-- Discussion containing changed information from previous version are highlighted. --
193
FXUS63 KJKL 210714
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
314 AM EDT Fri Jun 21 2024

.KEY MESSAGES...

- Hot and mainly dry weather will continue through the weekend.
  Afternoon heat indices will peak near 100 at some locations.

- The upper level high/ridge bringing our heat wave will weaken
  during the weekend and eventually allow a cold front to at least
  approach the area, with the PoPs peaking in the 40 to 60 percent
  range Sunday night ahead of the front.

- Uncertainty still exists concerning the progress of the cold
  front next week and whether or not a substantially drier air
  mass will arrive. For this package, Monday night through Tuesday
  afternoon were left dry, but with precipitation and
  thunderstorm chances returning late Tuesday night and continuing
  through Wednesday night.

&&

.UPDATE...
Issued at 1130 PM EDT THU JUN 20 2024

No significant changes to the forecast with just the inclusion of
the latest obs and trends for the T/Td/Sky grids with this update.
These minor adjustments have been sent to the NDFD and web
servers along with a freshening of the zones and SAFs.

UPDATE Issued at 750 PM EDT THU JUN 20 2024

23Z sfc analysis shows high pressure in place over the area
keeping the winds light and weather dry. Mainly just some cu are
continuing to clear out this evening while the heat of the day is
only slowly abating. Currently, temperatures are running in the
mid to upper 80s most places though a few of the valleys have
fallen to the upper 70s. Meanwhile, dewpoints are holding steady
in the upper 60s to lower 70s - in general. Have updated the
forecast mainly to 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.

&&

.SHORT TERM...
-- Changed Discussion --
(This evening through Friday night)
Issued at 345 PM EDT THU JUN 20 2024

Current surface analysis continues to show the surface high that`s
been parked over the eastern CONUS for the last several days. To the
north, a wavering stationary boundary will fire a few thunderstorms
across the Great Lakes but that boundary will remain well to the
north having no impact on the Commonwealth. Otherwise, a widespread
cumulus field has developed with temperatures warming into the upper-
80s to low-90s across eastern Kentucky.

This will persist through the overnight with cumulus field giving
way to mostly clear skies. Overnight, those clear skies will allow
for radiative cooling to occur and the development of river and
sheltered valley fog. Some of this fog will be thick and will
insulate the valleys to mid-60s. Fog will burn off early Friday
morning before another hot day expected. Similar conditions are
expected for Friday with highs in the upper-80s to low-90s. A bump
in moisture due to an approaching 850 feature will help to bring heat
indices back to approaching 100 for the afternoon. The approaching
850 wave would be the current invest 92L that the NHC is looking at
for tropical development. This low is forecast to move toward the
Florida/Georgia coast and inland through the day Friday. The rain
isn`t expected to have an impact on eastern Kentucky but a surge in
moisture and increasing clouds are expected for the region. Those
high clouds will hang around through the afternoon and overnight
Friday into Saturday but the dominate high pressure center we`ve
been under will continue to remain in place.

.LONG TERM...(Saturday night through Thursday)
Issued at 314 AM EDT FRI JUN 21 2024

We finally transition out of a dominating upper level ridging
pattern by the extended portion of the forecast, though it does look
to make it`s way back into place by next weekend. As the ridge loses
control across the region, this opens us up to a more active weather
period. It also allows for a bit more temperature swings as frontal
systems near and move through.

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 front will sink southward into Kentucky by
Sunday night, spreading pops across the state during the day Sunday.
It will then pivot SEward, lingering pops across the far eastern
portion of the state (JKL CWA) through much of the day Monday.

By Monday night into Tuesday, the system will exit to the east,
leaving KY in a brief area of high pressure at the surface.
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 quite a bit of 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. This precip
and frontal boundary should move through the state during the day
Wednesday. Again, given the model disagreement by this point, will
stick with the NBM, which shows pops moving in ahead of this system
as early as Tuesday night, ramping up during the day Wednesday. Will
note that both the GFS and ECMWF try to develop a secondary
shortwave across Kentucky for Wednesday afternoon/night, which is
likely the reason for the amplified 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. Meanwhile, the
NBM is trying to bring some low-end isolated pops into the southeast
during the afternoon Friday, which doesn`t seem to be reflected in
the models. Wouldn`t be surprised if these were removed by the next
run, but also wouldn`t be surprised if the models completely
changed their solutions over the next few days either.

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 mid 90s in many locations. Thankfully with more W
to NW flow aloft, the humidity hopefully won`t be as bad, but it
will still make it feel several degrees warmer than it already is.
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.
-- End Changed Discussion --

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 146 AM EDT FRI JUN 21 2024

In general, VFR conditions will prevail across all TAF sites
through the period. Clearing skies this morning will allow for
areas of valley fog to develop across the region. This will
probably bring KLOZ, KSME, and possibly KSYM and KSJS, to MVFR or
IFR viz from 09Z through 13Z before burning off and all TAF sites
return back to VFR. Winds will be light and variable through the
period.

&&

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

$$

UPDATE...GREIF
SHORT TERM...VORST
LONG TERM...JMW
AVIATION...CMC