Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
436 AM EDT Sat Aug 15 2026
Day 1
Valid 12Z Sat Aug 15 2026 - 12Z Sun Aug 16 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PARTS OF THE
OHIO VALLEY...

...Ohio Valley...
A Moderate risk has been expanded to stretch from portions of
eastern IL through IN and across much of OH. An MCS is forecast to
be ongoing at 12z this morning tracking across IL and IN. While
this complex should generally exhibit a weakening trend as the
morning progresses, it will be traversing a corridor of saturated
ground conditions. Consequently, scattered to numerous instances of
flash flooding remain expected into the morning hours.

Another threat will materialize by this evening into the overnight
hours, driven by the remnant MCV from the morning convection. This
feature will help focus additional convective development over OH,
eventually spreading east southeastward into WV and far southwest
PA by late tonight and early Sunday. A very moist airmass
characterized by PWs around 2.3" will support intense hourly
rainfall rates. A training and backbuilding signature again
exists, with deep layer westerly flow and strong low level
westerly moisture transport resulting in weak Corfidi vectors.
HREF neighborhood FFG exceedance probabilities range from 50-80%,
with HREF PMM QPF exceeding FFG thresholds by 200-300% in spots
and overall FFG exceedance spatial coverage topping 50%. These
impressive metrics support numerous instances of flash flooding
tonight over central and southern OH, with the threat spreading
into WV and southwest PA by early Sunday. Some of this flash
flooding will likely be considerable in nature.

...High Plains...
A Slight risk is maintained from eastern CO into central and
western KS, reflecting a southward shift relative to continuity.
The overall setup remains similar to recent days, with convective
forcing along the periphery of the upper ridge interacting with a
moist, unstable airmass.

A cold front will serve as a primary convective focus, with
activity developing north of the boundary where the better
moisture/instability will be pooling. Convection initiating over
the higher terrain will track eastward and may grow upscale
along/north of the front as it moves from CO into KS, aided by
upper level jet right entrance dynamics. Isolated to scattered
flash flooding is expected, particularly across eastern CO where
recent heavy rainfall has lowered FFG thresholds.

...Southeast...
A broad Marginal risk continues across the Southeast on the
periphery of the strong upper ridge centered over the southern
U.S. Anomalous moisture with PWs approaching the the percentile
for mid August will be present, and HREF neighborhood probabilities
support localized 3" rainfall totals However, overall convective
coverage is expected to remain low with a minimal HREF EAS signal.
While sea breeze boundaries may provide localized focus, any flash
flooding impacts should remain isolated.

Chenard


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt