173
FXUS63 KJKL 010335 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1135 PM EDT Sun Jun 30 2024

.KEY MESSAGES...

- A short-lived break from the heat and humidity is forecast
  tonight through Monday night behind the cold front, quickly
  followed by a return of sultry conditions mid to late week.

- An active period of showers and thunderstorms may occur
  Wednesday through Friday. The greatest probability for showers
  and thunderstorms appears to be on Thursday, Independence Day.
  Heat indices will return to near 100 degrees for many locations
  during this time.

&&

.UPDATE...
Issued at 1130 PM EDT SUN JUN 30 2024

Per the latest fog channel images from satellite, and obs trends
in the Cumberland Valley, have beefed up the fog in the valleys
there for the next several hours. The fog will likely be confined
to the deeper stream channels owing to the drier air moving in on
light north to northeast winds. Did also refine the small ridge
to valley temperature split through the night and included the
latest obs and trends for the near term T/Td/Sky grids. These
minor adjustments have been sent to the NDFD and web servers along
with a freshening of the zones and SAFs.

UPDATE Issued at 740 PM EDT SUN JUN 30 2024

23Z sfc analysis shows a welcomed cold front settling into the
area. This has pushed the bulk of any convection out of eastern
Kentucky with just a few lingering showers found in parts of the
Cumberland Valley. Clearing skies follow along with the potential
for fog - mainly in the valleys, though inbound drier air will
mitigate the worst of it. Currently, temperatures vary from the
mid 80s in the west, as they have rebound from the cooling brought
by the earlier storms, to the low 70s with the lingering showers
in the far east. Meanwhile, on stiff northerly winds of 5 to 10
mph and a few higher gusts, dewpoints are running in the pleasant
upper 50s north while still in the sticky low 70s south. Have
updated the forecast mainly to usher the last of the convection
out of the area while also fine tuning the fog threat later
tonight. Did also include the latest obs and trends for the
T/Td/Sky grids. These adjustments have been sent to the NDFD and
web servers along with a freshening of the zones, HWO, and SAFs.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 323 PM EDT SUN JUN 30 2024

The cold front continues to move southeast across the region,
producing scattered to numerous showers and thunderstorms.
Significantly drier air moves in later this evening and continues
through the overnight into Monday morning. This will make it hard
for widespread fog to develop overnight as dewpoint depressions will
likely remain sufficiently high. However, would expect the sheltered
deeper valleys will still see at least patchy fog development,
especially where rain has fallen today.

Cooler and dry conditions will occur Monday as upper ridging
builds across the Midwest and an upper trough exits the Mid-
Atlantic coastline, with surface high pressure nosing across the
area from the northeast. This will support highs only reaching the
mid to upper 70s. Cloud cover should be minimal; however, there
is some indication of an area of low stratus clouds moving south-
southwest into the area from West Virginia in the morning before
burning off in the early afternoon. Otherwise, a few wispy high
clouds may be seen later in the day from the next system.

Dry northeast low-level flow Monday evening becomes southerly by
Tuesday morning indicating increasing warm advection through the
overnight. As upper ridging continues to build over the area,
temperatures should drop under optimal radiational cooling
conditions Monday evening after sunset, with lows in the upper 40s
to mid 50s across the area Monday night into Tuesday night. Fog
should be a lot more widespread in the valleys Tuesday morning
than Monday morning given a stronger low-level inversion and warm
advection above the surface, closer to what is typical this time
of year.

.LONG TERM...(Tuesday through Sunday)
Issued at 253 PM EDT SUN JUN 30 2024

Models continue to be in good agreement with main synoptic
feature and pattern through the extended. At times, a moderately
amplified but progressive flow with generally weak to moderate
wind fields shout out a continuation of our summer time conditions
through the period. Ridging over the eastern CONUS gradually
breaks down as shortwave energy carves off the top through the
first 24-48 hours of the extended. Thereafter, flow aloft takes on
a more zonal flavor with an occasional passing short wave or
minor trough. At the surface, New England high pressure will drift
out into the Atlantic, allowing a frontal zone to develop across
the Midwest. A series of weak surface waves will track through the
Great Lakes along this baroclinic zone, effectively dropping and
lifting a frontal boundary southward and northward in response to
each passing wave of low pressure. With the zonal pattern aloft
keeping the steering flow generally west to east, the boundary
gradually drifts southward but never quite makes it through our
area until possibly at the very end of the forecast window.

After a seasonably warm (highs in the mid to upper 80s) and
relatively comfortable (surface Tds in the upper 50s to lower 60s)
start to the extended on Tuesday, our sensible weather will
generally be warm and muggy through the remainder of the period
under a very typical summer like pattern. With a frontal zone to
our north through a good part of the extended, and an occasionally
passing disturbance aloft, we should expect to see a chance for
showers and thunderstorms just about every day. However, with the
lack of strong ridging over the region and flow generally more
from out of the Deep South, temperatures will be much more typical
of this time of the year, or 80s versus the 90s experienced over
the past couple or few weeks. This will result in a bit lower heat
indices through the period as well, with peaks averaging in the
90s versus around 100 degrees or higher. Surface dew points in the
upper 60s to mid 70s will still make for some typically sticky
summer like weather.

Not seeing much in the way of hazards through the period. There
will be at least a climatologically low 20-30% or higher PoP each
day through the period. The best chance for rain and possibly more
organized convection will be during those period of time that the
frontal zone manages to dip southward, close enough to eastern
Kentucky to fire off convection, first Thursday...possibly into
Friday, and then again Saturday. Overall rainfall totals will be
localized with the hit and miss type convection we typically see
in the summer time. On average, QPF forecasts are not that
impressive, with ensemble probabilistic 24 hour averages showing
only a 25-35 percent chance of a half inch or more of rainfall
during any 24 hour period. Rest assured though, PWATs will be high
enough (~90th percentile of climatology) for some localized heavy
rainfall with any passing thunderstorms. Freezing levels will be
quite high (15-16 kft) and with relatively weak wind fields, mean
storm motions will be at or less than 10-15 kts through the
period. Consequently, any thunderstorms will be capable of
producing locally heavy rainfall.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 800 PM EDT SUN JUN 30 2024

VFR conditions are expected through the night and into Monday
morning in all but the most sheltered deeper valleys as dry air
moves into the region. At this time, fog is not expected to
impact TAF sites. While, VFR conditions are expected to hold
Monday morning it should be noted that there is some chance for
low stratus clouds to affect northeast parts of the area early in
the day, which may persist through mid morning before clearing
out. Confidence is too low to mention this in the TAFs at this
time, though, and would primarily only impact KSJS and possibly
KJKL. Winds will tend to switch to the north for a time this
evening at 5 to 10 kts before diminishing to light during the
night. Look for winds to then engage from the northeast at 5 to 10
kts on Monday.

&&

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

$$

UPDATE...GREIF
SHORT TERM...CMC
LONG TERM...RAY
AVIATION...CMC/GREIF