St. Matthews, Kentucky 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

630
FXUS63 KLMK 151952
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
352 PM EDT Thu May 15 2025

.KEY MESSAGES...

*  Strong to severe thunderstorms are possible late this evening
   into the overnight hours. Confidence in storms remains low, but
   any storms that develop will be capable of producing large hail
   and locally damaging winds.

*  Greater chance of severe storms is Friday evening into Friday
   night. All severe weather hazards are on the table, including
   damaging winds, large hail, tornadoes, and torrential rainfall. A
   few strong tornadoes and instances of very large hail are
   possible.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 352 PM EDT Thu May 15 2025

So far this afternoon, a summer-like air mass has spread into the
Tennessee and Ohio Valleys as temperatures are in the low-to-mid 80s
with dewpoints in the upper 60s and lower 70s. The surge in
temperatures and moisture has come from deep southwest flow between
a negatively-tilted trough which is morphing into a closed low over
the Red River Valley of the North and ridging over the southeast US.
Pressure falls to the north and west of the region have resulted in
breezy S/SW winds this afternoon, and 20-25 mph gusts should
continue into this evening.

A very active stretch of weather is expected over the next 36 hours
as the upper level disturbance to the northwest moves to the east.
This afternoon and evening, our first chance of strong to severe
storms will come from an ongoing cluster of cells over northern AR
and southern MO. As these storms move to the east, they should
encounter an increasingly unfavorable thermodynamic profile for sfc-
based convection, and should also outrun the best forcing which will
be near the sfc cold/occluded front and upper-level jet core over
the mid- and upper-MS valley. Latest ACARS soundings show a warm
capping layer between 850-700 mb, with surface-based LFCs up around
the 700 mb level. However, the cluster of cells to our west could
sustain itself if it develops a strong cold pool which could lift
otherwise capped parcels to the LFC, and DCAPE ahead of the ongoing
storms is fairly high (800-1200 J/kg). An elevated mixed layer atop
the capping inversion has 8.5-9 degree C/km lapse rates within it,
and a pool of around 3000 J/kg of MUCAPE would be available to
parcels which break the cap. Would expect damaging winds and large
hail to be the main threats with any storms this evening, and even
if storms dissipate, gusty winds from the decaying cold pool/outflow
would still be possible. This evening`s threat should move quickly
through the area between around 7 PM and midnight EDT.

There should be a few hours of a lull in convective activity during
the late evening and early overnight hours, though hi-res guidance
shows another wave of storms trying to develop between 2-4 AM EDT.
These storms are likely developing as a mid-level jet exit region
noses across the lower Ohio Valley. Sounding profiles show continued
instability aloft, though there should be a considerable amount of
stability within the boundary. Accordingly, would expect mainly
elevated storms late tonight into early Friday morning, with large
hail as the primary threat. Any convection which develops should
move off to the east and dissipate a few hours after sunrise Friday,
and another lull is expected Friday morning.

Any lull in convective activity Friday morning will give the
atmosphere a chance to reload, resulting in instability and shear
parameters which should be even more favorable for severe weather
Friday afternoon and evening. As the upper closed low over the upper
Midwest pivots to the east on Friday, troughing over the mid-MS
valley should amplify, with height falls taking place over the
region during the afternoon and evening hours. Near the sfc,
increasing south-southwest flow should send a convectively-enhanced
frontal boundary northward through the area tomorrow, with
temperatures recovering into the mid 80s and dewpoints rising into
the upper 60s and lower 70s. This should support MLCAPE values on
the order of 2500-3500 J/kg, sufficient for explosive convection
Friday afternoon and evening. Deep-layer shear on the order of 55-60
kts will help with storm organization Friday afternoon and evening,
and a combination of discrete cells and bowing segments would be
expected. Hi-res guidance has been fairly consistent in showing
storms growing upscale into one or several large bowing lines, and
DCAPE values of 1000-1200 J/kg support SPC`s wind probabilities
driving the moderate risk for tomorrow. Mid-level lapse rates will
still be around 7.5 degrees C/km tomorrow afternoon, so the large
hail threat will be supported if/while cells remain somewhat
discrete. Looking at the hodograph and low-level shear profiles,
while there is some curvature in the low-level wind field,
relatively veered near-sfc winds will limit storm-relative helicity
values. With this being said, any supercells which may develop would
have an increased threat to produce strong tornadoes, and it is also
possible that spin-ups could develop along the leading edge of any
MCS/QLCS structures.

Multiple waves of storms are possible Friday afternoon and evening,
with storm coverage gradually winding down and pushing into eastern
KY after midnight Friday night. All in all, the instability and
shear parameters in place (especially tomorrow) support a
significant severe weather event across the Ohio Valley. Make sure
to have multiple ways to receive warnings and a plan in place should
a warning be issued tonight through tomorrow night!

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 352 PM EDT Thu May 15 2025

By Saturday morning, the actual cold front will be pushing through
the area with most of the showers and storms exiting to our east.
The associated upper low will be over the Great Lakes with the
longwave trough axis extending south over the OH and TN Valleys
before flattening out against the subtropical ridge over the Gulf.
Weak CAA behind the front will result in climatological normal
temperatures for the weekend with highs in the mid to upper 70s to
lower 80s accompanied by breezy WSW winds on Saturday. Overall, most
will experience a fair weather weekend.

Southern KY will see a slight chance of showers on Sunday as the
southern edge of the new airmass begins to lift northward due to the
next low pressure system strengthening over the Central Plains. This
will begin another period of unsettled weather as we enter the
beginning of the new work week.

By Monday, a warm front will begin lifting across the region
resulting in warm and moist air advection, as PWATs surge into the
upper percentiles of SPC`s sounding climatology. Models tend to
agree on convection from our west moving into our area by Monday
morning with another round Monday evening. The warm front appears to
stall over the region, prolonging our shower and storm chances into
Tuesday and Wednesday before the occluded low pushes through on
Wednesday. With model soundings advertising sufficient instability
and ML guidance also showing enhanced severe probabilities, severe
weather can not be ruled out. Details remain hazy this far out, but
will continue to monitor closely with subsequent forecast packages.
Stay tuned.

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 148 PM EDT Thu May 15 2025

A narrow band of high-MVFR/low-VFR cumulus is passing across the
area this afternoon, with ceilings VFR outside of this short-lived
band. Gusty south-southwest winds are expected during the rest of
the afternoon, with 20-25 kt gusts likely. This evening, we`ll see
remnants of upstream storms move through the area between 23-04Z. By
the time it reaches area terminals, we should see mainly scattered
showers, though some showers could have gusty winds.

Overnight, mainly VFR conditions are expected with convective debris
clouds from upstream storms. There is a low confidence chance for
TSRA around 06-10Z across the northern terminals; we`ll keep mention
to PROB30 at this time. With a LLJ overhead, LLWS is possible;
however, it is uncertain whether or not winds will continue to mix
down to the surface.

Friday morning, another layer of high MVFR/low VFR stratocu are
expected to develop, with winds picking up during the mid-to-late
morning hours.

&&

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

&&

$$

SHORT TERM...CSG
LONG TERM...CG
AVIATION...CSG