254
FXUS63 KJKL 172001
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
401 PM EDT Sun Aug 17 2025

.KEY MESSAGES...

- Hot and humid conditions will persist through Tuesday.

- Expect isolated to scattered showers and thunderstorms into the
  evening, mainly across the far southeast portion of the state.

- Following minimal rain chances tomorrow and Tuesday, chances
  peak at midweek and then linger into next weekend.

- Temperatures return to near normal at midweek and remain so into
  next week once rain chances return.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 346 PM EDT SUN AUG 17 2025

Today has been an interesting day on the convection front. Models
have not had a good handle on any of the development, and therefore
haven`t been able to use the models with confidence. A dying MCS was
moving southeast from Indiana during the first part of the day. A
weak, but ever-present outflow boundary developed ahead of this
system, dropping itself southeastward through the Commonwealth
throughout the day. Starting in the late morning/early afternoon
hours, this boundary provided just enough lift for showers and
storms to begin developing. With temperatures already in the mid 70s
early this morning, it didn`t take much to start the lift/and
mixing. These storms have become scattered in nature along the
boundary line, as they continue to sink southward towards the TN and
WV border. For the most part these cells have been progressive, and
very pulsy, which is easing any hydro and severe concerns. However,
there are still a few storms that are pulsing to higher limits, with
brief heavy downpours, strong winds, and frequent lightning. As a
result, a couple SPS`s have been issues so far.

Expect this convection to begin quickly dissipating as we head into
the evening hours with the loss of mixing/heating, and once the
actual weakening boundary drops farther south away from state.

In it`s place, expect a moist atmosphere to persist overnight. Skies
should clear out for the most part, and high pressure is still
broadly in control across the region and points to our south and
west. The combination of subsidence, clear skies, and moisture will
also lead to another night of possibly dense fog (especially in the
deeper river valleys). Tried to denote this in the forecast, but do
expect some tweaks will need to be made as we start to see the white
of the eyes for the fog. Meanwhile, also dropped the deeper valley
location temperatures a bit overnight to account for ridge/valley
differences. Cooler valley temperatures may also lend themselves to
helping fog development, as will any showers that occur this
afternoon.

Tuesday will see a frontal boundary currently located well to our
north (the one which spawned the original southward tracking MCS)
also beginning it`s journey southward as a cold front. The boundary
should make it to the northern JKL CWA during the morning hours,
remaining in place across the region for much of the day and
upcoming overnight hours. Surprisingly the Hi-res CAMs don`t show
much in the way of organized convection - however, then again, they
didn`t today either. Can`t rule out an isolated shower or
thunderstorm during the afternoon, but overall just expect another
round of hot and muggy condition.

The boundary continues to sit across the state Monday night as well,
though again, no clear impacts along this boundary are noted at this
point. Rather, models seem to be trending towards a mostly clear
overnight with more valley fog and humid but cooler conditions.
Temperatures may also be just a slight bit cooler compared to
tonight, but not by much.

Overall, once this convection moves through this afternoon/evening -
it looks to be a pleasant forecast for the short term. If you like
hot and humid conditions that is.

.LONG TERM...(Tuesday through Sunday)
Issued at 340 PM EDT SUN AUG 17 2025

The period is expected to begin with the axis of an upper level
ridge extending from the Four Corners region the mid MS Valley to
VA while an upper level low should be centered west of BC with the
associated upper trough extending south to the west of the
Pacific Northwest. Multiple shortwaves are expected to be moving
around the riding across parts of the Northwest Conus to the
US/Canadian border area to the Great Lakes and northeast. One of
these shortwaves is progged to be working across the western Great
Lakes to parts of the upper MS Valley as the period begins. At
the surface, an area of low pressure is expected to be over the
western Great Lakes at that time with a warm front south and
southeast to VA and a cold front into the Central Plains. A sfc
ridge of high pressure should be centered over the Southern
Appalachians as the period begins as well.

Tuesday to Tuesday night, upper ridging per the consensus of
guidance is expected to build across the Rockies into the Plains to
the Canadian prairies and be centered near the Four Corners region.
Meanwhile, downstream troughing continues to be progged to take
shape from Quebec to the Great Lakes to mid MS Valley to Lower OH
Valley region with the axis of this troughing approaching eastern KY
Tuesday night. Further east, Erin should pass well to the east of
the Southeast US Coast. At the surface, low pressure should track
southeast to OH by late Tuesday night with the cold front
approaching eastern KY as the center of sfc high pressure moves to
the east and southeast.

