Mesoscale Precipitation Discussion 0480
NWS Weather Prediction Center College Park MD
716 PM EDT Wed Jun 18 2025

Areas affected...Southern OH...Central KY...Middle TN...

Concerning...Heavy rainfall...Flash flooding possible

Valid 182315Z - 190430Z

SUMMARY...Increasing convective coverage capable of locally
exceeding lower than normal hourly FFG due to well above normal
soil saturation.   Hourly 1-2" totals and some possible short-term
storm scale interactions may allow for some isolated totals over
2-3", resulting in widely scattered low-end incidents of flash
flooding through early overnight period.

DISCUSSION...RADAR mosaic depicts a mature, strong but very
progressive squall line crossing eastern IND into OH.  This line
has been fairly consistent in producing .5-1.25" totals along its
path through IND; however, this has not intersected areas of
recent saturation until moving into southwest/southern Ohio. 
Here, 0-40cm relative soil saturation ratios are at or above 60%
which is well into the 90th to 99th percentile per NASA SPoRT LIS
products and this is more so south across much of KY into western
and Middle TN. 

However, stronger surface to boundary layer convergence was
slightly weaker and could not break the cap across much of the
pre-frontal pressure trof/convergence boundary.  Air remains very
unstable with MLCAPE of 2500-3000 J/kg from Cincinnati across into
Western TN.  Ample moisture in the low to mid 70s (Tds) and total
PWats of 1.75 to 1.9", suggest any thunderstorms to develop will
have capability of producing 1.5-2"/hr rates.  VWP and RAP
analysis suggest as the MCV is lifting further north the winds had
not been strong enough or have sufficient directional convergence;
but recent trends suggest a slight increase in both wind speed as
the LLJ diurnally strengthens and a slight increase of about 10-15
degrees from 925-850mb has seen a steady southwestward expansion
of the deep moisture convergence axis into western and middle TN. 
As such, individual cells have broken the cap through much of the
line and continue to expand as they progress eastward. 

Further north into OH, stronger convergence/mature updrafts have
been been outdone by forward speeds to result in hourly FFG
exceedance, though as they reduce below 1.5" and forward
progression reduces slightly further from the lifting
shortwave/forcing increased duration suggests scattered incidents
of exceedance are possible.  Further south, deeper layer steering
flow is a bit more west to east and slower by 5-10kts, also
supporting increased duration.  Stronger upstream LLJ/moisture
convergence may also support flanking development within the storm
scale environment to further increase overall duration. Similarly
though, hourly rates of 1.5-2" are likely along the line with
sub-hourly totals expected to be at or slightly above scattered
along the line.  As such, low-end flash flooding incidents are
becoming increasingly possible through the late evening/early
overnight period.

Gallina

ATTN...WFO...ILN...JKL...LMK...MEG...OHX...PAH...RLX...

ATTN...RFC...ORN...TIR...NWC...

LAT...LON   39948284 39728209 39078151 38158205 37428310
            36678472 35418817 36328892 37788688 38748549
            39238484 39838404