Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
409 AM EDT Wed Sep 2 2026
Day 1
Valid 12Z Wed Sep 02 2026 - 12Z Thu Sep 03 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS...
...Eastern Texas and Southwest Louisiana...
Raining/backbuilding with high rainfall rates from tropical
cyclone Edouard are ongoing although there should be some
weakening by late in the morning, but periodic backbuilding
clusters will remain a possibility. Another uptick late Wednesday
night into Thursday morning likely as the low level vorticity
should remain fairly well defined. PWs of 2-2.25 inches will
support continued heavy rain with hourly rates of 2-3 inches/hour.
There is potential for a locally enhanced inflow band on its south
side which could prolong and enhance the rain across areas that
receive heavy rain. The Moderate Risk was expanded to include
Freeston, Anderson and Henderson counties as well more of Polk
county. The eastern boundary of the Slight Risk was adjusted
eastward a bit to reflect the latest QPF guidance and WPC forecast.
...Northern Mid Atlantic & Southern New England...
A stronger shortwave will interact with the slow-moving warm front
over the Northeast to trigger scattered to widespread showers and
thunderstorms across the region. There continues to be ample
support of training of clusters of thunderstorms with 1-2"/hr rain
rates. The guidance focuses this heaviest rainfall across portions
of Upstate New York, and while soil moisture is generally below
normal according to NASA SPoRT, this should support up to 3" of
rain in some areas leading to scattered instances of flash
flooding, with more isolated responses elsewhere.
...Florida...
The tropical moisture plume remains entrenched across Florida,
reflected by PW anomalies of +1.5 sigma stretching across most of
the state. Both coasts could experience slow moving storms with
2+"/hr rain rates, as well as across the inland portions of the
peninsula where storm mergers/collisions can occur. A Marginal Risk
was maintained for this period.
...Arizona...
Monsoonal moisture will return to southern Arizona to trigger
diurnal convection. Locally excessive rainfall may be possible
therefore a Marginal Risk is in effect.
Campbell
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 PM EDT Wed Sep 2 2026
Day 1
Valid 01Z Thu Sep 03 2026 - 12Z Thu Sep 03 2026
...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS...
...East Texas...
A High risk remains for a small area of southeast TX, primarily
across the Big Thicket into the Piney Woods region, where ongoing
heavy rain south of Edouard remnants is over areas most impacted
this morning. The center of Edouard is slowly shifting north, but
inflow is still converging over similar areas as earlier today as the
center received less convergent focus. This southern area should
run its course/diminish overnight with potential new development
farther north per recent CAMs. However, inflow from the Gulf will
allow some additional convection over the areas hardest hit today
into Thursday. Minimal changes to the existing outlook areas
including the High Risk which were well placed. Please see latest
MPD (soon to be 1178) in east Texas for further information.
...Eastern Great Lakes into Mid-Atlantic & New England...
Low over central Quebec will continue to deepen and drift east
tonight. Warm sector convective line progressing through western NY
may have some followup activity overnight with some activity ahead
warranting a larger Slight Risk over western NY and central PA.
Trimmed the Marginal Risk a bit over New England based on the 18Z
HREF while expanded over the Shenandoah Valley and southern MI for
ongoing activity. Please see MPD 1177 for further details on NY/PA.
...Florida...
Ongoing activity has consolidated south of Tampa Bay and should
continue a downward trend this evening. The Marginal Risk was
shrunk.
...Arizona...
Earlier monsoonal activity over southern has waned with a fair
amount of convective inhibition present. Removed the Marginal Risk.
Jackson
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 PM EDT Wed Sep 2 2026
Day 2
Valid 12Z Thu Sep 03 2026 - 12Z Fri Sep 04 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN TEXAS...
20z Update: Upgraded to a Slight and Moderate risk for portions of
east TX. An axis of training convection should be ongoing at 12z
Thursday to the south and Southeast of the remnant circulation of
Edouard. Given the system will be weaker by this time, we are not
expecting the flash flood threat to be as extreme as what occurred
Tuesday night into early Wednesday. However, the low level vort
center should be defined enough to focus another round of nocturnal
training/backbuilding convection by later Wednesday night into
Thursday morning. This activity should persist past 12z and into
this day 2 period...but should weaken towards 15z. The MDT risk may
be able to be removed with the 16z update tomorrow, but the
expectation is for a locally significant flash flood risk to be
ongoing to start the period Thursday morning. Some models indicate
another possible uptick Thursday night into Friday morning, but
this is lower confidence given more uncertainty regarding the state
of the remnant vort center by this time.
Chenard
...Previous Discussion...
...Southwest...
A Slight Risk remains in effect across southern Arizona and into
New Mexico for this period. An uptick in moisture should result in
increased convective coverage and a scattered flash flood risk.
This region will continue to be monitored over the coming days.
...Texas, Gulf Coast and Florida...
The remnant vort center of Edouard should be less defined by this
time, but still present over east Texas with lingering tropical
rain over sensitive soils. It could still help focus some
organized convective clusters, and thus an isolated flash flood
risk could linger into Thursday. Elsewhere onshore flow within the
pooled high PW values and stalled boundary could trigger convection
along the coastline and across the Florida Peninsula leading to
isolated areas of flash flooding/ponding. A Marginal Risk spans
from eastern Texas to Florida.
...Upper Midwest to Mid-Atlantic...
