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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 171740
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
140 PM EDT Wed Apr 17 2024

.SYNOPSIS...
Showers and a few thunderstorms will be found over the region
today ahead of a cold front crossing in the late day and early
evening. Zonal westerly flow will be found behind the front
until a surface low tracks through northern Ohio overnight
Thursday, with a trailing cold front affecting the entire
region. Building high pressure behind this second front will
keep a cool pattern in the Ohio Valley through the weekend.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
Looking at recent reflectivity data, storms being forced by the
cold front are starting to pop in western Indiana/ southwestern
Michigan. Satellite imagery depicts a wide dry slot moving into
our region at the time of this writing. Anticipating that this
insolation will help us destabilize a bit easier this
afternoon; ACARS out of IND supports this thinking.

12Z CAMs suggest that this line will swing through our area during
the mid afternoon hours extending through much of the CWA,
however, the greatest severe threat still appears to be along
and north of I-70 where forecast UH swaths gain intensity nearer
to central and eastern Ohio. With the conditional severe threat,
all hazards still remain on the table with MLCAPE of 1500+,
effective bulk shear values 40-45 kts, steepening lapse rates,
and subtle turning in the lowest levels. Any severe threat/
storms that do move through our region should have moved east by
evening hours- this looks to primarily be an afternoon show.

Outside of convection, gusty winds will move through the region
with the stronger pressure gradient and cold frontal passage.
For now, have highlighted this in the HWO.

Finally, continued high PWATs and wet vertical profiles will
result in effective rain rates, potentially leading to areas of
isolated flooding.

Previous discussion->There is a strong push
from the models to limit any showers over the region to the
northern CWA, where thunder will be at a peak from 19-23Z.
Strong winds 15-25 mph with gusts to 30-35 mph will make for a
breezy day. Day 1 outlook did not agree with the chance of
precipitation as noted by surrounding forecast offices including
ILN. Our forecast this morning looks overdone when compared to
surrounding offices, but it felt too hasty for our area to be
cut that much that early.

Severe threat appears to be limited to CWA along and north of
the I-70 corridor, probably a little more north than along. As
per usual lately, model agreement is not so easy to come by. A
few note a strong decrease in this afternoon`s dewpoints, into
the mid and lower 50s which would lead to little activity if
realized. The negatively tilting trough crossing through
northwest Ohio has been gaining some speed when compared to
prior models. This suggests a very narrow corridor where
dynamics /could/ come in play with an equally narrow corridor of
moderate instability. This instability is primarily aloft and
any lower based storms would need to punch through a fairly
strong cap. Likewise, elevated storms that may develop will
have a difficult time bringing the bulk of their energy to the
surface, and the bulk of the energy available looks to be
modest at best.

All this being said, a slight chance of severe winds near 60 mph
could accompany the strongest storms for a brief window of time
this afternoon over the northern third of the CWA. Expect the
trend will be to reduce even more the threat and footprint of
storms as new models come in this morning.

Highs today will be in the 70s with breezy conditions.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM THURSDAY/...
A cold front will have crossed most of the CWA by this time, but
may still be located east of the Scioto River. Winds will have
died down to a more manageable 8-12 mph overnight, more like
10-15 over the northern half. A surface ridge of high pressure
will work into western CWA by daybreak. This will cut winds even
more to the 5-10 mph category that should persist through the
day as the high crosses to the east.

With clearing sky cover, overnight lows will drop from the
upper 40s in the northwest, low 50s for most of the CWA, and
maybe only the mid 50s over parts of northern Kentucky and the
lower Scioto Valley.

Some increasing high clouds on Thursday will be found in the
latter half of the day, particularly in the northwest. A lighter
wind and abundant sunshine for most of the area will see highs
reach the mid and upper 70s, some lower 70s in west central
Ohio.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
The long term period is going to start off on an active note as
a midlevel S/W ejects E through the central/srn OH Vly within
the quasi-zonal flow aloft. This will be the impetus that
/finally/ brings a more concerted push of cooler/drier air back
into the region, which will settle in this weekend through early
next week.

But before we get to the quieter weather for this weekend, it
is worth noting that the signal for potential active weather has
increased over the past day or so (particularly for the Tri-
State and points further to the SW in KY). The reason for
heightened concern stems from the fact that the front that will
push through today/tonight (Wednesday/Wednesday night) will lose
southward momentum late tonight, essentially stalling out just
to our S and pivoting back to the N rather abruptly during the
day Thursday as the S/W moves into the mid MS Rvr Vly. The lack
of a stronger push of the front to the S means that the
reservoir of LL moisture/warmth will be able to filter back in
(to near/just N of the OH Rvr) by Thursday evening, and may do
so rather easily. The trend in temp guidance upward for Thursday
has been notable and points to at least some cause for concern
as the S/W moves into the region Thursday evening/night. Ample
forcing should spread W to E, with a pool of moderate SB-instby
on the order of 1500-2000 J/kg (courtesy of sfc DPs in the lower
60s) residing immediately ahead of it near/SW of the Tri-
State/N KY.

