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Area Forecast Discussion (AFD)

Issued by Wilmington, OH (ILN)

FXUS61 KILN 181810

National Weather Service Wilmington OH
210 PM EDT Tue Jun 18 2019

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.


Active pattern continues today. Primary hazard will be 
flooding/flash flooding into the evening hours, although
isolated strong to even damaging wind gusts can't be ruled out 
in the strongest storms this afternoon. 

Radar imagery at 14Z shows two areas of rain. First area 
resides from around Auglaize County east into Union County. Rain
in this area has been persistent and slow-moving. Expect this 
area to diminish/dissipate by midday, per most high resolution 
guidance, but until then high water issues will continue. Second
area resides across the Tri-State area eastward into south- 
central Ohio. While this area has also been persistent, it has 
better forward propagation than the northern area, and will 
continue pressing to the east over the next few hours. Given the
saturated ground, localized high water problems may also occur 
in association with this area. 

For the afternoon, upstream convection over southern 
Indiana/central Kentucky likely will hold together in some 
fashion, moving across the southern CWA this afternoon. In 
addition, as models suggest some instability for the afternoon 
(possibly aoa 1000 J/kg), expect an increase in convection most 
likely closest to the vicinity of the residual front draped 
across the CWA. While larger scale upper air support/shear to 
promote severe is lacking, given the high moisture content the 
strongest updrafts could produce locally strong or even damaging
wind gusts. But the bigger concern obviously will heavy 
rainfall leading to continued or renewed flooding problems. A
flash flood watch continues across the CWA -- until 2 PM in the
north and 8 PM further south. Will strongly consider extending
the northern portion of the Watch beyond that expiration time. 

All grids for today have been updated -- main change is for 
PoPs/Wx based on latest radar trends/expectations and guidance 
from most recent high resolution models.


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.


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.


Still have some low ceilings, mainly MVFR, lingering over a few
TAF sites. Ceilings may vacillate between VFR and MVFR this 
afternoon, as scattered showers and thunderstorms affect the 
terminals. Heavier rainfall will also bring episodes of low 
visibilities of IFR or lower. Expect today's action to be 
primarily diurnally driven, so mention of shra or vcsh 
disappears by dark. Then there is the potential for more 
widespread prevailing cigs developing during the evening -- and 
possibly low visibilities in fog. Went with MVFR, but there is 
the potential for IFR conditions to develop and they may 
eventually need to be included into TAFs. At this time, a
relative lull in showers is expected Wednesday morning as 
conditions improve to VFR, but convection is expected again 
Wednesday afternoon. 

OUTLOOK...Thunderstorms will be possible through Thursday, and 
again Friday night into Saturday.


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.


OH...Flash Flood Watch until 8 PM EDT this evening for OHZ026-034-
KY...Flash Flood Watch until 8 PM EDT this evening for KYZ089>100.
IN...Flash Flood Watch until 8 PM EDT this evening for INZ050-058-