143
AWUS01 KWNH 032130
FFGMPD
WVZ000-OHZ000-KYZ000-INZ000-040230-

Mesoscale Precipitation Discussion 0548
NWS Weather Prediction Center College Park MD
529 PM EDT Wed Jul 03 2024

Areas affected...Southern IND...Northern KY...Southwest OH...

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

Valid 032130Z - 040230Z

SUMMARY...Increasing moisture flux should support 2"/hr rates and
enough west to east cross-over tracks may allow for some localized
2-3"+ totals in 1-3hrs resulting in possible localized flash
flooding over the next few hours; particularly in/around the
steeper bluffs and urban centers of the Ohio River Valley.

DISCUSSION...RAP analysis suggest an elongated mid-level shortwave
is currently crossing central OH into east-central IND at the
distant periphery of right-entrance/anticyclonically curved
portion of the 3H jet across the Great Lakes.  This has maintained
low to mid-level confluence along the shear axis from NE OH across
S IL with CIRA LPW the narrow but vertically aligned plume from
KS/OK all the way through to IND/OH with 2" total PWat values
along/south of the shear axis.  Additionally, a pre-frontal trough
that was reinforced by last night`s convection/outflow has
provided sufficent surface to boundary layer convergence while
boundary layer to 700mb confluent flow through the Ohio Valley
adds to the flux convergence, particularly upstream across S IND.
`

Solid insolation prior to the boundary has seen temps into the
upper 80s, low 90s with low to mid 70s Tds, resulting in a very
unstable environment with 1500-2500 MLCAPE values along and south
of the boundary to feed stronger updrafts.   Recent convective
development has cooled rapidly along the line with overshooting
tops below -60C dotting the line, continuing to expand...and will
likely support 2"/hr rates over the next few hours.

Recently dry soil conditions have resulted in higher than normal
FFG values and these rates alone, minus a few steep river bluffs
and urban centers across the area these rates alone are not likely
to be exceeded, especially with modest 25-30kts of forward speed.
This will require repeating/training cells to result in 2-3"
totals and increase the risk.  Given the placement of the
elongated shortwave, the northern portion of the line should
become progressive enough across central OH and limit flooding
risk until the lower slopes of the Appalachian Plateau. However,
further southwest, the exiting shortwave and flatter 500-1000mb
thickness gradient suggest greater potential for a more west to
east orientation to cell motions and possible training.

This is conditional on cold pool generation that may increase
southward propagation and limit this potential. Yet, given the
shear intensity of the cells, broadening updrafts seen in spots
there is a low-end potential for streaks of 2-3" across the middle
Ohio River Valley and therefore flash flooding is considered
possible through evening.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...ILN...IND...JKL...LMK...PAH...RLX...

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

LAT...LON   39438441 39358298 38918217 38148257 37838402
            37788518 37788571 37888682 38008735 38298764
            38598727 38798664 39068586