AWUS01 KWNH 120808
FFGMPD
OHZ000-KYZ000-INZ000-121406-

Mesoscale Precipitation Discussion 1259
NWS Weather Prediction Center College Park MD
407 AM EDT Sat Sep 12 2026

Areas affected...portions of the Ohio Valley

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

Valid 120806Z - 121406Z

Summary...Showers and thunderstorms with heavy rainfall continue
moving northeast.  Hourly rain amounts to 2.5" with local totals
to 4" could lead to isolated to widely scattered flash flooding.

Discussion...Forward propagating convection along with development
out ahead of the activity continues to produce random cell
mergers/short periods of training.  The showers and thunderstorms
are forming within a zone of 850 hPa confluence and within an
instability gradient.  Precipitable water values of 1.8-2.1" lie
here per GPS data.  CIN has developed; MU CAPE Is 500-1000 J/kg
near the thunderstorms with slightly higher values to their
southeast.  Effective bulk shear is close to 25 kts.

While there's a bit of disparity amongst various pieces of
mesoscale guidance, with the 06z hi-res NAM abandoning the
prospect of this system's existence, the 00z HREF/REFS signal is
fairly cohesive.  The progress of the convective mass should shift
more east-northeast with time.  Where thunderstorms manage to
merge or briefly train, hourly rain amounts to 2.5" and local
totals to 4" are possible.  While the three hourly flash flood
guidance values are high in IN, they are lower in OH due to
partially saturated soils from heavy rainfall on the 9th and 10th.
 Isolated to widely scattered occurrences of flash flooding are
possible into late Saturday morning. 

Roth

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

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

LAT...LON   40588344 39968292 39158394 38548569 39038654 
            39558740 40068676 

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