498
FXUS63 KJKL 052121
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
521 PM EDT Sun May 5 2024

.KEY MESSAGES...

- Shower and thunderstorm potential lasts through the next 7
  days.

- Severe thunderstorms are possible Tuesday afternoon through
  Wednesday night. Large hail and damaging winds are the primary
  threats, with heavy rainfall producing localized flooding also
  possible.

- Above normal temperatures are forecast through Thursday. A cold
  front should pass late in the week and bring readings down to
  near or below normal.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 333 PM EDT SUN MAY 5 2024

A weak stationary front bisecting the forecast area from northeast
to southwest continues to be the focus for shower and thunderstorm
development this afternoon. Some of this activity has at least
briefly anchored to terrain features or the frontal boundary itself
and produced locally heavy rainfall via training, which has
necessitated the issuance of flood hazards.

This front will move little through the short term and will serve as
a focus mechanism for shower and thunderstorm development. While
today`s activity is occurring with little to no forcing for ascent
aloft, a stronger shortwave disturbance will approach the area
tonight and then cross the area Monday afternoon and evening,
bringing widespread showers and thunderstorms.

Transitory shortwave ridging builds over the area by late Monday
night and will likely limit shower and thunderstorm activity
somewhat before the next system approaches Tuesday.

Highs Monday will likely be limited by cloud cover and fairly
widespread precipitation, with highs in the mid 70s to lower 80s.
Lows tonight and Monday night will be dependent on cloud cover, with
fog formation likely where there is at least partial clearing by
dawn. Lows will range from the mid 50s in the coolest sheltered
valleys to lower 60s.

.LONG TERM...(Tuesday through Sunday)
Issued at 521 PM EDT SUN MAY 5 2024

Very active extended, with precip chances expected every day. The
first couple days of the period (Tuesday and Wednesday) will be the
most impactful, as two different strong frontal systems move
through.

The period will start off Tuesday morning with a shortwave exiting
the state to the east, brief ridging in place, and a very strong
upper level system across the Northern Plains creating deep
troughing across much of the central and western Conus. As we got
throughout the day Tuesday, the small ridge will quickly shift east
as the state begins to fall under the influence of the upper level
trough and increasing SW flow. This increased SW flow will easily
increase moisture and instability across the region, but will also
raise temperatures across the state, with highs in eastern KY
expected to top out in the upper 70s and low 80s. In fact, a warm
front will actually develop and be analyzed moving north of the
state by 15Z Tuesday. This warm front will be connected to an
occluding low pressure system over the Northern Plains, co-located
with the upper level system. As the day progresses Tuesday, WPC has
a secondary low forming at the triple point of the 3 boundaries
(occluded, warm, and cold), and the occlusion beginning to die off.
This new low will quickly make its way into the Great Lakes region
by Tuesday evening/night, with the associated cold front elongating
itself along the Ohio River. The front will drop south into the
state Tuesday  night, likely passing through the JKL CWA during the
late night/early morning hours Wednesday. However, this won`t be the
end of this system...

This cold front will be connected to another low pressure system to
our west, which will quickly gain strength Tuesday into Wednesday as
it shifts ENE. While the front is impacting the CWA Wednesday, the
low pressure system will move into the Mid-Mississippi Valley by the
afternoon, lifting the cold front back north as a warm front. By 0Z
Thursday, the GFS has the low analyzed across Indiana, with a cold
front attached and moving eastward into western Kentucky. This front
will continue to traverse KY, passing through the JKL CWA between
the early morning and early afternoon hours Thursday according to
the latest NBM.

After this system exits to the east of the state, we may have a super
brief break in the action. While the surface low will be out of the
region, an upper level shortwave/trough will be passing through
during the day Friday. This may be enough to bring another round of
chances of showers and thunderstorms to the region again. As this
exits, models are actually in good agreement that we may see some
dry weather during the day Saturday. That being said, the NBM is
going gung-ho on bringing pops back in from the west, but so far
models are trending away from this occurring. It looks like the
surrounding offices didn`t go as high on pops as the NBM, so expect
to see those chances decreasing with the coming forecasts so long
as the modeled pattern holds.

Now..for sensible weather. Obviously with several frontal boundaries
moving through the region, and strong SW flow in place, we are
setting ourselves up for potential showers and thunderstorms. The
first main round will be during the afternoon Tuesday, as the warm
front lifts north of the CWA and we find ourselves in a warm, moist,
and unstable sector ahead of the cold front. It will slowly
dissipate again overnight. SPC has placed much of this warm sector
and along the cold front in a slight risk area from 12Z Tuesday
through 12Z Wednesday.

From SPC: Deep-layer shear is forecast to be strong enough to
support organized convection, including some supercells. However,
with mid-level flow generally aligned with the forecast position of
the surface boundary, tendency may be for clusters/bowing line
segments to prevail. Regardless, scattered strong to severe
thunderstorms should spread east-northeastward across the OH Valley
Tuesday afternoon and evening, posing a threat for mainly damaging
winds and severe hail.

Wednesday morning will start off with lower-end pops, but will
quickly ramp up during the afternoon as the cold front makes its way
into the state and then begins to lift back north as a warm front in
the afternoon. These pops will likely be highest in the southern
portion of the state, where the best heat and instability are
located ahead of the front. Then by the overnight, the NBM has a
line of storms developing along and ahead of the next cold front,
passing from NW to SE through the CWA during the late night and
into the day Thursday. Again, can`t rule out some strong winds and
potential hail, though it`s passing during the late night/morning
will hopefully dampen some of the worst severe potential. Being on
Day 5, there is still quite a bit of evolution this system can take,
and still some model disagreement, but do keep an eye out as severe
potential can`t be ruled out.

Friday`s passing shortwave brings yet another influx of likely
showers and thunderstorms to eastern Kentucky, mainly during the
afternoon and early evening with best heating/mixing/instability.
Then for Saturday, as mentioned above, the NBM went with likely pops
for the CWA, however based on the latest models, wouldn`t be
surprised if this will continue to trend drier.

As for temperatures, almost every night, except for the very end of
the forecast, is expected to see cloud cover given the continued
precip chances. As such, did not do any ridge/valley temp
differences for these nights. The warmest days will be Tuesday
through Thursday, ahead of the final passing cold front, at which
point a change in airmass will take place as winds become more
northerly aloft and advect in cooler temperatures. Temperatures for
Friday and into the weekend will struggle to reach 70 degrees in
some cases.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 202 PM EDT SUN MAY 5 2024

VFR conditions are expected into this evening outside of brief
MVFR/IFR conditions in isolated to scattered showers and
thunderstorms. There are model discrepancies late tonight into
Monday which makes forecasting a bit difficult, depending on the
arrival of the next disturbance. Some models depict showers and
then thunderstorms moving in late in the overnight through Monday
morning, while other models depict partial clearing overnight
which would allow widespread fog formation during the few hours
straddling dawn, before the next round of showers and
thunderstorms move into the area after 12z-15z Monday. For now,
decided to split the difference, with future forecasts likely
being able to hedge more one way or the other with increasing
clarity on which scenario becomes more likely. At any rate, expect
widespread MVFR and possibly IFR/LIFR cigs and/or visibility after
06z through 13-14z Monday before beginning to gradually improve
through the end of the TAF period.

&&

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

$$

SHORT TERM...CMC
LONG TERM...JMW
AVIATION...CMC