While the details on where the heaviest rain will occur there
continues to be a signal for one or more rounds of organized
convection to track trough portions of this area through the day
into Thursday night. Parts of this region have had recent rains to
lower FFG and increase sensitivity to additional heavy rainfall. A
Marginal Risk was maintained from Minnesota/Iowa to Del-Mar-VA and
New Jersey.
...California into the Intermountain West...
A Marginal Risk continues from northern California into Idaho.
During this period a strong synoptic system will bring an axis of
heavy rainfall to the region. Not much instability, but just enough
showing up in model forecasts to suggest some potential for
localized higher rates and an isolated flash flood potential.
Campbell/Chenard
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 PM EDT Wed Sep 2 2026
Day 3
Valid 12Z Fri Sep 04 2026 - 12Z Sat Sep 05 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FRIDAY ACROSS
PORTIONS OF ARIZONA AND NEW MEXICO...
20z Update:
The Slight risk over the Southwest was realigned based on model
trends. The better moisture/instability axis is forecast farther
east than previously forecast, with the Slight risk shifting in
that direction as well. Still seeing a decent convective signal in
the guidance, including the 12z RRFS, over this Slight risk area,
and thus isolated to scattered flash flooding is expected.
A Marginal risk was added from southeast TX, along the Gulf Coast
and into FL. Lingering moisture and instability along this
corridor could result in a continued localized flash flood risk.
Chenard
...Previous Discussion...
...Northwest/Northern Rockies...
Marginal Risk area is in effect across portions of the interior
Northwest, particularly the area surrounding the northern Idaho
Panhandle. This area will be much closer to the upper level trough,
so forcing should be much better than in the Southwest. However,
moisture and instability will be much lower, resulting in more
likelihood of stratiform rainfall. Despite this, the rainfall
should still have modest amounts of instability to work with in a
generally dry, and therefore flash flood prone, area of the
country.
...Southwest/Four Corners/Central-Southern Rockies...
The signal for the return of heavy rain areas across the Southwest
into the Four Corners and central-southern Rockies remains strong
GEFS and ECENS PWAT anomalies increase back to 2-2.5 standard
deviations above normal with the axis of best monsoonal moisture
influx shifting slightly west. Still remains to be seen how much
influence the eventual tropical system that ultimately pulls west
of Baja will have in terms of the upper level moisture (potential
uptick in the PW anomaly). A Slight Risk was maintained for Arizona
while a broad Marginal covers southeast California the Four Corner.
...Upper Midwest/Ohio Valley/Central Appalachians...
Expect more additional organized/widespread convection downwind
of the upper ridge axis. Precipitable water values are high enough
with sufficient instability that embedded cells could produce
local downpours and isolated flooding. This will likely start over
eastern portions of the Upper Midwest, where the upper jet streak
to the northeast is expected to strengthen as the pivoting northern
stream trough impinges on the broad-scale ridge to the south. Have
essentially traced the Marginal Risk area southeast along the mean
850-300 mb thickness fields, where the upper level forcing
along/ahead of the surface front will be most supportive of more
organized activity. A Marginal Risk is in effect from Wisconsin to
West Virginia.
Campbell/Hurley
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 PM EDT Wed Sep 2 2026
Day 4 and Day 5
Valid 12Z Sat Sep 05 2026 - 12Z Mon Sep 07 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL SATURDAY AND
SUNDAY ACROSS PARTS OF THE SOUTHWEST...
A deep upper low persists over the Pacific Northwest through
Saturday before shifting south to far northern California for
Sunday. The trough around this low and a strong upper high
centered over the southern Plains U.S. will direct southwesterly
flow into the Desert Southwest and mover much of the Intermountain
West on Sunday. Confidence has increased on a more southward
suppressed moisture and instability axis that extends farther east
from southern California through central New Mexico. The Day 4
Marginal Risk is trimmed from Utah and expanded east through the
Sangre de Cristo/Sacramento Mtns. That said, a connection to a
tropical moisture plume from Marie is present, so this area will
continue to be closely monitored.
The farther south closed low into far northern CA on Sunday should
direct tropically sourced moisture up through the Intermountain
West to the central Rockies. The Day 5 Marginal Risk is expanded
farther east through western Colorado and New Mexico. Moisture may
end up lifting farther north and some 12Z guidance has decent QPF
in Montana, so please monitor future updates.
Jackson
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 PM EDT Wed Sep 2 2026
Day 4 and Day 5
Valid 12Z Sat Sep 05 2026 - 12Z Mon Sep 07 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL SATURDAY AND
SUNDAY ACROSS PARTS OF THE SOUTHWEST...
A deep upper low persists over the Pacific Northwest through
Saturday before shifting south to far northern California for
Sunday. The trough around this low and a strong upper high
centered over the southern Plains U.S. will direct southwesterly
flow into the Desert Southwest and mover much of the Intermountain
West on Sunday. Confidence has increased on a more southward
suppressed moisture and instability axis that extends farther east
from southern California through central New Mexico. The Day 4
Marginal Risk is trimmed from Utah and expanded east through the
Sangre de Cristo/Sacramento Mtns. That said, a connection to a
tropical moisture plume from Marie is present, so this area will
continue to be closely monitored.
The farther south closed low into far northern CA on Sunday should
direct tropically sourced moisture up through the Intermountain
West to the central Rockies. The Day 5 Marginal Risk is expanded
farther east through western Colorado and New Mexico. Moisture may
end up lifting farther north and some 12Z guidance has decent QPF
in Montana, so please monitor future updates.
Jackson
