664
FXUS02 KWBC 261847
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 PM 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, with the worse impacts now into the short
range period. 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 Wednesday.

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..
Confidence however in amounts and how expansive the heavy rainfall
shield will be is lower given smaller scale differences in the
guidance. In general, the ensembles seem a bit faster with the
front while the global/deterministic models are slower. The WPC
forecast for today tried to stay as close to continuity where able.
There also remains uncertainty with potential enhanced
tropical/Gulf moisture feed into the Gulf Coast region heading into
next weekend.

Greater differences continue for later next week in the West on
timing of the next trough into the coast. The GFS based guidance is
generally more amplified than other guidance, but the ECMWF/ECENS
is flatter. Stayed close to previous shift continuity with this,
with more weighting towards the EC-AIFS for a middle ground
approach.


...Weather/Hazards Highlights...

The western Atlantic Nor`easter will lead to broad onshore flow
from the Mid-Atlantic to the Northeast, weakening from this
weekend, but still 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, especially for
more urbanized areas. See WPC`s Key Messages regarding this coastal
low for further information.

Deep tropical Pacific and Gulf moisture will return ahead of the
large-scale troughing into an unsettled/cooled West, bringing
widespread rain to the Four Corners states north 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. There is increasing concern for some widespread
significant rainfall over already very saturated soils, and thus
WPC has highlighted a broad moderate risk from southeast Arizona
into the Texas and Oklahoma panhandles on Tuesday/Day 4. A larger
slight risk extends northeastward into the Central Plains and parts
of the Midwest. There is a bit more uncertainty on rainfall
amounts and system progression to hold onto a broad slight risk
across much of the Southern and Central Plains into the middle
Mississippi Valley for Wednesday. Heavy rainfall appears likely
beyond Day 5 as this system pushes slowly eastward, with flash
flooding risks to monitor. Some snow is also 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.

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. A
wet period for Florida is expected to linger into early October as
onshore moisture flow fuels enhanced daily rains all along the Gulf
Coast.

Santorelli/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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