285
FXUS63 KJKL 222104
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
504 PM EDT Mon Jul 22 2024

.KEY MESSAGES...

- Showers and thunderstorms will impact the region at times this
  week. Probabilities will generally peak each afternoon and
  evening.

- Any areas that receive successive rounds of heavy rainfall
  could experience instances of localized flooding.

- Highs will be near normal (mid 80s) to about 5 degrees below
  normal throughout the period, with humidity running high.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 452 PM EDT MON JUL 22 2024

Regional radar imagery shows convection over far southeastern
Kentucky generally waning, though additional pin-prick convection
has started bubbling up further northwest closer to Lake
Cumberland and also over the northern Kentucky River basin.
Temperatures at 2045z are mild, ranging from the mid 70s in
locations recently impacted by rainfall up to the lower/middle 80s
in the Lake Cumberland area where sunshine has been most
persistent. The regional surface analysis shows a wavering cold
front draped from southern West Virginia westward (bisecting the
WFO Jackson CWA roughly in half) to a subtle wave of low pressure
near Bowling Green. Aloft, a positively tilted trough axis lingers
from Eastern Canada down through the Mid-Mississippi Valley and
from thence into the Southern Plains. Upper level ridging remains
in place over the Great Antilles and far Southeastern US. Deep
southwesterly flow between the features continues to channel
moisture into eastern Kentucky, as evidenced by PWATs of ~1.5 to
1.6 inches.

The upper level pattern will remain largely unchanged during the
short-term period. Impulses embedded within the flow aloft, weak
convergence along the wavering frontal boundary, and differential
diurnal surface heating will, at different times and in unique
combinations, act as mechanisms for initiating and/or sustaining
convection. Convection late this afternoon and evening appears to
be due to a combination of all three. The subtle upper level
perturbation is fostering a very weak wave to ride along the front
this evening. Expect a brief uptick in convection this evening,
though mostly over the southern half of the CWA, before
diminishing with the loss of daytime heating. Most locations
should be dry after sunset, though an isolated rogue shower or
thunderstorm cannot be ruled out overnight. The combination of
recent rainfall, suppressed daytime highs and some partial
clearing overnight will set the stage for areas of fog in many
valley locations, and likely at least patchy fog elsewhere.
Temperatures will be mild only bottoming out in the middle to
upper 60s.

Looking ahead to Tuesday, any substantial breaks in the cloud cover
will fade as the next impulse arrives. Model agreement is fairly
good that convection will be likely south of the Mountain Parkway
(chance north), especially during the afternoon and early evening.
Though there could be a lull in the activity Tuesday evening, the
next disturbance follows quickly on Tuesday night with convection
again increasing overnight. Southeast Kentucky (roughly south of
the Mountain Parkway and the lingering frontal boundary) will
remain the focus area for most of this convection. Locations that
have received multiple inches of rain in recent days (most of Clay
and Owsley counties as well as smaller portions of Lee, Breathitt,
Perry, Leslie, Laurel, Knox, Bell, Harlan, Letcher, and Pike
counties) will be more vulnerable to future rounds of rainfall
causing excessive runoff and flooding. However, forecaster
confidence in any particular one or group of these counties seeing
the brunt of the additional rainfall is low due to the obscurity
of the weak forcing mechanisms. WPC has maintained a marginal risk
for excessive rainfall for portions of southeast Kentucky through
the short-term. The diurnal temperature cycle will also remain
subdued on Tuesday and Tuesday night with highs in the lower to
middle 80s and lows in the mid to upper 60s.

.LONG TERM...(Wednesday through Monday)
Issued at 504 PM EDT MON JUL 22 2024

Operational models are in good agreement through Dy4, Fri before
diverging from Dys 5-7, Sat-Mon. Ensemble solutions mirror their
respective parent models but show a little better agreement
through Dy5, Saturday. GFS/GEFS is a bit faster/stronger with
ridging over the eastern CONUS by Dy5, Saturday. Ensemble cluster
analysis confirms more uncertainty (lower confidence) in the
forecast for the Dys 5-7 time frame. Looking just at numbers,
majority of members appears to favor ever so slightly the idea of
some lingering troughiness over the upper portions of the Ohio
Valley by Dy5 and weaker ridging over the Upper midwest and
Midwest/Great Lakes proper. These upper level patterns will have a
significant influence on how strong surface high pressure (the
Bermuda High) eventually builds back into the southeastern CONUS,
if at all. This also has a direct impact on temperatures beyond
day 4-5 and whether we return back to the very hot muggy weather
that has defined much of the summer thus far, or whether we remain
closer to normal as experienced over the past week.

Sensible weather features a continuation of unsettled weather
through the first part of the extended, then a more likely return
to some semblance of more typical, summer like weather. A
noticeable trend will be for lower PoPs, less convection through
the period with time. Daily temperatures will also trend upwards,
from around or just below normal to just above normal. The surface
frontal zone in place across the area that is providing a focus
for mainly daytime convection will gradually dissipate by the end
of the week, only to be replaced by another surface cold front
that will drop southward into the Commonwealth by Thursday. At
this time it is uncertain how far this front will make it through
eastern Kentucky or if it will stall out across the area before
dissipating.

Main hazards through the period will remain hydro related, and
generally within the first half of the extended. PWATs generally
remain below 2 inches through that time frame and storm motions
remain relatively high at around 15kts. A surface front does drop
into the area by Thu/Fri, which would help enhance the threat of
more organized convection, and possibly some training along the
remnants of our current frontal zone, although it will be
dissipating as well. Ensemble probabilities continue to advertise
a low probability of widespread, significant rainfall. Thus at
this time, the overall threat for significant, widespread, high
impact flooding is low. Rainfall could be heavy at times, but
localized. Thus any flooding threats and corresponding impacts are
expected will be isolated and related to rounds of convection
passing over the same areas. A clearer picture will develop as
models have time to congeal on a solution that better captures the
evolution of the forecast with future runs.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 216 PM EDT MON JUL 22 2024

At the start of the TAF period, a mixture of low-end VFR and
high-end MVFR conditions were noted at terminals around eastern
Kentucky. Convection is increasing in coverage again and is
expected to peak between 20 and 22z followed by rapid
diminishment during the evening as diurnal heating wanes. While
most of this convection should remain southeast of the TAF sites,
if a storm does impact a TAF site, brief visibility reductions
into the MVFR if not IFR category are possible along with brief
wind gusts to around 20KT or so. Outside of convection, winds are
forecast to be light and variable. Although isolated convection
cannot be ruled out tonight, a lull is expected and along with
some clearing or partial clearing of low and mid clouds. Following
recent and expected rainfall later today, fog formation is likely,
at least in valleys and perhaps also affecting much of the region,
with reductions into the MVFR and or IFR category developing as
early as 04Z and 07Z.

&&

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

$$

SHORT TERM...GEERTSON
LONG TERM...RAY
AVIATION...GEERTSON