-- Discussion containing changed information from previous version are highlighted. --
524
FXUS63 KJKL 080437 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1237 AM EDT Wed May 8 2024

.KEY MESSAGES...

- Our main shower and thunderstorm potential lasts into early
  Thursday, with a smaller possibilities, at times, through the
  weekend.

- Severe thunderstorms are possible tonight through Wednesday
  night into Thursday morning. Large hail and damaging winds are
  the primary threats, but there is also a risk of tornadoes.
  Locally heavy rainfall could also lead to isolated flooding.

- Above normal temperatures are forecast through Thursday. A cold
  front should pass late in the week and turn temperatures below
  normal through the weekend.

&&

UPDATE Issued at 1210 AM EDT WED MAY 8 2024

Only now are we seeing a most distinct southward push to the
storms and outflow boundaries to the north. The latest CAMs bring
these into to the CWA between 04 and 06Z - running well ahead of
the current weather. Severe weather with all modes possible remain
a concern, but a lessening trend is noted with the current batch
of storms to the north. Have slowed their arrival down in the
grids before allowing it to blend with the CAMs during the early
morning hours. Have also included the current obs and trends for
the T/Td/Sky grids with this update. These adjustments have been
sent to the NDFD and web servers along with a freshening of the
zones and SAFs.

UPDATE Issued at 1015 PM EDT TUE MAY 7 2024

01Z sfc analysis shows a large area of low pressure moving through
the northern Ohio Valley placing Kentucky in its expansive warm
sector. Within this region, conditions are ripe for organized
storms - as well as for places lacking the better instability and
lapse rates of further north. In fact, even the showers have been
rotating and capable of blowing down trees, as seen out of
Natural Bridge State Park earlier in the evening. The radar has
gone quiet for eastern Kentucky for a time, but that lull is
expected to be temporary as a tornado watch extends into our
northwest 4 counties out of the Bluegrass. Better dynamics arrive
with a boundary dropping down towards midnight - per the CAMs and
radar trends. However, instability will be waning that long after
peak heating. This situation continues to evolve to the northwest
and as such, all modes of severe weather remain possible into the
late night hours. Have updated the forecast for the tornado
watches and to fine tune the PoPs through the night on account of
the latest CAMs guidance and current radar trends. Did also
include the most recent obs and tendencies from the T/Td/Sky obs
for those grids with this update. These forecast adjustments have
been sent to the NDFD and web servers along with a freshening of
the zones, HWO, and SAFs.

&&

.SHORT TERM...
-- Changed Discussion --
(This evening through Wednesday night)
Issued at 431 PM EDT TUE MAY 7 2024

A warm front has lifted northward toward the Great Lakes and a
cold front is pushing into the Midwest this afternoon. We have
been watching a line of storms track across parts of the CWA all
afternoon. As these storms have slowly worked east, the effective
shear has been on the increase though the afternoon. This has led
to some isolated strong to severe storms this afternoon. Even so
these will quickly move east this afternoon and push into West
Virginia. The question that remains is how much if any additional
storms develop this afternoon. The CAMs so far have been quite
lack luster with additional storms including the HRRR. Even so,
this will have to be watched closely over the late afternoon and
evening hours, as effective shear of 50-60 knots is possible, but
instability is in question. Now the CAMs are in reasonable
alignment with a line of convection later tonight into Wednesday
morning. This is expected to move into the I-64 area around 05-06Z
and then moving into far southeast Kentucky around 11-12Z.
Confidence in severe weather will be a bit lower that late tonight
as we lose the better instability, but upper dynamics remain
stout.

