606
FXUS02 KWBC 080753
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
353 AM EDT Wed Oct 8 2025

Valid 12Z Sat Oct 11 2025 - 12Z Wed Oct 15 2025

...Tropical Moisture to bring heavy rainfall hazards to parts of
the Southwest this weekend...

...Gusty wind, coastal flood, and heavy rainfall threats expected
along parts of the Carolina and Mid-Atlantic Coasts this weekend
and may linger through early next week...


...General Overview...

Active pattern with low development expected on both coasts this
weekend into next week. An upper low opens as it crosses the
Pacific Northwest coast Saturday morning and then progresses east,
reaching the northern Rockies Sunday. This is followed by a second
upper low then develops over the Salish Sea late Sunday and deepens
as it tracks down the Coast to northern California by Tuesday
night. Tropical tropical moisture from Priscilla and potentially
the next easter Pacific tropical system will be drawn up by these
lows/troughs and lead to widespread precipitation across The West.
A coastal storm will develop off the Carolina Coast Friday night
and drift up toward the Mid-Atlantic coast through the weekend and
may linger through early next week. In between these systems is
upper-level ridging centered over Texas with an axis that extends
up the Great Plains Saturday then shifts east to the Midwest for
Sunday through early next week.


...Guidance/Predictability Assessment...

The 00Z guidance suite has notably improved agreement on the
pair of Northwest lows/troughs, the central U.S. ridging, and the
developing East Coast low (and it`s interaction with a northern
stream low from the Midwest). The 12Z/18Z suite was in poorer
agreement across the CONUS, so the WPC forecast leaned toward a GFS
favored general deterministic blend for Days 3/4, then the EC/CMC
for Days 5/6 based on the Northwest troughs/lows.

00Z physical guidance trended a bit slower with the upper trough
tracking east over the Northwest this weekend (which is in line
with the EC-AIFS). Guidance is also in good agreement with the
subsequent trough that develops into a low Sunday night over
western WA (also trended toward the EC-AIFS) though the GFS still
has a more interior track to the offshore EC/CMC which were
preferred (and were in agreement with the EC-AIFS). Priscilla
moisture overspreads much of the Intermountain West on Saturday,
then from the next tropical system through southern AZ/NM on
Sunday.

Coastal cyclogenesis will occur off the Carolinas Friday night
with further development as it drifts north to at least the
outer banks if not the southern Mid-Atlantic coast this weekend.
Tracking uncertainty is notable on Monday with the EC and EC-AIFS
farther south (near NC coast), the GFS/UKMET (and now the 00Z CMC
which took a major leap northwest) in agreement to the north (off
NJ). Interaction now looks to take place with a northern stream
low tracking southeast over the Great Lakes Saturday and Ohio on
Sunday. The GFS/UKMET/CMC have more interaction (and thus a
farther north track) than the EC.


...Weather/Hazards Highlights...

An influx of tropical moisture ahead of Priscilla remnants and an
opening trough along the West Coast is expected across the
Intermountain West Saturday. Strong forcing from the approaching
trough (along with wet antecedent conditions) allow for a bit more
of an expansion of the Slight Risk for the new Day 4 ERO in
southeast Utah, northeast New Mexico as well as much of Arizona
and western Colorado. The tropical moisture surge on Sunday is now
focused over southern AZ/NM for remnants of the subsequent tropical
system where a Day 5 Slight Risk is raised.
The next system along
the West Coast sends a plume of enhanced moisture through CA Monday
and Tuesday. Under these lows/troughs expect mountain snow.

A low off the Carolina Coast Saturday sends a surge of heavy rain
through eastern North Carolina where a Day 4 Slight Risk remains in
place. There is uncertainty with how far the low tracks, but with
the likelihood of the low center reaching at least the Outer Banks,
the Day 5 Slight Risk for the southern and central Mid-Atlantic
(roughly south from Atlantic City NJ to the Outer Banks with
coordination with WFOs MHX, AKQ, and PHI). In addition to heavy
rain, gusty onshore winds will also accompany this system and
should cause a coastal storm surge in the Carolinas and Mid-
Atlantic despite the quarter moon phase/neap tides.

Cool conditions prevail under low pressure along the coasts (and
expanding over the Western U.S. under upper troughing) with above
normal temperatures in between under upper ridging. Max temps reach
15 degrees above normal in the Midwest by the middle of next week.
Max temps of 15-20 degrees above normal over the Great Basin and
California through much of the period.

Jackson


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw






$$