FOUS30 KWBC 240800
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri Oct 24 2025

Day 1
Valid 12Z Fri Oct 24 2025 - 12Z Sat Oct 25 2025

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

The large scale pattern still favors an active day for convection 
later today through early Saturday morning over portions of the southern
Plains as strong height falls associated with an upstream 
Southwest U.S. closed low/trough ejects out into the High Plains 
along with a cold front. Low level moisture and stability will be
in place across much of central and northern TX as the nose of a 
30 to 40+ kts southerly low-level jet rides up into the Red River 
Valley region. The expectation is that organized convection should
develop initially across areas of west TX and advance east by 
later in the afternoon/evening which will be capable of producing 
high rainfall rates upwards of 2 inches/hour with the stronger 
cells. However, the organized nature of the convection suggests 
some forward propagation potential that could mitigate the overall 
storm total amounts. In fact, most of the guidance supports a 
fairly well- organized MCS evolution into southeast TX and near the
northwest Gulf Coast region by early Saturday morning. Maintained 
the Slight Risk area with only some minor adjustments to the 
western and northern periphery of the area to account for where the
axis of better instability should be along with corridors of 
convective initiation. This is also in better alignment with the 
consensus of the 24/00Z HREF and 23/18Z REFS guidance. Scattered 
areas of flash flooding, especially for the more urbanized 
locations, will be a concern.

...Pacific Northwest into Northwest California...
Only small localized adjustments were made to the Marginal Risk 
area as a modest Atmospheric River (AR) pushes across the coastal 
and Cascade ranges of Washington and Oregon. The plume of deepest 
moisture and associated rainfall will slide southward with respect 
to the coastline into northwest California by early Saturday 
morning. Strong height falls and precipitable water values over 1 
inch total PWats into the coastal range set up the potential for 
rainfall rates of 0.75 inches to 1 inch through the Columbia Valley
into central WA with higher rainfall rates remaining off- shore. 
Winds of 45-50kts through 850-700mb will result in peak IVT values 
of 700-750 kg/m/s. Still agree that the duration of heaviest 
rainfall is going to be very limited given the strength of the 
height falls and forward propagation of the cold front. QPF signals
remain at the 2-4" range within the favored southwest facing 
orography with an occasional rate up to .5" though fleeting; all in
line with a broad Marginal Risk of excessive rainfall.

Bann


Day 2
Valid 12Z Sat Oct 25 2025 - 12Z Sun Oct 26 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF 
SOUTHEAST TEXAS INTO SOUTHERN ARKANSAS AND WESTERN LOUISIANA...

Multiple rounds of heavy showers and thunderstorms are expected to
impact the broader northwest Gulf Coast region this period, with 
one initial axis of convection likely ongoing Saturday morning 
across areas of southeast to east-central TX and advancing across 
western Louisiana and southern Arkansas. This will be the 
carryover of organized convection from the day 1 period which 
should be interacting at least initially with a 40+ kt southerly 
low-level jet off the western Gulf. Precipitable water values at or
above 1.75 inches and MUCAPE values locally of 2000+ J/kg will 
support high rainfall rates potentially exceeding 2 inches/hour 
with the stronger storms.

The arrival of an upper- level jet streak in the subtropical 
stream combined with the interaction with the southern stream 
closed low/trough axis crossing the southern Plains will favor a 
renewed convective outbreak across areas of eastern Texas through 
portions of western and southern Louisiana Saturday afternoon 
through early Sunday. Even though antecedent conditions are quite 
dry, the concern for multiple rounds of convection which combined 
may yield some 3 to 5+ inch totals, will probably be enough to 
support a threat for scattered areas of flash flooding. The more 
sensitive urbanized locations will be at greatest risk for impacts.
For this update, the Slight Risk area was expanded given the
footprint of 2+ inch rainfall amounts within a broadened region of
instability shown by the models. This is also consistent with the
latest deterministic QPF from WPC. 

...Pacific Northwest and Northwest California...

Multiple rounds of moisture transport into the coastal ranges will
continue for the period as atmospheric river activity continues. 
Locally a few additional inches of rain will be possible for the 
windward slopes of the terrain, but given the early-season and 
relatively modest nature of this atmospheric river activity, any 
flooding concerns are expected to be isolated at best. Therefore, 
the Marginal Risk area is maintained with no changes for this update cycle.

Bann

Day 3
Valid 12Z Sun Oct 26 2025 - 12Z Mon Oct 27 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID- AND LOWER-MISSISSIPPI VALLEY AND ALONG THE PACIFIC NORTHWEST COAST...

Maintained a Marginal Risk area across portions of the southern and
middle Mississippi Valley. The risk across the southern should
diminish once a cold front passes through the area early in the
period and the deeper moisture/instability get shunted eastward.
Farther north where the moisture is not as deep...concern is more
from mid-level frontogenesis and upper level divergence leading to
locally enhanced rainfall rates where antecedent conditions have
been somewhat wetter than other locations. There is plenty
uncertainty as to whether there will be a second round of storms
capable of producing locally heavy rainfall...so overall confidence
is below average which precludes anything higher than a Marginal risk.

Bann
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