Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
603 PM EST Sun Nov 1 2026
Day 1
Valid 2239Z Mon Nov 02 2026 - 12Z Mon Nov 02 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE FOUR CORNERS REGION...
...Southwest...
16Z Update: No changes to the previous forecast as everything
remains on track for a high-end MDT across portions of the Mogollon
Rim and San Juan Mountains with a widespread MDT risk extending up
through the canyon areas of northwest AZ into southwestern UT.
HREF/REFS EAS signals for >2" of rainfall are both over 70% for
areas of the Mogollon Rim and San Juan range with neighborhood
probs for locally 5" or greater still running between 60-90% in
both areas. This is consistent from the previous iterations of both
hi-res ensemble suites, backing the current forecast and
expectation for widespread flash and riverine flooding capable of
locally considerable impacts across the outlined domain.
Kleebauer
..Previous Discussion..
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.
Wegman
...Southeast...
2230Z Update: Rainfall totals today have been quite prolific across
much of the lower half of the FL Peninsula -- with many areas
topping 2-4". Localized 5-10" amounts meanwhile were noted around
Lake Okeechobee, and most recent HRRRs continue to show additional
3-6+ inches through the evening hours as the well-developed MCV
continues to drift slowly across the area. The area remains within
an area of difluent flow aloft, with the strong upper level
divergence (broad-scale low-mid layer ascent) owing largely to a
90-100 kt upper level jet streak oriented N-S over the eastern
Gulf, placing much of the FL Peninsula in the left-exit region of
this jet streak. Nearly optimal dynamical forcing for widespread
convection, along with the favorable thermodynamic profile (ML
CAPEs 1000-2000 J/Kg and PWs 2.1-2.2"), are the key factors in this
impressive heavy rainfall event. We've expanded the Slight Risk,
matching the recent HRRR trends and aligning where the latest HREF
and REFS have the highest probabilities (>60%) of 3-5+ additional
inches of rain. We've also included a 25% area (high-end Slight
Risk) across parts of the southeast coast (including the Treasure
Coast), where the HREF/REFS probs of >5" of additional rainfall are
highest (40-70%). For further information, please refer to the
latest Mesoscale Precipitation Discussion or MPD #1546, which is
valid through 03Z.
Hurley
..Previous Discussion..
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 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
603 PM EST Sun Nov 1 2026
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...
20Z Update: The setup remains consistent among guidance for a
continued threat of locally heavy rainfall in-of the eastern FL
coast with the primary concerns being urban flash flooding in-of
the I-95 corridor. Latest 12z HREF/REFS neighborhood probs remain
elevated for >2" between St. Augustine down to Homestead with the
consensus for heaviest precip between West Palm down to Miami.
Overall, not much of a deviation between forecasts with the only
adjustment being a trimming of the SLGT away from the Jacksonville
area as the prob fields indicate a very low likelihood of
appreciable precipitation in the vicinity of the metro corridor.
Kleebauer
..Previous Discussion..
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.
Wegman
...Midwest/Plains...
20Z Update: The trends continue in the trimming of the eastern
extent of the MRGL with more of WI down through the immediate
Mississippi Valley regions of IA/MO trimmed out of the risk as well
as trends have been for a slower push of precipitation into the
immediate area leading to less overall rainfall, and weaker rates.
This is correlated well with the little to no risk of >1"/hr rates
based off the latest HREF/REFS suite this morning, enough to
warrant the removal of the risk in this general area. Areas across
the Dakotas into northern MN still remain a focal point for
moderate to locally heavy rainfall with the main prospects likely
embedded heavier echoes in the vicinity of the maturing trowal on
the north to northwest side of the surface cyclone.
Further south, instability within the warm sector over the East-
Central Plains of KS/MO down through OK/TX will provide the best
opportunity for rainfall rates >1"/hr with some of the
deterministic indicating 1-2"/hr rates over the course of late-
Monday afternoon into the evening prior to the cold front approach
from the west. Models have been keying on that area of southeast KS
down through eastern OK and north TX as the main area of interest
with the neighborhood probabilities between 40-70% for >2" with
modest probs for >3" located over northeast OK into far
southeastern KS. There's a potential for a small upgrade in this
particular zone with the current look, but want to see future
trends with the CAMs as this area is on the drier side and could
very well handle local 2-3" of rainfall with the main concern over
the more urban footprints.
Kleebauer
..Previous Discussion..
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 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
603 PM EST Sun Nov 1 2026
Day 3
Valid 12Z Tue Nov 03 2026 - 12Z Wed Nov 04 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL PORTIONS OF THE
LOWER TO MID-MISSISSIPPI VALLEY...
...Lower and Mid-Mississippi Valley...
Surface low over the north-central CONUS will continue to move to
the northeast with a trailing cold front extending down through the
Plains, eventually maneuvering into the Mississippi Valley by
Tuesday morning and afternoon. Warm sector into the area of the
Lower to Mid-Mississippi Valley will be the focus of enhanced low-
level convergence with the arrival of the front leading to an
enhanced convective axis in the morning with further development
during the afternoon prior to the frontal passage. Latest ensembles
are bullish with a widespread 2-3" footprint located over the area
of southeast AR through southwest TN, down into northern MS with
the max located near the Memphis metro area. This is the most
notable area given the propensity of flash flooding into the urban
corridor, as well as an overlap of heavy rain into an area that was
already heavily impacted by heavy rain over this weekend.
Considering the setup and rainfall totals being forecast, this is
more likely to be a flash flood concern for these particular areas
with enough consensus among ensembles and ML guidance alike to add
a small SLGT risk with the centroid placed over the Memphis metro.
Kleebauer
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
603 PM EST Sun Nov 1 2026
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)...
2000 UTC Update: No changes were made to the Days 4-5 EROs based on
the 12Z guidance/trends.
Hurley
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
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
603 PM EST Sun Nov 1 2026
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)...
2000 UTC Update: No changes were made to the Days 4-5 EROs based on
the 12Z guidance/trends.
Hurley
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