Wednesday is much more interesting and concerning in terms of
severe weather potential. The previously mentioned line of
convection will settle across the TN Valley in the morning.
Meanwhile, a new low pressure will develop across the Plains and
push into the Middle Mississippi River Valley. This will help lift
a warm front north across the lower Ohio Valley. The question is
how far north does this warm front push. There is also indication
of a moisture boundary that pushes northward out of East and
Middle Tennessee as seen in the Theta-E fields. That being said,
several of the CAMs are highlighting the area of increasing
moisture pushing out of TN being a player for convection
Wednesday, with storm cells forming out ahead of a line of
convection. The environment is characterized by MLCAPE of
2000-3000 J/kg and effective shear of 40-50 knots. This would be
quite ample for rotating storms in the form of supercells. Now as
you move through the afternoon into the early evening the shear
increases, with effective SRH values increasing to 300-500 m2s-2.
Now the uncertainty remains with how this evolves, as early
morning convection will set the stage for the remainder of the
day. If storms can develop in this environmental space we could
see all hazards including large hail, severe winds gusts, and even
a few tornadoes. There is also this risk of flash flooding
Wednesday into Wednesday night. The issue with this is it will
take getting multiple rounds of convection given the antecedent
dry weather. By Wednesday night, the convection will dive
southward and eventually out of the area late Wednesday night.
This will lead to a decrease in severe weather risk, but some
isolated lingering flooding is not out of the question depending
on where the rain falls going through the day Wednesday.

.LONG TERM...(Wednesday night through Monday)
Issued at 411 PM EDT TUE MAY 7 2024

The period will start with a low pressure system traversing just
north of the Ohio River, dragging a cold front through far eastern
Kentucky before exiting to the east late in the day. Showers and
thunderstorms will be ongoing @12Z in the morning along this
boundary, especially in the far SE. Models have some lingering
chance pops across the CWA throughout the day, finally exiting
Friday night. This will also be our last warm day for a bit, as post
frontal temperatures cool things down on Friday.

Unfortunately, this won`t be the last we see of the pops. Although
the surface system is well to our east, an upper level shortwave
trough will pass through Friday, bringing another round of scattered
pops to the region. Every model has a different solution for this
system, so kept with the chance pops of the NBM. This shortwave will
rotate back out of the area by Friday night, giving way to clearing
skies. Flow aloft will also be more northerly, which will help to
advect cold air into the region. Temps will drop into the low to mid
40s, with coolest temperatures likely in the deeper valleys.

Saturday will be similar to Friday, with yet another shortwave
passing through the Great Lakes and Ohio Valley. This time models
drop it a bit farther south, with scattered to likely pops
throughout the day. Both of these days, Friday and Saturday, should
be more pop up convection without any real forcing to lead to a
severe threat. By Saturday night, the shortwave will have exited
according to the latest ECMWF, giving way to high pressure and even
strong NW flow into the region. This will result in even cooler
temperatures, and also set the stage for more robust ridge/valley
differences. This clearing and cool night is also what the NBM
picked up on. The wrench, however, is that the latest GFS shows this
shortwave morphing into a larger troughing pattern, by which precip
will continue to impact the state both Saturday night and Sunday.
Meanwhile, the ECMWF shows high pressure across the region with dry
weather and likely clear skies. Kept with the NBM for now which
shows only a slight chance of pops in some locations during the day
Saturday, but otherwise keeps the weather dry.

Models continue to diverge in their solutions after this point, with
very little confidence in the forecast. Kept with NBM which shows
isolated to scattered pops throughout the rest of the period. This
will likely change as models come into better agreement, but given
the lack of confidence, had no need to change the NBM at this time.
The NBM also shows a warming trend through the weekend, but again,
with the uncertainties in the forecast, expect the temperatures may
also fluctuate as well.
-- End Changed Discussion --

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 820 PM EDT TUE MAY 7 2024

All quiet on the aviation front this evening ahead of renewed
storm development expected towards midnight north and carrying
south through the night. This round of convection could also lead
to another period of lower CIGs and visibilities, but still lots
of questions on how this will evolve. Then we should see yet
another lull in activity through the morning and early afternoon.
Overall, a fair amount of uncertainty remains for when and how
this activity evolves and moves through the area. The winds will
remain out of the south and southwest at 10 knots or less through
the period, but some brief higher gusts are always possible with
any thunderstorm activity.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...DJ
LONG TERM...HAL
AVIATION...DJ/GREIF