict as a 30-35 kt westerly LLJ. While upshear Corfidi
vectors are 20-30 kt (towards the southeast), which by itself would
suggest enough storm motion to keep the hydro risk low, training
cells could lead to repeated rounds of heavy rainfall over the same
areas if the boundary lays out in a north-south orientation. As with
the evening MCS, uncertainty is high in where (and even whether)
this will set up, but concern is greatest in areas east of a roughly
Madison, Indiana to Lexington, Kentucky line where WPC has a level 3
of 4 (moderate) risk for excessive rainfall, and where the HREF and
REFS ensemble max depict swaths of 6+ inches of rainfall in just a
few hours tonight into Wednesday morning.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 316 AM EDT Tue Aug 11 2026

***** ADDITIONAL STORMS WEDNESDAY INTO WEDNESDAY NIGHT *****

Depending on how things evolve tonight, we could have storms ongoing
during the morning commute tomorrow, with the effective boundary
fueling continued storms throughout the day. However, the highest
chance for storms over the local area will once again be during the
evening when another shortwave digs across the Upper Ohio Valley,
providing a lifting mechanism and better (30-40 kt) deep layer shear
to sustain convection. Uncertainty surrounds how much of a severe
risk will accompany this activity given potential for widespread
clouds and early-day storms which could limit instability, but if we
see enough breaks of sunshine the environment would certainly be
favorable, once again, for one or more MCSs capable of damaging
winds and torrential rainfall leading to localized flash flooding.
At this time, SPC has areas west of I-65 outlooked in a level 2 of 5
(slight risk) for severe weather.

***** THURSDAY THROUGH MONDAY *****

Global deterministic models and their respective ensembles suggest
ridging should build over the Midwest and Ohio Valley into the
weekend, suggesting a downward trend in precipitation chances and
continued warm, muggy conditions. However, particularly Thursday and
Friday, we remain preciously close to the ring of fire - the
northeast periphery of the ridge where the best overlap of
instability and deep layer shear will favor MCS activity. Storm
chances, around 40-50% northeast of a Jasper, Indiana to Somerset,
Kentucky line Thursday into Friday, will finally drop below 20% by
Saturday.

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 128 AM EDT Tue Aug 11 2026

A weakening ridge of high pressure should maintain VFR conditions at
all of the airfields through mid afternoon, though there will be a
low (15-20%) chance of a stray morning storm at RGA. More numerous
storms will develop over Indiana during the late afternoon and may
(50-70% chance) drop southeast to affect all of the terminals except
perhaps BWG during the evening into early overnight period. While
confidence is low on timing, prob30 groups highlight the period of
greatest concern at each terminal. Outside of storms, winds will
blow out of the southwest, with gusts upwards of 20 kt at times
during the afternoon.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Heat Advisory from 11 AM this morning to 8 PM CDT this evening
     for KYZ023-026-061-070>073.
IN...Heat Advisory from noon EDT /11 AM CDT/ today to 9 PM EDT /8
    PM CDT/ this evening for INZ083-089.

&&

$$

SHORT TERM...JRB
LONG TERM...JRB
AVIATION...JRB