885
FXUS02 KWBC 011807
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
107 PM EST Sun Nov 1 2026

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


...Storm system to spread heavy rains/thunderstorms across the
Appalachians into the East/Northeast mid to late week...


...Overview...

A relatively progressive pattern over the nation is expected to
focus activity into eastern U.S. mid-late week, as the amplified
upper trough and associated frontal system ejects towards the East
Coast. The system will support widespread thunderstorms and showers
along/ahead of the frontal boundary, with locally heavy rainfall
possible across portions of the Southeast and Tennessee/Ohio Valley
and the Appalachians. The moist system in concert with a lifting
western Atlantic low will shift focus to portions of the Mid-
Atlantic then Northeast late week. Across the western U.S.,
additional Pacific shortwave energies/frontal surges will bring
several enhanced precipitation chances into the Pacific Northwest.

...Guidance/Predictability Assessment...

Forecast spread has improved through medium-range time scales with
the latest guidance cycles, but that may not directly relate to an
equal improvement in predictability given recent run to run
sensitivities and the nature of the flow with multiple embedded
systems and stream phasing complexities. Accordingly, a broad
model, ensemble mean and machine learning guidance blend seems to
provide a good basis for threat messaging generally in line with
the National Blend of Models and with weather focusing feature
variances smoothed in line with individual predictability. This
strategy also acts to maintain reasonable WPC product continuity.

...Weather/Hazards Highlights...

The amplified upper trough and associated surface frontal system
will progress eastward from the Mississippi Valley into the
Ohio/Tennessee Valley and into the Southern Appalachians 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 and thunderstorms from portions of
the Mid-Atlantic to the Northeast into the weekend as also enhanced
by moisture interaction with a lifting western Atlantic coastal low.

Across western U.S., a closed southern stream upper low/trough
will progress eastward across the Southwest/Four Corners. Some
light precipitation may develop along the Four Corners
Region/Rockies 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/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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