FOUS30 KWBC 290819
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 AM EDT Tue Sep 29 2026

Day 1
Valid 12Z Tue Sep 29 2026 - 12Z Wed Sep 30 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM THE
SOUTHWEST INTO THE CENTRAL HIGH PLAINS...

The remnants of Hurricane Polo will make their way out of Mexico,
near El Paso, then track generally northward, roughly following the
NM/TX border. The heaviest rains of the event are likely to follow
along the track of the center. However, a much broader rainfall
shield will continue to envelop the Southwest. A large Moderate
Risk remains in effect from south-central Arizona through
southwest Kansas. A higher-end Moderate Risk remains from about
the middle of New Mexico to southern Colorado including the
Sangre de Cristos, the northwest corner of the Texas Panhandle
and extreme southwest corner of Oklahoma. Nearly saturated soils,
low FFGs, instability associated with Polo's center, as well as
moisture influx from the south will all work to highlight this
region as the area most likely to experience locally catastrophic
flooding from the 2-4 inches (locally higher) of rain expected
through the period.

Once again guidance shifted south and east across the Plains from
Nebraska through Iowa, with a lack of instability along that warm
front still suggesting that most rain that occurs here will be
stratiform, and therefore limit the rates enough to avoid numerous
and/or widespread cases of flash flooding. The Slight Risk was
maintained across parts of the Central Plains.

Campbell/Pereira/Wegman
 

Day 2
Valid 12Z Wed Sep 30 2026 - 12Z Thu Oct 01 2026

...THERE ARE MODERATE RISKS OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL/SOUTHERN HIGH PLAINS AND SOUTHERN PLAINS...

During this period the developing low over the High Plains, which
have absorbed the remnant energy and moisture from Tropical
Cyclone Polo, will strengthen and take on a much more classic comma
shape, with the warm front extending towards the Upper Great
Lakes. Tropically enhanced heavy rainfall will continue to spread
from the Southwest to the Southern/Central Plains and into the
northern Mississippi Valley. Multiple days with overlapping heavy
rain footprints will keep elevated threats for excessive rainfall
and flash flooding. Locations particularly sensitive will be dry
washes, burn scars, slot canyons, and areas of higher terrain.

Focusing on topographic effects, the Colorado/New Mexico Moderate
Risk area was maintained for the upslope flow into the southern
Front Ranges. From the High Plains to Wisconsin/Illinois the
greatest QPF is expected to fall along and north of frontal
boundary. With the instability being offset to the south, rainfall
rates may not support widespread flash flooding, instead favoring scattered
instances consistent with a Slight. However, further monitoring
will be needed as the expected amounts are flirting with a possible
Moderate Risk.

To the south an organized line of convection is expected to setup
across central Oklahoma and Texas. The Moderate Risk in
Texas/Oklahoma was nudged a bit to the west, with growing consensus
that a line of convection will be slow- moving as well as expanded
southward to the Mexican border. Interactions with the dry slot to
the west will ultimately determine where the storms form and how
much flash flooding results. Finally, speaking of the dry slot,
growing consensus that it will track through eastern New Mexico and
the Panhandles, (which makes sense given the track of Polo), means
that fortunately many of these very hard hit areas from Tuesday
will finally get to dry out under the dry slot. Thus, the no-risk
area and Marginals were expanded northeast to include these areas
as the risk of flooding rainfall is very low.

Campbell/Hurley/Wegman
 

Day 3
Valid 12Z Thu Oct 01 2026 - 12Z Fri Oct 02 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHERN PLAINS...

During this period a postively-titled upper level trough is
expected to weaken, then stall over the Central and Southern
Plains. Along the surface frontal boundaries heavy rainfall will
persist with potentially numerous instances of flash flooding for
the Southern Plains. A Moderate Risk was maintained southeast
Oklahoma to the Texas Hill Country and South Texas where large-
scale ascent afforded in part by favorable upper jet forcing will
continue to interact with an axis of anomalous moisture (2-2.25+
inch PWs). This multiple day event will have possible overlap, thus
keeping an elevated risk for flooding.

A broad Slight Risk extending north from Texas to Wisconsin and
northern Indiana and then west to eastern Colorado. While areal
average rainfall amounts are expected to be less in this region,
moisture drawn north and focusing ahead of a cold front settling
south across the region is likely to fuel the potential for
widespread moderate to localized heavy rainfall, resulting in at
least isolated runoff concerns.

Campbell/Pereira
 

Day 4 and Day 5
Valid 12Z Fri Oct 02 2026 - 12Z Sun Oct 04 2026

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTHERN TEXAS ON DAY 4 AND FROM THE CENTRAL GULF COAST INTO THE
TENNESSEE VALLEY ON DAY 5...

Day 4...
Mid-level energy associated with the trough moving into
the central and southern Plains on Thursday will remain over the
region into at least the early part of the weekend. Deep moisture
will remain as well over parts of the southern Plains --
maintained by backing low level winds tapping Gulf moisture and
drawing it westward into a lingering low level boundary. As this
moisture interacts with the slow-moving mid-level energy that is
forecast to remain over the area, there will continue to be some
potential for heavy rainfall producing storms, impacting some areas
that are likely to be left vulnerable to excessive runoff by the
previous day(s) heavy rains. While forecast confidence has
diminished some, there remained enough of a signal in the
overnight guidance that showed additional heavy accumulations
centered across parts of South to South-Cental Texas to maintain a
Slight Risk over the region. Farther north and east, a cold front
will continue to settle southeast through the Ohio Valley, with
some potential for heavy rain along and ahead of the boundary.
Supported by deep southerly flow along the western extent of the
subtropical ridge, guidance continues to show a broadening pool of
anomalous moisture spreading from the Gulf Coast into this
boundary. Mid-level energy embedded within the flow may help
produce areas of heavy rain, with some guidance indicating heavy
amounts along the Gulf Coast from Mississippi to the Florida
Panhandle this period.

Day 5...
Moisture will continue to deepen from the Gulf Coast northward into
the Tennessee Valley -- with PW anomalies increasing to 2-3 std
dev above normal across much of the region during this period. A
Slight Risk was drawn along the axis of deepest moisture (PWs at
or above 2.25 inches) which is expected to extend from the central
Gulf Coast northward into an area of enhanced ascent centered in
the vicinity of the Tennessee Valley. The previously noted front
dropping south into the area along with mid-level energy emanating
from the Plains are expected to help focus heavy rainfall
development over this region. Forecast confidence was limited in
part by model spread regarding the placement of the front, which is
likely to play a role in where the heaviest amounts occur.
Therefore, notable adjustments to at least the northern extent of
the Slight Risk may be required in future updates.

Pereira
$$
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 * Origin: capitolcityonline.net * KY, USA (618:250/10)