Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
737 PM EST Mon Nov 24 2025

Day 1
Valid 01Z Tue Nov 25 2025 - 12Z Tue Nov 25 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE LOWER MISSISSIPPI VALLEY INTO NORTHEAST TEXAS...

...01Z Update...

The primary changes to the ERO risk areas this evening were to trim
the west and northwestern portions of the risk areas in Texas and
Arkansas, as the steadiest, heaviest rains have ended in the
trimmed areas. Elsewhere, the ERO remains unchanged. A slow moving
front is drawing sufficient Gulf moisture northeastward from
eastern Texas into portions of the southern Tennessee Valley. Along
this corridor of moisture, prodigious lightning producing storms
are also peaking in intensity with rainfall rates topping 2 inches
per hour. In the areas where this heavy rain is falling, flash
flooding has been occurring. Fortunately storms reaching an
intensity capable of this intensity of rainfall have been quite
isolated among the larger complex of storms. The Slight Risk area
continues to highlight the area where enough rainfall has been
falling that should a storm move over those areas with heavier
rainfall rates, then resultant flash flooding is likely.

Slow moving storms associated with the southern end of the line
will likely impact the Houston metro later tonight. Much of the
CAMs guidance have suggested that by then the storms will be in a
progressive line, limiting the amount of time heavy rain is
occurring over the flood-sensitive metro. 
On the other end of the Slight, storms with embedded moderate to 
briefly heavy rainfall are also moving into northern Mississippi. 
Guidance suggests moderate rain will continue over this area for
much of the night. This too could result in widely scattered
instances of flash flooding. Since by late tonight instability will
be waning, most of Mississippi other than the northwestern-most 
counties remain in a Marginal Risk. Thus, it should be noted that 
both these areas are in the higher end of the Marginal Risk threat.

Wegman

...Previous Discussion...

The overall forecast philosophy remains on track for this update.
Areas of showers and thunderstorms are expected to redevelop from
southwest to northeast within an 850mb low-level jet axis extending
from near Austin, TX through the ArkLaTex. Some of the convection
will interact with left over low-level boundaries from this
morning's convection, further enhancing rainfall potential and
resulting in localized 2-4 inch daily totals. The greatest risk of
these enhanced rainfall totals will focus around northeast Texas
into northwest Louisiana and vicinity.

The overall convective scenario should translate eastward toward
the Lower Mississippi Valley through the overnight hours and become
increasingly displaced from surface-based buoyancy focused across
southeast Texas/southwest Louisiana. Flash flooding should remain
possible, but gradually decrease in coverage with eastward extent.

Risk areas across Oklahoma, northern/central Arkansas, and parts of
west-central Texas were trimmed as ongoing convective trends
suggest that any remaining flash flood threat has lessened for the
remainder of the forecast period.

Cook


Day 2
Valid 12Z Tue Nov 25 2025 - 12Z Wed Nov 26 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHEAST, TENNESSEE VALLEY, AND SOUTHERN APPALACHIANS...

20Z Update...
Overall, no large changes were made to the previous area. Both the
HREF and RRFS guidance indicate locally heavy amounts, with an
isolated threat for flash flooding, are possible in the region.
The 12Z HREFmean continues to highlight the southern Appalachians
with higher probabilities for amounts of 2-3 inches, whereas the
06Z RRFSmean suggests a broader threat that is centered farther
southwest from northwestern Georgia back through central Alabama.

Previous Discussion...
The low pressure system will continue advancing through the Gulf
states and into the Southeast/Carolinas. The latest guidance
continues to depict localized totals as high as 2-3" especially
near the higher terrain of the region. Should these occur over a
short enough period (or exceed 3"+ in areas farther south) than
isolated instances of flash flooding are possible. A Marginal Risk
remains in effect from eastern Mississippi to extreme southwest
Virginia and western North and South Carolina.

Pereira/Campbell


Day 3
Valid 12Z Wed Nov 26 2025 - 12Z Thu Nov 27 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN
WASHINGTON AND NORTHWEST OREGON...

20Z Update...
Made only minor adjustments to the previous outlook.

Previous Discussion...
An atmospheric river directed toward the Pacific Northwest will
advect copious moisture towards the terrain, with some 2 to 3 inch
rainfall totals likely. This will increase the threat for runoff
and localized flash flooding therefore a Marginal Risk is in
effect.

Pereira/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