932
FXUS63 KLMK 031048
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
648 AM EDT Thu Apr 3 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

* HISTORIC AND POSSIBLY LIFE THREATENING FLOODING AS A RESULT OF
  NUMEROUS THUNDERSTORMS COMING THROUGH THE OHIO VALLEY TODAY
  THROUGH THE WEEKEND

* SEVERE WEATHER THREAT CONTINUES TODAY THROUGH SATURDAY WITH
  HAIL, WIND AND TORNADOES POSSIBLE IN THE STRONGEST STORMS

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 251 AM EDT Thu Apr 3 2025

07z upper air and surface analysis shows a large and intense squall
line extending from the Great Lakes, through central Kentucky and
back south and westward through central Arkansas.
The line of storms is aided by intense lift from a 130 kt jet in the
Great Lakes and a 50-70 kt low level jet bringing in moisture from
the Gulf. Kentucky mesonet sites just since midnight have shown a
swath of 0.5-1.5 inches of rain and total rainfall amounts in the
last 24 hours have already amounted 1-2 inches of rain from north
central through southwest Kentucky.
This rain is the start of what is to be several days worth of rain
which as we go through the event could lead to catastrophic
flooding.

Throughout today a stalled frontal boundary through central Kentucky
will combine with robust gulf moisture from surface winds out of the
south and an upper level pattern which will continue to bring
moisture in from the southwest.  Thunderstorms look to be constant
throughout the day with rainfall rates at 0.25-0.5 inch per hour or
more at times.  Later this afternoon a warm front in Tennessee will
move northward into south central Kentucky and with robust CAPE
values and wind shear in the vicinity of the front we could once
again see strong to severe thunderstorms mainly through southern
Kentucky and northern Tennessee.  Hail, wind, and tornadoes are all
possible later this afternoon.  ECWMF and NAEFS PW values during the
day hover around 1.5 inches meaning these storms will have a lot of
moisture to ring out over a long period of time.

Tonight into Friday as the large longwave trough and closed low in
the desert southwest intensifies it should cause the upper level
flow to lift slightly northward and take the train of heavier rain
slightly northward into Indiana and Illinois and we could even see a
break in the rainfall activity in southern Kentucky for a time.  NBM
probabilities of seeing 12 hour rain greater than 0.5 inch during
the day on Friday are highest in southern Indiana (50%) and lowest
in southern Kentucky (~10%).  The severe weather threat also shifts
to the north and west with areas from southwest Indiana through
western Kentucky having the higher threat for strong storms.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 251 AM EDT Thu Apr 3 2025

The slow moving trough in the desert southwest moves eastward during
the weekend and this will setup a long duration heavy rainfall event
through the Ohio Valley especially from Saturday night through
Monday morning.  EFI forecasts shows good ensemble agreement in the
Euro models of a widespread high precipitation event as confidence
is around 90% and shift of tails at 1 indicating better confidence
in an extreme event.  THis rain combining with the rain received
already from Wednesday night through Friday is having total forecast
amounts at around 8-9 inches widespread through central Kentucky and
possibly locally higher amounts.  NBM probabilities of receiving at
least 5 inches of rain from the event are widespread 60-80% across
central Kentucky.  It can`t be said enough that if you are in flood
prone areas be prepared to move to higher ground quickly.  The
longwave trough finally exits from west to east during the day on
Sunday and we should see the rain finally end for the area by Monday
morning.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 646 AM EDT Thu Apr 3 2025

Light to moderate rain showers will continue across the area, with a
mix of VFR and MVFR ceilings across the area. May see a bit of a
break in the rain through the mid to late morning hours, however
another wave arrives through the afternoon into the evening. Added
prob30 mention for some heavier showers and storms during this time.
Will keep off an on showers going through the end of the TAF cycle,
along with lowering ceilings into to low MVFR or even IFR range.
Surface winds will be quite erratic given the wavering frontal
boundary over the area. Also mentioned a possible LLWS scenario
again tonight down near BWG. The rest of the TAF sites should be too
far north to get into the low level jet quite as well.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flood Watch through Sunday morning for KYZ023>043-045>049-
     053>057-061>067-070>078-081-082.
IN...Flood Watch through Sunday morning for INZ076>079-083-084-
     089>092.

&&

$$

SHORT TERM...WFO DDC
LONG TERM...WFO DDC
AVIATION...BJS