-- Discussion containing changed information from previous version are highlighted. --
617
FXUS63 KJKL 201755
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
155 PM EDT Fri Sep 20 2024

.KEY MESSAGES...

- A potential for showers and thunderstorms returns tonight and
  Saturday and then persists much of the time over the next week.
  The highest probability is around mid week.

- Daily high temperatures will be in the 80 through early next
  week, and should then cool to the 70s.

&&

.UPDATE...
Issued at 105 PM EDT FRI SEP 20 2024

Updated the zones earlier to remove morning fog. As expected
seeing a bit of a Cu field developing under some streaming high
Ci. Forecast is on track. Stayed with original highs, though some
spots in our south have been a little slow to respond to heating.
Did adjust hourly grids to reflect this. Otherwise, no further
changes to the forecast package.

UPDATE Issued at 743 AM EDT FRI SEP 20 2024

Forecast is on track. Morning obs were blended in without
substantive changes.

&&

.SHORT TERM...(Today through Saturday)
Issued at 358 AM EDT FRI SEP 20 2024

Early this morning, upper level high pressure is centered over TX
and is ridging northeast over the lower Great Lakes. A shortwave
trough is over the upper Midwest, along with an associated surface
cold front. The shortwave trough will propagate along the
northeast periphery of the ridge and should be getting picked up
by the back side of a weak upper level trough off the New England
coast by late Saturday. Along its journey, it will support
southeast movement of the aforementioned cold front. The front
will be weakening with time and will probably be ill defined by
late Saturday, but it is expected to be near the Ohio River at
that time. Modest moisture advection on southwest low level flow
ahead of the front could result in elevated instability overnight
tonight into Saturday, and surface based instability on Saturday
afternoon. Although supporting features will be weak, some showers
or thunderstorms won`t be ruled out, and 20-30% POPs will be
used.

.LONG TERM...(Saturday night through Thursday)
Issued at 358 AM EDT FRI SEP 20 2024

The suite of available forecast guidance continues to exhibit a more
active weather pattern during the extended forecast period, and rain
chances are featured in the forecast for much of next week as a
result.

The warmest day in the forecast period will be Sunday. In the wake
of Saturday`s rather weak first frontal boundary, ridging looks to
briefly build back in. Relatively clearer skies and southwesterly
flow (albeit weak) in the column will allow temperatures to warm up
to near the 90 degree mark on Sunday afternoon. The warm/moist air
advection processes associated with this flow may foster diurnal cu
development on Sunday, and some of this activity may turn into
showers/storms. This appears most likely in our northwestern
counties (slight chance PoPs), which will be closer to the incoming
frontal boundary, but most of the area should stay dry during the
day on Sunday.

From Sunday night to Tuesday, the aforementioned upper ridge axis
slides to the east, which allows westerly to southwesterly flow to
gradually strengthen. As this occurs, more moisture returns to the
column, and the air in Eastern Kentucky becomes more supportive of
shower and thunderstorm development. Rain chances gradually increase
overnight on Sunday and reach an initial peak on Monday afternoon in
accordance with the diurnal heating cycle. Expect Monday`s
convection to be more scattered in nature, with the frontal boundary
still displaced to the Northwest. Highs on Monday will reach the
mid 80s, and overnight lows into Tuesday morning will only fall
into the upper 60s given antecedent cloud coverage and continued
warm air advection. By midday Tuesday, the frontal boundary will
be on our doorstep, and the warm/moist air will combine with
increasing frontal lift to produce more widespread showers and
storms. PoPs peak in the 60-70% range across much of the area,
with greater morning chances in the NW and greater
afternoon/evening chances in the SE. Probabilistic ensemble
guidance does not resolve particularly favorable thermodynamic and
environmental shear parameters with this system, and organized
severe weather does not appear likely at the moment. It is
plausible that leftover cloud coverage from Monday`s activity will
limit Tuesday`s afternoon highs to near 80 degrees and thus
decrease the available instability for storms. Thunder remains in
the grids for now, but any decreasing thermodynamic trends will
need to be monitored for future forecast issuances. Nevertheless,
Tuesday looks to be the wettest day in the extended period as the
second frontal boundary passes through the area from NW to SE.

Typically, one would expect things to quickly dry out and cool off
after a frontal boundary has moved through the forecast area. This
particular frontal boundary, however, looks to stall as the parent
troughing phases into a closed upper level low in the vicinity of
the Great Lakes. This leads to a cooler, but still wet, second half
of the work week. Models generally agree that the upper level
pattern will evolve in this manner, and thus rain chances stick
around through the end of the extended period. However, the
associated northwesterly flow will drop temperatures lower and lower
into the 70s with each passing day. The subsequent reduction of
instability means that any post-frontal activity will fall in the
form of showers. This rain will be very beneficial to the
Commonwealth given the region`s recently worsening drought. The
cloud coverage associated with this shower activity will limit the
potency of ridge-valley thermal splits next week. Expect afternoon
highs in the mid to low 70s on Wednesday and Thursday, with
overnight lows in the mid to upper 50s.

&&

.AVIATION...
-- Changed Discussion --
(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 155 PM EDT FRI SEP 20 2024

VFR flight conditions expected through the period. Expecting
valley fog again tonight, but impacts at any flight terminals
should be minimal. Winds will be light and variable through
Saturday morning, then increase a bit from the west-southwest to
around 5 kts ahead of a weak cold front that is expected to stall
north of our area, along the Ohio River Valley. Besides being
closer to the surface front, southwest winds at KSYM tend to be a
little stronger due to terrain effects, thus went with a slightly
higher gradient wind there.
-- End Changed Discussion --

&&

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

$$

UPDATE...RAY
SHORT TERM...HAL
LONG TERM...MARCUS
AVIATION...RAY