Mesoscale Precipitation Discussion 0130
NWS Weather Prediction Center College Park MD
342 PM EDT Tue Apr 02 2024

Areas affected...Much of the Upper OH Valley

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

Valid 021940Z - 030140Z

SUMMARY...Increasing coverage of shower and thunderstorm activity
going through the afternoon and evening hours will set the stage
for renewed concerns for flash flooding.

DISCUSSION...In the wake of morning convection, and with diurnal
heating resuming across large areas of southern IN and through
much of central/southern OH, the airmass across the region will be
destabilizing rather quickly over the next couple of hours. This
will set the stage for new areas of heavy showers and
thunderstorms, which inclusive of severe weather concerns, will
also be capable of producing sufficient levels of additional
rainfall for a renewed flash flooding threat.

A strong upper-level trough and associated area of surface low
pressure will be traversing the OH Valley and portions of the
Great Lakes region through the afternoon and evening hours, and
this will drive a cold front steadily off to the east. MLCAPE
values on the order of 1000+ J/kg are nosing northeast up across
southern IN currently just ahead of the cold front, and this
coupled with strong vertical shear and pockets of locally focused
surface moisture convergence aided by a southwest low-level jet of
40 to 50 kts will favor an increase in the coverage of heavy
showers and thunderstorms over the next few hours. This will
especially be the case as the downstream boundary layer along and
south of a west/east oriented warm front continues to destabilize.

The more organized pockets of convection, which should gradually
include some supercells and linear convective segments, will be
capable of producing rainfall rates that reach 1.5" to 2"/hour.
The relative moist environment with PWs approaching 1.25 inches
and the strong and sustainable updrafts within the stronger cells
will be key contributors to the locally enhanced rates.

Some localized training of these convective cells will be possible
as the activity gradually expands in coverage, and this may
produce some linear swaths of 2 to 4 inches of rain where this
occurs. Given the heavier rains earlier in the day and last night,
many areas across the broader Upper OH Valley are rather sensitive
to any additional heavy rainfall. Therefore, additional concerns
for flash flooding will exist heading into the evening hours.

Orrison

ATTN...WFO...CLE...ILN...IND...IWX...LMK...PAH...PBZ...RLX...

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

LAT...LON   41408056 41117933 40317917 39747951 39458021
            39158163 38998330 38528519 37688714 37998776
            39148693 39948580 40658442 41208242