659
FXUS02 KWBC 010628
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
128 AM EST Sun Nov 1 2026

Valid 12Z Wed Nov 04 2026 - 12Z Sun Nov 08 2026


...A slowly progressive storm system will bring heavy
rains/thunderstorms across the eastern U.S. by mid to late week...


...Overview...

A active and relatively progressive pattern is expected to move
into eastern U.S. by mid-week, as the amplified upper trough and
associated frontal system moves towards the East Coast by late week
into the weekend. The system will support widespread thunderstorms
and showers along the frontal boundary, with locally heavy rainfall
possible across portions of the Southeast and Tennessee/Ohio
Valley. The system will progress northeast into portions of the
Mid-Atlantic and Northeast by late week. Across western U.S.
additional Pacific shortwave energy will bring an increase in
precipitation chances across the Pacific Northwest.


...Guidance/Predictability Assessment...

Models continue to show the progression of the trough moving into
eastern U.S. as well as the associated frontal system. The GFS,
ECMWF, and CMC solutions support the development of a surface
cyclogenesis over the Plains and the eastward progression of the
frontal system. However, differences remain in the amplitude and
timing of the upper trough. One of the primary forecast challenges
involves the interaction of the northern- and southern-stream
shortwave energy. Differences in the timing and phases of theses
disturbances will influence the strength and position of the
surface low, the speed of the frontal boundary, and location of the
heaviest rainfall. These uncertainties are particularly important
across the Mississippi, Tennessee, and Ohio Valleys during the
early portion of the period. Further west, models continue to show
some disagreement with timing of shortwave features as it
progresses inland, especially with the GFS/GEFS solutions.
Therefore, a multi- model blend incorporating GFS/ECMWF/CMC
solutions were used for the first portion of the period, with less
weight on GFS. To alleviate some of the differences among the
deterministic models, a heavier weight towards the ensemble means
were used for the late period.


...Weather/Hazards Highlights...

The amplified upper trough and associated surface frontal system
will progress eastward from the Mississippi Valley into the
Ohio/Tennessee Valley by Wednesday. Southerly flow will transport
Gulf moisture northward ahead of the system, supporting widespread
showers and thunderstorms along the boundary. Periods of moderate
to locally heavy rainfall are possible where deep moisture, strong
low-level convergence, and enhanced forcing overlaps. WPC
Excessive Rainfall Outlook maintain a Marginal Risk for portions
of the Ohio/Tennessee Valley and Southeast for Wednesday.

As the frontal boundary advanced eastward on Thursday, showers and
thunderstorms is expected to develop across portions of the Mid-
Atlantic, Northeast, and lower Great Lakes. There is some
uncertainty on storm development, as the strength and timing of
the secondary surface front will influence the duration and
coverage of rainfall across eastern U.S. By late week, the main
frontal boundary will progress offshore along the East Coast.
Cooler and drier condition are expected to spread into areas behind
the front, although lingering moisture and additional shortwave
energy could maintain showers across portions of the Northeast and
Mid-Atlantic into the weekend.

Across western U.S., a shortwave trough will progress eastward
across the Southwest/Four Corners and a short-lived ridge will
develop across portions of the Intermountain West and northern
Rockies. Some light precipitation may develop along the Four
Corners and central Plains, with possible high-elevation snow. As
another Pacific energy ejects into the Pacific Northwest,
precipitation chances increases. Onshore flow and additional
shortwave energy will support isolated showers mostly along the
coastal and mountain areas from mid week into the weekend.



Oudit


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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