FOUS30 KWBC 070045
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
745 PM EST Fri Nov 6 2026

Day 1
Valid 01Z Sat Nov 07 2026 - 12Z Sat Nov 07 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
SOUTHEASTERN NEW ENGLAND...

01Z Excessive Rainfall Discussion...
Maintained the Slight Risk over parts of New England as the next
wave propagates on-shore. This has resulted in renewed growth in
areal coverage of rainfall over southern New England by early
evening and should continue to traverse northeastward within the
previously issued Slight Risk area. Rainfall rates have largely
stayed at or below one-half inch per hour across the region...so
the concern for excessive rainfall is based on the cumulative
effect of the rainfall total (especially in urbanized areas and
places of poor drainage),

Elsewhere along the Eastern Seaboard, the instability has shifted
off shore and any additional rainfall amounts will be little to
none. The Marginal Risk area was removed there.

In the Southwest U.S....trimmed some territory over southeast New
Mexico from the Marginal Risk area behind a passing shortwave but
maintained the risk area to the east where there was still some
instability present.

Bann

Previous Excessive Rainfall Discussion...

...Southeast New England...

Only very minor edits were needed to the inherited Slight Risk
stretching from eastern Connecticut/Long Island northeastward
through Rhode Island and into portions of eastern Massachusetts. As
the mid/upper trough takes on a more neutral to negative tilt,
mean low- mid layer flow will back more southerly (parallel to the
surface front), thereby prolonging the favorable moisture flux off
the Atlantic Gulf Stream and thus axes of heavier rainfall through
the day and into the evening hours. TPWs approaching 1.75" is close
to 3 standard deviations above normal for early November, while
IVT values exceed 750 KG/m/s through late afternoon per both the
GFS and ECMWF. The latest 12Z HRRR and RRFS suite of guidance show
areal average rainfall in the 2-3" range with locally heavier
totals of 5" possible, supported by the impressive influx of
moisture off the Atlantic. A slower progression of the front as the
flow backs will also help to maintain storm development/coverage
over the region for a longer period of time increasing the chance
for these heavier totals. Some storms are also possible further
north along the coast of Downeast Maine depending on when the front
clears the coast. However, given dry antecedent conditions and
proximity to the coast do not expect a notable flood threat.

...Southeast VA into Northeast NC, the DelMarVa, and coastal NJ...

Further south, another maxima of heavy rainfall is expected across
portions of southeastern VA and perhaps into northeastern NC. The
latest hi-res guidance continues to show the potential for some
locally heavier totals in the 3-5" range. Modest instability (~1000
J/KG CAPE) should lead to some more robust storms with waves along
the front potentially helping to slow its progression and allow
for at least brief training potential, both contributing to higher
totals. Locally backed and enhanced southerly flow will also aid in
increased moist flow from the Atlantic and enhanced convergence.
This would result in a greater concern for scattered flash flooding particularly for the more urban areas around Norfolk/Virginia
Beach. However, given the relatively isolated nature of the threat
and drier conditions overall, have maintained a Marginal Risk. See
additional details in WPC Mesoscale Precipitation Discussion (MPD)
#1558.

A Marginal Risk extends both further north through the DelMarVa
and southwest through eastern North Carolina where additional,
ongoing storms along the front will continue to lead to heavy
rainfall, though the progressive nature of the front should keep
any threat of flash flooding isolated.

...Southeastern AZ/Southwest NM...

A targeted Marginal Risk remains across southeastern Arizona and
far southwest New Mexico. A developing upper-level wave in the
southern stream will pass over the region today leading to isolated
to scattered thunderstorm development. While not quite as
anomalous as recent events, increasing moisture as well as modest
instability could lead to a few more robust downpours producing
~1-2" or so of rain, which is more than sufficient for at least
isolated flash flooding concerns, especially for more sensitive
terrain and urban areas.

Putnam/B Hurley


Day 2
Valid 12Z Sat Nov 07 2026 - 12Z Sun Nov 08 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
SOUTH, CENTRAL, AND WEST TEXAS...

Have maintained the Marginal Risk across much of south to south-
central and west Texas for Saturday. Expect a slow ramp-up of
storms through the day with the approach of the southern stream
upper-wave from the west and increasing low-level flow from the
Gulf, which will likely leave the chance for more widespread,
intense rainfall for Sunday. There were a couple corridors of
potentially heavier rainfall noted in the now available hi-res
guidance. The first is with the potential for modest instability to
develop through portions of the lower Rio Grande Valley leading to
a cluster of more intense storms as indicated by the HRRR. The
second is with enhanced upslope flow into the higher terrain of
northeast Mexico increasing storm coverage and potential rainfall
along the south Texas Plains/Rio Grande as noted by the suite of
RRFS guidance. However, given the bi-modal distribution of
circumstances and potential rainfall, as well as the concern some
of the heaviest rainfall could ultimately end up mostly in Mexico
in either case, the risk for flash flooding broadly remains
isolated for now.

Putnam


Day 3
Valid 12Z Sun Nov 08 2026 - 12Z Mon Nov 09 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTH-
CENTRAL AND SOUTH TEXAS...

...2030 UTC Update...

