Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
331 PM EDT Sun Sep 6 2026
Day 3
Valid 12Z Tue Sep 08 2026 - 12Z Wed Sep 09 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR NORTHERN
MONTANA, UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES, THE
SOUTHWEST, AND PORTIONS OF THE SOUTHEAST...

1930Z Update...

After reviewing 12Z guidance and the latest WPC QPF, only minor
adjustments were made to the Marginal Risks to account for small
changes to the QPF footprints. No upgrades were made this forecast
cycle.

Mullinax

---Previous Discussion---

...Marginal Risks...

Lingering moisture from the departing low into Canada could allow
for a continuation of flooding that likely starts on Monday into
the day on Tuesday. Any new instances of flash flooding on Tuesday
should remain isolated.

Monsoonal moisture in the Southwest may diminish somewhat from
previous days, but enough should still be around for widely
scattered shower and thunderstorm development from southern Arizona
into southwestern Colorado. An isolated instance of flash flooding
or 2 are possible.

The trailing cold front behind the low moving into Canada will slow
its forward movement from eastern Nebraska into the upper Great
Lakes. Afternoon and overnight thunderstorms ahead of the front may
backbuild and train in some areas. Isolated flash flooding is
possible where backbuilding and training occur over flood-prone
areas.

Numerous showers and thunderstorms will impact the Gulf Coast and
the Florida Peninsula on Tuesday. Due to high FFGs and generally
low storm organization, once again isolated instances of flash
flooding will be possible, but nothing out of the ordinary is
expected.

Wegman

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