827
FXUS61 KILN 211347
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
947 AM EDT Tue May 21 2024

.SYNOPSIS...
Much above normal temperatures continue about the region through
midweek, with episodic showers and storms expected Wednesday
into the upcoming weekend. Although slightly cooler temperatures
may return for the end of the week, temperatures will likely
stay above normal for the foreseeable future with an unsettled
pattern persisting into early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Dry weather conditions favored across the CWA today. Main story
will be the hot and humid air mass that will continue to provide
warmer than normal temperatures throughout the Ohio Valley. A
few locations may be able to reach the 90 degree mark today,
with dewpoints hanging around the lower to middle 60s.

While no large-scale forcing/ascent will be in place, this
unstable air mass may allow for diurnally driven
showers/storms, mainly across portions of southern OH/northern
KY. Anything that develops will be isolated in nature, but a low
chance does exist for this potential.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
The short term period will turn a bit more active than has been
the case the past several days. And it will start with a
weakening MCS that should move into the local area during the
predawn hours Wednesday morning. This bowing/linear structure,
emanating from IA/IL, should outrun its source forcing/lift and
encounter an increasingly unfavorable (more stable) environment
with eastward extent. This being said, due to the organization
of the convection, often times the storms are able to survive
and maintain a bit longer than perhaps some guidance suggests.
So the inclination is that at least /some/ structure of the
convection will be maintained into the ILN FA during the predawn
hours, likely providing a few rumbles and perhaps some brief
gusty winds. This being said, the overall LL thermodynamic
environment shouldn`t be terribly favorable for strong/gusty
winds to be maintained in a widespread sense. Any gusty wind
potential would likely occur coincident with any N-S oriented
segment that is able to be maintained with eastward extent,
especially near the Tri-State between about 09z-12z Wednesday.

At the very least, some patches of light rain and extensive
cloud cover will overspread parts of the local area Wednesday
morning, continuing to wane with SE extent. Subsidence and a
stable environment should develop in the immediate wake of this
feature, delaying the best destabilization efforts toward mid
afternoon. While significant destabilization should eventually
evolve, especially for locales near/W of I-71 by mid/late
afternoon, there remain some questions regarding coverage of
redevelopment during the afternoon itself as the LL
southwesterly flow is largely parallel to the front/boundary,
with very little in the way of pronounced LL convergence. This
is not to say at all that there won`t be a few storms that
redevelop amidst the strongly unstable environment during
mid/late afternoon, but the real impetus for redevelopment is
likely going to be better S/W energy coming in from the srn
Great Lakes, with additional S/W energy (perhaps an MCV remnant)
drifting to the NE into the SW OH Vly, near/after sunset. This
slightly better forcing, amidst strong instability, should
allow for better blossoming of storm activity toward/beyond
sunset, initially to the W of the immediate local area.

For Wednesday evening/night, while confidence in storms
occurring is high, confidence in severe potential or coverage of
severe storms, is somewhat lower. The greatest severe potential
locally may end up being during the evening hours itself as
there should be sufficient overlap of good deep-layer shear and
strong instby (owing to impressively-steep midlevel lapse
rates). This suggests that, pending sufficient CI, there could
be some storm organization posing a damaging wind and large hail
threat. But, pushing aside questions of afternoon/early evening
coverage, as we progress later into the evening and into the
overnight, the thermodynamic environment should become a bit
less favorable for maintenance of strong/severe storms, despite
the potential maintenance of quite a bit of storm coverage.
There is little doubt that there will be rumbles persisting
through parts of the area through the nighttime into early
Thursday morning, but do think the best severe potential, with
robust updrafts, would likely manifest itself during the
evening, particularly near the Tri-State/along I-71.

As we progress later into Wednesday night, the main concern may
shift to a localized heavy rain/flooding threat, especially if
convection trains over the same areas. The anomalously-high
PWATs combined with the largely boundary-parallel flow suggests
that repeated storms/heavy rain over the same areas is very-much
in play into early Thursday morning, particularly near/S of I-70.
Will add mention of heavy rain/flooding to the HWO for awareness
purposes.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The extended period begins Thursday with showers and storms exiting
the middle Ohio Valley as a surface wave of low pressure shifts off
to the east. In its wake, the overall pattern will consist of
positive height anomalies over the southern Plains and negative
height anomalies across the northern tier of the United States. This
sets the stage for multiple disturbances moving east in zonal flow
through our local area.

Temperatures will continue at above normal levels without a source
of cooler drier air through the period. The first disturbance
arrives Friday, with showers and a few storms likely, particularly
during the afternoon hours. PoPs will be highest near and south of
the Ohio River. The next major disturbance arrives on Sunday with
widespread showers and a few storms.

To close the period on Monday, we get our first signs of a pending
pattern shift as a sharp mid-level trough is kicked east from the
northern Rockies heading toward the Great Lakes and Ohio Valley.
This will cause showers ahead of the trough on Monday.

Details on severe threat aren`t clear at this time. However, from a
broad perspective, we will need to watch for hydro impacts depending
on where the heaviest rainfall is focused through the extended
period.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
SCT/BKN convective blowoff cirrus continues to migrate through
the region, with a few patches of 6-8kft clouds also percolating
about the area. VFR conditions will prevail with some
diurnally- driven VFR Cu sprouting about again around 15-16z,
with a bit more coverage expected today owing to better LL
moisture content.

Cannot completely rule out a spotty SHRA/TSRA during the peak
heating hours between 18z-23z, especially near KCVG/KLUK/KILN,
but coverage should remain fairly limited and did not yet have
the confidence to include even a VC at these sites. The better
chance for more widespread SHRA/TSRA (albeit still somewhat low)
will arrive after 09z Wednesday in the form of a weakening MCS
that should move into the ILN FA toward daybreak Wednesday. Have
included a VCSH for KCVG/KLUK for now, but even this may be
overdone.

Light southerly flow at 5kts or less will increase to 10-12kts
and become more southwesterly by/past 15z. Could even see a few
gusts in the 15-20kt range before gustiness subsides once again
toward/beyond sunset.

OUTLOOK...Thunderstorms likely at times Wednesday into Thursday.
MVFR CIGs possible Wednesday into Thursday. Additional chances
for thunderstorms will return Friday and Saturday.

&&

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

&&

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