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Area Forecast Discussion (AFD)

Issued by Wilmington, OH (ILN)

                            
000
FXUS61 KILN 180755
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
355 AM EDT Tue Jun 18 2019

.SYNOPSIS...
A stalled frontal boundary draped across Ohio and Indiana, and
numerous ripples of energy moving through the Ohio Valley will
combine to produce more showers and thunderstorms today. Some of
the storms could produce heavy rain and the flooding threat will
continue. Activity will be on the decrease tonight before
strengthening low pressure approaches the area Wednesday night
and Thursday. This will induce more showers and storms across
the area. Little rest for the weary in terms of rain chances
into the weekend as an extremely moist airmass will continue to
be situated across the Ohio Valley, with frequent disturbances
moving through offering chances of showers and storms. 

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Plenty of active weather still ongoing in the wake of last
evening's severe MCS with localized flash flooding. Two areas of
interest in relation to today's weather and impacts - the first
across the northern forecast area from Kenton and Delaware on to
the northeast. This is a strung out shortwave trough moving
slowly through weak westerly flow while agitating an old
convergence zone draped across central Ohio. A persistent
/nearly stationary at times/ band of rain with embedded heavier
elements has been working very slowly eastward with warm rain
processes dominating the stratiform rain region. Radar likely
underestimating in this area and thus thinking that 1-2" of rain
has fallen since late last evening from Botkins through Kenton.
Likely some advisory level flooding impacts along small creeks
and streams. Earlier, Shelby County indicated roads were
beginning to close from inundation around Botkins. This rain has
shown some weakening trends in the last hour but the axis will
be in place through the morning hours where more very slowly
moving showers and storms will be possible. 

Across the southern forecast area this morning, a renewed area
of showers and storms is pressing steadily northeast through
northern Kentucky downstream of yet another weak /and further
weakening/ shortwave trough moving through TN/KY. Somewhat
enhanced low level moisture transport on the warm conveyor belt
into gently convergent flow over the southern CWA promoting this
activity, and there is good agreement that rain/storms will
spread back over the Ohio River counties through sunrise and
thereafter. This will produce a continued warm rain process /
heavy rain threat per HRRR/RAP soundings showing tall/skinny
CAPE amidst very weak lapse rate tropospheric profile and
anomalously high PWAT toward 1.9". This rain should begin to
diminish/scatter out by later in the morning, but may continue
to exacerbate any ongoing flooding.

In the afternoon, think convection will once again increase
primarily in vicinity of the old frontal boundary draped across
the central part of the forecast area. It will be scattered -
probably more so than in previous days owing to an overall lack
of a shortwave trough/MCV, but there will once again be ~1000
j/kg of MLCAPE and some low level convergent/confluent flow of
an extremely moist airmass to generate scattered, slow moving
storms. Heavy rainfall rates and flooding the primary threats.
Can't completely rule out a water-laden downdraft causing some
wind damage near/just after peak heating, but not expecting much
SVR today in comparison to previous days. Low/mid level flow is
awfully weak today and one the more limiting factors.  

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Dare we say a break in the action? This time period will feature
a /relative/ minimum in shower and thunderstorm activity due to
an overall minimum in shortwave trough action and subtle height
rises over the Ohio Valley. Given anomalous moisture in place,
still can't rule out a few meandering showers/storms in a
loosely focused sense, but don't see a concentrated rain threat
through Wednesday morning. Rain chances return in earnest
Wednesday afternoon and especially Wednesday night as next upper
trough shifts into the forecast area. There is timing/strength
issues in the NWP with this trough, with 18.00Z NAM seemingly an
outlier in comparison to ECMWF/GFS which are slower and a little
weaker. Either way, increasingly strong flow brings enhanced
moisture transport back into the forecast area from south to
north on Wednesday afternoon and especially Wednesday night via
a strong low level jet and background forcing for ascent. Should
see a large complex of showers/storms develop to the west and
move into the forecast area later Wednesday night - and some of
this could be strong to severe given increasingly favorable
shear profiles and a still extremely moist airmass. SWODY2 has
expanded convective risks into the ILN CWA and we could see this
continue to increase as timing differences get resolved. Could
be an active night in the Ohio Valley given low/mid level shear
profiles and overall synoptic setup.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Would like to say the pattern is going to offer some breaks -
but we just don't see much in the way of a respite. Friday
offers the best chance of dry weather in the wake of the strong
wave on Wednesday night/Thursday, as decent subsidence signal
shifts through the flow. Next shortwave trough and returning
warm/moist advection along and north of the re-developing
stalled frontal zone will likely allow an MCS to form Friday
evening in the Corn Belt and this will drop southeast on an
increasing feed of southerly flow. Could be a decent MCS
knocking on our door late Friday night/Saturday morning. Good
agreement in 18.00Z GFS/ECMWF in this scenario.
Saturday/Sunday/Monday all look potentially active as numerous
shortwaves move through the Ohio Valley as extremely moist
airmass remains in place, and heat slowly builds. 

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
IFR ceilings and visibilities are developing early this morning
across many areas in wake of showers/storms which crossed the
area last evening - and are still ongoing in some areas.
Guidance has trended toward a higher confidence period of IFR
conditions through sunrise at many sites so have trended that
way especially with numerous observations now coming in with
ceilings below 1kft and pockets of dense fog. The most favorable
locations will be ILN/DAY/CMH/LCK which fits pattern well as
these areas are in weakly convergent areas near/ahead of
persistent frontal zone across central Ohio. Showers may tease
CMH/LCK through the next 3-4 hours as mid level wave pivots
slowly through central Ohio. Most heavier/impactful activity
should remain north of these sites. Further south, renewed
showers are lifting northeast toward CVG/LUK and will arrive
toward sunrise with potential for some lower visibility in heavy
downpours. Coverage is a little uncertain, but enough to add
some TEMPO groups through the early morning hours. Expect low
clouds to be prevalent through the morning hours before
lifting/breaking to some degree into the afternoon. Expect
showers/storms to redevelop in scattered fashion this afternoon
into this evening across many areas owing to extremely moist
airmass and front continually draped across the area.  

OUTLOOK...Thunderstorms will be possible through Thursday.

&&

.HYDROLOGY...
It's no secret by now that the ILN CWA is saturated and
waterlogged to the point that any thunderstorm complex/rain band
is going to cause runoff issues. This potential remains in play
today with slow moving/low centroid heavy rain elements
dominated by warm rain processes. Several rivers already in
flood and many are running high. Flash Flood Watch remains in
effect until early afternoon area-wide, and into the evening in
the south/central portions of the CWA. 3-5" have been common in
many areas in the last 3 or 4 days, and could easily see another
2-4" through the rest of the week and into the weekend with the
various thunderstorm complexes. Given crops have been slow to be
planted /a historically slow planting season/ many fields are
still not covered with vegetation thus runoff will continue to
be higher than normal. Expect more instances of river flooding
and flash flooding in the next 3-5 days.  

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Flash Flood Watch until 2 PM EDT this afternoon for OHZ026-034-
     035-042>046-051-052-060.
     Flash Flood Watch through this evening for OHZ053>056-061>065-
     070>074-077>082-088.
KY...Flash Flood Watch through this evening for KYZ089>100.
IN...Flash Flood Watch until 2 PM EDT this afternoon for INZ050-058-
     059.
     Flash Flood Watch through this evening for INZ066-073>075-080.

&&

$$
SYNOPSIS...Binau
NEAR TERM...Binau
SHORT TERM...Binau
LONG TERM...Binau
AVIATION...Binau
HYDROLOGY...Binau