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715
FXUS61 KILN 230717
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
317 AM EDT Sun Jun 23 2024

.SYNOPSIS...
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Showers and thunderstorms are expected ahead of a cold on
today. A brief respite in the heat and humidity is expected on
Monday, before warmer and more humid air quickly builds back
into the region on Tuesday, along with chances for storms
Tuesday night through Wednesday. Drier and cooler conditions
will then return for the last part of the workweek.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The first main item of interest for the near term period will be
timing the large broken line of convection currently upstream
stretching from srn MI back into srn IL, which will continue to
progress to the ESE and into the local area around daybreak.
The expectation is that this line of SHRA/TSRA will become
increasingly disorganized as it encounters a slightly less
favorable environment for maintenance of coverage/intensity with
eastward extent. This is depicted well on ACARs soundings in
the downstream environment, which sampled several layers of
warm air aloft and only marginal/skinny deep-layer instby. This
suggests that, although there will be some individual cell
interactions that promote pulse ups from time-to-time as the
activity moves into the ILN FA, the overall trend should be one
of further disorganization and decreased intensity. This is
already being seen to some extent via a decrease in lightning
and warming cloud tops. And even with this being said, with
some CIN locally and a near-sfc inversion, the convection should
become increasingly elevated, suggesting the overall threat for
gusty to damaging winds locally with this initial activity is
rather low.

However, PoPs were increased across the board from the blend to
account for the expectation that most spots will see at least
/some/ rain out of the morning SHRA/TSRA, even if it only
amounts ranging from a few hundredths to a quarter to third of
an inch. This line of convection should be very near the I-71
corridor by about 12z, pushing further to the SE through 15z
and eventually moving out of the local area around noon.

Focus will then shift to the expectation of additional
development of TSRA /behind/ the morning activity as we progress
into early/mid afternoon. There will be quite a bit of LL
moisture that will have filtered into the area ahead of the
front, with dewpoints largely in the lower 70s, supporting
moderate instby within a narrow SW-to-NE oriented axis. Within
this moist LL environment will also be a favorable DCAPE
environment for downward momentum, suggesting that localized
gusty to damaging winds will be the primary threat with the
strongest storms. LL and deep-layer shear will be decent, with
0-6km shear on the order of ~30kts and good speed shear through
the column. LL flow will increase as well with a tightening of
the pressure gradient, with H8 flow generally about 25-30kts
into the afternoon. This being said, the best LLJ will be
pulling to the E of the area by early afternoon, with the subtle
LL convergence amidst a largely-uncapped environment providing
the main source for lift to promote ISO/SCT redevelopment,
primarily near/SE of the I-71 corridor. The best overlap of
instby and shear parameter spaces will probably be within a
corridor from about Licking Co OH through Robertson Co KY and
points to the east within the 18z-22z time frame. Thereafter,
the front will begin to shift far enough to the SE that the best
coverage and intensity of storms should focus outside the local
area, with quiet (and sunny) skies returning for the area
toward sunset. Do think that a few strong to severe storms will
be possible this afternoon in the aforementioned areas, but
there are uncertainties regarding the coverage of the strongest
storms and just how many spots locally will see this potential.

Wind gusts (outside of storm activity) will be on the order of
20-25kts today, subsiding abruptly toward/beyond sunset.

Highs should generally top out in the lower to mid 80s amidst
very muggy conditions late morning through late afternoon. Drier
air will filter in from the NW toward sunset and beyond.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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Tranquil conditions will prevail through the short term period
as /much/ drier air briefly settles into the OH Vly tonight
through the day Monday. This will mean slightly cooler
conditions tonight (with lows generally in the lower to mid 60s)
and abundant sunshine on Monday as highs top out in the mid to upper
80s.

Light northerly flow will keep the dry air entrenched across the
local area through Monday night, before the humidity returns
rather aggressively by late Tuesday.
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&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Some of the driest air of the period will be departing the region at
the start of the extended period. Monday night`s low temperatures
will fall to the low 60s with Tds in the upper 50s. A welcome
relief compared to how it`s been feeling.

However, we quickly rebound quickly rebound on Tuesday with another
surge of theta-e into the region ahead of the next system... a
rather potent low are of low pressure that is carving its way
through Canada. Most recent run of the blend has backed off a bit
the heat indices on Tuesday by about 8 to 10 degrees. We`ll see if
this trend continues. Either way, should still be a warm day on
Tuesday with feels-like temperatures reaching the 90s.

As a cold front is dragged into the Ohio Valley Tuesday
afternoon/evening, showers and storms will be forced out ahead of
it. Right now, there is still some ambiguity as to when storms will
move through (Tuesday late night? Wednesday day? Perhaps more than
one round?). Some guidance still hints at a MCS blowing through the
region at some point, but consistently between runs in terms of
timing/location has been lacking. Either way, the area is still lit
up by Colorado State machine learning Tuesday/Wednesday and given
ample instability that will be in place combined with the parent low
pressure moving through, would expect some type of organized
convection. Would also be remiss not to note that with PWATs 2
standard deviations above normal, any storms that roll through will
likely have some efficient rain rates. Any training that occurs may
result in areas of localized flooding or runoff.

Thursday will provide another break from the excessive heat in the
post frontal air with highs in the low/mid 80s with dry weather as
weak ridging and surface high pressure move into the region. By
Friday, temperatures look to warm again as southerly flow returns
ahead of another disturbance.
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&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
A few VFR Cu continue to percolate about the area, with
increasing/thickening mid/high clouds set to move into the local
area within the first few hours of the TAF period. This will be
accompanied by a weakening/decaying broken line of SHRA/TSRA,
but latest guidance suggests the activity will hold together
through most, if not all, of the local area between about
12z-15z. Some brief MVFR VSBYs will be possible with the
heaviest activity. Behind the morning SHRA/TSRA, there may be a
brief break before ISO/SCT convection redevelops, especially
by/after 17z. This will be most favored for locales near/SE of
I-71 until about 21z-22z before activity moves to the SE of the
local terminals thereafter.

Some VFR CIGs are expected, with borderline MVFR CIGs possible
at nrn sites of KDAY/KILN/KCMH/KLCK between about 14z-17z.
However, did not yet have confidence to add MVFR CIGs to the
fcst at any of these sites, but it is mentioned here for
awareness purposes.

SW winds around 8-10kts will increase to 12-15kts, with gusts
between 20-25kts, developing by/after 15z. A wind shift to out
of the NW will occur between about 21z-22z for the local sites,
with gustiness tapering off toward/beyond sunset.

OUTLOOK...Thunderstorms possible late Tuesday through Wednesday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...KC
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...CA
AVIATION...KC