312
FXUS63 KJKL 291853
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
253 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...(Sunday night through Friday)
Issued at 510 AM EDT SAT JUN 29 2024

Models are in good agreement with the main synoptic features and
pattern evolution aloft through the extended. Low amplitude trough
will be passing from the Great Lakes through the Upper Ohio Valley
and New England at the start of the period. Southern CONUS ridging
aloft will shift eastward and amplify as the center of the high
transitions to the southeastern CONUS. This results in ridging
building over our region within 24 hours of the start of the period.
Ridging remain generally over the eastern CONUS through the first
half of the extended. Short wave energy then begins to ride across
the northern periphery of the ridge and suppresses it southward
through the latter half of the extended, putting eastern Kentucky
under an increasing threat of unsettled weather with each passing
day. At the surface, Canadian high pressure will move into the
region behind an exiting surface cold front, transiting the Ohio
Valley, moving from the Upper Midwest to the east coast by
Wednesday. Thereafter, southerly return flow kick in for the
remainder of the forecast window.

Sensible weather features a continuation of seasonably hot, muggy
weather in general. However, the Canadian high pressure system will
provide another temporary (day or so) break from the summer heat and
humidity (lower dew points) from Sunday night through Tuesday
morning. This brief cool off will be very similar to the recent 1-2
day breaks from the humid, hot summer weather we have experienced on
and off over the past few weeks. Southerly flow will bring moisture
back into the area by midweek. Combined with the heat, the muggy
conditions will make our environment ripe for additional shower and
thunderstorm activity through the latter half of the extended.

For hazards, afternoon MLCAPES increase to between 1000 and 1500
J/kg on from Wednesday through Friday. However, as has often been
the case of late, bulk shear is marginal at best, less than 25 kts
on Wednesday and Thursday. The exception is our Bluegrass Counties,
where the shear creeps up to around 30 kts late Thursday. Bulk shear
increased more readily across the entire area by Friday, to around
30 kts. Thus while there will be the potential for strong to severe
storms, prefer to see overall better bulk shear (35 kts or more) for
the stronger more widespread or organized convection. In addition,
mid-level lapse rates and wind fields are rather unimpressive. Thus
at this time, any severe thunderstorm potential will be limited and
generally restricted to a wind threat. PWATS increase to around the
90th percentile of climatology by Thursday and Friday. Therefore can
not rule out some locally heavy rain, especially with any stronger
storms.

&&

.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...RAY
AVIATION...CMC