400
FXUS63 KJKL 171804
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
204 PM EDT Fri May 17 2024

.KEY MESSAGES...

- Shower and thunderstorms are expected today through Saturday
  evening before tapering off Sunday.

- High pressure brings dry weather back to the area Sunday night
  through Tuesday. A couple areas of low pressure will bring rain
  back to the area Tuesday night through Thursday.

- Near normal to slightly above normal temperatures are expected
  to continue into the weekend. A further warm up is then
  expected into the first part of next week.

&&

.UPDATE...
Issued at 1250 PM EDT FRI MAY 17 2024

Clouds and light rain are holding temps down. Without any
appreciable sun expected, have lowered the max temp forecast for
this afternoon. This will also limit instability, and the thunder
probability has also been reduced.

UPDATE Issued at 958 AM EDT FRI MAY 17 2024

Light precip has been measuring as it moves over the region this
morning. Have raised the POP faster today to account for this.
Have also made some adjustments for later periods heading into the
weekend to consider latest model trends. In general, this involves
a faster decrease in POPs.

UPDATE Issued at 643 AM EDT FRI MAY 17 2024

Just sent out a quick update to expand 15 (i.e., slight chance) PoPs
quicker across the area this morning as light rain begins to move
into areas west of Interstate 75. The forecast looks good
otherwise.

&&

.SHORT TERM...(Today through Saturday)
Issued at 320 AM EDT FRI MAY 17 2024

A large-scale positively-tilted pair of northern stream and southern
stream upper troughs will bring unsettled weather to the region for
the short-term (through early Saturday evening), with much of the
jet energy ahead of the southern stream system moving across the
Gulf Coast states and Tennessee Valley. With the region on the cold
side of the jet stream, instability will be modest by mid-May
standards. Nevertheless, showers and a few thunderstorms will move
into the region by early Friday afternoon and persist into Friday
overnight and early Saturday morning, before high pressure ridging
aloft builds over the Midwest Saturday, causing the upper trough to
pinch off over the Southeast US. Thus, another round of showers and
thunderstorms is expected to develop Saturday afternoon within a
weakly unstable and modestly moist environment.

With modest shear and instability, no severe weather is expected,
with showers more likely to be the prevailing precipitation rather
than thunderstorms today and tonight. Instability increases a bit
Saturday but within an environment with practically no wind shear.
The main concern especially today and tonight is the potential
for locally heavy rain causing minor flooding concerns, but even
this concern is very low.

With thickening cloud cover and precipitation concerns, temperatures
will be limited to near normal with 70s for highs, cooler in the
west where precipitation will arrive earlier in the day and a bit
warmer in the east where precipitation may not arrive in some
locations until late afternoon or early evening. Lows tonight will
return to the upper 50s and lower 60s with precipitation chances
continuing, with mid-50s in the deeper sheltered valleys, especially
where any partial clearing can occur. A more uniform distribution of
mid-70s can be expected Saturday given expected redevelopment of
showers and thunderstorms by early afternoon and continuing into the
evening.


.LONG TERM...(Saturday night through Thursday)
Issued at 404 AM EDT FRI MAY 17 2024

The 17/00z model suite upper level analysis is in fair agreement at
the start of the long-term forecast period on Saturday evening. A
very weak upper level low, embedded within a split flow pattern,
will be found over the Ohio and Tennessee valleys. This system
drifts southeastward on Sunday, through there is disagreement as to
how rapidly, and thus there is uncertainty as to how widespread
shower and thunderstorm activity might actually be on Sunday.
Presently, forecast retains a 30 to 60 PoP on Sunday afternoon with
lower values northwest of I-64 and highest values near the
Virginia border. However, some solutions are quite dry. Additional
refinements in the forecast will likely be needed as Sunday comes
into the range of the full CAM suite.

Once that upper level trough/low drifts southeast of area, ridging
will build in at the surface and aloft Sunday night and persist into
Tuesday. Cannot rule out a stray instance of deep convection on
Tuesday afternoon, but the lack of forcing is evident from neutral
to weak height rises. The ridging will finally break down Tuesday
night and Wednesday as a complex upper low potentially coalesces
and passes over/just north of the Great Lakes -- the system
appears to be the end result of interactions/phasing between
a stronger upper low initially over the Canadian Prairies, a
shortwave trough over the Pacific Northwest and another weak low
over the East Pacific. The models are clearly still trying to
resolve how this system will evolve. In general, there seems to
be a trend towards a weaker and less phased solution at this
point. This would support the slower arrival of a cold front
(associated with the upper low) across the Ohio Valley late
Wednesday or Thursday. While the parameter space certainly
appears favorable for severe weather with the front, there are
scenarios in which organized convection splits as it approaches
eastern Kentucky as suggested by the 00z deterministic GFS and
GDPS. It is not difficult to imagine the northern convection
becoming more tied with the better forcing to our north while the
southern convection drops into the Tennessee Valley toward better
instability.

In more sensible terms, look for showers and storms to wane going
into Saturday night. Any clearing should promote fog formation,
especially in the valleys. Temperatures should remain mild, with
lows in the mid 50s to lower 60s. An uptick in the shower and
thunderstorms is possible on Sunday, best chances adjacent to the
Virginia border. Forecast temperatures are seasonable, topping
out in the mid 70s to lower 80s. For Monday night into Tuesday,
fair and mainly dry conditions can be expected with just a stray
chance for a shower or storm late Tuesday. Low temperatures in the
mid 50s to lower 60s should be common while highs warm into the
lower to middle 80s on Monday and well into the mid 80s on
Tuesday. Nighttime/early morning valley fog is also likely
through Tuesday morning in the favored locales. Forecaster
confidence then lowers from Tuesday onward as the timing of the
next cold front remains uncertain due to model-to-model and run-
to-run inconsistency. In general, a cold front is likely to pass
sometimes Wednesday or Thursday and is favored to be attended by
showers and thunderstorms. Temperatures then trend back closer to
the seasonal norms behind the front late in the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 204 PM EDT FRI MAY 17 2024

Conditions at TAF issuance ranged from LIFR to VFR across the JKL
forecast area, with VFR being the most prevalent. Light rain was
also affecting many places.

Showers are forecast to increase in coverage as we move into the
evening, which would lead to deteriorating conditions. IFR or
worse conditions are forecast to develop in most places from
03-06Z and then persist into Saturday morning even though most
precipitation will taper off overnight. Improvement is expected
near the end of the period, mainly north of the Mountain Parkway.
With that said, forecast confidence is only modest.

&&

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

$$

UPDATE...HAL/CMC
SHORT TERM...CMC
LONG TERM...GEERTSON
AVIATION...HAL