Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
846 PM EDT Fri Aug 7 2026
Day 3
Valid 12Z Sun Aug 09 2026 - 12Z Mon Aug 10 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
UPPER MIDWEST AND UPPER MISSISSIPPI VALLEY...

20Z Update..

Minimal changes were needed for this update, other than cosmetic
changes to match with the latest run of global models and
ensembles. There was a surpring level of agreement with the global
models, even more so than for Day 2. The inherited Slight remains
to be in good shape for this update, and further refinements may be
possible as later model runs come in and CAMs guidance become
available.

Blanco-Alcala

Previous Discussion...

...Upper Midwest...

Multiple rounds of storms are expected on Sunday across portions of
the upper Midwest, specifically from the southeast corner of
Minnesota southeast through northern Indiana. With plentiful
moisture from an LLJ originating from the Gulf being advected
northward into the storms, there is little reason to see why the
storms won't be able to backbuild and train both with the morning
convection with an MCS, and then secondarily with late afternoon
through the Sunday night convection across these same areas. Since
guidance has come into better agreement, even better than Days 1
and 2, a Slight Risk upgrade was introduced with this update.

...Elsewhere...

Elsewhere, the Southwest monsoon will continue to promote afternoon
and evening convective development into the 4 Corners region, and
southwesterly moisture advection into the southern Appalachians
could also provide a focus (due to terrain) for afternoon and
evening storms. As on prior days, widespread widely scattered
convection is likely all across the Southeast Sunday afternoon and
evening. Should storms merge over urban areas, then flash flooding
is quite possible outside of the drawn Marginal Risk area. Thus,
it's probable additional expansions and changes will be needed over
the coming days into the Southeast.

Wegman

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt