-- Discussion containing changed information from previous version are highlighted. --
967
FXUS63 KJKL 041512 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1112 AM EDT Sat May 4 2024

.KEY MESSAGES...

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

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

&&

.UPDATE...
-- Changed Discussion --
Issued at 1112 AM EDT SAT MAY 4 2024

A short wave trough is currently rotating through the region. The
best coverage of convection has been across far southeastern
Kentucky, with more widely scattered shower activity popping up
further northwest. Forecast soundings do not reveal much of a cap
this afternoon, and even with the exit of this short wave trough
early this afternoon, 500 mb heights are still dipping later, as
we still remain in a broad trough. As such, have adjusted PoPs
mainly for the next few hours, attempting to capture the radar
trends a bit better. There should be an uptick once again through
peak heating, although coverage should be mainly scattered, with
more modest forcing and instability in place. High temperatures
in the mid to upper 70s look on target, although did lower these
a bit across far southeastern Kentucky, given the better
convective coverage and cloud cover in place. Updates have been
sent.

UPDATE Issued at 855 AM EDT SAT MAY 4 2024

Issued an update primarily to get forecast grids in tolerance with
neighboring offices. Otherwise, the current forecast for this
morning looks satisfactory.

UPDATE Issued at 700 AM EDT SAT MAY 4 2024

The forecast overall is looking pretty good early this morning.
Isolated showers and storms area moving through portions of the
area, per the current forecast, and should gradually increase in
coverage through out the day, especially this afternoon during
peak heating. The latest obs were used to establish new trends in
the forecast grids, but as mentioned earlier, things are in pretty
good shape so far. The pre-first period that was included with
the 4 am forecast package will need to be removed in an hour or
so, but until then, things should be good as is.
-- End Changed Discussion --

&&

.SHORT TERM...(Today through Sunday)
Issued at 449 AM EDT SAT MAY 4 2024

Isolated rain showers were ongoing at time of forecast issuance
early this morning, and were beginning to slowly increase in
coverage, especially north of the Mountain Parkway. This trend is
expected to continue through sunrise this morning. Once the sun is
up, isolated to scattered showers are expected to fire across
eastern  Kentucky. The primary challenge in the short term portion
of the forecast will be how widespread will showers and storms
become today. To answer that question, the latest model data was
consulted and revealed that in spite of ample moisture and
instability being in place, the lack of a clear cut triggering
mechanism will limit shower and storm coverage today. With several
models all supporting this scenario, the HRRR, NAMNEST, and CAMS in
particular, it made sense to go with much lower precip chances for
today than previously forecast. The same scenario looks reasonable
for Sunday as well. The 6Z analysis showed a stationary front in
place from the eastern Great Lakes into southwestern Indiana and
then across Missouri where it merged with a surface low situated
over southeastern Nebraska. A weak trough of low pressure was also
analyzed over central Kentucky, just south of the Ohio River, but
due to the weakness of this feature, it appears it will not offer
enough lift to spark widespread convection today. Instead, it looks
like todays showers and storms will be diurnally driven, and will
peak in coverage this afternoon into early this evening, before
quickly tapering off after dark, when instability will also quickly
wane. Another frontal boundary extended southwestward through Kansas
into far western Oklahoma and then further west out to Nevada. A well
defined dry line was also in place extended southward from a
surface over the Oklahoma pan handle through eastern New Mexico
and across extreme western Texas. This set of boundaries and
surface lows will be the focus for severe weather across the
southern Plains later today.

Temperatures will continue to run above normal over the weekend,
with todays highs maxing out in the upper 70s, and Sundays max
readings in the upper 70s and lower 80s. Tonights lows should fall
to around 60, with only minimal ridge valley differences due to
extensive cloud cover and little radiational cooling expected. No
significant weather concerns are expected at this time, with only
garden variety thunderstorms on tap today and tomorrow. Winds should
be generally from the south or southwest and 5 to 10kts today and
tomorrow, and light and variable tonight.

.LONG TERM...(Sunday night through Friday)
Issued at 449 AM EDT SAT MAY 4 2024

The long term period continues to look wet. Prevailing large
scale flow aloft will be persistent from the west southwest
through at least Thursday, while low level flow is out of the
southwest off the gulf. This pattern of warm/moist advection will
favor precip whenever there are triggers/forcing mechanisms. A
wavering frontal boundary will approach from the northwest at
times, but being largely parallel to the upper level flow until
near the end of the period it is not likely to make a forceful
passage until then. This will leave us in a modestly humid air
mass with surface dew points mainly in the lower to mid 60s. The
main drivers for precip will be mid/upper level waves along with
diurnal heating/destabilization cycles. The mid/upper level waves
with the most agreement in the models are ones that would affect
us on Monday, and also Wednesday night into Thursday, and these
time frames contain the highest POP area wide at mainly 70%+.

There are some model discrepancies in the Thursday-Friday time
frame concerning timing of an eventual cold frontal passage. In
the 00Z deterministic/operational runs, the GFS is faster than the
ECMWF with the passage of the primary cold front, and this results
in lower forecast confidence. The current forecast is a model
blend, but temperatures are likely to end up being either warmer
or colder, depending on timing of cold fropa. Also, a faster
fropa would result in the POP dropping off faster, and a slower
passage would allow precip to linger longer.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 700 AM EDT SAT MAY 4 2024

MVFR CIGs at SME and SYM to begin the 12Z forecast period, with
JKL, LOZ, and SJS holding at VFR. Isolated showers and storms were
moving through the area at TAF issuance. These will continue to
gradually increase in coverage through out the day, especially
this afternoon and early this evening during peak heating and
instability. The rain is not expected to be widespread, but enough
showers and storms will be around to warrant VCTS mention at each
TAF airport later today into early this evening. Winds will be
generally from the south or southwest at 5 to 10 kts today and
light and variable overnight. MVFR fog could affect that TAF sites
toward the end of the TAF period due to any rainfall that is
received at those locations, but confidence is not high at this
time. Brief periods of IFR could also occur at any TAF site
during a thunderstorm, but outside of that, MVFR or VFR will be
most common.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...AR
LONG TERM...HAL
AVIATION...AR