While the attendant sfc low is not all that strong/deep, it
will have plenty of mid/upper level support to promote broad-
scale lift with the diffuse warm front able to make it to near
I-70 by Thursday evening. Sufficient deep-layer (sfc-6km) shear
on the order of 40kts should promote some storm organization,
with indications for one or more bowing structures to track/ride
to the ESE along the nosing instby gradient NE near the OH Rvr
from Bloomington, IN to CVG. The best SB-instby should pinch off
with north/eastward extent, but there is considerable
uncertainty in just where this will occur. Of course, pattern
recognition tells us that it is likely that the clusters/bowing
segments of convection will take on more of a SE trajectory with
time (tending to go toward the richer LL moisture to the S),
perhaps only grazing the Tri-State of SE IN, SW OH, and N KY
between about 02z-06z Friday, with additional (potentially
slightly elevated) convection extending further N in EC IN and
WC OH and the Miami Valley. The LL thermodynamic environment
should be increasingly questionable closer to I-70 Thursday
evening/night, lending doubt to the prospect of strong/severe
storms this far north. However, should sufficient sfc-based
destabilization occur immediately ahead of the convection, the
greatest (conditional) threat with the activity near the Tri-
State into N KY will undoubtedly be strong to damaging winds,
especially in such a favorable (~1000J/kg) DCAPE environment. Of
course, if the convection is able to grow upscale into a larger
bowing segment, the potential for more widespread strong/severe
wind gusts would evolve, likely focusing /just/ to the SW of
the ILN FA in parts of NW/central KY late Thursday evening.
Nevertheless, there is enough of a signal to add mention of
strong to severe storms (with damaging wind gusts) for parts of
the Tri-State late Thursday evening based on recent trends. This
potential will likely reside in a rather small temporal and
spatial capacity, but will add mention nonetheless.

As we progress later into the night Thursday, there still
should be SCT to numerous TSRA activity, although likely in a
weakening trend with northward/eastward extent. Do think that
most spots see /some/ pcpn Thursday evening/night, with the
severe threat focusing near the Tri-State from about 02z-06z or
so.

The SHRA/TSRA activity will sweep through the remainder of the
area late Thursday night into Friday morning, trend dry
progressively from W to E between 12z-15z. Much cooler/drier air
filters in from the NW in the post-frontal environment, with
some sunshine likely to return for most spots by Friday
afternoon as daytime highs generally range from the upper 50s to
mid 60s.

Several chilly nights are on tap each night Friday/Saturday/Sunday
as very broad-scale troughing evolves for the OH Vly and points
eastward this weekend. The coldest nights are likely to be
Saturday night and Sunday night as temps dip into the mid to
upper 30s. Some frost will be possible both of these nights,
particularly near/N of the OH Rvr and in the typical sheltered
locales. Expect that SHRA activity associated with the system
darting across the TN Vly late Saturday into Sunday should stay
S of the ILN FA, with dry conditions expected to prevail Friday
morning through Monday.

Daytime highs Saturday will generally be in the upper 50s,
followed by lower 60s Sunday and mid 60s Monday. The next
widespread chance for rain will arrive Monday night into
Tuesday, with temps generally getting back close to, or above,
normal by midweek next week.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
A line of storms ahead of a cold front currently moving into
northwest Ohio will continue eastward this afternoon. All site
(except KCVG/KLUK) has a period of TSRA when storms are forecast
to move through. For the two southern sites, confidence is
lower that storms will reach that far south, so opted to keep
TAFs cleaner for the time being.

Outside of storms, CIGs have cleared up to a scattered deck of
stratocu and will continue clearing through the evening hours.
Strong southwesterly winds, gusting to 35 knots, shift to out of
the west after frontal passage. Winds remain elevated through
the afternoon but will decrease around sunset.

Clouds continue to decrease into the overnight hours and VFR
conditions should prevail into Thursday morning. Some hi-res
guidance hints at patchy fog development in southwest Ohio/
northern Kentucky after winds die down, however, doesn`t look to
be widespread or dense, therefore have not included in TAFs.


OUTLOOK...Showers and thunderstorms with MVFR CIGs/VSBYs are
possible Thursday evening into Friday. Wind gusts around 30
knots are possible Friday.
-- End Changed Discussion --

&&

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

&&

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