-- Discussion containing changed information from previous version are highlighted. --
680
FXUS63 KJKL 221440 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1040 AM EDT Sat Jun 22 2024

.KEY MESSAGES...

- Hot and mainly dry weather will continue for most locations
  today. Afternoon heat indices will peak near 100 at some
  locations.

- The upper level ridge bringing our heat wave will move away from
  the region through Sunday, allowing more unsettled weather to
  take hold across the state.

- An approaching cold front will bring much needed rain to eastern
  Kentucky Sunday afternoon and night. A few storms may approach
  severe limits on Sunday with damaging winds the primary threat.

- Another round of showers and thunderstorms is expected from late
  Tuesday through Thursday, peaking during the day Wednesday as a
  shortwave passes over the state.

&&

.UPDATE...
-- Changed Discussion --
Issued at 1040 AM EDT SAT JUN 22 2024

14Z sfc analysis shows high pressure to the southeast of the area
still keeping things hot and humid, amid light winds. The morning
river valley fog has cleared with just some small cu starting to
develop in the southwest. Still expect a potential for spotty
showers or thunderstorms this afternoon - mainly southeast.
Otherwise, the hot and humid conditions will dominate along with
a tinge of haze in the air. Currently, temperatures are running in
the low to mid 80s most places while dewpoints are peaking in the
upper 60s to lower 70s. Some drying in the afternoon will keep
the heat from being overly oppressive, but heat indices will
still approach triple digits in a few spots at its worst this
afternoon. Have updated the forecast mainly to remove mention of
the morning fog and add in the current obs and trends for 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 813 AM EDT SAT JUN 22 2024

Minor forecast update was made to blend the latest T/Td/ and Sky
cover observations into the grids. Forecast still appears to be on
track for another hot and muggy day with just a possible shower
or storm in a few spots.
-- End Changed Discussion --

&&

.SHORT TERM...(This afternoon through Sunday evening)
Issued at 607 AM EDT SAT JUN 22 2024

At 9z, satellite imagery shows hints shallow fog through many of the
deeper river valleys. Otherwise, all is quiet across eastern
Kentucky with warm and muggy temperatures ranging from the mid 60s
in the cooler valleys to the lower 70s on the warmer ridges. The
latest analysis shows sprawling high pressure centered off the
North Carolina coast but still dominating the weather across much
of the eastern CONUS. Aloft, upper level ridging extends west-to-
east from the Desert Southwest to the Southeast US. To the north
of the ridge, a wavy boundary extends from southern New England
through the Southern Great Lakes and Midwest and then into the
Central High Plains. Shortwave troughing aloft is fostering weak
waves of low pressure along the boundary.

The upper level ridging will retreat westward today and tonight
while troughing deepens and shifts southeastward across the Great
Lakes/Ohio Valley on Sunday. At the surface, low pressure over
southcentral Nebraska/northwest Kansas early this morning will ride
along the surface boundary, crossing the Great Lakes tonight and
Sunday. In the wake of this stronger wave of low pressure, the
aforementioned surface boundary will make a more decisive
southward push toward the Ohio River on Sunday. Across eastern
Kentucky, weak height falls aloft combined with differential
surface heating may lead to sporadic convective initiation this
afternoon, particularly over the high terrain of far southeastern
Kentucky, though the 06z CAM guidance has trended less supportive
of this potential versus the 00z suite. The best chances for
convection during the short-term period will hold off until
Sunday when the upper level trough and cold front approach. With
plenty of instability, mid-level dry air and modest shear, cannot
rule out a few thunderstorms with strong to damaging wind gusts on
Sunday.

In more sensible terms, look for continued heat and humidity today
with just some sporadic relief this afternoon wherever showers and
thunderstorms manage to develop -- primarily south of the Mountain
Parkway and near/east of I-75. Temperatures are expected to once
again reach the lower to middle 90s at lower elevations under mostly
sunny skies. Tonight will again be warm and muggy with some patchy
fog in the typically prone locations along with lows in the mid 60s
to lower 70s. Sunshine will give way greater cloud cover and a
rising threat for showers and thunderstorms (~60% chance) on Sunday
as the cold front approaches. This will keep high temperatures
cooler, primarily in the mid 80s to around 90.

