097
FXUS02 KWBC 081942
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
342 PM EDT Wed Oct 8 2025

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

...Tropical Moisture to bring heavy to excessive rainfall to much
of the Southwest and Four Corners region this weekend and into
early next week...

...A strong coastal low may bring significant impacts to parts of
the East coast...


...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 that deepens as it tracks down the Coast to northern
California by Tuesday night. Tropical moisture from Priscilla and
potentially the next eastern Pacific tropical system will be drawn
up ahead of the western systems and lead to widespread
precipitation across The West. Meanwhile, 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 bringing potentially significant coastal impacts.
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 12z guidance suite continues to show increased agreement on
both the West Coast trough/upper lows and the developing East Coast
low, but still with some uncertainty in the details and potential
sensible weather impacts.

Out West, there is good enough agreement for a multi-model blend
the first half of the period. But there is some disagreement as the
second upper low drops southward and the overall trough tries to
shift eastward by mid next week. The GFS remains on the faster side
of the guidance, with the ECMWF and CMC holding an upper low
near/off the California coast a bit longer. The ECMWF/CMC idea is
supported by the ensemble means so the WPC forecast trended more
towards the ensemble means late period.

Coastal cyclogenesis will occur off the Carolinas Friday night
with further development as the low drifts north to at least the
southern Mid-Atlantic coast this weekend. There remains significant
uncertainty in the track and evolution of this system next week,
with some better consensus this system may interact with an
approaching upper low from the Great Lakes allowing it to linger
off the coast Monday to Tuesday before moving eastward. Including
the new 12z guidance today, the GFS pulls the low farther north
than the better consensus, with a position just east of New York
City on Monday, while the ECMWF and EC-AIFS at the same time are
more south off the DelMarVa. The WPC blend tends to favor the ECMWF
and ensemble means for this system and was comparable to previous
shift continuity.


...Weather/Hazards Highlights...

An influx of tropical moisture (with precipitable water values 4
to 5 standard deviations above normal) ahead of what should be, by
the start of the medium range period, remnants of Priscilla, 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) allows for a sizable
Slight Risk area for the Day 4/Saturday ERO in from Arizona and
western New Mexico northward to southeast Utah and western
Colorado. For Sunday and beyond, the next potential tropical system
behind Priscilla will bring another batch of highly anomalous
tropical moisture focusing over southern AZ/NM. A Slight Risk is in
place for the Day 5/Sunday ERO in this region. An upgrade to a
moderate is not out of the question on either day, especially given
expected precipitation in the short range period too. The next
system along the West Coast sends a plume of enhanced moisture
through CA Monday and Tuesday with heavy rainfall possible over the
coast and snow further inland across the mountains.

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 north the low itself
tracks, but increasing signal moisture from this low may interact
with the approaching compact upper low from the Great Lakes to
extend heavy rain signal further north than previous shift. Opted
to extend the Day 5 Slight risk northward along the coast to New
York City to account for this potential. In addition to heavy rain
threats, the combination of persistent and strong onshore winds,
high surf, and above normal tides may lead to significant coastal
flooding impacts along with strong rip currents and potential beach
erosion. See Key Messages being issued by WPC for the latest on
this system.

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 below normal over the Great Basin and
California through much of the period.

Santorelli/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








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