Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 PM EDT Sat Oct 3 2026
Day 1
Valid 16Z Sat Oct 03 2026 - 12Z Sun Oct 04 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST, THE LOWER TEXAS COAST, AND EASTERN NORTH CAROLINA...
...Central Gulf Coast...
16Z Update: Little change necessary for the SLGT risk located
across the Central Gulf coast as the latest 12z CAMs and associated
HREF remain confident in their presentation of locally 4-6+" of
rainfall through the period with a majority of the rainfall
occurring with the approach of weak wave out of the eastern Gulf
later this evening. HREF neighborhood probabilities for >5" remain
elevated (50-80%) across the immediate coastal areas of southern
MS/AL with the eastern extent right over the far western FL
Panhandle. Some of the deterministic outputs from the CAMs are
quite robust with 6+ inches of rain within that immediate coastal
plain thanks to the greatest instability source co-located with the
immediate Gulf waters. The area along I-10 between Biloxi to Mobile
Bay continues to be the most noteworthy area for the higher probs
for >5", a signal that has been prevalent now for multiple runs of
the hi-res guidance. This lends credence to the local threat of
flash flooding and the continuation of the high-end SLGT risk
located over southeast LA into the western FL Panhandle.
Kleebauer
..Previous Discussion..
A tropical wave moving across the Gulf will funnel record to near
record amounts of atmospheric moisture into much of the Gulf Coast
on Saturday. A 15-25 kt southerly flow into the coast at 850 mb
will support numerous showers and thunderstorms associated with the
wave moving into the central Gulf Coast both today and tonight.
PWATs will be at or above 2.5 inches for many areas. Extensive
cloud cover and the October sun should limit instability
considerably with any reasonable distance from the coast. Thus, any
convection that impacts the coast is unlikely to be able to travel
too far inland without significant weakening. Thus, the Slight
highlighting much of the coast remains unchanged. A higher-end
Slight Risk was added with this update from New Orleans through
much of the western Florida Panhandle. They were primarily
included due to urban impacts and the sheer volume of water
expected, as the coast can expect 3-6 inches of rain today, with
locally higher amounts. Despite very high FFGs and dry soils in
this area, this amount of rainfall may overcome that, especially in
urban areas to result in widely scattered instances of flash
flooding.
Wegman
...Lower Texas Coast...
16Z Update: No changes to the previous SLGT risk were necessary
with this forecast update as the latest hi-res guidance continues
to hint at elevated convective threat along the immediate TX coast
from CRP down to BRO and points just inland. Greatest signal
continues to be within that zone with the maxima for both rainfall
outputs and subsequent HREF probabilities noting the King Range
area between the metro areas as the primary area of concern. A
pretty solid HREF EAS signal for at least 2" exists right along
that immediate coastal area just north of South Padre Island,
correlated with the best frictional convergence regime likely
materializing later in the period. Surface analysis depicts a
surface trough off the TX coast into the western Gulf which would
indicate a prevailing easterly flow moving into the coastal plain.
PWATs between 2.1-2.3" and generally formidable low to mid-level
instability max situated across South TX should be enough to garner
local rates upwards of 2-3"/hr in the stronger cell cores that move
ashore. Given all of the above, felt this was more than enough to
warrant a continuation of the SLGT risk with little deviation from
the previous forecast(s).
Kleebauer
..Previous Discussion..
The Slight risk remains in place along the coast of Deep South
Texas as well. Onshore northeasterly flow of the same deep tropical
moisture impacting areas further north and east may impact some
urban areas such as Brownsville. As this portion of the Lower Texas
Coast is roughly perpendicular to the mean flow, expect the onshore
push to allow convection to try to move a few miles inland before
dissipating. No changes were made to the area included in the
Slight Risk with this update.
Wegman
...Eastern North Carolina...
The combination of an approaching front and deep layer moisture
presence across eastern NC will generate a period of enhanced low-
level convergence and heavy rain prospects over areas west of the
Pamlico Sound, impacting some of the more notable population
centers just inland of the coast. Recent trends within the
HREF/REFS mean QPF and associated probability fields indicate
enough of a signal to warrant a targeted SLGT risk for areas of
eastern NC with a centroid focused near New Bern and surrounds.
PWATs between the 90-99th percentile continue to plague the eastern
Carolina's and this setup is no different. Anticipate an increase
in convergence between 925-700mb by late-afternoon and evening as
the cold front to the north slowly sags southward into the
vicinity and taps into the modest instability pool residing in the
region. Light mean winds ahead of the front will keep general storm
motions on the slower side with a potential for cell training after
initiation, something prevalent within the latest CAMs as most of
the guidance indicates thunderstorm genesis with little forward
propagation over the course of their life cycle. A "bullseye" of
>80% probabilities for at least 3" exists over that area northwest
of the Morehead City to Wilmington, NC line based off both the 12z
HREF and REFS depictions. After further coordination with the
local MHX/RAH/ILM office, a targeted SLGT risk was added over the
aforementioned area to account for the threat of locally heavy
rainfall with localized amounts between 3-6" possible in the
hardest hit locations.
