LMK issues Area Forecast Discussion (AFD) at Aug 17, 1:01 AM EDT
956
FXUS63 KLMK 170501
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
101 AM EDT Sun Aug 17 2025
.KEY MESSAGES...
* Hot and humid tomorrow through Tuesday. Heat index values of 100-
105 are possible.
* Isolated to scattered showers and thunderstorms will be possible
late this evening into Sunday. This activity may bring brief heavy
rainfall and relief from the heat.
* A cold front will likely bring relief from the heat, along with
increasing thunderstorm chances, by the middle of next week.
&&
.UPDATE...
Issued at 1051 PM EDT Sat Aug 16 2025
After scattered afternoon showers and storms over the eastern
portion of the region, patchy fog development will be possible in
the early morning in this area. Radar is currently silent over the
region, however, a decaying storm complex is moving south over
central Indiana and will likely make it to southern Indiana before
completely dissipating. Have increased PoPs over southern Indiana
for the next few hours. In the early morning, a decaying MCS will
move in from the north bringing some showers, storms, and winds
gusting up to 30mph along the outflow. Model guidance still shows
some discrepancies on timing, but should be within the dawn hours.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 346 PM EDT Sat Aug 16 2025
Lingering outflow boundary from convection overnight across central
IN that worked into northern/central KY this morning has help fire
off convection mainly along the I-75 corridor this afternoon. Gusty
winds, frequent lightning and gusty winds have all been the main
impacts with just a few of these cells. These showers and storms
will diminish later this afternoon/evening with the lower sun angle
and loss of daytime heating. The rest of the CWA has been mostly
sunny and hot. Highs so far this afternoon have topped out into the
low/mind 90s with heat index values about where we expected them in
the upper 90s to low 100s.
Overnight, an MCS across southern WI will quickly dive southward
through IL and IN as it becomes cold pool dominant. The hi-res model
trends have remain consistent, showing this complex dying out as it
approaches southern IN and the Ohio River in the early morning hours
of tomorrow between 10 and 12z. While the bulk of the activity looks
to diminish before it reaches the CWA, decided to keep a low end
chance of showers/storms for tomorrow for southern IN and along the
Ohio River. Could get some gusty winds from this as the remaining
boundary rolls through right around or just after sunrise. Lows
overnight will be in the low 70s with the exception of our
traditional urban heat island locations where lows may stay in the
mid 70s.
Expect more heat and humidity tomorrow as the upper-level ridge hold
over the central Plains and Mid MS Valley for the end of the
weekend. Dewpoints will be in the low 70s again for the afternoon
with highs in the low/mid 90s. Lingering outflow boundaries
associated with the overnight MCS will likely linger over the CWA
during the day, and as we've experienced the last couple of days, a
weak boundary is enough to get isolated showers and storms to form
during the heat of the day. Main impacts from any activity will be
gusty winds, localized heavy rainfall and frequent lightning.
Heat index values will once again be in the upper 90s to low 100s
tomorrow but look to remain below criteria categories, so decided
with more cloud cover and uncertainty of potential afternoon
convection, not to issue a Heat Advisory.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 346 PM EDT Sat Aug 16 2025
The current period of hot and humid weather will reach its climax
Monday into Tuesday as mid- and upper-level ridging builds across
the Ohio Valley and Midwest. On Monday, we should be right on the
edge of expansive sfc high pressure centered over southeastern
Canada, which will provide light NE winds and slightly lower dew
point temperatures. This should lead to a NE-SW temperature
gradient, with highs ranging from the low 90s across the KY
Bluegrass to the mid-to-upper 90s across SW Indiana and western KY.
Soundings do show a stronger subsidence inversion on Monday, and
while a stray shower or storm can't be completely ruled out, Monday
would be our best chance to remain dry across the area.
By Tuesday, the effects of Hurricane Erin will begin to be felt on
the mid-latitude wave pattern as troughing over eastern Canada and
the north Atlantic amplifies to pick up the disturbance. At the same
time, a low over the Gulf of Alaska is expected to retrograde
slightly, with upper ridging over the central CONUS also undergoing
retrograde motion. Height falls will begin to take place over the
Ohio Valley Tuesday night into Wednesday as a cold front sinks into
the area; however, with the front still to the north on Tuesday, it
could be the hottest day of the entire stretch with mid-to-upper 90s
expected for highs. NBM probabilities of 100 degree temperatures
approach 50% along and west of I-65 Tuesday afternoon, and a heat
advisory may be needed on Tuesday.
Depending on how fast the upper ridge weakens, more widespread
chances for showers and storms may return Tuesday afternoon, though
the best signal for rain chances continues to be on Wednesday with
the aforementioned front nearby. Increased cloud cover/rain chances
should knock temperatures back a few degrees, though slower
solutions (like the ECMWF) could see portions of the area return to
the mid 90s. Storms should be fairly slow-moving, with heavy
rainfall looking like the main threat from mid-week convection at
this time.
Behind the mid-week front, temperatures should return to more
seasonable levels for the end of the week and the beginning of next
weekend. Highs are expected to reach the upper 80s and low 90s, with
lows ranging from the mid 60s to the low 70s. Precipitation chances
should also subside, though isolated afternoon and evening showers
and storm chances will continue, especially along and east of I-65.
&&
.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 100 AM EDT Sun Aug 17 2025
Watching a small cluster of storms moving into southern IN this
hour. Satellite briefly shows some colder cloud tops with these, and
they will approach the SDF terming in the next hour or two...if they
survive. May see a brief bump up in winds from the north with the
ourflow from these storms. Another wave of storms is over the
central IN/IL border now, and these too may make it into SDF around
daybreak, so kept the prob30 group from the previous forecast. For
the rest of the day, we'll see isolated storms in the afternoon, but
confidence and coverage is too low to include in this set of TAFs.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...SRW
SHORT TERM...BTN
LONG TERM...CSG
AVIATION...RJS
Source: LMK issues Area Forecast Discussion (AFD) at Aug 17, 1:01 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202508170501-KLMK-FXUS63-AFDLMK)
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