FOUS30 KWBC 100807
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
407 AM EDT Fri Oct 10 2025

Day 1
Valid 01Z Fri Oct 10 2025 - 12Z Fri Oct 10 2025

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

...Southwest...

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...

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 Fri Oct 10 2025 - 12Z Sat Oct 11 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...

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...

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 Sat Oct 11 2025 - 12Z Sun Oct 12 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....

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...

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
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