699
FXUS63 KJKL 141139
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
739 AM EDT Wed Aug 14 2024

.KEY MESSAGES...

- Temperatures return to near normal levels through the remainder
  of the week.

- Humidity and the possibility of showers and thunderstorms will
  increase late in the week, with the highest probability of
  storms arriving Friday afternoon and evening.

&&

.UPDATE...
Issued at 739 AM EDT WED AUG 14 2024

Update this morning increases Sky cover for the next few hours
over the southern part of the forecast area to match current cloud
trends. This activity should diminish and move south into
Tennessee over the next few hours. Grids were updated with
initialization using the latest hourly observations.

&&

.SHORT TERM...(Today through Thursday)
Issued at 310 AM EDT WED AUG 14 2024

Northwest flow aloft continues through the first half of Thursday,
when a disturbance moving into an upper ridge axis approaches the
Mid-Ohio River Valley. At the surface, high pressure continues to
usher a drier air mass in from the north and east, but warm moist
advection increases through the day Thursday ahead of the
approaching upper disturbance, with a warm front moving to the
northeastern third of the forecast area by the end of the period
early Thursday evening.

For today, drier air moves into the region from the northeast
through the daytime hours as a disturbance skirting us to the
northeast moves away from the area. With the drier air and nearly
full sun for most locations, highs should rise a degree or two
from yesterday, with highs on the upper end of the mid-80s.

Upper ridge axis approaches tonight from the west, while the lower
atmosphere begins to transition from departing surface high pressure
to approaching low pressure. This sets up an ideal situation for
decent ridge/valley splits, especially in the deeper sheltered
central and northeastern valleys that are removed from any bodies of
water. Lows tonight will range from the lower to mid-50s in the
coldest valleys to lower to mid-60s on the ridgetops.

Warm, moist advection gradually increases from the southwest
during the day Thursday. A couple of CAMS even develop isolated to
widely scattered showers in the afternoon, particularly the 4-km
NAMNest and to a lesser degree the NSSL-WRFARW-4km models.
However, most models remain dry with just increasing cumulus in
the afternoon as the lower atmosphere begins to moisten and
stability decreases, so will keep PoPs less than 10 through
Thursday afternoon. With warm advection increasing, highs will
begin to rise to as high as 5 degrees above normal for mid-August,
warmest in the northeast where clouds will be slowest to increase
and where there will be some south to southeasterly surface winds
causing some weak downslope compressional warming through much of
the daytime hours.

.LONG TERM...(Thursday night through Tuesday)
Issued at 255 AM EDT WED AUG 14 2024

The extended period will start out Thursday night into Friday, right
as heights start to fall once more across the region due to a
strengthening upper level low and trough that will be making their
way towards the Ohio Valley. The upper level low will arrive at the
Upper Great Lakes by Friday evening/night, with KY in the apex of
the troughing pattern through the day Saturday. The system should
then begin to slowly shift eastward on Sunday, keeping KY in deep NW
flow well into Monday. It is at this point that models really start
to diverge in solutions. Much like yesterday`s forecast,
unfortunately they have not started aligning at this point, so
confidence on impacts across the Ohio Valley are quite low. The GFS
shows rising heights across the region and the influence of an upper
level ridge, while the ECMWF keeps us in a deep troughing pattern -
two very opposite solutions. This disagreement will continue through
the remainder of the forecast period.

At the surface, models are at least coming into better agreement
concerning the Thursday night/Friday system. A surface low will be
co-located across the Upper Great Lakes during this time, dragging a
cold front southward through the Ohio Valley, crossing Kentucky
throughout the day Saturday. Ahead of this front, with the help of
the upper level disturbance moving overhead, precip is expected to
overspread much of the CWA. Precip should peak during the afternoon
and evening hours both days, and seems to be a bit more widespread
during the day on Friday compared to when the front moves through on
Saturday. WPC does have us in a marginal outlook for excessive
rainfall for Friday morning through Saturday morning, which makes
sense with the precip amounts combined with the fact that many
people will have been dry for much of the week leading up to this.

Once the frontal boundary moves through, KY will find itself in the
apex of the trough axis, allowing deep NW flow into the region. This
will advect cooler and somewhat drier air into the region once more.
While highs on Friday and Saturday will be in the mid and upper 80s,
with added humidity from the rain, Sunday and Monday will be the low
to mid 80s, with limited humidity. The question is, will this trend
persist through the rest of the forecast period, and given the
uncertainty in the models, mentioned earlier, it`s really hard to
know. Kept with NBM pops at this point since confidence is quite
low. Interestingly enough, the NBM still has scattered showers and
thunderstorms Sunday into Monday, despite being post-frontal NW
flow. Looking at the individual models, it is likely due to the fact
we are still in the belly of the upper level trough, and therefore
able to create enough instability to generate generally diurnally
driven scattered showers and thunderstorms. Meanwhile, it then keeps
the forecast much drier for Tuesday and Wednesday. However, again,
don`t put much trust in these last two days, as it could easily
change as models hopefully start to trend closer to one another.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
ISSUED AT 711 AM EDT WED AUG 14 2024

VFR flight conditions will prevail through the period at the TAF
sites. Mainly just passing mid- and high-level clouds are
anticipated and a few valley locations immediately near larger
bodies of water may experience valley fog between about 04Z and
13Z tonight with reductions to MVFR/IFR. However, fog is not
expected to impact any of the TAF locations. Winds will be light
through the period, averaging between north and northeast this
afternoon at 5 kts or less but then gradually trending toward the
southeast late tonight.

&&

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

$$

UPDATE...CMC
SHORT TERM...CMC
LONG TERM...JMW
AVIATION...CMC