Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1153 AM EDT Tue Aug 11 2026
Day 1
Valid 16Z Tue Aug 11 2026 - 12Z Wed Aug 12 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE OHIO VALLEY...

...Midwest/Ohio Valley/Mid-Atlantic States...
1330Z Update: Have issued non-routine update to the Day 1 ERO that
will account for the most recent MCS (more widespread convection)
that will be traversing central and southern OH and western WV this
morning. The latest Flash Flood Guidance (FFG) from the OHRFC is
quite low -- down to a quarter inch within both the 1/3 hour
timeframes. This is indicative of the highly saturated soils based
on the heavy rainfall over the past 24 hours. For further details,
please see the latest Mesoscale Precipitation Discussion (MPD
#1007) that extends across this Moderate Risk area, including the
expanded area to the north, where additional flash flooding is
likely through 18-19Z.

Hurley

Previous discussion below..

The general flow pattern remains fairly static since yesterday.
The equatorward edge of the Westerlies is forecast to lie from the
Northern Plains into portions of the Ohio Valley and Mid- Atlantic
States where there is also low- level confluence, difluent 1000-500
hPa thickness, and an instability gradient to focus organized
convection. Precipitable water values are forecast to be 2"+ in
spots. Hourly rain amounts to 3" and local totals to 6" remain
possible given the available ingredients. Previous days' rains over
these areas have saturated the soils further across portions of
northern IL/northern IN/OH/WV/southwest PA. When combined with the
general very flashy nature of the rivers/terrain of West Virginia,
the Moderate Risk level continues to make sense. Recent guidance
led to some southward shift/expansion in the Slight/Moderate Risk
areas. An eastward expansion of the Slight Risk area into Richmond/
Baltimore/Washington DC was made as several members of the global
guidance had a heavy rain signal over or very near the region which
received heavy rainfall on Monday.

Roth

...Cen-Srn Rockies...4 Corners...Cen Great Basin...Southwest...
1600 UTC Update: Southeast AZ and southwest NM remains most at risk
for more persistent heavy rainfall, and as such the Slight Risk
from yesterday's Day 2 ERO remained intact based off last night's
00Z and today's 12Z guidance. Across the Great Basin, the Marginal
Risk was broadened as moisture subtly increases as an upper level
trough settles in to the CA Coast and ridging near the Four Corners
weakens, which should lead to less mid-level capping and broader
convective coverage.

Hurley/Roth


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