Severe Thunderstorm Warning 134, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
325 PM EDT Tue Apr 29 2025

.KEY MESSAGES...

*  A cold front will bring showers and storms to the region today
   and tonight. The most likely time for severe storms will be this
   afternoon and early this evening. Strong gusty winds and hail
   will be the main threats.

*  Showers and thunderstorms will continue into Wednesday as
   Tuesday's cold front stalls over the area. Strong to severe
   isolated storms will be possible.

*  Additional strong to possibly severe storms are possible for
   Thursday as another cold front approaches the area. Rain lingers
   into Friday.

*  Dry and sunny weather is forecast to return for the weekend.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 325 PM EDT Tue Apr 29 2025

The low pressure system is currently located over the northern Great
Lakes and will continue northeast in to southern Canada. The cold
front is draped through central IN and southern IL. The cold front
will continue to push southeast through the afternoon and evening
before stalling in the vicinity of the Ohio River.

For the remainder of the afternoon, isolated to scattered storms
will develop and move ENE through the region. There is a week
boundary over southern Indiana from earlier morning convection that
is allowing for the needed lift to develop storms. As storms create
their own boundaries, new cells begin to form. These storms are
driven by reaching convective temperatures (~80F), ample instability
(2500-3000 J/kg), plentiful moisture (1.5-1.8 PWATs), enough shear
to support storms over southern Indiana (30-35kts of 0-3km Bulk
Shear along the Ohio and north), a 30-40kt LLJ brushing southern
Indiana (which is increasing low level shear), steeping lapse rates,
a well developed Cu field. This environment will support strong
storms with a wind, hail, and lightning threat. Greatest threat area
is over the Ohio River and north.

In the evening, the cold front will slow as it enters the region. A
line of thunderstorms will be out ahead of this front, bringing
another wind, hail, and lightning threat. This line of thunderstorms
is currently over southern MO and southern IL moving into western
KY. There is a severe thunderstorm watch out until 1Z for southern
Indiana and 3 counties in our NW KY area. This line will progress
through the region, possibly outrunning the better forcing on the
cold front. Therefore, we will likely see slowly weakening storms
over the eastern portion of the region. The main severe threat
timing will be now through 10PM EDT with weaker isolated-scattered
storms lasting through most of the night in the far SE.

The stalled front will remain over the Ohio River through Wednesday.
Troughing over the Desert SW will begin to swing into the southern
Plains and develop a low pressure system. This will then lead to an
intensifying ridge over the region on Wednesday. This will help to
keep the region drier, through most of the day. There is a scattered
chance for storms in the late afternoon as instability increases and
the environment destabilizes. Main threats would again be wind and
hail. High temperatures on Wednesday will be in the low-mid 80s
south of the front and the upper 70s north of the front.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 325 PM EDT Tue Apr 29 2025

===== Wednesday Night - Thursday =====

By Wednesday night, the frontal boundary will be parallel but north
of I-64, shifting the main focus for PoPs to be across southern
Indiana and north-central Kentucky. A low level inversion will be
setting up as diurnal heating is lost, which will help keep severe
concerns limited as we get into the evening hours. A lull in precip
is possible overnight for mainly central Kentucky folks, though PoPs
across the Bluegrass and southern Indiana areas are 25% or less.

On Thursday, the upper ridge will be shifting eastward as an upper
shortwave trough pivots from the Ozarks to the lower Great Lakes.
The stalled boundary from Wednesday night will push north overnight,
and will be near the Great Lakes by sunrise Thursday. This will help
open up the warm sector across our area ahead of another approaching
cold front. The primary sfc low will track from northern Missouri to
the Great Lakes, with the cold front trailing to the south through
the Midwest. Ahead of the front's arrival, strengthening LLJ will
increase WAA and moisture transport into the area, helping to raise
PWATs up to 1.30-1.40". Sfc temps will likely reach the lower 80s,
and with dewpoints climbing into the lower 60s, the environment will
be primed for afternoon destabilization ahead of the front. Model
soundings suggest SBCAPE values could reach 2000 J/kg, but the main
uncertainty remain how much shear will be present. Guidance
certainly agrees on at least scattered strong storms to be possible
Thursday afternoon and evening.

Shower and storm chances will continue into the evening and
nighttime hours, but coverage may end up being more isolated as
instability decreases due to loss of daytime heating.

===== Friday =====

The cold front is expected to pass through the area during the
daylight hours on Friday. While best chances for showers and storms
will be along and ahead of the front, PoPs will linger through much
of the day as we deal with upper shortwave energy. Showers and
garden variety storms are possible throughout the day. With most of
the area post-frontal, shear parameters will be weaker, and
instability will not be quite as strong as in previous days.

