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FOUS30 KWBC 200901 AAA
QPFERD

Excessive Rainfall Discussion...UPDATED
NWS Weather Prediction Center College Park MD
401 AM EST Thu Nov 20 2025

Day 1
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 AND
SOUTHERN CALIFORNIA...

Maintained the targeted Moderate Risk for portions of Soth-Central
Texas given persistent signals for localized 5"+ storm totals from
the HREF and the RRFS guidance. That amount of rainfall 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). The overnight
runs of the HREF and RRFS While 6-hr FFG exceedance probs from the
HREF and RRFS both rise to at least 60 percent later today
(generally in the morning perhaps into early afternoon) before
enough westerly flow develops in the mid-levels which shifts the
focus farther eastward. The probabilities diminish during the
afternoon and evening. As a result...expanded the surrounding
Marginal/Slight risk areas just a bit in the inflow region. Some
nudges were made to the placement of the western/northern boundary
of the northern Slight Risk area based on latest probabilistic
guidance. Some lingering questions remain regarding the eastward
extent of both the South-Central TX and Ozarks clusters of
convection...however. Introduced a Marginal risk area across parts
of southern New Mexico which was a continuation of the area in
effect until 20/12Z...as convection moves eastward in response
height falls and increasingly difluent flow aloft.

..California...

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

Day 2
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...

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...only limited changes necessary from the previous
forecast due to general run- to- run continuity with 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 now, will maintain relatively continuity of
the MRGL with some minor adjustments overall.

Bann

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 per cent.

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