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

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


...Midwest/Ohio Valley/Mid-Atlantic States...
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.


...Southern Arizona...
Southeast AZ remains most at risk for more persistent heavy
rainfall, so left the Slight Risk intact. 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.

Roth


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