Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
808 AM EDT Tue Apr 22 2025

Day 1
Valid 12Z Tue Apr 22 2025 - 12Z Wed Apr 23 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE TEXAS PANHANDLE INTO WESTERN OKLAHOMA AND THE CENTRAL GULF
COAST INTO THE SOUTHEAST...

12z Update: The Marginal risk was expanded over the Southeast and
now stretches from LA northeastward into portions of MS/AL and the
southern Appalachians. Convection near a stalled boundary will be
capable of producing heavy rainfall rates today across this
corridor. See MPD 147 for more info on the near term possible
flash flood risk across portions of northern MS and AL.

Chenard

...Previous Discussion...

...Texas and Oklahoma...

A west-east orientated warm front paired with a dryline over West
Texas will maintain an environment conducive for convection through
the night. An expeditious shortwave ejecting out of the Southern
Rockies will navigate over the Caprock aiding in focused mid-level
ascent within the confines of the boundary and relative instability
maximum situated near the front and points south and east.
Scattered convection will likely billow up off the eastern New
Mexico Caprock down into the Stockton Plateau leading to strong
mesoscale cores maintaining a prevalent convective footprint over
the Southern Plains.

Cell propagation will be east to southeast motions given the
850-250mb shear field, entering into fairly unstable environments
downstream that will be capable of holding the convective pattern
well into the evening. Precipitable water values will be 1+
deviations above season average which could yield hourly rates of
1-2 inches/hour. These types of setups tend to be tricky, but the
setup is historically one that favors isolated flash flood
concerns, especially within any urbanized areas across the Caprock
into the western Red River Basin. The inherited Marginal Risk
continued to highlight the region with an elevated threat for heavy
rainfall and flash flooding.

...Gulf Coast...

Convection will focus along the slow-moving frontal boundary over
the Lower Mississippi Valley, particularly across southern
Louisiana. Locally heavy rain with cores generally anchored to any
remnants of the front as it decays within the southern Parishes of
the state. Several CAMs indicated a heavy rainfall footprint from
the Texas/Louisiana border to the New Orleans metro area. The
flooding threat is modest at best due to the uncertain nature of
where the pulse convective regime will initiate, however the
individual totals being depicted via CAMs (5-8") and some global
deterministic (3-5") are very much capable of causing some flash
flood concerns across the area. A Marginal Risk remains in effect
for this portion of the state, with only minor reshaping from the
previous issuance.

Campbell/Kleebauer


Day 2
Valid 12Z Thu Apr 24 2025 - 12Z Fri Apr 25 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS...

Several shortwaves will be exiting the Rockies throughout the day
with several pockets of convective development sprawled across the
Central and Southern High Plains by the evening hours. While the
confidence continues to be lower on the maximum amounts there is
however higher confidence on the potential for scattered flash
flood prospects. Although the location of QPF maxima vary, there
is a general consensus of a widespread 1 to 2 inches from the Front
Range of Colorado/Wyoming/Nebraska south to the Red River Basin
near Texas to Kansas/Oklahoma. Some of these areas will have seen
significant rainfall prior to any additional impacts leading to
some localized lower FFG indices once the event occurs. The
inherited Marginal continued to mostly highlight areas across the
Plains that had an elevated threat for heavy rainfall and flash
flooding. The latest guidance and WPC QPF trended higher with QPF
over northeast Kansas, southern Nebraska, southwest Iowa and
northwest Missouri. As such, the Marginal Risk area was modified to
encompass that part of the region.

Campbell/Kleebauer


Day 3
Valid 12Z Thu Apr 24 2025 - 12Z Fri Apr 25 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
KANSAS, OKLAHOMA, ARKANSAS AND MISSOURI...

The pattern will be favorable for multiple rounds of showers and
thunderstorms to move through the south-central U.S. With a moist,
unstable flow expected and shortwave energy passing through heavy
rainfall will likely develop across the region which may lead to
local flash flooding. Areal averages of 1 to 2 inches are forecast
with locally higher amounts possible. A Slight Risk for excessive
rainfall is in effect for a large portion of Kansas, northern
Oklahoma, far northwest Arkansas and western Missouri. A Marginal
Risk area spans from northern Texas to southern Nebraska and
extreme southwest Iowa.

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