Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
358 PM EDT Sat Oct 25 2025

Valid 12Z Tue Oct 28 2025 - 12Z Sat Nov 01 2025

...Heavy rain possible for the eastern U.S. next week...

...Overview...

Models continue to advertise an amplified and active upcoming
medium range pattern. Deep troughing over the Central U.S. to start
the period on Tuesday looks to close off an upper low as it drops
south/southeastward into the Mid-South on Wednesday. Meanwhile, a
retrograding upper low over the Northeast may interact with the
central U.S. low resulting in possibly a large closed upper low (or
at the very least amplified troughing) into the East mid to late
week, leading to surface cyclogenesis and a heavy rainfall threat.
Upper ridging will build over the interior West through the period
with weak shortwaves moving into the Pacific Northwest.


...Guidance/Predictability Assessment...

Recent model guidance shows good agreement with the pattern
described above in the first day or two of the forecast period, but
quickly diverge with the pattern specifics in the East later next
week. There is general agreement on some form of amplified upper
troughing or a closed low over the East but the evolution of that
low and interactions with the retrograding low over the Northeast
are highly variable. This makes the surface low track, which shows
good agreement with its position near Paducah or so Wednesday
morning in the 12Z guidance, diverge quickly. ECMWF runs including
the new 12Z have a more northerly and farther inland track with the
surface low as the upper low shows consolidation farther north,
with the surface low moving across the Ohio Valley and then
pivoting northward across the Lower Great Lakes by Friday. The 12Z
CMC is closer to the EC track though a bit slower. Meanwhile the
GFS/GEFS/GFS Graphcast runs that dig the upper low deeper have more
of a coastal low type of track at the surface, across the
Southeast and then up the Eastern Seaboard. This, of course, has
major impact on the QPF amounts and distribution across the East
next week. The WPC forecast attempted to keep more QPF southwest of
the NBM early in the period to be closer to continuity, but there
will certainly be additional changes to future forecasts with the
rainfall pattern and amounts so sensitive to the low track.

Upstream, a potential shortwave in the Upper Midwest around Friday
also varies in part due to the uncertainty to the east. This
shortwave was pretty clear in the 00/06Z guidance and maintained a
frontal system there, but the 12Z guidance has backed off this
feature. At least the ridging in the interior West shows reasonably
good agreement, though with some amplitude variations, while there
are some minor differences in Pacific Northwest shortwaves on the
periphery of a large scale low in the northeast Pacific. The WPC
forecast tonight was able to use a majority deterministic guidance
the first half or so of the period but quickly transitioned to
heavily weighted with the ensemble means Days 6-7.

Meanwhile, Hurricane Melissa in the Caribbean is forecast to be a
slow moving major hurricane at the start of the medium range period
near or over Jamaica. Its track is also highly influenced by the
developing trough/low over the East next week. The bulk of models
continue to show a track well off the East Coast, even once it gets
picked up by the trough/low as it exits the Northeast late next
week, but there is a lower probability solution that CMC runs have
been favoring that shows Melissa getting picked up and pulled back
in towards the Canadian Maritimes. Melissa continues to be worth
monitoring for any potential changes to the forecast. The WPC
forecast will follow the official forecast track from the National
Hurricane Center.


...Weather/Hazards Highlights...

Consolidating low pressure over the Mid-South by Tuesday-Wednesday
should produce a swath of rainfall centered over the Mid-
Mississippi Valley, with lesser rainfall amounts ahead of a front
across the Upper Midwest and east into the Ohio/Tennessee Valleys
into the Carolinas and Mid-Atlantic towards a coastal low on
Tuesday. Rain totals may reach an inch or two where the
upper/surface low pivots, but given limited instability, this does
not seem to warrant any Marginal Risk area. Meanwhile most rain
with the coastal low currently looks to fall offshore. However, by
day 5/Wednesday as the upper/surface low deepens and pivots, it may
pull more tropical Atlantic moisture into the Carolinas/Mid-
Atlantic region and back into the Southern Appalachians and eastern
portions of the Ohio/Tennessee Valleys. This should lead to
heavier rain by Wednesday. A Marginal Risk is in place in the Day 5
ERO, focused over the Southern Appalachians (that tend to be
sensitive to flash flooding), and stretching north and west a bit
compared to the previous issuance due to model trends. Instability
will be pretty modest but the forcing for ascent will be strong.
The uncertainty in the low track means that this area may need to
shift over time, so continue to monitor forecasts. The low will
generally track northeastward into later week and spread moderate
to heavy rain across the Mid-Atlantic and Northeast, but the timing
and position of rainfall still has quite a bit of variability.

The Pacific Northwest should see rounds of rain and mountain snow
chances through next week as shortwaves and fronts move through.
Wednesday and Thursday may have a relative break before a renewal
of perhaps heavy amounts late week, ahead of a large northeast
Pacific low.

The southwestern U.S. can expect warmer than average temperatures
underneath upper ridging for much of next week. Highs are forecast
to be in the 90s in the Desert Southwest. Though in Southern
California highs should not reach the 90s, there is some Moderate
HeatRisk shown there with 80s possible for highs. The area of above
normal temperatures will increase through next week and overspread
much of the West into the High Plains by next Saturday. Meanwhile,
the southeastern quadrant of the lower 48 should see below average
temperatures through much of the week under the developing upper
low. Highs may only reach the 50s and low 60s in much of the
Southeast, around 10-15 degrees below average. These cool
temperatures should moderate as the week progresses as the low
lifts through the East.


Tate/Santorelli


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