Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
406 AM EDT Fri Aug 28 2026
Day 2
Valid 12Z Sat Aug 29 2026 - 12Z Sun Aug 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHWEST AND GREAT BASIN INTO THE ROCKIES AND FRONT RANGE,
NORTHERN PLAINS INTO THE UPPER MIDWEST, AND THE SOUTHEAST TO THE
CAROLINAS...

...Southwest and Great Basin into the Rockies and Front Range...

The upper high weakens/flattens across the Southern Plains as
troughing becomes increasingly established over portions of the
West and Northern Plains. Moisture gets funneled in between the two
features, which may have a connection to a future northeast
Pacific tropical cyclone. A Marginal Risk of excessive rainfall
remains for Sat-Sat night as above average moisture for the
monsoon fuels diurnally driven widely scattered to scattered
convection. The pattern would support isolated flash
flooding, with favored terrain, urbanized areas, box/slot canyons,
arroyos/dry washes, and burn scars being the most prone to
flooding.

..Southeast...

A quasi-stationary frontal boundary will be draped across the Gulf
Coast region during this period and will continue to provide a
focus for convection capable of producing heavy to excessive
rainfall along with aforementioned disturbance in the central
Gulf. Increasing ridging poking in from the western subtropical
North Atlantic should lead to a decreasing heavy rain threat across
the Carolinas with time. With precipitable water values of 2"+
expected, hourly rain amounts to 3" are possible where cells merge
or train, particularly near the Gulf Coast.

...Northern Plains into the Upper Midwest...

Shortwave energy will be traversing the edge of the upper ridge along
with the persistent moisture anomaly in place (PWATs ~2 standard
deviations above normal. Given the degree of instability and
moisture in play, some of the stronger storms will be capable of
intense short-term rainfall rates and localized flash flooding. A
Marginal Risk spans from the Dakotas to Wisconsin and portions of
Upper Michigan.

...Southeast and Gulf Coast...

The tail-end of the longwave upper trough, with distinct shortwave
energy traversing the Gulf Coast, along with the attendant
(eventually quasi-stationary) surface front, will provide the
dynamical focus for more organized (widespread) areas of convection
across this region. Multiple rounds of potentially heavy rainfall
for this period will support widely scattered instances of flash
flooding. Rainfall and thunderstorms will bring heavy rainfall to
Alabama and Georgia as well, and the previously mentioned trough
encounters a similarly moist airmass being pushed northeastward in
the lower levels. This will support several rounds of storms in the
form of multiple lines across Georgia and parts of South Carolina.
The storms moving northeastward could allow for some training as
the cold front moves through, and could bring widely scattered
instances of flash flooding. A Marginal Risk area remains in effect
for this period.

...Southwest...

The upper ridge will continue its gradual eastward shift across the
Southwest which in turn will also shift the footprint of the
heaviest precipitation. For this period, it is expected to set up
mainly east of Utah into the Central High Plains. Given the ridge,
storms will generally lack organization therefore the Marginal Risk
continues to focus on the areas where either terrain or prior
rainfall could locally increases the risk of flash flooding.

Campbell


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