Kleebauer
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 PM EDT Sat Oct 3 2026
Day 2
Valid 12Z Sun Oct 04 2026 - 12Z Mon Oct 05 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHEAST AND LOWER TEXAS COAST...
...Southeast...
20Z Update: Changes for the D2 SLGT were minimal across Gulf coast
and portions of the Southeast with an area of very heavy rainfall
likely occurring along the immediate Central Gulf coast into the FL
Panhandle. The SLGT risk further north was scaled back, however, as
the trends on the latest guidance were for a more progressive push
of the cold front and wedging stable airmass into the Piedmont of
the Carolinas and Virginia. This has led to the heaviest
precipitation threat located further south with the eastern
periphery of the better forcing and moisture pushing offshore for
eastern NC which would end a more appreciable threat.
The general synoptic pattern remains favorable for continued
onshore flow and frictional convergence along the coastal plain
with ample buoyancy and well- above normal PWATs integrated across
the Southeast. Cold front to the north will slowly press southward
leading to enhanced convergence away from the immediate coast with
a mid-level steering pattern influencing the moisture advection
scheme with the deep moisture layer moving inland and then pivoting
to the northeast through southern AL, central and southern GA,
into the northern half of FL. Models are in agreement on a
widespread 1-3" inland of the immediate coast, with locally higher
totals embedded within the mean QPF distribution, positioned across
southern and eastern GA into the FL Panhandle. The area situated
between Mobile to Tallahassee continues to be the most prominent
area of heavy rainfall with convective threats abound for much of
the D2 thanks to a lingering surface wave progged to move into the
general vicinity of the above area and maintain a prolonged axis of
heavy rain within the eastern confines of the circulation. HREFpmm
output of 5-8" remains consistent from the previous runs of the
ensemble, leaving a good agreement on the prospects of at least
scattered flash flooding within that area of the I-10 corridor to
just inland. The high-end SLGT risk was maintained as a result of
the continuity in the expected evolution of the synoptic forecast
and coupled results in the precip distribution. A non-zero threat
for an upgrade in the area of the Central Gulf coast remains, but
an upgrade may be contingent on what transpires in the D1. We will
be monitoring closely on the threat as it evolves the next 24hrs.
Kleebauer
..Previous Discussion..
The combination of the continued funneling of record to near-
record atmospheric moisture across the Southeast from a tropical
wave over the Gulf, and an approaching cold front will allow for a
swath of heavy rainfall to expand from the Central Gulf Coast
northeast to portions of the Carolina coast. PWATs will range from
2.25 to 2.5 inches, which with good instability would be ample
moisture to produce areas of significant flash flooding. However,
the October sun and extensive cloud cover will instead limit
instability significantly, with most areas struggling to reach even
1,000 J/kg of MUCAPE. Thus, this is likely to end up being a long-
duration highly-efficient rainfall across the Slight Risk area.
The Slight was also expanded north a bit to include the
Birmingham, AL and Atlanta metros. Both of those cities will be on
the northern edge of the rainfall plume, so there's considerable
uncertainty given recent southward trends in the guidance as to the
extent of any flash flooding. The urban nature of the area will be
countered by weak instability.
Once again the heaviest rains on Sunday will be in many of the same
areas hit hard on Saturday, with perhaps a slight eastward shift
from Saturday. Areas from Mobile, AL east across most of the
Florida Panhandle are likely to see the most rain. Since there is
significant overlap from Saturday, another higher-end Slight was
introduced for this region. There is a non-zero chance, depending
on how extensive any flash flooding from the rains today are, that
a Moderate Risk upgrade may be needed for Sunday.
...Lower Texas Coast...
20Z Update: SLGT risk was maintained across the immediate South TX
coastal plain with the best threat likely over the King Ranch area
down towards South Padre Island and areas just inland of the coast.
HREF neighborhood probability for >5" remains elevated (50-80%)
centered over Kennedy and Willacy counties, sneaking into the
northeastern portion of Cameron. This area can take a lot of
rainfall overall thanks to the sandier soil composition, however,
the threat for 5+ inches of rainfall does leave the door open for
scattered flash flood prospects as we monitor any potential the
heavier rain can sneak into the more urbanized areas centered along
the lower RGV. A high-end SLGT or further upgrade may be necessary
pending the impacts from the previous period of rainfall.
Kleebauer
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 PM EDT Sat Oct 3 2026
Day 3
Valid 12Z Mon Oct 05 2026 - 12Z Tue Oct 06 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHEAST AND LOWER TEXAS COAST...