.LONG TERM...(Sunday night through Friday)
Issued at 547 AM EDT SAT JUN 22 2024

The upper level ridge will suppress southwestward during the
weekend, giving way to lowering heights across the Ohio Valley by
Sunday. This will be amplified by a shortwave turned upper level
low, which will move through the Upper Great Lakes Sunday afternoon
and night, then the Lower Great Lakes on Monday. A surface low will
be associated with this system, and will provide a cold front
stretching to the SW. The period will start off Sunday  night as the
front continues to sink southeastward through the JKL CWA. These
pops will linger in the far southeast part of the state through
Wednesday afternoon due to upslope flow, before finally departing.

By Monday night into Tuesday, the system will continue to exit to
the east, leaving KY in a brief area of high pressure at the
surface. Even so, with the latest NBM runs, it does try to put in
some isolated afternoon precip chances in the far SW CWA.
Unfortunately, in such a pattern without an upper level banked ridge
to keep it in place, these surface high pressure systems are short-
lived, as a shortwave begins to develop upstream in south-central
Canada by Tuesday morning. There is still some disagreement in the
models at this point, but they do at least both show precip along a
frontal boundary which will develop, connected to a surface low
pressure system co-located with the upper level low. While the ECMWF
doesn`t show precip from this system entering into KY until
Wednesday, the GFS brings two rounds, the first starting Tuesday
night. This seems to have been picked up by the NBM, which shows
slight chance pops overspreading the CWA Tuesday night. The rest of
the precip and frontal boundary should move through the state during
the day Wednesday. Will note that both the GFS and ECMWF also move a
secondary shortwave across Kentucky for Wednesday afternoon/night,
which will likely amplify the precip chances and QPF during this
time. This will be a slow moving system, so the front and lingering
precip could continue to impact the CWA through the day Thursday as
well before finally exiting to the east Thursday evening.

Surprisingly there is decent agreement at this point that another
round of surface high pressure may settle in across the Ohio Valley
for Friday, despite differing upper level solutions. As expected via
yesterday`s morning discussion, the slight chance pops were removed
by the NBM in the southern CWA. However, did note that the latest
ECMWF is snow trying to increase pops along the highest terrain now
Friday afternoon. We shall see if the NBM stays dry or if it trends
back towards isolated pops.

This high pressure will hold into the first part of Saturday, before
the next frontal boundary moves toward the state late in the day.

As for temperatures... This last week has been pretty stagnant,
temperatures in the 90s and humidity making it feel even hotter.
When we transition out of the ridging pattern, this also opens us up
to more temperature fluctuations. As frontal systems near, this will
increase SW flow across the state, providing warmer temperatures and
higher humidity. However, conversely, once the frontal system passes
through, this will bring some cooling NW flow to the region, albeit
even if it`s a few degrees and lower humidity. Tuesday is currently
the hottest forecasted day in the extended, as high pressure settles
overhead for much of the day giving maximum radiational heating,
despite having followed a cold frontal passage. Temperatures may
easily reach the low to mid 90s in many locations. Added humidity
will make it feel several degrees warmer than it already is,
reaching the upper 90s for many. The coolest day of the forecast
period is currently Thursday, behind the departing cold front and
with sharper height drops (per the ECMWF) allowing cooler air to
advect in from the NW. Either way, it`s late June...as long as the
sun is shining, it`s likely going to be a warm one. Even with the
cool down, temps will still top out in the mid and upper 80s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 813 AM EDT SAT JUN 22 2024

Any valley fog quickly burns off this morning, after which an
extensive cumulus field is expected to bubble up with diurnal
heating. A few showers or thunderstorms with sub-VFR conditions
are possible in far southeast Kentucky this afternoon but
probability of impacts at the TAF sites was too low to include at
this issuance. Valley fog is then expected to develop again
tonight in the deeper valleys away from the TAF sites. Otherwise,
VFR conditions are expected through the period, with light and
variable winds.

&&

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

$$

UPDATE...GREIF
SHORT TERM...GEERTSON
LONG TERM...JMW
AVIATION...GEERTSON