653
FXUS02 KWNH 260813
PREEPD

Preliminary Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
412 AM EDT Sat Sep 26 2026

Valid 12Z Tue Sep 29 2026 - 12Z Sat Oct 03 2026


...Early season New England Nor`easter lingers early next week...

...Major Four Corners states to Plains/Mississippi Valley/Midwest
heavy rain/runoff/tropical moisture connection threat next week...


...Overview...

It generally remains the case that an early season Nor`easter will
linger off New England early next week before exiting into the
Canadian Maritimes. Strong/gusty winds with potential for coastal
flooding, beach erosion, and rip currents are possible, along with
heavy coastal rains. Meanwhile, an upper trough will work through
the West/Southwest early next week and move east into the Plains
midweek and beyond. Heavy precipitation will be widespread ahead of
this trough and with lead/wavy multi-stream frontal system
interactions. A tropical moisture connection as East Pacific
Hurricane Polo landfalls in Mexico favors multiple days of
rain/storms and some mountain snows in the Four Corners states.
Widespread heavy rainfall/flooding issues will slowly spread over
the Plains/Mississippi Valley/Midwest as next week progresses, with
an overall slow translation to the East heading into next weekend.


...Guidance/Predictability Assessment...

Forecast confidence remains high with the lingering of an early
season Nor`easter, but models continue to come into better
alignment on how long this system may linger off the Northeast
coast, with push off towards the Canadian Maritimes by midweek.

There remains questions on timing of an upper low over the
Southwest and its progression into the south-central U.S. next
week. Regardless though, confidence is high for leading tropical
moisture from East Pacific Hurricane Polo to enhance rainfall
across the Southwest and into the Central and east-central U.S..
However, there remains uncertainty with potential enhanced
tropical/Gulf moisture feed in advance heading into next weekend.

Significant guidance differences have recently developed for later
next week as yesterdays GFS/GEFS/AI-GFS and Canadian/Candadian
Ensembles all favored ample upper trough digging and amplification
into the West/Rockies later next week into next weekend. This was
in stark contrast to ECMWF/ECENS/EC-AIFS solutions that showed much
less amplitude/digging in a more split flow pattern. Overall, WPC
has been favoring ECMWF/ECENS/EC-AIFS solutions and now much of the
latest 00 UTC GFS/Canadian model and ensemble guidance has
strongly trended in line, bolstering forecast confidence deeper
into these medium range time scales.

...Weather/Hazards Highlights...

The western Atlantic Nor`easter will lead to broad onshore flow
from the Mid-Atlantic to the Northeast, continuing early next week.
The lingering storm could lead to coastal flooding and beach
erosion, as well as marine hazards like rip currents and high surf.
Heavy rain could cause inland flooding across southeastern New
England. See WPC`s Key Messages regarding this coastal low for
further information.

Deep tropical Pacific and Gulf moisture should return ahead of the
large-scale troughing into an unsettled/cooled West, bringing
widespread rain to the Four Corners states northward and eastward
into early next week. Moderate to heavy rain spreads across the
Plains and Mississippi Valley into early-mid next week. A slow
moving upper low will interact with tropical moisture from Polo,
leading to heavy to excessive rainfall threats across the Four
Corners into Tuesday/Wednesday. Expansive WPC Excessive Rainfall
Outlook (ERO) Marginal Risk and embedded Slight Risk areas are in
place Monday into early Wednesday. Vulnerable soils from recent
heavy rainfall could exacerbate flash flooding concerns. Some snow
is possible in the higher peaks of the Intermountain West/Rockies
with the precipitation, as the trough pushes east into the Plains
on Wednesday/Thursday and cools temperatures. Large Marginal and
embedded Slight Risk ERO threat areas are also in play across much
of the south-central U.S. Tuesday into Wednesday/Thursday, with
later week risks to monitor as focus shifts slowly downstream.

Elsewhere, early week and less certain late next week system
energies should work into the Northwest and inland to produce
organized precipitation chances with focus over favored terrain.

Meanwhile, a wet period for Florida is expected to linger into
early October as onshore moisture flow fuels enhanced daily rains.

Schichtel


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, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
are at:

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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