Locally, once valley fog lifts and dissipates on Tuesday, high
pressure should lead to sufficient capping to keep any convection
isolated on Tuesday. What that manages to develop should be in the
far southeast in the vicinity of the Cumberland Mtns near the KY/VA
border and especially further south into the Southern Appalachians.
The approaching wave and frontal zone will lead to chances for
convection on Tuesday night which could either develop over or move
into the area with the mid level height falls providing some
forcing. Temperatures will remain warm on Tuesday with low to mid
90s common and heat indices could approach 100 in a few of the
warmer spots.

Wednesday to Thursday night, Erin should gradually move north and
northeast and pass between the eastern seaboard and Bermuda though
guidance has quite a bit of spread as to how quickly this occurs
with the recent GFS runs generally faster than recent ECMWF runs. To
the west, the consensus of guidance has the axis of upper troughing
moving only slowly south and east and becoming more northeast to
southwest oriented. The GFS is generally lower with 500 heights and
500 mb height falls. Well to the west, upper ridging is progged to
remain centered near or to the west of the Four Corners region but
also build toward the Pacific Northwest to BC while an upper level
low treks from northern BC to Manitoba. The sfc wave is expected to
pass across the Appalachians to the eastern seaboard Wednesday to
Wednesday evening with the front dropping south across eastern KY.
However, an inverted trough may linger into eastern KY for Thursday
to Thursday night in response to the axis of troughing at 500 mb
near or west/northwest of the area.

The highest chances for convection during the week should come with
the frontal zone dropping across the area on Wednesday into
Wednesday evening combined with the approach of troughing at 500 mb.
Weak steering flow/shear and a frontal zone aligned more or less
from east to west, combined with seasonably high PW in the 1.5 to
1.7 inch range per the 00Z LREF mean may set the stage for isolated
areas that pick up multiple rounds of showers and storms and heavy
rain. Overall, there has been a drop in NBM pops at midweek which
generally would reflect the weaker forcing in the recent ECMWF runs.
Temperatures should drop back to near normal for Wednesday and
Thursday.

Friday and Friday night, downstream of upper ridging over the
western Conus, the lingering weak troughing from the Appalachians to
TX/western Gulf should gradually merge with an upper low that moves
from Manitoba to Ontario with that initial 500 mb trough axis also
shifting east. However, an upper level low should move to Quebec
over the weekend with a trough taking shape south into the Great
Lakes to OH Valley to Southeast. The associated cold front should
gradually move east toward the Appalachians including eastern KY
over the weekend. Chances for showers and storms linger into Friday
mainly in the south and east, generally peaking during the afternoon
and evening as the first shortwave moves east. However, with the
gradual approach of the next front and upper trough over the
weekend, chances fro showers and storms will linger with a general
peak each afternoon and evening though at least isolated showers and
storms may occur on Saturday night as well. Temperatures to end the
week and into next weekend are forecast within a couple degrees of
normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 357 PM EDT SUN AUG 17 2025

An outflow boundary moving south through the state has become the
epicenter for isolated to scattered showers and thunderstorms early
this afternoon. Expect these shower/thunderstorm chances to
continue mainly in the far southeast portion of the state. KLOZ
and KSME seem to be the most likely to be impacted at this point,
but so far things seem to be staying far enough away from the TAF
sites. The boundary will continue to drop south of the state by
the evening, with daytime mixing quickly dissipating any
remaining storms as well. Expect mostly clear skies and light
winds overnight with high pressure in charge. However, much like
last night, lingering moisture (especially for locations that were
impacted by rain showers this afternoon) and cooling temps will
lend themselves to more fog development. Most TAF sites may be
impacted with at least MVFR VIS, but models are really pegging
KJKL and KSJS for VLIFR conditions. Heading into the daytime hours
Monday, once fog has lifted and cleared, a frontal boundary will
begin approaching from the north. However, overall conditions are
expected to remain calm. Light and variable winds are on tap,
along with mostly sunny VFR conditions.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

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