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Area Forecast Discussion (AFD)

Issued by Wilmington, OH (ILN)

                            
000
FXUS61 KILN 170841
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
441 AM EDT Mon Jun 17 2019

.SYNOPSIS...
An oscillating frontal boundary in the region will provide daily
chances for showers and thunderstorms through Thursday
afternoon with a brief dry period possible Thursday night into
Friday. Additional rounds of showers and storms are possible
this weekend, with seasonable temperatures and very humid
conditions persisting through the foreseeable future.

&&

.NEAR TERM /THROUGH TONIGHT/...
Most of the widespread shower and storm activity has tapered off
across the immediate ILN FA, with just a few lingering light
rain showers close to the front north /and approximately
parallel to/ the I-70 corridor. Although forcing is relatively
weak, with the abundant deep-layer moisture entrenched across
the region, spotty shower activity may linger in the far
northern parts of the local area through much of the day today
(with some increase in re-development/coverage later in the
afternoon with the increase in diurnally-driven instability).

A bit further to the south of the broad surface boundary, which
locally stretches from north-central Ohio through north-central
Indiana, a weakening MCV across the Tri-State area will continue
to push east-northeast through daybreak. Although light showers
continue to show a weakening trend ahead of this feature, a few
spotty light rain showers certainly cannot be ruled out closer
to the Ohio River towards sunrise either -- especially with the
arrival of some weak midlevel energy from the southwest during
this time frame. 

As much as we may need an extended dry period, it certainly does
not appear like we are going to get a break from repeated rounds
of showers and storms -- especially in the short and near term
periods. This is due, in part, to a deeper S/W centered over the
southern Missouri Valley which continues to provide impulses of
energy that eject east-northeastward in the quasi-zonal
mid/upper level flow right across the Ohio Valley. This train of
embedded disturbances /and sources for lift amidst a very humid
airmass/ has been proceeding right across the region for several
days now -- and potentially is poised to continue for several
more days in one way or another. 

Although the aforementioned S/W will become a bit more sheared
out as it makes its way toward and through the Ohio Valley
during the near and short term periods, several impulses of
energy will ripple through the region today before the main S/W
arrives by late tonight. Once again we will see diurnally-
driven instby on the order of 2000-3000j/kg develop into the 
area by peak heating in an environment with rather weak /but 
still sufficient/ deep-layer shear to re-initiate convection 
this afternoon. The deep-layer flow is by no means as strong as 
it has been over the past several days, but with enough 
instability still expect some disorganized scattered 
thunderstorms to initiate this afternoon. Although certainly one
favored corridor for such activity will be close to the front 
(near/just north of the I-70 corridor), the forcing for ascent 
is rather broad and ill-focused -- essentially meaning that 
storm coverage and location is a bit difficult to hammer out 
even at short time ranges. With this being said, much of the 
region has received 2 to locally 4 inches of rain over the past 
several days -- with soils very saturated and primed for 
additional rainfall to cause more immediate flooding issues than
would otherwise be the case. So although the convection may be 
disorganized and somewhat chaotic in nature this afternoon, any 
sustained and slow-moving activity may pose a flooding and/or 
flash flooding risk with the wet antecedent conditions. 
Moreover, as the better forcing for widespread ascent arrives 
tonight (via the aforementioned S/W moving northeast into the 
area), the threat for scattered showers and storms (as well as 
the potential for one or more corridors of training storms/heavy
rain) will continue through the end of the near term period. 
With PWATs still in the 1.75"-2" and continued deep warm-cloud 
depths, the environment certainly will be conducive for 
additional instances of heavy and efficient rain and potential 
flash flooding. With all of this in mind, decided to again 
expand the flash flood watch to cover the entire local area and 
carry it through at least part of Tuesday.

As mentioned, additional showers/storms, potentially more
widespread than this afternoon/evening, are expected through the
overnight period and into Tuesday morning. However, it appears
the best coverage (and therefore greatest flash flood risk) will
generally start to shift southeast Tuesday morning into the
afternoon as the S/W begins to pull east of the area. 

Highs today will top out in the upper 70s and lower 80s with
dewpoints around 70 degrees. Another muggy night is expected
tonight, with lows only bottoming out in the mid/upper 60s.

