270
FXUS63 KJKL 191955
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
355 PM EDT Fri Jul 19 2024

.KEY MESSAGES...

- Showers and thunderstorms will impact the region at times
  through the middle of next week. There will be a minimum in rain
  chances into this evening, before higher probabilities set in
  over the weekend and continue into the new week.

- Continued relief from the hot temperatures of earlier in the
  month will be with us throughout the period, though humidity
  makes a comeback heading into next week.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 350 PM EDT FRI JUL 19 2024

19Z sfc analysis shows high pressure from the north having had the
biggest influence on our weather today with slightly cooler than
normal conditions, at least partial sunshine, and drier air in
place. However, a stalled frontal boundary is lingering just to
our south and this remains a source for potential showers and
thunderstorms along our southeast borders this evening. It is also
responsible for more clouds working in from the south with time
into the night. Currently, temperatures are running in the low to
mid 80s most places while dewpoints are generally in the upper
50s to lower 60s, amid light and variable winds.

The models, and their individual ensemble suites, are still in
near excellent agreement aloft through the the short term portion
of the forecast. They all depict general troughiness through the
Great Lakes and Ohio Valley with a tendency for a local minimum in
heights to consolidate to the west over the Middle Mississippi
Valley with time. This will collect much of the mid level energy
in the pattern through the weekend with a few weaker elements
drifting over eastern Kentucky during the short term portion of
the forecast in broad, weak 5h flow. Given the small model
spread, again have gone with the NBM as the starting point for the
forecast grids with little adjustment needed aside from some
incorporation of the latest CAMs guidance for PoPs this evening
through Saturday night.

Sensible weather features a moderation of our less humid and
somewhat cool end to the work week with moisture on the increase
along with milder nights on tap. This also means an increasing,
but only gradually into Saturday morning, threat for showers and
thunderstorms working up from the south as the front lifts back
north and becomes more active. Still see a window consisting of
much of the night for the northwest half of the area to have
thin enough clouds to allow for some radiational cooling and
limited terrain distinctions along with valley fog formation. For
Saturday night, expect more uniform temperatures amid deep layer
cloud cover and higher baseline dewpoints. Some places will see
cooler conditions on Saturday but that is mainly due to more
clouds in place and the convection around, otherwise near normal
temperatures are anticipated.

The main changes to the NBM starting point consisted of adding in
some PoPs details from the CAMs for this evening through Saturday
night. Did also tweak northwest parts of area for some minor
terrain distinctions in temperatures through the night.

.LONG TERM...(Saturday night through Thursday)
Issued at 430 AM EDT FRI JUL 19 2024

he period is expected to begin with an upper level ridge extending
from portions of the Atlantic into the southeast Gulf of Mexico and
another ridging centered over the western Conus. In between, an
upper level trough is expected to expected across the Great Lakes
region into portions of the Central Conus toward the southern
Plains. To end the weekend and into the middle of next week, upper
level ridging is expected to remain in place from the western
Atlantic into the eastern Gulf of Mexico with upper level ridging
remaining centered over the western/southwestern Conus and an upper
level trough axis in between. The axis of the upper trough may move
slightly east and nearer to the Lower OH Valley region by the end of
the period. At the surface, as the trough evolves to the west, a
warm front or leading edge of deeper moisture should lift north
across the region to end the weekend and remain north of the area
before becoming diffuse at midweek. Another frontal zone should
gradually drop into the Great Lakes from early to midweek, before
slowly nearing the OH Valley region to end the period.

In the southwest flow ahead of the trough axis, multiple hard to
time shortwave troughs should impact the region. However, the
predictability of timing of any individual shortwaves into the OH
Valley and Appalachians is too low for any confidence at this time
range. In general, pops were given a diurnal flavor through the
period, with the most likely time for the greatest coverage from mid
afternoon to early evening each day of the period. With the
anticipated moisture advection from south or southwest to north
and northeast, chances will be lowest in the north to begin the
period Saturday night and Sunday before becoming more uniform
through the period. Pops were carried during the night time periods
as well given the pattern.

Moisture will increase to begin the period across the region. South
to southwest flow between the upper ridging generally extending
from near Bermuda to the eastern Gulf of Mexico and upper level
troughing extending from eastern Canada into the upper MS
Valley/Central Conus to Southern Plains will transport moisture into
the Appalachians and OH Valley regions. Per LREF mean, PW is
forecast to initially be in the 1.2 north to 1.6 inch south range
Sat evening, before increasing to 1.3 north to 1.5 south around 0Z
Monday, the 1.6 to 1.7 inch range on Monday, 1.7 to 1.8 inches
Tuesday, and remain in the 1.7 to 1.9 range through the end of the
period. Values in the 1.7 to 1.9 inch range would be close to the
90th percentile for the timeframe. Any repeated rounds of convection
or training across an area over multiple days could eventually lead
to hydro concerns. WPC EROs for the Day 4 and Day 5 periods, Monday
and Monday night and Tuesday and Tuesday night include the region in
a marginal risk of excessive rainfall. Some concern of possible
localized issues would likely linger beyond that point through the
end of period with the trough axis remaining west of the region and
the lack of a cold frontal passage.

With the trough in place, clouds should be rather prevalent through
the period, especially during each afternoon and evening. This and
anticipated convection from time to time will lead to cooler highs
that what has been experienced for much of the month to date. In
fact, highs will be near if not a few degrees below normal for this
time of year. Normal highs outside of the highest terrain are
generally in the mid 80s. With increasing moisture at the surface
and through the column diurnal ranges will be a bit limited as well
with lows anticipated in the mid to upper 60s for most nights.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 145 PM EDT FRI JUL 19 2024

VFR conditions will prevail at all the TAF sites through the end
of the period. A few showers and possible storms are expected to
move out of TN and into our southern counties later this evening,
with an uptick in coverage overnight. The showers and storms
should not directly affect any of our TAF sites until nearer
towards dawn and then be around through the end of the period.
Winds will remain light and variable during the period, as well.

&&

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

$$

SHORT TERM...GREIF
LONG TERM...JP
AVIATION...AR/GREIF