Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
256 PM EST Thu Nov 20 2025

Day 1
Valid 16Z 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 CONCHO VALLEY AND
EDWARDS PLATEAU...

...Texas...

16Z Update: Dynamic synoptic setup across the western half of the
CONUS will continue to promote a heavy rainfall threat across the
Southern Plains into the Ozarks. Heaviest rainfall is currently
located over the Lower Concho Valley and Edwards Plateau in TX
where the location is currently situated right in the heart of a
textbook coupled jet max with cores located OK and back into MX.
The positioning of the jet maxima allow for a broad axis of ascent
situated in-between the two cores leading to enhanced rainfall
pattern across North TX back towards the Rio Grande Valley.
Rainfall totals are on the order of 2-5" across the Lower Concho
Valley and Edwards Plateau with 2-4" over portions of the DFW
metro. The former is currently ongoing and will exhibit the highest
potential for north just flash flooding, but more considerable
flash flooding and accompanying impacts.

LCRA and West Texas Mesonet observational sites both confirm
rainfall rates reaching between 2-3"/hr in the strongest cores with
relatively slow cell propagation with some modest training focused
in-of the aforementioned zones. Convergence signal from hi-res is
steady within much of the CAMs in that general corridor with PWATs
approaching 1.7-1.9", well-above the climatological norm for mid to
late November. Additional totals for the area are forecast to be
between 1-3" with locally as high as 5" in a few pockets before the
setup finally shifts east-northeast with the final shortwave
ejection anticipated later today. Considering the multitude of
impacts ongoing and expected rainfall prospects through at least
this afternoon, the previous MDT risk was shifted north to
encompass those zones within the Lower Concho Valley into the
Edwards Plateau.

Further north towards the DFW metroplex, heavy rain this morning
has enhanced some regional streamflows as emphasized by the gauge
responses in-of the metro corridor and areas just to the south.
This was in conjunction with a series of heavier echoes that passed
through the area early this morning from a generally strong
shortwave perturbation that ejected northeast within the mean flow
downstream of the mean trough. Totals between 2-4" were seen across
portions of the metroplex, enough to warrant a few FFW's and
allowing for primed soils that will be easier to promote run off
potential, not even including the general urbanization factors that
accompany the metro. A slight lull will occur now through the next
few hours, but another round of moderate to heavy rainfall
potential with convective modes allowing will add to the already
saturated grounds and elevated streamflows. This setup is conducive
for additional flash flood prospects necessitating an upgrade to a
SLGT risk with high-end SLGT characteristics meaning some locally
significant impacts are plausible if rates between 2-3"/hr
materialize over the urban center directly, or over those areas
that were hit earlier this morning where elevated streamflows are
anticipated to continue. The SLGT expands the rest of central TX as
convergence pattern and positioning within the favorable jet
pattern should promote heavy rain prospects this afternoon and
evening before the threat pivots east as the surface pattern
matures and begins an occlusion phase overnight into tomorrow.

Kleebauer

..California...

16Z Update: Changes were minimal with the D1 update as the heaviest
rainfall will occur across southern CA with the target located over
the Peninsular Range due to the aided upslope components with the
low-level flow expected to remain semi-perpendicular to the
terrain. Totals between 1-2" will be common in those higher
elevations between 2-5k ft MSL with some localized amounts closer
to 3" for areas in the San Jacinto Mtns.

Kleebauer

..Previous Discussion..

Decided to upgrade to a Slight Risk area for portions of coastal
Southern California as the next area of low pressure over the
eastern North Pacific drops along the California coast and brings
another round of rainfall later today into early Friday. There has
been an uptick in rainfall amounts in the numerical guidance over
the past 24 hours but still generally under an inch...although
locally higher amounts could fall in terrain. Concern is that
antecedent conditions have been wet for the better part of a
week...suggesting some of area could be more sensitive to run off
problems even away from the highly urbanized areas.

Bann

...New Mexico...

16Z Update: Broad negatively-tilted trough located over the Great
Basin will lead to an area of diffluent flow located over New
Mexico and far eastern AZ today. Scattered showers and
thunderstorms across the aforementioned areas will occur with
pockets of heavier rainfall plausible in the period. Antecedent
conditions over the two areas are worthy for possible run off
enhancement considering the footprint of 0.5-1.5" rainfall totals
already positioned over the region. Isolated flash flood chances
continue through the afternoon before diminishing this evening.
Maintained general continuity from previous forecast with a low-end
MRGL positioned over the southern half of NM over into far eastern
AZ.

Kleebauer


Day 2
Valid 12Z Fri Nov 21 2025 - 12Z Sat Nov 22 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTHEAST California AND SOUTHWEST ARIZONA...

20Z Update: Little to no changes to the previous forecasts as the
overall synoptic pattern maintains continuity with little run-to-
run variance in both the QPF presentation and evolution. 

Kleebauer

..Previous Discussion..

Model guidance continues to lift the Plains system northward into
portions of the Ohio Valley. Above normal levels of moisture being
transported into the region from the south and encountering an east
to west oriented boundary...there is still the possibility for
isolated areas of moderate to heavy rainfall that leads to spotty
problems from run- off. However...the flow aloft becomes
increasingly flat and confluent during the day which will reduce
the risk of any excessive rainfall.

In California...we will carry a Slight risk across portions of the
desert areas of southeast CA into southwest AZ. Lobes of vorticity
east of the closed low will produce periodic rounds of showers and
embedded thunderstorms. Instability looks pretty weak, which will 
likely be a limiting factor, however some brief heavier rates are 
still possible from short training segments within the deep layer 
southerly flow. 

Bann/Chenard

Day 3
Valid 12Z Sat Nov 22 2025 - 12Z Sun Nov 23 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann/Kleebauer


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