&&

.SHORT TERM /TUESDAY/...
As briefly mentioned in the near-term discussion section, the
axis of the S/W and better forcing will begin to move east
through the local area by Tuesday afternoon with a gradual shift
in best coverage of scattered showers/storms drifting southeast
with time on Tuesday afternoon. As such, decided to end the
flash flood watch for west-central Ohio by 18z Tuesday and keep
it up for the remaining parts of the local area through 00z
Wednesday before finally a brief dry period arrives for Tuesday
night. 

Although the overall widespread rainfall amounts may not be
impressive on their own (up to 2-3+ inches), the prospect of
having even 1-2 inches of rain on these wet soils between now
and Tuesday evening will pose a greater/quicker runoff of 
excessive rainfall than would otherwise be the case. The overall
setup for heavy rain, in terms of environment of forcing, jet 
energy, focused convergent axes, etc. will not quite be as 
impressive as was the case Saturday night into Sunday morning, 
but enough environmental ingredients are there, in conjunction 
with the antecedent conditions, to warrant a flash flood watch 
through part of the short term period. 

The best coverage of showers/storms will be near and south/east
of the I-71 corridor by later Tuesday afternoon, with most (if
not all) of the local area expected to see drier conditions for
Tuesday night. 

Highs on Tuesday will top out in the mid to upper 70s with a
slight (but brief) decrease in humidity near/north of I-70 as 
the front shifts south with time. 

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
An active weather pattern is expected to continue in the long term 
period.  Several rounds of thunderstorm activity is expected from 
Tuesday through Thursday.  While widespread severe weather is not 
expected at this time, there is at least an isolated damaging wind 
threat through this time.  In addition with the several rounds of 
thunderstorm activity, there will be continued flooding concerns as 
well.  There will be a brief break in the precipitation for Friday 
before additional thunderstorm chances on Saturday.

While temperatures most of the week will be in the middle 70s to low 
80s, temperatures are expected to rise into the 80s area wide on 
Saturday.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Showers and thunderstorms have developed along an east-west
oriented front stretching just north of the northernmost local
TAF sites of KDAY and KCMH. Nevertheless, with a very saturated
profile, isolated showers may continue to linger near the I-70
corridor for several hours overnight, with corresponding MVFR
CIGs as well. This activity will be hit-or-miss and disorganized
in nature. Therefore, it appears more likely than not that even
the northern terminals will not see a shower move directly over
a site, although this appears like a shower may be most likely 
for KDAY through the first couple hours of the TAF period. 

Further south, a broad area of stratiform rain continues to 
weaken -- without much in the way of additional development 
expected until around daybreak. However, confidence was low on
this occurring so decided to withhold from the TAF at the
current time. This being said, isolated to scattered and 
disorganized showers (and eventually thunderstorms) will become 
a bit more widespread during the morning and especially in the 
afternoon. There may in fact be two favored corridors of 
activity -- one near the weak surface boundary near the I-70 
corridor and other along the better instability axis centered 
closer to the Ohio River. Either way, timing out individual dry 
periods for each of the terminals is quite a challenge even at 
these short time ranges. Nevertheless, tried to time out favored
windows for convection for each of the sites, with an earlier 
initiation expected for northern terminals along the 
aforementioned weak frontal boundary. 

Light southerly winds will go more southwesterly this morning 
and even a bit more west-southwesterly this afternoon before 
going light and variable or even calm past about 00z or so. 
This may allow for some MVFR VSBYs to develop towards the very 
end of the period with ample low level moisture entrenched 
across the region. However, another more cohesive and widespread
area of showers and storms may be moving into the southwest 
part of the local area toward the very end of the period through
12z Tuesday morning. 

OUTLOOK...Thunderstorms will be possible through Thursday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Flash Flood Watch through Tuesday afternoon for OHZ026-034-035-
     042>046-051-052-060.
     Flash Flood Watch through Tuesday evening for OHZ053>056-
     061>065-070>074-077>082-088.
KY...Flash Flood Watch through Tuesday evening for KYZ089>100.
IN...Flash Flood Watch through Tuesday afternoon for INZ050-058-059.
     Flash Flood Watch through Tuesday evening for INZ066-073>075-
     080.

&&

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