141
FXUS63 KJKL 132326
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
726 PM EDT Mon May 13 2024

.KEY MESSAGES...

- Dry weather holds into the afternoon, before an approaching
  system from the Plains brings more unsettled conditions.

- Shower and thunderstorm chances will be around through Wednesday
  with a lull on Thursday then renewed chances to close out the
  week.

- Near, to a little above, normal temperatures are expected
  through the work week.

&&

.UPDATE...
Issued at 726 PM EDT MON MAY 13 2024

The NBM, and the current forecast, still depict high-end chance to
categorical PoPs (50 to 90) developing by mid-evening with the
increase in southerly low-level winds after dark. However, given
how dry it looks and given eastern Kentucky lies on the cool side
of the upper-level jet stream, am inclined to think those PoPs are
overdone. If showers do not begin to develop shortly after dark,
will lower PoPs accordingly.

Main change with the early evening update is to lower temperatures
in the south where cloud cover has kept temperatures in the lower
60s late this afternoon into early evening. Otherwise, just
blended in the near-term forecast with current observations.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 337 PM EDT MON MAY 13 2024

The afternoon surface analysis shows high pressure is still out to
the east along the North Carolina coast line. Meanwhile, low
pressure is developing across Missouri along with a cold front.
This is providing south and southeast flow at the surface, which
has led to mostly downslope flow. This has kept it dry this
afternoon and will continue to be the case until we can moisten up
in the low levels later this afternoon and evening. In the mid-
and upper levels an upper low will push toward the Ohio Valley
tonight. The CAMs and ensembles like the HREF have been in decent
agreement with bringing a line of showers and possibly a
thunderstorm across the area later this evening into the overnight
hours. This could be in response to a slight increase in the low
level jet noted in some of the ensembles. Given this opted to stay
closer to the NBM PPI for PoPs this evening and into tonight, as
it seemed to have this handled fairly well.

Tuesday, this upper low meanders eastward toward the Ohio Valley.
This coupled with and area of low pressure and some upper level
divergence will give way to another shot (70-90 percent) of
showers and thunderstorms through the day. However, there will be
a lull in activity early in the day. Some of the data suggests
there would be just enough instability (MUCAPE around 1000-2000
J/kg) and shear (effective shear of 30-40 knots) to help organize
some of this convection. The HRRR and other CAMs want to bring an
line of convection through the area tomorrow afternoon around 17Z
and progresses across the area through the remainder of the
afternoon into the evening. Right now, it looks like a marginal
set up for severe weather, but strong storm or two can`t be
completely ruled out. The primary risk would be small to perhaps
marginally severe hail. SPC did push the marginal risk into a very
small portion of the Cumberland Valley. Tuesday night, the shower
and thunderstorm chances roll on given upper low is still
meandering east. However, its a little more uncertain how
convection will evolve through the evening given the line that is
expected to move through in the afternoon and early evening. For
now will keep highest PoPs in the evening time and lessen some
through the night.

.LONG TERM...(Wednesday through Monday)
Issued at 400 PM EDT MON MAY 13 2024

Still looking at an active weather pattern in the extended, as a
series of low pressure systems are forecast to move across the
eastern half of the CONUS. The models were in pretty agreement with
the overall large scale pattern aloft and systems evolution. The
ECMWF was a bit wetter at times than the GFS, but overall the models
had similar solutions. Used the GFS Ensembles for overall pattern
details and locations and evolution of lows and highs. Precipitation
details were derived from combination of the GFS and ECMWF models.
The pattern will begin with a weak trough of low pressure, both
aloft and at the surface, moving through the Ohio and Tennessee
Valleys Wednesday and Wednesday night, and eventually out to sea off
the southeast CONUS Atlantic coast by Thursday afternoon. In the
meantime, we should see a weak northern stream trough moving quickly
across the Canadian border region and across the Great Lakes to end
the week. Another more pronounced trough aloft is forecast to be
making its way through the southern stream and through the southern
Plains and Gulf to end the week and on into the weekend. These two
troughs are forecast to phase on Friday, and will bring rounds of
rain to eastern Kentucky Friday through Sunday. The initial trough
will bring widespread showers and storms to the area Wednesday and
Wednesday night, with some precip lingering behind the trough as it
departs late Thursday.

Another system will be right on the heels of the first, and will
bring another batch of showers and storms to our area Thursday night
through Saturday, as it slowly moves through the region. The highest
rain chances during the second system passage will be Friday, as a
cold front pushes through. This batch of rain should taper off late
Friday night and Saturday, with a few showers and storms lingering
behind the departed front. The details for the end of the extended
are a bit murkier, due to model uncertainty, but it appears that we
will see scattered showers and storms moving through the area again
Sunday through Monday, perhaps triggered by the passage of either a
northern or southern stream low, or from the phasing of each. Due to
this, precip chances for Sunday through Monday were kept fairly low,
20 to 40 percent to be exact, for now. The best times for showers
and storms will be during the afternoon and evening hours, when peak
heating and instability will be maximized. There will be, however,
enough instability left over to allow for some night time
thunderstorms as well through out the extended period.

Aside from Wednesday, when highs are expected to be slightly below
normal, we should see above average temperatures, both day and
night, through most of the period. Daytime highs will average from
the upper 70s to lower 80s, and night time lows the upper 50s to
lower 60s. Persistent southerly and southwesterly flow will keep a
steady flux of warm, moist air feeding into the area and should help
keep temperatures up in spite of the expected clouds and rain.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 142 PM EDT MON MAY 13 2024

VFR skies will be the story for the first 6 hours at most sites,
but a few showers and thunderstorms will push across the area
later this afternoon and evening. These storms could help to
bring temporary Vis and Cig restrictions to some sites. Another
round of showers and thunderstorms are possible late in the period
that could also lead to some temporary restrictions. The winds
will remain out of the south and southeast at 5 to 10 knots and
then expect winds to calm this evening.

&&

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

$$

UPDATE...CMC
SHORT TERM...DJ
LONG TERM...AR
AVIATION...DJ