The prior forecast reasoning remains on track on a possible
eventful day across south to south-central Texas. The latest global
12Z guidance continues to show the potential for areal average
rainfall in the 2-3" range and locally heavy totals in the 4-8"
range. However, there remains a higher than normal amount of
uncertainty with where the heaviest rainfall and flash flood risk
may occur. The guidance shows several scenarios including a coastal
convergence focus along the Gulf (GFS), an enhanced low-level jet
from the Gulf further inland across south Texas (ECMWF), or
enhanced upslope flow into the higher terrain of northeastern
Mexico with a heavy rain focus along the south Texas Plains/Rio
Grande (CMC/UKMET). The risk could also be influenced by a
combination of these factors, including both along the coast and
with enhanced flow inland through south-central Texas, that lead to
multiple enhanced corridors of rainfall. The Slight Risk will
likely need adjustment including potentially trimming regions where
the threat ultimately is not as high, but for now have left the
risk rather broad until there is more clarity in the forecast.

Putnam

...Previous Discussion...

...South Texas...

A anomalous upper pattern over the Southwest will shift focus to
the South-Central Plains with eyes on the southern half of TX as we
head into Sunday. Digging mid-level trough out of the Southwestern
CONUS will eventually close off over northern MX and drift eastward
leading to increasingly diffluent flow over west TX and points
south and east. At the surface, modest surface ridging to the
north will send a cold front southward, gradually, with eyes on
Deep South TX by the end of the period. The synoptic evolution
lends to a classic isentropic pattern situated over the Edwards
Plateau through Hill Country, sinking southward into South TX as we
move into the back half of Sunday. Prevailing southeast between
the surface to 850mb will lead to an ushering of low-level moisture
that will send PWATs surging between 1.5-2.1" with the highest
moisture prevalence located over the Southern RGV over to the Gulf
Coast, mainly south of Corpus Christi. Directional shear will
entice the potential for mesocyclone development and the ability
to sustain convection, even elevated to the north of the front
leading to enhanced precipitation rates with longevity due to the
persistence in the diffluent flow aloft. This whole setup will
materialize and become a fixture for at least 24 hrs with a broad
area of moderate to heavy rainfall with embedded convection
situated across Southern TX with the core located along and south
of I-10.

Models are consistent in the presentation of bouts of heavy
rainfall throughout the period with some enhancement expected in
the afternoon and evening as the ascent pattern is maximized with
the mid and upper level evolution, as well as the additional
diurnal instability element that will occur south of the cold
front. Widespread 2-4" with locally higher totals are already being
forecast within the numerical suite, even the ML coming in with a
solid 1-3" from northwest to southeast with the max focused over
the lower Rio Grande Valley (RGV). Despite some of the higher FFG
indices, this type of setup can surprise and offer some sneaky
flash flood prospects, especially within more urban settings and
locally flashier creeks and arroyos across the region. In
coordination with the local WFO's over South TX, a SLGT risk was
added for those areas along and south of I-10 down to the lower
RGV. Main areas of concern will be that area of South-Central TX
near San Antonio and the RGV areas between Eagle Pass down to
Brownsville.

Kleebauer


Day 4 and Day 5

Valid 12Z Mon Nov 09 2026 - 12Z Wed Nov 11 2026

2030Z Excessive Rainfall Discussion...

An overall downward trend is expected across Texas on
Monday...especially during the latter part of the period. The
signals for heavy rainfall in the Pacific Northwest remain muted so
was not inclined to introduce an outlook area at this time.

Bann

Previous Excessive Rainfall Discussion...

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL SUNDAY ACROSS
DEEP SOUTH TEXAS ON DAY 4...

D4 will be the period where the pattern breakdown over TX and the
threat for heavy rainfall begins to dwindle from north to south
with the loss of the primary ascent, along with more stable air
advecting into the region post-front. There is some discrepancy in
the amount of lingering heavy rain/convection in the region from
the deterministic output with some lighter amounts overall in the
various ensembles. Leaning towards a MRGL for South TX with mainly
areas along and south of a line from Laredo to Corpus Christi.
Rainfall totals will vary in terms of magnitude with perhaps even a
threat for an additional 1-3" according to some global
deterministic outputs. Eventually, this setup will translate into a
quieter pattern and limited impacts are anticipated for the back-
half of D4 and beyond for TX.

Across the Pacific Northwest, our first true atmospheric river of
the season will impact the region with a steady stream of heavy
precipitation into northwest WA, sinking south into northeast OR
and the neighboring Cascades between WA/OR. Current setup is not
conducive for flash flood scenarios at this time as the antecedent
soils in the area lean dry and capable of the initial intake of
heavy rainfall in the region. A nil ERO is forecast for D5, but
will keep an eye on trends for this period and beyond as the
synoptic pattern unfolds and rainfall continues into the second
half of next week.

Kleebauer


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt__;!!DZ3fjg!5f_rN0q8Cm33eDQhRfyRxc2qvwXlWCexpX7r5HX1D4gcXd-GGCgQGOx1dXTe9Q4wQ2sLbZRu4g5lE4-MQ4LB3TsJmRg$
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt__;!!DZ3fjg!5f_rN0q8Cm33eDQhRfyRxc2qvwXlWCexpX7r5HX1D4gcXd-GGCgQGOx1dXTe9Q4wQ2sLbZRu4g5lE4-MQ4LBzceMMCw$
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt__;!!DZ3fjg!5f_rN0q8Cm33eDQhRfyRxc2qvwXlWCexpX7r5HX1D4gcXd-GGCgQGOx1dXTe9Q4wQ2sLbZRu4g5lE4-MQ4LB0MJgj8U$



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