836
FXUS02 KWBC 052001
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
401 PM EDT Sun Oct 5 2025

Valid 12Z Wed Oct 08 2025 - 12Z Sun Oct 12 2025


...General Overview...

A trough-ridge-trough upper-air pattern is forecast to set up across
the mainland U.S. with increasing amplitude through the medium-
range period into next weekend. A deep upper low that is on track
to develop off the coast of the Pacific Northwest mid to late
week will open the door for tropical moisture to be drawn northward
and potentially through the interior western U.S. by next weekend.
Uncertainty remains high regarding the ultimate track of tropical
cyclone Priscilla in the eastern Pacific where the tropical
moisture originates. Meanwhile, there is increasing model signals
for a coastal storm to form off the southeastern U.S. and then
track up the Mid-Atlantic coast next weekend.


...Guidance/Predictability Assessment...

The medium-range period will begin with a major synoptic trough
fracturing off to the southwest British Columbia on Wednesday. Model
solutions are now in agreement on closing the upper low off to the
west of the Pacific Northwest Thursday-Friday before slowly
swinging it onshore into the West Coast during the weekend.
Meanwhile, there remains a high degree of uncertainty on the
ultimate track of tropical cyclone Priscilla as it is forecast to
reach a position west of Baja California next weekend. The ECMWF
cluster remains the guidance that brings Priscilla faster and
closer to the Mexican coast. This would result in an earlier
arrival time and more abundant moisture from Priscilla to reach the
Southwest and then further downstream through the interior western
U.S. The GFS has sped up some but still significantly lags the
ECMWF solution. The 12Z ECMWF adopted an even faster solution on
drawing Priscilla`s moisture into the western U.S.

Meanwhile, models have been trending toward establishing a stronger
high pressure system over New England late this week leading to a
stronger northeasterly flow down the Eastern Seaboard, along with a
stronger coastal front to linger just off the coast of the
southeastern U.S. The last few runs of the EC-AIFS have settled
into a solution with a rather notable nor`easter centered near the
North Carolina coast on Sunday. The latest from the 12Z ECMWF also
has switched to a more amplified solution with a major nor`easter
forming and tracking just off the East Coast through next weekend.
All in all, there is increasing model signals for a coastal storm
to form off the southeastern U.S. and then track up the Mid-
Atlantic coast next weekend. In addition, there could be an
increased threat of heavy rain across southeastern Florida late
this week as lingering tropical moisture may interact with the
beginning stage of formation of the coastal storm.

The WPC medium-range forecasts were based on the consensus of 40%
from the 00Z EC/CE mean, 40% from the 06Z GFS/GEFS, and 20% from
the 00Z CMC/CMC mean. This blend agrees reasonably well with the
previously WPC forecast package but with a better-defined front and
coastal wave off the East Coast, and the development of a low
pressure system farther north into the lee of the Canadian Rockies
during next weekend.


...Weather/Hazards Highlights...

Lingering moisture anomaly in New Mexico on Wednesday with
potential presence of a stalled frontal boundary warrants
maintaining a Marginal Risk of flash flooding for Day 4 over the
Sacramento Mountains and the higher elevations to the west.

An influx of tropical moisture from the eastern Pacific ahead of
Priscilla may reach into the Desert Southwest Thursday night. This
solution is driven by the ECMWF which has trended even more
progressive with this moisture than other guidance. Meanwhile, the
GFS, which favors much less involvement with Priscilla, nonetheless
brings precipitation into the Southwest and then up through the
Intermountain West, albeit one day later than the ECMWF for the
weekend. It appears that the strong dynamics associated with the
upper low off the West Coast alone would support expansion of
precipitation up through the interior western U.S. with wintry
precipitation across the higher elevations in the interior Pacific
Northwest and northern Rockies by the coming weekend.

A cold front progresses through the Mid-Atlantic and the Carolinas
Wednesday and Thursday. As of now this appears progressive enough
to consider it beneficial rain and no ERO at this time. Meanwhile,
the trend toward a nor`easter near the East Coast will need to be
monitored this weekend for significant rain and wind potentials.

Cool conditions with max temperatures five or so degrees below
normal shift east with a cold front from the Great Lakes Wednesday
through the Northeast and Eastern Seaboard for Thursday/Friday.
Meanwhile, ridging over the Gulf Coast drifts west through Texas
and amplifies up the Rockies this weekend which will maintain above
normal temperatures over south-central states through next weekend
with much above normal temperatures expected to build through the
Great Plains Thursday through this weekend.


Kong/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







$$