428
FOUS30 KWBC 220004
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
704 PM EST Fri Nov 21 2025

Day 1
Valid 01Z Sat Nov 22 2025 - 12Z Sat Nov 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA...

Showers and thunderstorms remain possible for border areas of AZ
and CA with MX to the east-northeast of an incoming upper level
disturbance. Moisture amounts, considering the low 1000-500 hPa
thickness values of 5490-5550 meters, are sufficient for
atmospheric saturation. The problem so far has been the
instability, which is very near 100 J/kg. When combined with the
precipitable water values of ~1", hourly amounts in the 0.4" remain
possible overnight, with additional local totals of 1-2" through
12z. The mesoscale guidance is keying in on the southernmost
portion of the Peninsular Ranges east of San Diego for local
amounts in the 2" range, but this is only one spot. Given the
above, downgraded the Slight Risk to a Marginal Risk for the
overnight period (Saturday 01-12z). Any heavy rainfall related
issues are expected to be isolated.

Roth


Day 2
Valid 12Z Sat Nov 22 2025 - 12Z Sun Nov 23 2025

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

Churchill/Campbell


Day 3
Valid 12Z Sun Nov 23 2025 - 12Z Mon Nov 24 2025

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

...20z Update...

Maintained the inherited Slight Risk with only minor adjustments
made, primarily to shift the axis slightly south to southwest and
tighten the gradient along the north and south. This reflects the
latest trends in QPF, which are fairly tightly clustered for this
time range (relatively high spatial confidence). This is somewhat
concerning, as this brings the forecast axis of QPF even more into
alignment with areas that realized heavy rainfall in prior days.
However, the categorical outlook is still held at a Slight Risk
due to a combination of meaningful time between the prior event
and the upcoming event (three full days inbetween should allow for
soil moisture and streamflow recovery) and uncertainty with regard
to the amount of training and resultant QPF (with most of the new
guidance suggesting localized 2-3" totals, while some solutions,
including the downscaled 12z ECMWF, depict localized totals of up
to 4-5").

Churchill


...Previous Discussion...

The low pressure system that brought heavy rainfall for the West
Coast during the Day 1 period will be exiting into the Southern
Plains and the warm, moist air will support scattered to widespread
heavy rainfall. There is an increasing signal that this setup could
be a significant event, especially for north-central portions of
Texas and into southern Oklahoma where a couple of solutions are
suggesting a narrow swath of 4 to 6 inches possible. A Slight Risk
for excessive rainfall is in effect for for much of north-
central/northeast Texas and south/east Oklahoma. A broader Marginal
Risk spans from the Big Bend vicinity to southwest Missouri and
western Arkansas. This part of the country will continue to be
monitored for a possible upgrade to a Moderate with future updates.

Campbell


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