FOUS30 KWBC 190825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
325 AM EST Wed Nov 19 2025

Day 1
Valid 12Z Wed Nov 19 2025 - 12Z Thu Nov 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTH-CENTRAL TEXAS, THE CONCHO VALLEY, AND TEXAS HILL COUNTRY...

A large mid/upper trough over the southwestern U.S. will take on a
negative tilt while moving slowly eastward toward the southern
Rockies through 12Z Thursday. As this occurs, abundant Gulf
moisture will be drawn northwestward across much of central and
southeastern Texas. Low-level trajectories indicating upslope into
higher terrain of northern Mexican provinces and areas of 1000-1500
J/kg SBCAPE are supportive of scattered thunderstorms developing
over northern Coahuila and the general vicinity of Del Rio/Eagle
Pass. CAMs depict a concerning signal for training in this region
as cells both 1) migrate northeastward beneath southwesterly
steering flow aloft while 2) redeveloping upstream closer to higher
terrain. A narrow corridor of 1-3 inch rainfall totals could
develop in these areas. Ultimately, local convective evolution will
determine the degree of training and length of heavier rain rates
in this area. Slight Risk and attendant probabilities are
maintained for this forecast as there is some lingering uncertainty
regarding specific location of this axis of heavier rain. However,
PW values approaching 1.5 and slow right-moving motions with any
cells that can acquire mature cold pools/updraft rotation may
force a locally significant flash flood threat occurring during the
overnight and early morning Thursday. Convective/rainfall trends
will be monitored for any enhanced training that would necessitate
a Moderate Risk upgrade.

Farther northeast, models depict deep convection in a more
scattered fashion toward Dallas/Fort Worth and into northeast Texas
(and perhaps western Arkansas). While thermodynamic profiles will
gradually become more supportive of heavy rainfall, weak forcing
(with the mid/upper wave well west of the region), weak/non-
existent low-level convergence, and subtle ridging aloft just east
of the region casts some doubt on convective coverage and
resultant flash flood risk. A Marginal Risk remains in place for
locally training storms, although this risk appears to be quite
conditional.

Across Arizona and New Mexico, deep southerly flow aloft will allow
for scattered shower and thunderstorm activity to drift northward
through much of the day. An uptick in convective coverage is
expected during peak heating hours, with isolated/localized flash
flood potential existing across any low-lying, sensitive, and/or
urban areas. Heavy rainfall (exceeding 1 inch) is expected to occur
on a relatively localized basis. Later in the forecast period
(between 00Z-12Z Thursday), models depict potential for heavier
rainfall to develop in a few locales across southern New Mexico
near several active burn scars. Isolated flash flooding could
occur near these burn scars.

Cook

Day 2
Valid 12Z Thu Nov 20 2025 - 12Z Fri Nov 21 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE
SOUTHERN PLAINS INTO ARKANSAS/MISSOURI...

...Southern Plains...
The environment continues to becomes more supportive of storms
capable of producing heavy to potentially excessive rainfall as the
flow aloft backs over portions of Texas and Oklahoma and becomes
increasingly diffluent as an upper trough approaches the region. At
lower levels...an airmass with precipitable water values gets
drawn northward an converges along a surface front over parts of
Texas and Oklahoma. Excessive rainfall is possible by means of
intense rainfall rates by individual storms in regions with the
highest amount of instability (presumably ahead of the approaching
cold front) and by training of cells/multiple rounds of convection
(more of a factor where synoptic scale forcing and mesoscale
forcing act in tandem farther north). The axis of highest
precipitable water values... 1.5-1.75"...sets up over the eastern
half of Texas into southeastern-most Oklahoma and into Arkansas.
Those values are well above average for mid-November. Localized
rainfall amounts up to 2.5" in an hour with additional local totals
of 5" possible within this set up which would result in scattered
instances of flash flooding.

...California...
Maintained a Marginal Risk area from continuity for portions of
coastal Southern California as the next area of low pressure over
the eastern North Pacific drops southward off the California coast
and brings another round of rainfall Thursday into early Friday.
Rainfall amounts at this point look to be pretty modest but the
rain will be falling on areas where antecedent conditions have
been wet for the better part of 5 or 6 days. That may result in
additional localized flooding on Thursday or Thursday night.

Bann


Day 3
Valid 12Z Fri Nov 21 2025 - 12Z Sat Nov 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE OHIO VALLEY AND PORTIONS OF THE SOUTHWEST US...

...Ohio Valley...

Rain will be spreading northward and eastward from the Plains on
Day 2 into the Ohio Valley on Friday and Friday night in
association with the surface low coming out of the mid-Mississippi
Valley. Between above normal levels of moisture being transported
into the region from the south and flow aloft becoming
confluent...there is still the possibility for isolated downpours
that lead to spotty problems from run-off despite the set up
becoming less favorable with time,

...Southwest US... A mid- and upper-level trough with an embedded
closed low will continue to drop southward on Friday...with an
e,bedded closed low expected near the US border with Mexico by 00Z
on Saturday.  Showers and embedded thunderstorms should be
developing in the highly difluent flow to the east of the trough
where precipitable water values approaching an inch rotate into
southern California and western Arizona. Opted to remain at a
Marginal threshold given the timing of the best upper support but a
Slight may still be needed.

Bann


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