442
FXUS63 KJKL 291915
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
315 PM EDT Sat Jun 29 2024

.KEY MESSAGES...

- Hot and humid weather is expected today, with afternoon highs
  around 90 degrees and heat indices peaking around 100 to 105
  degrees in some places.

- Thunderstorms are possible through Sunday as a cold front
  approaches and moves through. A few storms this afternoon
  through the early overnight could produce strong wind gusts and
  heavy rain.

- A short-lived break from the heat and humidity is forecast on
  Monday behind the cold front, quickly followed by a return of
  sultry conditions.

- An active period of showers and thunderstorms may impact the
  Fourth of July holiday period from Wednesday through Friday.
  Best chances for showers and thunderstorms as of now are
  expected Thursday July 4th during the afternoon and evening.
  Heat indices will return to near 100 degrees for many locations
  as well during this time period.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 253 PM EDT SAT JUN 29 2024

A series of shortwaves will maintain a broader upper level trough
moving east across the Midwest, northeast CONUS, Ontario, and Quebec
this weekend. We are on the southern edge of the prevailing
westerlies aloft associated with the trough. The trough will support
a surface cold front which will approach tonight and then pass
through from northwest to southeast on Sunday. Low level southwest
flow ahead of the front has transported warm and humid air across
the region, with highs in the upper 80s to lower 90s and dew points
in the mid 70s, with heat indices in the upper 90s to lower 100s
this afternoon.

Forecast soundings indicate capping in the middle atmosphere this
afternoon as mid-level heights continue to rise, which has
seemingly thus far prevented anything more than spotty shower
activity. However, by mid-evening height falls occur as a strong
shortwave moves across the Great Lakes region, and all models
indicate the atmosphere becomes uncapped, with CAMS depicting one
of more thunderstorm clusters moving across the forecast area from
northwest to southeast, likely emanating from upstream
development. As for the severe threat, the 20 to 30 kts of shear
with moderate instability supports a Marginal Risk especially as
any potential MCS moves southeast into the forecast area primarily
this evening.

With expected shower and thunderstorm activity occurring mainly
this evening into the overnight, any rain followed by partial
clearing toward dawn will support fog development. Regardless,
expect warm and "soupy" conditions through the overnight with even
the valleys remaining at 70 degrees or higher.

The cold front will move southeast through the forecast area on
Sunday with a similar atmospheric set-up ahead of the front.
Southeast KY won`t have fropa until late Sunday and stands the best
shot at seeing more thunderstorms, while the far northwest part of
the forecast area is likely to have fropa before sufficient heating
to support development.

A much cooler and drier air mass moves into the region behind the
front, with temperatures falling into the mid 50s to lower 60s, with
warmer conditions in the valleys, especially if mixing from cool air
advection continues through the night.

.LONG TERM...(Monday through Saturday)
Issued at 315 PM EDT SAT JUN 29 2024

The various guidance including the ensembles are showing that a cold
front will push south of eastern Kentucky by early Monday. Then high
pressure builds into the Ohio Valley ushering in northeast flow
at the surface. This will aid in ushering in a much cooler and
drier airmass into the region. The airmass will be anomalous for
the first day of July, with PWATs running around 2 standard
deviations below normal and even some indication in ensembles we
could see near record min PWAT values for this time of year. The
afternoon highs will be running in the mid to upper 70s for most
locations and that around 5 to 10 degrees below climate normals.
These cool temperatures and decent afternoon mixing will set the
stage for a cool readings Monday night into Tuesday morning. That
said, lows in the low to mid 50s in the valleys and mid to upper
50s on the ridges under clear skies and good agreement on building
mid-level ridge for Monday night into Tuesday morning.

By Tuesday, there is good agreement on mid-level heights continue to
rise and high pressure pushes east allowing for some moisture
return. The cold front also pushes northward as a warm front Tuesday
afternoon. Even so, while warming into the upper 80s to lower 90s we
will see most locations see heat indices remain in the lower 90s.
This as moisture will lag behind some. However, ensembles and
deterministic guidance continue to build heights and moisture into
mid and late week timeframe. This will lead to warming, with
highs in the low to mid 90s by Wednesday and near 100 heat indices
possible at some locations. While most of Wednesday will be dry,
we could see some weakening in the ridging leading to the
potential for some shower and thunderstorm activity in the
afternoon (around a 15-30 percent chance of rain). The various
suites of guidance show this ridging breaks down further and we
become quasi-zonal mid-level flow across the Ohio Valley opening
up the potential for ridge riding mid-level waves. The NBM ramps
up chances of showers and thunderstorms to around the 60-70
percent range peaking Thursday afternoon. This seems reasonable
and some of these could be efficient precipitation producers given
the PWATs come back up closer to 2 inches or higher.

By the end of the week, there is some uncertainty on the
evolution of the waves mentioned before. However, given the ample
moisture and upstream cold front will stick with the NBM chances
of rain in the 60 percent range Friday. After this the models
really struggle with the passage of the previously mentioned cold
front and therefore keep Saturday chances of rain in the 30 to 50
percent range for now. However, could see this fluctuating before
that timeframe with some guidance suggesting it would be dry most
locations Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 132 PM EDT SAT JUN 29 2024

Showers and thunderstorms will impact the TAF sites at times
through the period. Main window of concern is between 00z and 12z
with one or more thunderstorm clusters depicted by high-resolution
mesoscale models. With a clear trend in these models, decided to
be a little more on the aggressive side with timing TSRA activity
this evening into the overnight. Meanwhile, until around 00z
expect more isolated to widely scattered showers and
thunderstorms. The spotty nature of this activity precludes
anything other than a mention of VCTS at this time. A few storms
could be strong to severe and produce gusty winds. If
rain/thunderstorms impact TAF sites and there is any partial
clearing by dawn, fog will likely impact those TAF sites. Aside
from fog and precipitation, VFR conditions are expected. Light but
occasionally gusty southwest winds will gradually diminish into
the overnight, then become northwesterly late in the TAF period at
KSYM as a cold front bringing much cooler and drier air begins to
move across the area from northwest to southeast during the day
Sunday, mostly after 18z.

&&

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

$$

SHORT TERM...CMC
LONG TERM...DJ
AVIATION...CMC