Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
317 AM EST Sun Nov 1 2026

Day 1
Valid 12Z Sun Nov 01 2026 - 12Z Mon Nov 02 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE FOUR CORNERS REGION...

...Southwest...

Few changes were needed to the ongoing risk areas across the
Southwest. An anomalously strong atmospheric river is driving a
plume of moisture and heavy rain into the Southwest from the
Pacific. PWATs remain 4-6 sigma above normal for this time of year,
with values between 3/4 inch and 1.5 inches. Further, essentially
all of the Southwest has been in a very wet period, so this highly
anomalous event is at the tail end of a long stretch of wet weather
that has left the soils saturated already in most areas. Thus, all
of today's rains will be converting to runoff, leading to numerous
instances of flash flooding. Dry washes, arroyos, slot canyons, and
burn scars will remain the most susceptible areas.

The Moderate Risk for portions of Arizona into southern Utah
remains largely unchanged as far as the area impacted, as for much
of it, the risk area is tied to the terrain. That said, the latest
guidance shows rainfall amounts have a 70-90% chance of exceeding
the 100 year ARI. This is generally the threshold for considering a
High Risk area, which remains possible. Ultimately, the rather fast
forward speed of the plume of moisture, as well as a lack of
instability will be two limiting factors which for this update will
keep these areas shy of the High Risk threshold. Nonetheless, with
the aforementioned highly anomalous moisture and strong upper level
forcing from a pair of jet streaks and a vigorous trough following
behind the rain, expect a widespread 3-5 inches of rain into
portions of the Mogollon Rim, particularly areas most perpendicular
to the southwesterly flow and in the core of the moisture plume. A
higher-end Moderate risk is in effect for these areas, mainly north
and east of Phoenix. Into Utah, the threat for flash flooding turns
to the typical slot canyons and steep, rocky terrain, as well as
numerous large burn scars that dot the southern Utah landscape.
Each of these areas could see more severe flooding, despite not
being quite in the core of the heaviest rainfall.

A second Moderate Risk is in effect for the San Juans of southwest
Colorado. Here too, due to a very high likelihood of exceeding
100-year ARIs, a higher-end Moderate Risk was introduced. For this
area, the very recent high-impact flash flooding event from last
week is top of the mind. Expect essentially a repeat, albeit with
slightly lower snow levels. This might nominally mitigate any
flooding concerns in river basins that drain the San Juans. It's
likely that spot areas will see more total rainfall here than along
the Mogollon Rim, due to steeper topography more efficiently
wringing out the abundant moisture.

...South Dakota...

A small, low-end, and low confidence Marginal Risk was shifted
north and west with this update. This will be remnant moisture from
the major flooding event occurring over the Southwest, generally
targeted at the post-midnight period tonight. Soils are around
normal for moisture levels for this time of year, and instability
will be nominal over this otherwise generally tough to flood area.
Training cells are possible, which could lead to an isolated flash
flooding risk.

...Southeast...

A westerly wave that has been traversing the Gulf will move into
the Florida Peninsula today. Abundant Gulf moisture will converge
over the Peninsula as a weak upper level trough moves over the
state, further increasing atmospheric lift. A widespread 1-3 inches
of rain is expected over much of the Peninsula. This will be the
latest in a string of days that has caused areas of heavy rainfall
over the east coast. With heavier and more widespread rain expected
today, areas where soils are already saturated from previous days
remain in a Slight Risk, which generally covers the I-95 corridor
from the Georgia line south through Miami. Some instability and an
amazing history of isolated cells producing rains of 3+ inches per
hour for 6+ hours have led to incredible rainfall totals in very
isolated spots. This may potentially continue over the lower
Mississippi Valley today. The Marginal Risk remains in place with
some small expansions.

Wegman


Day 2
Valid 12Z Mon Nov 02 2026 - 12Z Tue Nov 03 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE EAST COAST
OF FLORIDA...

...Florida...

Continued easterly flow of deep tropical moisture from the Atlantic
will allow for frictional convergence along the east coast of
Florida Monday and into Monday night. Heavier totals are expected
during the day Monday and across southeast Florida, where
instability will be a bit higher, with better moisture. The highly
urbanized I-95 corridor will also support widely scattered
instances of flash flooding where nearly stationary storms can
persist the longest. The inherited Slight Risk area was left
largely unchanged. Rain should be lighter across the west coast, so
the threat level will be much lower there.

...Midwest/Plains...

The large Marginal Risk area in place across much of the Midwest
and Plains was also left largely unchanged with this update. The
greatest flooding threat within the Marginal will be for southern
areas from Texas through Missouri, where greater instability and
terrain concerns around the Ozarks should work to raise the
flooding threat locally higher. Nonetheless the instability will
remain near the lowest thresholds supporting convection. The nature
and coverage of that convection will determine how high the
flooding threat gets. Since those parameters remain uncertain, the
Marginal remains in place. Further north across the northern Plains
to the upper Lakes, there should be very little to no instability.
However, steady rainfall will persist for far longer in this area,
resulting in more widespread higher rainfall totals, but over a
much longer period of time. Thus, the Marginal also remains in
place there with few changes. A small trim on the eastern side of
the risk area, to remove much of southeastern Wisconsin was made
due to slower forward speed expected of the rainfall shield.

Wegman


Day 3
Valid 12Z Tue Nov 03 2026 - 12Z Wed Nov 04 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
LOWER AND MID-MISSISSIPPI VALLEY AS WELL AS THE EAST COAST OF
FLORIDA...

...East Coast of Florida...

Lingering moisture over much of Florida as well as some daytime
heating will once again lead to periods of rain across the state on
Tuesday. Fortunately, organization, coverage, and intensity of rain
will all be lesser on Tuesday as compared with previous days. Thus,
the Marginal Risk is essentially covering the hardest hit areas of
Florida where renewed convection on Tuesday may cause renewed
isolated flash flooding.

...Lower and Mid-Mississippi Valley...

A line of storms will track east across the lower and mid-
Mississippi Valley on Tuesday. The forward speed of those storms
will be slow enough that isolated flash flooding could result,
especially in areas where cell mergers lead to longer periods of
heavy rain. Antecedent very dry soils and high FFGs should limit
any flash flooding to isolated instances, but that will need to be
reevaluated as Tuesday approaches for a possible Slight, especially
into the Ozarks due to terrain worsening any flash flooding.
Further north towards Illinois, the flash flooding threat will be
much more isolated and conditional, with the Marginal Risk
generally covering urban and low-lying flood-prone areas.

Wegman


Day 4 and Day 5
Valid 12Z Wed Nov 04 2026 - 12Z Fri Nov 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE
TENNESSEE AND LOWER OH VALLEYS TO THE SOUTHERN APPALACHIANS (DAY
4)...

While differences in the details remain, the latest model runs are
showing better agreement with the evolution of an amplified upper
trough and its associated frontal boundary that are expected to
move east of the Mississippi Valley midweek. This system will
continue to produce widespread precipitation, with the threat for
areas of heavy rain and possible flash flooding continuing into
early Thursday. Deep moisture (1.50-1.75+ inches) coinciding with
strong southerly flow is expected to interact with an area of
strong ascent, afforded in part by right-entrace region upper jet
forcing, to produce widespread moderate to heavy rain (accums 1-2+
inches) across the Tennessee into the lower Ohio valleys and the
southern Appalachians. While some models suggest a Slight Risk may
be necessary at some point, dry soils (high FFGs) and remaining
forecast uncertainty support maintaining the Marginal Risk at least
for now.

Pereira


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt