Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Thu Apr 24 2025

Day 1
Valid 12Z Thu Apr 24 2025 - 12Z Fri Apr 25 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE CENTRAL/SOUTHERN PLAINS AND IOWA...

The latest suite of guidance continues to be be highly variable
with the placement of highest QPF; however persisted with increases
over Iowa as well as Oklahoma and Texas. The Slight Risk saw a
southward expansion for the Hill Country and to the northeast
placing the northern boundary into central Iowa. Meanwhile there
was a reduction across western Oklahoma and along the Missouri and
Kansas border. Areal averages of 1 to 2 inches with local maximums
of 4+ inches possible.

Multiple clusters of thunderstorms will likely be ongoing. With peak
heating and the increased instability there will be renewed rounds
of showers and thunderstorms. Since this is likely to occur over
many of the same areas hit with recent heavy rain this will once
again renew the potential for localized flash flooding over
portions of the Southeast. There will be a steady influx of Gulf
moisture streaming over the stalled boundary which will maintain
support for heavier rainfall with the strongest storms, and greater
coverage of showers and storms in general. A Marginal Risk covers
the northern Gulf states and Southeast.

Campbell


Day 2
Valid 12Z Fri Apr 25 2025 - 12Z Sat Apr 26 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS, MID-MISSISSIPPI VALLEY, OHIO VALLEY, AND
PORTIONS OF THE NORTHEAST...

A strengthening surface low developing ahead of a strengthening
upper level shortwave trough will drive the storms from a forcing
standpoint through the period. Starting in the Plains it will track
northeast into the Great Lakes Friday evening, with showers and
storms forming along the cold front to the south and east of the
low center. This will bring periodically heavy rainfall to
portions of the Northeast, which has been in a drier period the
past week. Gulf moisture continuing to advect in from the south
will lead to shower and thunderstorm activity starting Friday
afternoon across the Tennessee and Ohio Valleys, and continuing
into Friday night as the front lags behind (south and west) of the
surface low. Meanwhile, the trailing (western) end of the cold
front may be the trigger for additional thunderstorms into southern
Oklahoma, north Texas, and the southern Texas Panhandle.

In coordination will the offices in the Northeast the Marginal Risk
was removed from New Hampshire, Vermont, much of New York and
northeast Pennsylvania. This area has been drier of late and with
green up already in progress, much of the rain will be absorbed
with minimal if any flooding possible. Elsewhere, the Marginal had
minor reshaping to reflect the latest WPC QPF and model trends.

Campbell/Wegman


Day 3
Valid 12Z Sat Apr 26 2025 - 12Z Sun Apr 27 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS AND FOR PORTIONS OF NEW ENGLAND...

...New England...

Showers and thunderstorms are expected to pass through New England
thanks to upper level shortwave energy and wavy surface fronts.
The flow is expected to be fairly progressive so it will help limit
the potential for flash flood. Given the recent QPF trends and
placement, the inherited Marginal Risk area was significantly
modified to only include northeast Vermont, northern New Hampshire
and the majority of the state of Maine.

...Southern Plains...

The steady influx of rich moisture ahead of a deeply strengthening
storm system ejecting into the Plains will fuel rounds of heavy
rain and thunderstorms across portions of the central U.S. from the
weekend into next week. Guidance has improved its focus on where
the higher QPF will occur. The old Day 4 Marginal Risk was reduced
out of Nebraska and Kansas, now spanning from Texas to western
Arkansas as the new Marginal Risk area for this period. Heavy rain
will be favorable with the upper trough diffluence combined with
front/dryline instabilities.

Campbell


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