-- Discussion containing changed information from previous version are highlighted. --
705
FXUS63 KJKL 230557 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
157 AM EDT Mon Sep 23 2024

.KEY MESSAGES...

- A potential for showers and thunderstorms will persist through
  much of this week.

- After high temperatures well into the 80s to near 90 earlier
  today, readings will trend downward through the week.

&&

.UPDATE...
-- Changed Discussion --
Issued at 157 AM EDT MON SEP 23 2024

Additional shower and thunderstorm activity redeveloping upstream
of our forecast area. Updated PoPs to cover trends being seen in
regional radar mosaic. Otherwise tweaked grids towards latest
surface obs. No significant changes other than to the PoPs, mainly
for our Bluegrass counties and our far southwest where overnight
convection continues to impact those areas. Updated zones and grid
have been issued.

UPDATE Issued at 1045 PM EDT SUN SEP 22 2024

No significant changes to the forecast with mainly the adjustments
to the PoPs and Wx grids per the latest radar and CAMs trends. The
latest obs and tendencies were included in the T/Td/Sky grids.
These minor adjustments have been sent to the NDFD and web servers
along with a freshening of the zones and SAFs.

UPDATE Issued at 910 PM EDT SUN SEP 22 2024

00Z sfc analysis shows eastern Kentucky southeast of a slowly
approaching cold front. This allowed temperatures to approach
record highs in the upper 80s to lower 90s for most of the area
this past afternoon. This also allowed instability to build and,
combined with relatively high PWs, resulted in slow moving and
merging thunderstorms affecting mainly the area east of Corbin
into the start of the evening. The initial merger was strong
enough to blow down a tree on the powerlines near Rockholds. This
cell then slowed to a crawl and brought heavy rains as it back-
built for the next hour or so. This resulted in heavy rain and
water flowing across highway 1064 in that same area. Now the
convection in the south has mostly faded out while lighter amounts
are streaming over the northern parts of the area. Currently,
temperatures are running in the upper 70s to lower 80s outside of
the rain areas and in the upper 60s to lower 70s within it.
Meanwhile, amid light winds away from any convection, dewpoints
are in the mid 60s to lower 70s, most places. Have updated the
forecast to add in the latest obs and trends for the T/Td/Sky
grids as well as adjusting the PoPs through the rest of the night
per the current radar and tendencies of the CAMs. These
adjustments have been sent to the NDFD and web servers along with
a freshening of the zones and SAFs.
-- End Changed Discussion --

&&

.SHORT TERM...(This evening through Monday night)
Issued at 302 PM EDT SUN SEP 22 2024

The frontal boundary that had been draped across far northern
Kentucky has begun to move north into Ohio and West Virginia as warm
advection increases across central and eastern Kentucky. Upstream
over the mid-Mississippi River Valley, a disturbance continues to
move east toward eastern Kentucky, and will be the primary trigger
for shower and thunderstorm development later this afternoon into
the early evening. The greatest instability will be over the
southwestern quadrant of the forecast area, but there will be
sufficient instability for thunderstorms anywhere across the
forecast area into this evening.

Additional rounds of showers and thunderstorms are possible into the
overnight tonight, with the greatest instability over the southern
half of the forecast area, as an active jet stream continues to
usher disturbances across Kentucky. With at least broken cloud cover
and continued warm advection, expect little in the way of any ridge-
valley temperature differences. Fog will be dependent on the amount
of cloud cover.

A stronger southwesterly jet stream develops over Kentucky Monday,
and this combined with stronger moisture advection into the area
will result in MLCAPE values approaching 1500-2000 J/kg by early
to mid-afternoon. The increasing shear and sufficient instability
will mean a Marginal Risk for severe thunderstorms, with gusty
winds and large hail the primary severe threats. A mitigating
factor may be that the better shear does not arrive until after
sunset, when instability becomes more limited, especially if
earlier convective overturning has resulted in stabilization of
the atmosphere. With the strong upper trough still approaching
from the west, showers and thunderstorms are likely to continue
through the overnight Monday night. Despite the recent dry
conditions, isolated/localized instances of high water are
possible where storms train across particular area.

