Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Sat Sep 19 2026
Day 2
Valid 12Z Sun Sep 20 2026 - 12Z Mon Sep 21 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MIDWEST AND THE OHIO VALLEY...

...Ohio Valley/Southern Great Lakes...
Very few changes were made to the placement of the Day 3 Excessive
Rainfall Outlook as it propagated into the Day 2 period. There was
a tightening of the east-west length and a subtle southward shift
to match the latest guidance but maintained the focus for heavy
rainfall in the Ohio Valley, There remained some potential for
backbuilding and training convective bands affecting those areas
from late tonight into Sunday. Confidence is low on placement or
convective evolution beyond the first 36 hours of the forecast, so
this is being noted as a possibility for now. Anyone within the
Slight Risk area should be monitoring the potential for flash
flooding, however, given just how anomalously high the moisture
levels are.

Farther to the east, the Slight Risk was removed as model and
ensemble QPF dwindled. Cool, stable air being fed out of Canada
by a sprawling area of high pressure will overspread the area and
limit rainfall rates over an increasing amount of New England and
the Northeast states. A boundary separating this airmass with
moister and more unstable conditions (still fairly modest magnitude
of instability) to the south may still prove to be the focus for
convection capable of producing moderate to heavy rainfall rates
but the signals for heavy rainfall have become weaker and more
isolated in nature.

Rockies to the Central Plains...
There continues to be a Marginal Risk of excessive rainfall from
the Southern High Plains northward to the Western High Plains
adjacent to the Northern Rockies as deep moisture remains in place
with weak shortwave energy embedded helping to fuel scattered
convection.

...Elsewhere...
A large Marginal Risk area was maintained from the northern Rockies
through much of the Plains and into western Texas. Scattered
thunderstorms embedded within a large plume of anomalously high
moisture will pose the threat for localized heavy rainfall and high
instantaneous rain rates. However, confidence is low on placement,
so a Marginal Risk seems appropriate.

Bann


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt