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Area Forecast Discussion (AFD)

Issued by Wilmington, OH (ILN)

                            
000
FXUS61 KILN 241858
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
258 PM EDT Mon Jun 24 2019

.SYNOPSIS...
Strong weather disturbance will drive a cold front through the
Ohio Valley tonight with widespread showers and storms out in
front. Some of these may be severe. Clearing skies expected in
the wake of the front with a mix of sun and clouds on Tuesday. A
weak front will drop into the Great Lakes on Wednesday afternoon
and evening with a threat for scattered storms as a warm and
humid airmass takes hold of the Ohio Valley. 

&&

.NEAR TERM /THROUGH TONIGHT/...
Please reference recent SPC SWODY1 and SWOMCDs for the ILN area
for larger scale thinking of the severe weather threats. More
specifically - as of 18Z threats are just starting to
materialize as previously discussed in the morning AFD update.
Weak low level circulation over southern KY continues to slowly
develop and enhance low to mid level shear profiles to our
south. In fact, discrete cells /now tor-warned/ in central KY
area are manifestation of the enhanced SRH and deep shear 
profile that is in place attendant to this migrating wave. 
Expect this environment to spread into and through the ILN CWA 
in the 3P-7P timeframe - primarily through the SVR Watch area. 
So while the overall shear/instability profile is more toward 
wind damage threats with amalgamating cold pools /like what is
currently moving through south-central Ohio as of 1845Z/, 
there's enough of a push of low level flow through northeast KY 
and south- central OH where any discrete cell or favorably 
orthogonal line segment to the low level shear vector to rotate 
and produce a brief tornado in the 3P-7P timeframe as it moves
south to north.

A good dose of convective rains expected with the deeper
convection pushing up the Scioto Valley too. There is some
concern for localized flash flooding with this activity should
it repeat over similar areas /especially considering flash-flood
prone terrain in this area and recent anomalous wet spell we've
been in/. Storm motions should be progressive however which
should limit flash flood potential in time and space. Most
concern is Hocking/Ross/Pike/Scioto/Lewis/Mason counties for
that threat.

Further west - it was noted on the collaboration call with SPC
/and we agree/ that the western fringe of severe potential is
tough to diagnose but in general feel that I-71 from Columbus to
Cincinnati is a realistic demarcation from no threat to some
marginal threat, with the better relative threat in that
corridor in the Columbus area. Across northern KY south of CVG,
just not enough destabilization plus this area will quickly get
on the backside of the low level circulation passing by to the
east. West of I-71 in Ohio/eastern Indiana - just too stable and
this area not likely even to see much thunder owing to thick
clouds and temperatures which have actually leveled off or
fallen a little this afternoon. 

Things will wind down quickly early this evening. Likely a
several-hour dry period between exiting precipitation shield in
the eastern CWA to inbound frontal-forced showers later this
evening and early overnight. This will be in a weakening state
owing to veering profile in the boundary layer reducing
convergence - and entering the stability maximum from afternoon
rains. 

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Quiet weather as high pressure builds into the Ohio Valley. 
Before the drier atmosphere completely builds into the ILN CWA 
/PWATS below 1"/ there are hints that there may be just enough 
early afternoon diurnal instability to pop a shower or two in 
southern Ohio before mixing of low level dewpoints toward the 
later afternoon hours reduces instability. Overwhelming signal 
in NWP is dry - so will keep any showers out of the forecast for
right now with the expectation that this will max out as some 
taller cumulus.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
A weak surface front will nose into the northern CWA from the Great 
Lakes region as a wave of mid level energy translates east in the 
mean westerly flow aloft. A shower may present itself about any time 
during the day with a more robust shower or thunderstorm more likely 
with peak daytime heating. The upper forcing is east of the area by 
the time peak heating occurs, and the surface front is quite 
diffuse, leading to a late day threat that should tail off quickly 
in the evening. 

High pressure at the surface will build in as heights increase 
aloft, limiting any shower activity through early Friday to be very 
widely scattered if they present themselves. Models are indicating 
an upper level disturbance to work into the Ohio Valley from the 
west-northwest on Friday and dissipate as it stretches out over the 
Ohio River Saturday. This feature may combine with daytime heating 
to pop a few storms but the airmass it is working into is not as 
receptive to storm development. Expect isolated to widely scattered 
pop-up storms to be possible in the late day through Saturday, 
diminishing just as rapidly in the evening for a generally dry 
overnight period everywhere. The upper forcing gets shunted 
southwest as the ridge in the mid section of the country builds and 
a stronger upper low in New England pulls energy into the Ohio 
Valley from the north behind a surface cold front. Models show a 
large swing in the chance of precipitation during this time but have 
a general good agreement on the broader features. Have a low chance 
of thunderstorms that are not necessarily diurnally driven from 
Sunday onward. 

Models have increased temperatures slightly through the period and 
are generally looking for lows in the upper 60s to near 70 and highs 
approaching 90. Dropped readings on Sunday by a few degrees and only 
have highs in the low to mid 80s on Monday following the cold front. 
Overnight lows will be from 65-70 through the period and be fairly 
uniform across the CWA. 

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Widespread showers will cross the TAF sites this afternoon into
early evening. While a thunderstorms and associated brief
restrictions to IFR are possible just about at all the TAF
sites, the better relative likelihood will be at LCK/LUK/CMH 
and perhaps ILN. Have included prevailing showers with MVFR
restrictions at all sites, and hit visibilities the hardest in
TEMPO at LCK/CMH/LUK where the best chance of some heavier
activity will occur. This precipitation will exit by 00Z in
central Ohio - a little earlier at DAY/CVG/ILN/LUK. Winds will
mostly be from the southwest, but some local variation to the
west/northwest will occur in the wake of a weak low pressure
which ripples northeast into central Ohio this evening. Thus,
wind forecasts later this afternoon and evening are of lower
confidence in both speed and direction. Secondary band of
showers on the cold front itself will spread into the area later
this evening and early in the overnight. Don't expect coverage
will be high enough to mention beyond a VCSH at CVG/DAY. Expect
these to be rapidly weakening. Should be some clearing
overnight outside the band of showers. Some light gusts of
westerly wind under a mix of clouds and sun on Tuesday with no
flight restrictions expected.  

OUTLOOK...Thunderstorms are possible Wednesday afternoon and
evening.

&&

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

&&

$$
SYNOPSIS...Novak
NEAR TERM...Binau
SHORT TERM...Binau
LONG TERM...Franks
AVIATION...Binau