Mesoscale Precipitation Discussion 0237
NWS Weather Prediction Center College Park MD
725 PM EDT Tue May 07 2024

Areas affected...Central to Southeastern IND...West-Central to
Southwestern OH...

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

Valid 072325Z - 080430Z

SUMMARY...Stripes of enhanced rainfall totals (1.5-3") as multiple
discrete supercells orient to mean flow for repeating while
slowing becoming more efficient in rainfall production with
intense sub-hourly totals of 1-1.5".  As such, scattered incidents
of flash flooding possible to accompany ongoing severe weather
threat.

DISCUSSION...Regional RADAR mosaic depicts multiple discrete
supercells extending from NE IND southward to west-central IND,
along/just east of EML (noted well in CIRA LPW 700-500mb layer)
with strongest supercells coincident with enhanced pocket of
mid-level moisture from 850-500mb across south-central to
southeast IND into SW OH.  Combined with an increased area of
surface Tds into the low 70s; a secondary warm frontal feature
evident in Theta-E and MLCAPE fields as a tighter gradient
extending near Muncie, IND southeastward into SW OH.  Supercells
are ingesting high moisture through the boundary layer with
enhanced isallobaric influence flux convergence for moisture
loading to the up/down drafts.  Intense downdrafts of up to 1+"/15
minute (per HRRR/WoFs) are likely to expand with increasing LLJ
expected in the next few hours.  Even with right-turning, cell
motions are still a negative factor toward FF, reducing duration,
as well as, areal coverage with narrower downdrafts, at this time.

However, stronger moisture flux should broaden updrafts and
rainfall efficiency, but of greater concern is further upstream
development along the SW to NE instability axis back into SW IND.
Cells here, are also discrete but will be traversing similar paths
and may intersect flanking line of initial cell to help corral
tracks to similar paths.  HRRR and WoFS runs continue to trend
upward toward this evolution as well, suggesting narrow west to
east streaks of 1.5-2.5" totals; though 90th percentile from
recent WoFS runs continue to increas to as much as 3.5"...further
bringing confidence to rainfall efficiency potential.

Duration between rounds is likely to add to localized FF concern,
which is reduced nearer the intersection of the SW to NE
instability boundary and the NW to SE higher theta-E boundary
which appears to maximize near I-70 between KIND and KDAY through
the next 4-6 hours.  Further spread in time across South-central
IND into SW OH may allow creeks/streams to rebound, but FFGs are
even lower across this area and soils are a bit more saturated per
SPoRT LIS 0-40cm ratios.  

All considered the sub-hourly totals near 1hr FFG and spotty
2-2.5"/3hr also near the 3hr FFG especially further east, which
aligns with better timing of low-level flux.  As such, scattered
incidents of flash flooding are considered possible.

Gallina

ATTN...WFO...CLE...ILN...IND...IWX...

ATTN...RFC...OHRFC...NWC...

LAT...LON   41198405 40918304 39788295 39148396 38958555
            39128680 39698692 40308588