285
FOUS30 KWBC 110036
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
836 PM EDT Fri Oct 10 2025

Day 1
Valid 01Z Sat Oct 11 2025 - 12Z Sat Oct 11 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF ARIZONA AND SOUTHERN UTAH...

...Southwest...

16Z update... Overall, the anomalously moisture pattern will
continue to pose elevated threats for excessive rainfall and flash
flooding to particularly vulnerable areas, including steep terrain,
slot canyons and burn scars. The Moderate Risk was expanded a bit
to the southeast over southwest Colorado and a bit further western
into eastern Nevada. The Slight Risk was adjusted westward near the
California and Nevada border and eastward across western Colorado.

Campbell

Overall, not much change to the previous forecast, with widespread
showers and storms expected to develop across the region today into
tonight, producing moderate to heavy accumulations, with numerous
flash floods possible.

An amplified upper trough centered along the West Coast will slowly
shift east. Mid level energy embedded within the base of the
trough, along with energy associated with Tropical Cyclone
Priscilla, will converge upon the Southwest today. This energy,
interacting with moisture associated with the tropical system will
support widespread showers and storms, with repeating development
possible. Guidance continues to indicate impressive PW anomalies -
over 5 std dev above normal in some locations according to the GFS.
And while instability may be generally modest across much of the
region, deep saturation through the column will support efficient
rainfall rates, possibly reaching 1-2 in/hr at times.

A Moderate Risk remains in place across central into northern
Arizona, reflecting higher probabilities for amounts over 2 inches
from both the HREF and RRFS. A second Moderate Risk area was added
over portions of southern Utah, including the more vulnerable slot
canyon and national park areas. Overnight hi-res guidance has
trended up across this area, showing storms training from southern
Nevada into the region, with probabilities for amounts over 2
inches increasing. Higher probabilities for similar amounts also
center along the upslope areas of the San Juans. Currently
considered a higher-end Slight, this area may also be considered
for an upgrade later today.

...Southeastern U.S. Coastal Areas...

16Z update... The latest observations and guidance show training
of showers and thunderstorms across parts of the Florida Keys and
the southern tip this morning with additional development expected
later in the day/overnight. The Marginal Risk was expanded further
south/west to cover these areas. Also, easterly flow is allowing
for convection to push further inland thus warranting a small
westward shift of the Marginal Risk from coastal Georgia to areas
north of Lake Okeechobee.

Campbell

An area of low pressure will become better organized east of
Florida this period. As the system strengthens, onshore winds
north of the center will begin to direct deeper moisture toward
the coast. However, the overnight hi-res guidance continues to
indicate that the greater instability will remain offshore,
confining the threat for heavy amounts to the immediate coast.
While widespread heavy rains are not expected, coastal flooding
driven by the strong onshore winds, may elevate runoff concerns for
any rains that do fall across the area.

Pereira

Day 2
Valid 12Z Sat Oct 11 2025 - 12Z Sun Oct 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
FOUR CORNERS STATES AS WELL AS FOR PORTIONS OF COASTAL NORTH
CAROLINA AND SOUTHEASTERN VIRGINIA...

...Southwest to the Northern Rockies...

20Z update... Scattered to widespread convection expected across
the Southwest/Rockies region thanks to strong instability and the
northward influx of tropical moisture from Priscilla. Strong to
severe thunderstorms will lead to locally enhanced rainfall and the
latest guidance had an uptick in coverage and amounts for northern
Arizona, southern and eastern Utah. As such, the Slight Risk had a
sizable change across this part of the region. Further north, the
orientation of the footprint has changed from the previous
forecast. Most solutions bring higher amounts further east across
central/eastern Montana. The northern bounds of the Marginal Risk
area was reshaped to cover this shift.

Campbell

Overall, not much change to the previous forecast. Heavy rain
with flash flooding will remain a concern from the Southwest into
the central Rockies, as deep tropical moisture continues to spread
north. While moisture and energy associated with the remnants of
Tropical Cyclone Priscilla will be quickly lifting north,
additional moisture emanating from Tropical Cyclone Raymond will
begin to spread into the Southwest as well. This combination of
moisture and increasing upper level jet support will likely produce
another day of widespread shower and storm development, albeit a
bit further east than the previous day, with the greater threat for
heavy rain and flash flooding centered over central and
southeastern Arizona and over the San Juans. Although instability
may again be limited, the available moisture and lift may be
sufficient to support rainfall rates over 1 in/hr in some
locations.

Farther north, moisture will be drawn out ahead of a highly-
amplified upper trough. While rates may be less intense, this
combination of moisture and strong lift may generate showers and
storms that produce localized runoff concerns as far north as
parts of southwestern and central Montana before snow levels begin
to fall late in the period.

...Mid-Atlantic Coast...

20Z update... Given the westward shift of the precipitation shield
with the coastal low the Marginal Risk was expanded westward to
include the eastern half of South Carolina, North Carolina and more
of southeast Virginia. The Slight Risk was expanded 1-2 counties
westward across eastern Virginia and North Carolina. The risk for
flooding/coastal flooding will be compounded by high tides.

Campbell

There remains uncertainty in the exact track of a low-pressure
system that is forecast to deepen as it moves along the Southeast
and Mid Atlantic coasts this period. What remains more certain is
the heavy rain that is likely to impact portions of eastern North
Carolina and southeastern Virginia. Deep moisture (PWs 1.75-2
inches) along with strong forcing will support heavy rains within
the associated comma-head. The heaviest amounts are expected to
focus across coastal North Carolina, with some deterministic models
indicating that several inches are possible. Similar to the
previous period, a tight east-to-west gradient is likely. However,
as the system intensifies, expect some heavier amounts to spread
further inland than during the previous period. Compound flooding
will remain a concern as coastal flooding generated in part by
strong onshore winds combines with the runoff from the heavy rain.

Pereira


Day 3
Valid 12Z Sun Oct 12 2025 - 12Z Mon Oct 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN ARIZONA AND NEW MEXICO, FAR WEST TEXAS, AND ALONG
PARTS OF THE MID ATLANTIC COAST...

....Southeastern Arizona, Southwestern New Mexico, and Far West
Texas....

20Z update... Overall, little change was made to this part of the
country. A northwest nudge of the Slight was made across south-
central Arizona and an eastern shift into West Texas to reflect
the latest WPC QPF.

Campbell


The pattern will remain active for at least a part of the Southwest
as moisture and energy associated with the remnants of Tropical
Cyclone Raymond move into the region. Anomalous moisture along
with large-scale ascent afforded in part by favorable upper jet
forcing will support widespread precipitation and the potential for
heavy amounts from southeastern Arizona to Far West Texas.

...Mid Atlantic and the Northeast...

20Z update... The latest guidance and WPC QPF brings some higher
rainfall totals up the coast as the deep coastal low tracks
northward. The Slight Risk was expanded into southern New England.
The Marginal was expanded further west into Virginia and
Maryland while the northern boundary was lifted into southeast New
York and Massachusetts.

Campbell

A coastal low will continue its slow track to the north along the
northern Mid Atlantic this period, with strong onshore winds
driving deeper moisture and the potential for heavy rains north of
the center. The track of the storm and rainfall details remain
uncertain. However, widespread moderate to heavy rain is expected
from the northern Mid Atlantic coast to southern New England, with
coastal flooding likely to compound runoff concerns where heavy
rain does occur.

Pereira


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