Light showers are possible through Friday night as the upper
shortwave struggles to push east of the area.

===== Weekend - Early Next Week =====

Global deterministic guidance has diverged some for the weekend,
which has led to some uncertainty with this forecast. The GFS
suggests the upper shortwave axis will clear the area by Saturday
morning, making way for high pressure to quickly filter in and dry
weather for the weekend. The ECMWF is quite different, with it
holding the upper trough axis across the area through the weekend
and into early next week, which would favor continued PoPs.

Will continue to lean on the upper ridge pushing the shortwave east
this weekend, resulting in a dry forecast for Saturday afternoon and
especially Sunday, but confidence is limited given the model
variability. Dry wx continues into Monday and Tuesday.

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 106 PM EDT Tue Apr 29 2025

Main impact: Afternoon/evening TSRA
Confidence: High in the occurrence of TSRA, medium in the exact
timing of TSRA

Today a cold front will approach from the west, reaching the Ohio
River early this evening. Organized storms will be ahead of the
front in the 17-01Z time range. Some of these storms could be strong
and cause chaotic winds and significantly reduced visibility for a
brief time as they move over any given location. Showers and a few
thunderstorms will then continue into the late evening hours as the
cold front stalls across the region. Additional showers will be
possible in the early morning. CIGs will likely deteriorate to
low-end MVFR or high-end IFR after 6Z.

&&

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

&&

SHORT TERM...SRW
LONG TERM...CJP
AVIATION...SRW

Hazardous Weather Outlook
National Weather Service Louisville KY
328 PM EDT Tue Apr 29 2025

KYZ026>043-045>049-053>057-061>067-070>078-081-082-301930-
Ohio-Grayson-Hardin-Bullitt-Jefferson-Oldham-Trimble-Henry-Shelby-
Franklin-Scott KY-Harrison KY-Spencer-Anderson-Woodford-Fayette-
Bourbon-Nicholas-Nelson-Washington KY-Mercer-Jessamine-Clark KY-
Larue-Marion-Boyle-Garrard-Madison-Butler-Edmonson-Hart-Green-Taylor-
Casey-Lincoln-Logan-Warren-Simpson-Allen-Barren-Monroe-Metcalfe-
Adair-Russell-Cumberland-Clinton-
328 PM EDT Tue Apr 29 2025 /228 PM CDT Tue Apr 29 2025/

This Hazardous Weather Outlook is for portions of southern Indiana
and central Kentucky.

.DAY ONE...Tonight.

Storms arrive this afternoon and evening, with severe storms
possible. Damaging gusty winds will be the main threat, with large
hail and an isolated tornado secondary threats. The storms will
produce heavy downpours as well.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Periods of thunderstorms will continue Wednesday through Friday.
Brief localized flooding will be possible under stronger storms.
Isolated strong to severe storms may also be possible again on
Wednesday and Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed.

GENERAL STORM MOTION OF THE DAY:

Storms this afternoon and evening will move towards the east
northeast around 30 to 40 mph.

Any users of this storm motion must be aware that thunderstorm activity
can be erratic and constantly evolving.  Please use this with caution
and be prepared for changing conditions.

&&

More information, along with other weather, hydrological and
climate information can be found, at weather.gov/louisville.

INZ076>079-083-084-089>092-KYZ023>025-301930-
Orange-Washington IN-Scott IN-Jefferson IN-Dubois-Crawford-Perry-
Harrison IN-Floyd-Clark IN-Hancock-Breckinridge-Meade-
328 PM EDT Tue Apr 29 2025 /228 PM CDT Tue Apr 29 2025/

...SEVERE THUNDERSTORM WATCH 189 IN EFFECT UNTIL 9 PM EDT /8 PM CDT/
THIS EVENING...

This Hazardous Weather Outlook is for portions of southern Indiana
and central Kentucky.

.DAY ONE...Tonight.

Storms arrive this afternoon and evening, with severe storms
possible. Damaging gusty winds will be the main threat, with large
hail and an isolated tornado secondary threats. The storms will
produce heavy downpours as well.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Periods of thunderstorms will continue Wednesday through Friday.
Brief localized flooding will be possible under stronger storms.
Isolated strong to severe storms may also be possible again on
Wednesday and Thursday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures.

GENERAL STORM MOTION OF THE DAY:

Storms this afternoon and evening will move towards the east
northeast around 30 to 40 mph.

Any users of this storm motion must be aware that thunderstorm activity
can be erratic and constantly evolving.  Please use this with caution
and be prepared for changing conditions.

&&

More information, along with other weather, hydrological and
climate information can be found, at weather.gov/louisville.

SRW/CJP

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