919
FXUS63 KJKL 130734
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
334 AM EDT Sat Jul 13 2024

.KEY MESSAGES...

- Increasingly hot conditions expected through at least Tuesday,
  with increasing humidity Monday and Tuesday resulting in
  widespread heat indices averaging around 100 degrees both days.

- The next significant chance of rain will hold off until the
  middle of next week.

&&

.SHORT TERM...(Today through Sunday)
Issued at 332 AM EDT SAT JUL 13 2024

High pressure remains over eastern Kentucky in the lowest levels of
the atmosphere, with the flow becoming more weakly cyclonic with
height. A nearly stationary southwest-northeast oriented trough axis
remains roughly aligned with the Ohio River Valley at 300-mb and at
the tropopause level, with a narrow southwesterly jet stream
entrance region extending across central and eastern Kentucky just
downstream of this upper level trough axis. This trough is perhaps
best depicted by plotting the pressure of the 1.5 PVU level. This
upper tropospheric disturbance will slowly push into eastern
Kentucky today through Sunday. Meanwhile, weakly cyclonic westerly
flow will become west-northwesterly tonight into Sunday in the mid-
levels, while in the lower levels high pressure will gradually push
south and allow for slightly more westerly flow into the area. The
overall effect will be gradually increasing instability though with
limited moisture.

Tricky PoP (probability of precipitation) forecast today given
limited moisture, much like Friday, but with slightly more
instability at least a few showers and thunderstorms can be
expected. The tricky part is that it takes 15 PoPs in the grids to
trigger any mention of showers and thunderstorms in zone and
point-and-click forecasts, and it just does not seem to reach
that 15 criteria at any one location. Thus, will have widespread
PoPs of around 10 percent, but will mention the thunderstorm
possibility in the Hazardous Weather Outlook. The vast majority
of locations will remain dry today, but given the subtle height
falls in the afternoon and aforementioned upper features, as well
as persistence, it seems plausible if not inevitable a few
locations will get some precipitation.

PoPs rise a little further Sunday as the aforementioned upper-level
features are directly over eastern Kentucky, with slightly better
moisture and instability compared to today. Therefore, will have
more 15 to 20 PoPs which will allow for more of a mention of showers
and thunderstorms, but the limited moisture will still likely allow
for just isolated activity.

The overall trend in temperatures will continue to be gradually
upward, with lower 90s for highs today becoming lower to mid 90s
Sunday. Lows will tick upward as well with primarily mid to upper
60s for lows tonight. At least the drier air mass will help keep the
humidity from becoming too oppressive, though even by Sunday
afternoon a few areas may begin to see heat indices approaching 100
degrees.


.LONG TERM...(Sunday through Friday)
Issued at 432 PM EDT FRI JUL 12 2024

There is reasonable agreement among models up until about mid week.
We should reside near the southern edge of the westerlies aloft on
Sunday. Our surface air mass is expected to modify to dew points in
the 65-70 range by then, with strong sun pushing highs to about 90
or a little warmer. The resulting forecast soundings show ample
instability. The question is whether or not there will be any
feature on which convection can focus. Being at the southern edge of
the westerlies aloft could provide something (perhaps a MCS
remnant), and a 20% POP was used. After this, the faster flow aloft
retreats to our north and northeast, and with this a dry forecast
was used for Monday. However, heat will remain.

After this, a large scale upper trough will be dropping southeast
out of Canada toward the Great Lakes and Ohio Valley. It will result
in geopotential height falls over our region for Tuesday, and
increasing mid/upper level flow by Wednesday along with further
height falls. The trough will also support a cold front which is
expected to approach Tuesday night and reach KY on Wednesday. Low
level flow ahead of the front will bring higher dew points off the
gulf into our area. The approaching upper level trough and
increasing dew points may allow for a few showers/thunderstorms on
Tuesday and Tuesday night. However, the highest POP looks like
Wednesday as the front arrives, and likely category was used area
wide.

Model agreement drops off after this point with regard to frontal
progression. The 12Z run of the GFS takes the front far enough to
our south to allow for dry weather here on Thursday and Thursday
night. The ECMWF is slower, with precip lingering longer, especially
in our southeast counties. A model blend being used will take the
differences into account in its averaging.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 134 AM EDT SAT JUL 13 2024

VFR conditions are expected to prevail. Decided to remove any
mention of fog with the exception of TEMPO groups to 6SM in BR at
LOZ and SME between 08z and 13z. Otherwise, next concern will be
the potential for an isolated shower or thunderstorm during the
afternoon Saturday, with the highest probability toward SME and
LOZ. With confidence low, will keep any mention of VCSH or VCTS
out of the TAFs with the 06z package, but may add it in for the
12z package if confidence increases. Cloud bases look to average
between 4 kft and 5 kft during the afternoon. Light winds are
expected, with the exception of a light west-northwest breeze
between 5 and 8 kts developing between 15z later this morning and
01z this evening.

&&

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

$$

SHORT TERM...CMC
LONG TERM...HAL
AVIATION...CMC