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QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
244 PM EST Wed Nov 19 2025

Day 1
Valid 16Z Wed Nov 19 2025 - 12Z Thu Nov 20 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTH-CENTRAL TEXAS, INCLUDING PORTIONS OF THE HILL COUNTRY...

...Special 1915z Update...

A targeted Moderate Risk was introduce in collaboration with the
San Antonio and San Angelo local offices, generally encompassing
Del Rio and points east-northeast(including much of Val Verde,
Kinney, Edwards, and Real Counties). This is where 5" exceedance
probs are maximized (12z HREF indicating probabilities near 20%
through 12z with experimental 06z REFS indicating probs as high as
60%). Given the sensitivity of the Hill Country with the potential
for 3"+/hr rainfall rates developing rapidly late tonight, it was
decided to introduce the Moderate Risk for the Day 1 period (with
greater confidence in realizing 5"+ localized totals just beyond
the Day 1 period ending at 12z Thursday). An updated Day 2 outlook
will also reflect this upgrade shortly (as the bulk of the realized
impacts of the Moderate Risk are anticipated to occur around or
just beyond 12z Thu).

Churchill


...16z Update...

Minimal adjustments to the ERO areas with this update, as the
inherited Slight Risk area is still positioned well within the
consensus of the 12z CAMs 3"+ QPF signal (40-70% odds per latest
40-km neighborhood 3" exceedance HREF probabilities). While this is
also the higher confidence corridor for localized 5"+ amounts (per
both the 12z HREF PMM and 10-20% probs for 5" exceedance), there
are indications of a secondary training corridor by some of the
CAMs (mainly the ARW and ARW2) across portions of North TX into the
ArkLaTex (20-30% and 5-15% for 3" and 5" exceedance, respectively).
While this area remains more of a conditional flash flood threat
(dependent on west-to-east training convection along the quasi-
stationary boundary with weak forcing), the Marginal Risk was
expanded more into the ArkLaTex to account for the latest QPF
spread in the 12z guidance (with the bulk of the QPF still expected
late in the period for both regions).

Maintained the Marginal Risk elsewhere (Southwest U.S.) where
longer duration rainfall (with instability being the main limiting
factor for convection and higher rainfall rates) could result in
localized flood impacts for sensitive areas.

Churchill

...Previous Discussion...

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 MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTH-CENTRAL TEXAS, INCLUDING PORTIONS OF THE HILL COUNTRY...

...20z Update...

A couple of significant changes to the outlook areas for this
update.

This first is to introduce a targeted Moderate Risk upgrade for
the same areas as detailed for Day 1. This is due to increasing
likelihood for localized 5"+ storm totals beyond the 12z Thursday
Day 1/2 cut- off, which may result in numerous instances of flash
flooding in a relatively small area (with higher confidence overall
in locally significant flash flooding as opposed to the total
areal coverage). While 6-hr FFG exceedance probs from the HREF are
below 20% through the end of Day 1, they increase meaningfully to
near 60% going into Day 2 (through 18z Thu).

The second significant change was to split up the larger Slight
Risk area into two distinct areas, 1) South-Central TX and 2)
eastern OK into northern AR and southern MO. This reflects the
consensus of the latest CAM guidance which suggests a large gap in
convection across North TX during the period (with questions still
lingering regarding the eastward extent of both the South-Central
TX and Ozarks clusters of convection into the later half of Day 2).

Churchill

..Previous Discussions..

...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...

20Z Update: Limited changes necessary from the previous forecast due
to general run-to-run continuity. Heaviest rainfall still trending
closer to the southern Peninsular Range with an extension of
convection back over the southeast CA deserts and southwest AZ for
the MRGL over the west. Moderate to locally heavy rain possible for
the Ohio Valley. Steady forward propagation of broad QPF shield
should limit the necessity for more than the current MRGL risk. Will
assess the southern portion of the risk area closely in the coming
days as this region, extending into the Southeast CONUS will be most
coincident with a purely convective regime as instability is
prevalent within a broad, but modest theta_E depiction. This area
would promote higher rate potential, but could be a case where
forcing is not enough to activate the better thermodynamic
environment. For now, maintain relatively continuity of the MRGL
with some minor adjustments overall.

Kleebauer

..Previous Discussions..

...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 embedded closed low
expected near the US border with Mexico by 00Z on Saturday. Showers
and embedded thunderstorms should be developing in the highly
diffluent 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