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241
FXUS63 KJKL 281929
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
329 PM EDT Fri Jun 28 2024

.KEY MESSAGES...

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- Hot and humid weather is expected Saturday, with afternoon
  highs around 90 degrees and heat indices peaking around 100
  degrees in some places.

- There is potential for thunderstorms area-wide Saturday into
  Sunday as a cold front approaches and moves through. A few
  storms on Saturday afternoon and evening could produce strong
  wind gusts, large hail, and heavy rain.

- Another short-lived break from the heat and humidity is
  expected on Monday behind the cold front, quickly followed by a
  return of sultry conditions.

- An active period of showers and thunderstorms may impact the
  Fourth of July holiday period from Wednesday through Friday of
  next week. Best chances for showers and thunderstorms as of now
  are expected Thursday afternoon and evening.
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&&

.SHORT TERM...
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(This evening through Saturday night)
Issued at 320 PM EDT FRI JUN 28 2024

Eastern Kentucky will reside between a west-east ridge gradually
strengthening with time across the Deep South, and fast westerly
flow moving across the Upper Midwest and Great Lakes into the
northern Mid-Atlantic region. Upper-level heights will be building
with time into Saturday evening, then begin to fall a bit more
abruptly Saturday night as an upper disturbance moves toward the
region.

Warm and moist air continues to advect north into the region with
low-level flow becoming more southerly, with dew points generally
rising about 10 degrees over the last 6 hours ending at 2 PM this
afternoon. With the moisture advection there has been scattered to
broken cumulus development across the area, but this activity is
struggling to punch through a warmer, stable pocket of air aloft.
Overnight models last night suggested some weakening of the cap late
this afternoon through mid-evening, especially as low-level winds
increase toward dark, but 12z models somewhat backed off of this
idea. Nevertheless, while the afternoon package backs off PoPs
somewhat there is an the possibility of an isolated shower or
thunderstorm late this afternoon into the evening.

The bigger story tonight will be poor temperature recovery as lows
are likely to remain well into the 70s as warm advection
strengthens. The European model Extreme Forecast Index (EFI) depicts
lows on the high-end of the climatological range. Have also adjusted
Sky cover upwards toward the CONShort model rather than the NBM
given the warm moist advection into the region. Even the typically
cooler sheltered valleys are likely to remain on the upper end of
climatology, with only a few locations likely to drop into the 60s.

Shower and thunderstorms increase through the day Saturday as an
upper disturbance moves east across the Ohio Valley through the
afternoon. Drier mid-level air will likely get advected over the
humid lower atmosphere, which should allow convection to initiate
despite subtle upper-level height rises. The NBM suggests high-end
chance to likely PoPs (50 to 60) for the afternoon and these seem
reasonable extending into the evening and overnight with some
reduction in PoPs to 30 to 40 percent in the western and
northwestern parts of the forecast area after midnight. With dew
points remaining well into the 70s ahead of a cold front, expect
another night of warm temperatures and high humidity.

Increasing winds aloft associated with the passing disturbances
aloft Saturday into Saturday night will provide sufficient shear to
support a marginal severe weather risk, with damaging winds the
primary threat and large hail a lesser threat. The greatest severe
risk is toward Interstate 64 and points north, though severe weather
can not be completely ruled out anywhere. Additionally, with PWs on
the upper end of climatology, torrential downpours with storms will
be possible. Any training of storms would increase the likelihood of
flash flooding, with this threat also falling into the category
of Marginal by the Weather Prediction Center.

Lastly, the combination of oppressive humidity and high temperatures
near 90 degrees Saturday will mean heat indices approaching or
perhaps slightly exceeding 100 degrees during the afternoon. Note
that while the criteria for a Heat Advisory is fairly widespread
coverage of heat indices at or above 105 degrees, the heat will
still have impacts on more vulnerable populations, such as young
children, the elderly, livestock, and pets.

.LONG TERM...(Saturday night through Thursday)
Issued at 337 AM EDT FRI JUN 28 2024

The large scale flow pattern aloft to begin the extended will
feature a large and broad trough of low pressure move eastward
through the Great Lakes and New England. To the west, strong
ridging, both aloft and at the surface, will be in place from the
western CONUS to the central and northern Plains. The surface ridge
will be centered over the northern Plains, while the upper ridge
will be located over the northern Rocky`s. A cold front extended
southwestward from the Great Lakes trough will be the focus for
shower and storm activity across eastern Kentucky Saturday night and
Sunday, as it sinks slowly southeastward into the Tennessee Valley.
The front should clear the area by late in the day Sunday, with the
last showers or storms exiting the area by around 0Z Monday. After
that, the northern Plains ridges if forecast to expand and
strengthen, and should make a strong and steady eastward push
heading into the first of the upcoming work week. This ridge will
also push the eastern trough into New England, and on out to sea by
Tuesday.

Dry and much cooler conditions will accompany the ridge, as it
initially settles over the region Sunday night and Monday, as a
cooler air mass moves in. In fact, we will likely see the coolest
temperatures we`ve seen over the past several weeks on Monday, with
forecast highs on that day only in the upper 70s and lower 80s. As
the ridge continues expanding east, the air mass will modify due to
strong subsidence and compressional warming due to sinking air in
the center of the high. Because of this, the cool weather we see on
Monday will be short lived. Highs on Tuesday and Wednesday will
rebound to summer like readings in the upper 80s and lower 90s as we
see mostly clear skies and strong sunshine across the region. The
good news is that dewpoint temperatures should be 15 to 20 degrees
lower Tuesday and Wednesday than what we see on Sunday(dews in the
70s), allowing for much less oppressive conditions, in spite of the
higher temperatures.

After dry weather Sunday night through Tuesday night, another area
of low pressure is forecast to move our way by mid-week. A cold
front extending southward from yet another northern stream trough is
forecast to move through the region Wednesday through Thursday. This
boundary will bring more chances for showers and storms to finish
out the week. After a couple of days with dewpoints in the 50s, we
will see rapid moisture recovery ahead of the approaching trough on
Wednesday. In fact, dewpoints will likely rise into the 60s and 70s
once again Wednesday and Thursday, providing fuel for shower and
storm activity along and ahead of the approaching front. We will see
highs back in the upper 80s and lower 90s Wednesday and Thursday, as
southerly flow pumps warm, moist Gulf of Mexico air back into the
Tennessee and Ohio Valleys.

The forecast concerns will be the potential for locally heavy
rainfall with any storms we see Sunday and Wednesday through
Thursday. The Storm Prediction Center also currently has a Day 4
marginal risk for severe weather for Sunday, so we`ll also be
monitoring the potential for severe weather for far eastern Kentucky
to end the weekend. The good news is that the marginal risk means
there is only about a 10% chance of severe weather occurring
anywhere in eastern Kentucky on Sunday, so not really worth worrying
about at the moment.
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&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 124 PM EDT FRI JUN 28 2024

VFR conditions will generally prevail through the TAF period. There
is a slight chance of showers and a very slight chance of a
thunderstorm this afternoon and early evening over south central
and southeast KY, but there is not enough confidence in
timing/placement to include it in TAFs. Valley fog is forecast
again late tonight, but not at TAF sites. Aside from the fog and
thunderstorms, VFR conditions and light south to south-southwest winds
are expected during the period.

&&

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

$$

SHORT TERM...CMC
LONG TERM...AR
AVIATION...CMC