Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
404 AM EDT Wed Mar 22 2023

Day 1
Valid 12Z Wed Mar 22 2023 - 12Z Thu Mar 23 2023

...THERE IS A MARGINAL FOR EXCESSIVE RAINFALL ACROSS SOUTHERN
CALIFORNIA AND CENTRAL ARIZONA...

Lingering rains from a departing AR will continue as the upper
trough tracks from southern California into the Desert Southwest.
New accumulations of 1 to 2 inches (mainly focused in/near the
terrain) that fall on areas that are already hydrologically
sensitive to additional precipitation will keep the potential for
excessive rainfall going over portions of southern California and
central Arizona.

Campbell



Day 2
Valid 12Z Thu Mar 23 2023 - 12Z Fri Mar 24 2023

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FROM THE SOUTHERN
PLAINS TO THE OHIO VALLEY...


A steady stream of Gulf of Mexico moisture will surge northward
along a frontal boundary spanning from the Great Lakes region
southwest to New Mexico and produce widespread rain from the
Southern Plains to the Ohio Valley. Low level flow transporting PW
values of 1.25 (+2 std dev) into the heart of the nation will be
nearly parallel to the frontal boundary. A southwest to northeast
orientated swath of QPF is expected to setup from Texas to
Pennsylvania with some of the highest amounts aligning in a narrow
band from eastern Oklahoma to Indiana. The 3-hr FFGs across the
general area are 1.5/2 inches with areal averages of 1 to 3+
inches forecast. There were already Slight and Marginal Risks for
excessive rainfall in effect. Given the latest trends and WPC QPF,
the Marginal Risk and Slight Risk areas were expanded south and
west across parts of Oklahoma, Texas and Louisiana. The Marginal
Risk was expanded a few counties southward from eastern Kentucky
to West Virginia. The eastern bounds of the Slight Risk was
narrowed a bit to be near/south of I-70 in Indiana and Ohio.

Campbell

Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt