379
FXUS63 KJKL 260843
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
443 AM EDT Wed Jun 26 2024

.KEY MESSAGES...

- Heat and humidity lingers today.

- The next good chance of rain comes today into this evening.

- Hotter weather is expected to make a comeback by Friday and
  especially Saturday, with afternoon highs in the low to mid 90s
  and heat index values peaking around or in excess of 100
  degrees.

&&

.SHORT TERM...(Today through Thursday)
Issued at 443 AM EDT WED JUN 26 2024

Early this morning, an upper level ridge was centered over New
Mexico and extended north through the Rockies while an upper level
low was centered northeast of Hudson Bay with a trough south
across the Great Lakes and into the eastern Conus. A shortwave
trough was nearing the mid MS Valley and Lower OH Valley while
another shortwave trough was further north and nearing Lake
Superior/western Great Lakes. At the surface, an area of low
pressure was centered over Quebec with a frontal zone extending
into the Great Lakes to Central Plains and then into the western
Conus. Locally, sprinkles or light showers falling mostly from mid
level clouds were moving across south central KY and eastern KY
while further west nearer to the approaching shortwave trough,
deeper convection including some thunderstorms extended from IN
into western portions of KY and TN. Cloud cover and a more moist
airmass in general was leading to milder temperatures compared to
24 hours ago. At present, PW is analyzed in the 1.2 inch to 1.5
inch range from southeast to central KY while PW increases further
toward the 2 inch mark in portions of the Lower to Mid MS
Valleys.

Today, the initial shortwave trough is expected to progress east
and more or less merge with the more potent shortwave to its
north that rotates across the Great Lakes and then works into the
Northeast, Mid Atlantic states, and Appalachians this evening and
tonight. The axis of the trough at 500 mb should shift east and
southeast of the Lower OH Valley late tonight and on Thursday with
a trend of increasing 500 mb heights during that timeframe.
Meanwhile, sfc low pressure will track into the Maritimes with the
trailing cold front sags southeast into the OH Valley today,
dropping south of the OH River this afternoon and evening and
southeast of eastern KY tonight. Sfc high pressure builds from the
Northern Plains into the Upper MS Valley and Great Lakes as well
as the OH Valley on Thursday behind the boundary.

Ahead of the boundary today, PW is forecast to climb to about the
1.5 to 1.9 inch range while dewpoints climb further through the
60s to near the 70 degree mark. Debris clouds from upstream
convection could limit instability during peak heating, and 0Z
HREF mean MUCAPE is forecast to climb to about the 1000 to 1750
J/kg range and bulk shear of about 20 to 25KT while 03Z RAP has
MUCAPE values peaking about 500 J/kg higher and bulk shear of
about 15 to 20KT in the south to nearly 30KT in the north.
Meanwhile, the 03Z RAP has MLCAPE peaking at about 1000 to 2000
J/kg. The 0Z HREF has the highest 2-5km UH probabilties in the
north where guidance generally has the higher MLCAPE and slightly
better shear. If debris clouds are more on the minimal side, the
higher end of the instability range would be realized while more
in the way of clouds would lead to cooler temperatures and less
instability. Low level lapse rates are forecast to peak in the 7
to 9C/km range with rather meager mid level lapse rates in the 5.5
to 6.5C/km range. Overall, these parameters as well as CAMS point
toward marginally severe wind gusts being the primary threat this
afternoon and evening with locally heavy rain possible with any
training cells and small hail not out of the question with the
strongest cells. The highest chances for convection are expected
this afternoon and evening near peaking heating which should
coincide with the front working into eastern KY and the approach
of the 500 mb trough.

Moisture will linger a bit longer over the southeastern portions
of the area later tonight and into Thursday as compared to
locations further north. Showers or an isolated thunderstorm will
be possible into Thursday south of the Mountain Parkway and
especially for areas south of the Hal Rogers Pkwy and KY 80
corridor with drier air moving into the area and height rises
combining for diminishing chances even in the south on Thursday
afternoon.

Highs today should be similar to Tuesday if not a degree higher
on average for most areas assuming debris clouds do not limit
temperatures. Highs mainly in the upper 80s to low 90s combined
with dewpoints well into the 60s if not around 70 should result in
peak heat indices in the mid 90s to near 100 for many locations.
Highs for Thursday are expected to be similar to what was
experienced with the post frontal airmass back on Monday, in the
low to mid 80s and in the 70s above 2500 feet.


.LONG TERM...(Thursday night through Tuesday)
Issued at 443 AM EDT WED JUN 26 2024

The long term discussion will be issued shortly.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 220 AM EDT WED JUN 26 2024

VFR conditions were prevailing across the area at issuance time
and VFR and will generally persist through 00Z, before more
widespread convection will lead to areas of MVFR generally in the
north. Sprinkles and or mainly light showers are expected over
the first 6 to 12 hours of the period, before renewed chances of
showers and thunderstorms to all TAF sites after 18Z/Wednesday
through the remainder of the period as a cold front and shortwave
trough work across the Lower OH Valley. Lastly, light and
variable winds are largely expected except where convection
exists.

&&

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

$$

SHORT TERM...JP
LONG TERM...JP
AVIATION...JP