877
FXUS63 KLMK 131036
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
636 AM EDT Tue May 13 2025

.KEY MESSAGES...

*  Scattered to numerous showers and thunderstorms are expected this
   afternoon and evening, lingering into Wednesday. Heavy rainfall,
   lightning, and gusty winds are the main threats.

*  A warming trend is expected later in the week, with highs well
   into the 80s Thursday and Friday. The potential for waves of
   strong, possibly severe storms late Thursday through Friday night
   is increasing.

&&

.UPDATE...
Issued at 635 AM EDT Tue May 13 2025

Latest obs and nighttime microphysics satellite imagery show a
mixture of fog and low stratus across the area. Most of the fog
showing up in KY Mesonet cameras/obs is located in places which
received rain Monday afternoon and evening, though this fog is still
fairly patchy. Have gone ahead and issued an SPS for locally dense
fog through 13Z, at which point fog should begin to scatter into a
stratocu layer given daytime heating.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 308 AM EDT Tue May 13 2025

A couple of vortmaxes wrapping around each other are making up the
broad upper low dominating our weather early this morning. The
northwest is noted both in water vapor imagery as well as with the
broad cluster of showers/occasional storms over far southwest IN and
southern IL. The trough between the two is allowing some showers
over our western counties this hour.

As the day wares on, the southern vortmax will meander into our
area. As we get even a little bit of heating, we should see numerous
showers and some storms pop up quickly around lunchtime and
continuing through the afternoon. Any location will have a fairly
high rain chance for the day, but overall amounts are not too
impressive. That said though, will have to watch for individual
stronger cells...as storm motions won`t be too fast. Otherwise, not
concerned about severe potential, given widespread cloud cover
helping limit instability.

Convective coverage will weaken quickly with sunset, though an
isolated shower/storm can`t be ruled out through the evening. After
highs in the mid to upper 70s today, look for lows to fall off into
the lower 60s for most tonight...even a few upper 50s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 308 AM EDT Tue May 13 2025

Wednesday we start to get out of the influence of the upper low as
it both fills in some and gets replaced locally by shortwave ridging
moving into the MS Valley. The better moisture and residue of that
low likely will spark more coverage of showers/storms in the
afternoon across the eastern half of the state, including our
Bluegrass counties. Activity should quickly die down by evening.

Thursday, that ridging will have its axis right over us. Soundings
show the strong cap aloft. Strong southerly surface flow through the
day likely will bring us our warmest day of the year so far.
Question mark is, are we too green to get that first 90? Raw NBM #`s
look good with 88 for SDF. Regardless, with dewpoints likely at
least in the mid to upper 60s Thursday afternoon, that day will be
muggy.

Speaking of that cap, convective temperatures are in the mid 90s,
per GFS forecast sounding at SDF Thursday afternoon. There`s quite a
bit of elevated above that cap as well as nice shear. As mentioned
in the previous discussion, the main concern will be, can something
developing upstream that organizes and pushes eastward within the
zonal flow aloft...or even southeastward along any gradients. If it
can, then it will have plenty of energy to gobble up as it
approaches...potentially Thursday evening. 00Z Euro hints at the
latter potential, with a northern IL/IN border line at 00Z laying
out east/west into SE IN by 06Z. Early NSSL ML severe guidance is
focused on Indiana with highest probs, though it does seem to have
an overly large area of relatively high risk through all of KY for
the late Thu period.

Friday`s activity will depend greatly on what does become of
activity Thursday evening. The more likely solution allows for new
development during the day...as the cap is not quite as strong as
Thursday`s. Shortwave energy riding in ahead of an upper trough by
later Friday afternoon should allow a complex of storms to develop.
Once again the question of severity comes in. If we go with a
cleaner solution to start with, then with another relatively hot and
muggy day, we`ll have plenty of instability to work with. That
energy aloft will promote the severe potential...with all hazards on
the table.

Saturday we should get a brief pause in the rain chances as the
Friday system stabilizes us a bit. Sunday could see another impulse
move through our briefly zonal flow aloft before ridging tries to
build in. NBM is not overly convinced in the strength of this
ridge...given some timing difference in the various model camps.
Thus a solution leaning closer to climo is favored.

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 119 AM EDT Tue May 13 2025

Broad upper low centered over the Tennessee Valley this hour will
wobble slowly northward into central KY today. Moisture under this
low could briefly bring some MVFR cigs early this morning before
additional scattered to numerous showers/storms develop this
afternoon. Coverage will die down in the evening. Winds will be
fairly weak through the period, but generally from the southeast and
south today.

&&

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

&&

$$

UPDATE...CSG
SHORT TERM...RJS
LONG TERM...RJS
AVIATION...RJS