...Southeast...
20Z Update: The cold front will continue to moving to the south
with eyes on the Gulf coast into FL by the D3 period. Pending the
positioning of the boundary, a SLGT risk may be necessary across
portions of the FL Panhandle as noted via some of the ensemble
members and bias corrected QPF outputs. There's discrepancy in the
latitudinal push of the cold front and that will be play a big role
in the alignment and placement of the heaviest rainfall. Global
deterministic outputs were all over the place with some maintaining
a less than enthusiastic signature on the prospects, to others
putting a significant amount of rainfall in areas of southern GA
and northern FL, overlapping some of the expected areas of impact
from periods prior. This time frame is subject to adjustments of
the MRGL risk in place, as well as potential upgrades pending the
trends in guidance. The overall environment is more than capable of
producing locally significant rainfall, but where it falls in this
area of the CONUS is important, so it will be a period to monitor
for any enhancements to the threat.
Kleebauer
..Previous Discussion..
Very few changes were needed with this update across the Southeast.
While the trends in the guidance continue to suggest a southward
trend, given the heavier rains from Sunday, the ERO remains
generous on the northern side of the rainfall footprint, to account
for potential ongoing flooding continuing into Monday. The heaviest
rains on Monday will focus in far southeastern Georgia and from
Jacksonville north and west in Florida. As on previous days,
instability will be at a premium due to extensive cloud cover from
the extremely high moisture amounts in the atmosphere. Much of the
Florida Peninsula will have PWATs at or above 2.25 inches,
supporting highly efficient warm rain processes. This will be
countered by the lack of instability, which will limit the lift any
storms will have to work with. By Monday, a somewhat faster
southward movement of the cold front lifting all this moisture
should significantly limit overlap in the forecast rainfall
footprints from Sunday to Monday. Given how difficult most of
southeast Georgia can be to flood due to flat, sandy terrain and
numerous swamps, a high-end Marginal remains in place.
A continued southward trend in the front could allow for trimming
on the northern end of the Marginal with future updates.
...Lower Texas Coast...
20Z Update: No changes necessary to the previous forecast as the
expected synoptic evolution remains consistent in-of the western
Gulf into South TX. The threat for heavy rainfall will subside into
Monday with the threat weakening as we step forward in the D3.
Great chance for flash flooding will occur the first half of the D3
time frame (Monday AM through the afternoon), weakening as we head
into Monday evening into Tuesday morning. Additional rainfall of
1-3" is forecast over the immediate South TX coastal plain
extending inland towards areas like McAllen and Brownsville. The
MRGL risk was maintained as a result.
Kleebauer
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 PM EDT Sat Oct 3 2026
Day 4 and Day 5
Valid 12Z Tue Oct 06 2026 - 12Z Thu Oct 08 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL TOWARDS MIDWEEK
IN AND NEAR FLORIDA...
A stationary surface front is expected to be the focus for heavy
rainfall Tuesday into late Wednesday in and near Florida. The axis
of highest PWs (2.25-2.5") and mid- level shortwave energy will be
be in the front's vicinity, as well as instability from the nearby
Gulf. Deep west/west-southwesterly flow will enhanced the risk for
training cells coming off the eastern Gulf across central FL, while
anti- parallel flow to the front's north across northern FL
bringing in instability from the subtropical Atlantic and could
lead to very high precipitation efficiency. Effective bulk shear
values over 20kts could allow for some degree of organization.
Hourly rain amounts to 3" with local totals to 6" are possible,
given the expected ingredients available. Despite greater
dispersion in the guidance Wednesday when compared to Tuesday,
opted to include a Marginal Risk due to the possible impact.
Roth
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 PM EDT Sat Oct 3 2026
Day 4 and Day 5
Valid 12Z Tue Oct 06 2026 - 12Z Thu Oct 08 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL TOWARDS MIDWEEK
IN AND NEAR FLORIDA...
A stationary surface front is expected to be the focus for heavy
rainfall Tuesday into late Wednesday in and near Florida. The axis
of highest PWs (2.25-2.5") and mid- level shortwave energy will be
be in the front's vicinity, as well as instability from the nearby
Gulf. Deep west/west-southwesterly flow will enhanced the risk for
training cells coming off the eastern Gulf across central FL, while
anti- parallel flow to the front's north across northern FL
bringing in instability from the subtropical Atlantic and could
lead to very high precipitation efficiency. Effective bulk shear
values over 20kts could allow for some degree of organization.
Hourly rain amounts to 3" with local totals to 6" are possible,
given the expected ingredients available. Despite greater
dispersion in the guidance Wednesday when compared to Tuesday,
opted to include a Marginal Risk due to the possible impact.
Roth
