992
FXUS63 KJKL 212353 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
753 PM EDT Sat Sep 21 2024

.KEY MESSAGES...

- A potential for showers and thunderstorms will persist through
  much of the next week.

- High temperatures will approach 90 degrees tomorrow, then trend
  lower as time goes by during the week.

&&

.UPDATE...
Issued at 753 PM EDT SAT SEP 21 2024

Brought temperatures grid in line with trends in recent surface
obs. Surface frontal boundary has stalled across our northern
zones this evening, and models show some pooling of moisture along
and south of the front through the remainder of the night. Also
noticed model guidance trending towards fog through the overnight.
Seeing some weak subsidence just above the boundary layer and
winds continue to slacken off as skies clear across the area.
Ensemble guidance also showing more likely probabilities for the
development of fog and stratus over a large part of the forecast
area as well. Considering the more favorable conditions for
radiative cooling conditions, the proximity of the surface front,
and the trends in guidance, decided to beef up the fog across the
area through the overnight period. Updated grids and zones have
been issued.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 543 PM EDT SAT SEP 21 2024

Aloft, ridging in place across the Ohio Valley and Midwest is
gradually being worn down and suppressed by a combination of short
wave energy lifting out of the Four Corners and tracking across
the Northern Tier and Great Lakes during the short term. This
results in some significant height falls across our area as the
eventual lowering of H850 temps from 18-20C to around 16C by the
end of the period. At the surface, a stalled out frontal boundary
just north of our forecast area will lift northeast back towards
the upper Ohio Valley tomorrow...all as another, stronger surface
cold front approaches from the northwest reaches the Ohio River by
late Sunday night or early Monday morning.

Sensible weather features the beginning of a trend towards a more
unstable or unsettled pattern. Showers and thunderstorms have
dissipated across our area late this afternoon. But isolated
convection continues to fire upstream to our northwest, one being
quite healthy as of this writing. Met watch will continue in case
they creep into our area over the next hour. However, the overall
trend is for a continued weakening and activity over the next
couple of hours.

Overnight is expected to be mainly dry with at least some partial
clearing, especially over our northern zones. This may set up
favorable conditions for the development of some fog, especially
for areas that saw some afternoon rainfall. Will be watching for
this potential through the evening.

Expecting one more day of above normal temps tomorrow. With clear
to partly cloudy skies, temperatures should have no problem
climbing back up into the mid to upper 80s. H850 temps are just
slightly lower than the previous few days. That being the case,
and especially with some rainfall over portions of the areas,
thinking is that we may be spared the 90s. However, still would
not be surprised if one or two location eked out a 90 degree
reading somewhere. Otherwise, look for an increase in cloud cover
and PoPs late in the day tomorrow. MLCAPEs increase to between
1000-1500 J/kg by Sunday afternoon. Mid level lapse rates steepen
just a bit as well, particularly over our far southwest. Thus
could not rule out some thunderstorm activity tomorrow afternoon
through tomorrow night, though the best potential will be found
over our southwest tomorrow afternoon where ensemble probabilistic
data shows the highest likelihood of sufficient CAPE.

.LONG TERM...(Monday through Saturday)
Issued at 351 PM EDT SAT SEP 21 2024

The latest model runs are showing pretty much the same pattern in
the extended as the previous few days. A trough of low pressure over
the central Plains will be our primary weather maker to begin the
upcoming work week. Another trough of low pressure is forecast to
intensify over south central Canada and move north, with a cold
front extending southward from it to the central Plains trough. The
Plains trough and cold front will move through our region Monday and
Tuesday and will bring showers and a few storms to eastern Kentucky
to begin the week. Another more developed trough is expected to form
over the northern Plains Tuesday night into Wednesday. This system
is forecast to move slowly eastward into the central Mississippi
Valley and western Tennessee Valley by mid-week. This system will
likely bring another round of showers and storms to our area, along
with cooler temperatures, Wednesday and Thursday. The wild card in
this scenario will be whether or not a tropical system forms over
the Gulf of Mexico. The latest runs of the GFS and GFS Ensembles
have a tc forming over the southwestern Gulf and moving northward
toward the central Gulf Coast Thursday and Thursday night. If this
tropical system does form, its evolution and track will have a
degree of influence on the second Plains trough. For now, we will go
with the general pattern the models are showing, with repeated
rounds of showers and storms moving through eastern Kentucky Monday
through Wednesday, with the rain quickly tapering off to isolated
showers and storms by the end of the week, but having the rain
persist through Friday night.

After a day of slightly warmer than normal temperatures across the
area on Monday, the passing troughs, and their associated widespread
cloud cover and rain, along with winds shifting to the west or
north, will lead to below normal temperatures in the 70s for the
rest of the week past Monday. The overall pattern looks to be
chances of rain each day in the extended, with generally cooler than
normal temperatures, especially during the daytime periods. The only
weather hazard of note will be any cloud to ground lightning
associated with some thunderstorms.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 753 PM EDT SAT SEP 21 2024

Surface frontal boundary has stalled across the northern sections
of our forecast area this evening, and models show some pooling
of moisture along and south of the front through the remainder of
the night. Also noticed model guidance trending towards fog
through the overnight. Seeing some weak subsidence just above the
boundary layer and winds continue to slacken off as skies clear
across the area. Ensemble guidance also showing more likely
probabilities for the development of fog and stratus (lower flight
conditions) at our terminals as well. Considering the more
favorable conditions for radiative cooling conditions, the
proximity of the surface front, and the trends in guidance,
increased fog inpacts at all of our terminals during the
overnight, generally in MVFR territory to our southwest (KLOZ &
KSME) where there was little if any afternoon preceipitation. Our
other termminals (KJKL, KSYM, KSJS) saw at least some rainfall and
impacts are expected to be more substantial with a period of late
night LIFR flight conditions in the hours leading up to sunrise.
Winds will be light through the period, 5 kts or less, but with a
westerly tendency through the day on Sunday.

&&

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

$$

UPDATE...RAY
SHORT TERM...RAY
LONG TERM...AR
AVIATION...RAY