Mesoscale Precipitation Discussion 1079
NWS Weather Prediction Center College Park MD
330 AM EDT Mon Aug 17 2026

Areas affected...Lower OH Valley

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

Valid 170730Z - 171330Z

SUMMARY...Showers and thunderstorms with potential for multiple
rounds of heavy rainfall will continue to impact portions of the
Lower OH Valley going through the early morning hours. Areas of
flash flooding will be possible.

DISCUSSION...The latest GOES-E IR satellite imagery shows a
cold-topped MCS (tops to near -75 C) advancing eastward across the
Lower OH Valley, with one strong convective segment moving across
far southwest IN and into parts of northwest KY, with some renewed
convective development see back to the west across southern IL.

This activity is associated with a shortwave impulse and
associated surface low crossing the region while interacting with
a frontal zone and the pooling of moderate instability along it.
MLCAPE values are locally around 1500 J/kg with PWs of 2+ inches.
There is a west-southwest low-level jet of 30+ kts around the
southern flank of the vort energy that is overrunning this front,
and that along with focused moisture convergence is helping to
support the organized nature of the MCS.

The forward propagation of the MCS to this point has mitigated the
flash flood threat. However, radar imagery showing some new
convective development back to the west of the initial convective
line. Rainfall rates of 1.5 to 2 inches/hour have been noted with
the strongest cores of the MCS, and this has been allowing for
some brief spotty FFG exceedance.

Since there is some additional upstream convection that will cross
areas that have seen the initial round of heavy rainfall, there
may be sufficient totals to foster some areas of mainly urban
flash flooding in the near-term.

However, the other consideration over the next few hours will also
be areas downstream across central and eastern KY where antecedent
conditions become more sensitive due to recent heavy rainfall.
This is where FFG values are lower and USGS data shows
elevated/high streamflows. If the current MCS can maintain its
character downstream across central and eastern KY through early
this morning, the threat of flash flooding will increase in
coverage and magnitude.

As such, the latest model guidance does support some heavy
rainfall (spotty 2+ inch totals) making it east across these areas
early this morning. Therefore, at least regionally there should be
a concern for localized flash flooding.

Orrison

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

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

LAT...LON 39118458 38868335 38448263 37938242 37478279
37208375 37058511 37068720 37318872 37768933
38388917 38818834 39078687