.LONG TERM...(Tuesday through Sunday)
Issued at 335 PM EDT SUN SEP 22 2024

The latest run of the GFS has an active flow pattern aloft across
the CONUS. A trough of low pressure is currently forecast to be
coming onshore in central California on Tuesday, with another
well developed trough positioned over the northern Plains.
Another persistent trough is still in the picture off the eastern
seaboard to begin the period on Tuesday, but looks like it will be
a bit further offshore. Another feature of great interest in the
extended will be the development of a tropical cyclone in the
southern Gulf of Mexico toward the middle of the week. Based on
the latest model runs, it is looking more and more likely that a
tropical cyclone will form somewhere over the Gulf of Mexico, and
perhaps rapidly intensify over those extremely warm waters as it
moves northward toward the central or eastern Gulf Coast. There is
quite a bit of uncertainty regarding how this system will evolve
and progress once it moves inland, should it indeed form, and how
it might affect the weather of eastern Kentucky, so we`ll be
watching this particular feature quite closely over the coming
days.

Our first weather maker, however, will be the northern Plains
trough and frontal systems that will be extending from it. The
latest models suggest that a weak shortwave may also form along
the leading edge of the approaching trough on Tuesday. This, along
with the passage of a surface cold front, will act as sources of
lift to support shower and storm formation across our area.
Showers and storms will move in from the north and west, as the
cold front moves through. With a potential tropical cyclone moving
in from the south, the front could slow up greatly, or even stall,
over our area. If this scenario occurs, it would mean an extended
period of light to perhaps moderate rainfall across our area
Tuesday through Thursday. As much one to three inches could fall
over the area during that three day period.

With extensive cloud cover and persistent precipitation expected
across our area for at least a few days, temperatures should be
near normal during the extended, and perhaps even a few degrees
below normal at times. Daily highs will range from the low to mid
70s on the coolest days, to the mid to upper 70s or even lower 80s
on the warmest day. As far as hazards go, we`ll be watching
closely for the potential for locally heavy rainfall during the
Tuesday through Thursday time frame, when the most widespread and
persistent rain is expected to occur. There is also a marginal
risk, or 10% probability, that severe storms will occur on Monday,
as the cold front makes its initial push through the region.

&&

.AVIATION...
-- Changed Discussion --
(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 157 AM EDT MON SEP 23 2024

Surface cold frontal zone is draped along the Ohio River just to
our northwest. Subtle disturbances continue to track through the
Ohio Valley, producing additional shower and thunderstorm
activity, some of which is redeveloping just upstream of our
forecast area at TAF issuance time. The strongest of this activity
will impact mainly KSYM, KSME, and possibly KLOZ. Otherwise, some
light showers are also moving through the area. Thus far activity
could be described as sporadic and diverse in nature, making it
more of a forecast challenge with respect to predominant weather
groups at any given location. Overall this leads to a lower than
normal confidence level with respect to flight categories at any
given period of time. In general, feel VFR conditions are a
reasonable bet, but there will be drops in flight conditions,
particularly VSBYS where showers and thunderstorms do pass. Model
guidance, and especially higher resolution short term convective
allowing models show an overall downward trend in activity through
the remainder of the overnight. Thereafter, expect convection may
redevelop and overspread eastern Kentucky from southwest to
northeast by around mid-afternoon. Once this activity dies down,
fog will likely redevelop late in the period. Winds will be light
and variable through the period, except in the vicinity of any
thunderstorms where winds could become gusty.
-- End Changed Discussion --

&&

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

$$

UPDATE...RAY
SHORT TERM...CMC
LONG TERM...AR
AVIATION...CMC/GREIF/RAY