Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
355 PM EDT Sun Oct 26 2025

Valid 12Z Wed Oct 29 2025 - 12Z Sun Nov 02 2025

...Heavy rain likely for the eastern U.S. mid to late week...

...Overview...

Models continue to advertise an amplified and active upcoming
medium range pattern which features a deep trough/upper low over
the eastern U.S. and a building ridge out west. The eastern upper
low looks to drop south and east into the Mid-South Wednesday-
Thursday, and eventually back northward across the East as its
easterly movement gets blocked by a strong ridge over the Atlantic.
This likely brings a risk for heavy rainfall to much of the East
mid to late week. Meanwhile, weaker shortwaves into the Pacific
Northwest will cause precipitation chances there late week, and may
help to reinforce deep troughing again over the East by next
weekend.


...Guidance/Predictability Assessment...

The primary model diagnostics concern remains the upper and
surface lows pivoting through the eastern half of the U.S. mid to
late week. Model guidance unfortunately continues to show a lot of
run to run variability with the track and timing of these lows even
toward the start of the medium range period. For the most part,
the 00/06Z suite of model guidance that was available at forecast
generation time slowed down with the upper/surface lows compared to
yesterday's 12Z models, so the WPC forecast for the low pressure
system and resulting QPF also slowed compared to the previous
forecast using a multi-model deterministic blend. However, today's
incoming 12Z guidance switches back to a faster trend, with the
upper low moving more quickly out of the Lower/Mid-Mississippi
Valley early Wednesday into the Ohio/Tennessee Valley and into the
Appalachians by Thursday as it starts to pivot north and interact
with retrograding Northeast U.S. energy. So expect the next
forecast cycle to have to trend back to a faster track. The 12Z
ECMWF, AIFS, and UKMET are particularly fast. Within this faster
trend there is still spread in the position of the low in terms of
how far inland or coastal the low could be, with 00Z dynamical and
AI models split in which low track they favor. The new 12Z GFS
trended farther inland/west for the stronger low, closer to the
non-NCEP models, so models seem to be converging on that type of
solution. The low system could be made more complex by an occluded
structure with a triple point low though. Generally the upper and
surface lows should track northward into Canada around Friday to
early Saturday, while differences in timing remain.

A shortwave is likely to be located atop the Pacific Northwest
Wednesday, which then moves quickly east through south-central
Canada and shows more model spread as it reaches the Midwest around
Friday. This looks to move southeast across the Mississippi Valley
or so by Saturday, but with increasing spread. This feature may
interact with the original upper low too. After that in the West,
models were generally agreeable with showing ridging in the
Southwest with more zonal flow in the Northwest. Overall, the WPC
forecast trended toward more ensemble means for the latter part of
the forecast next weekend.

Meanwhile, Hurricane Melissa is likely to be located near/over
eastern Cuba early Wednesday and then track more quickly across the
Atlantic for the latter half of the week as it gets picked up by
the Eastern U.S. trough/low. Models are agreeable that Melissa
should not directly impact the U.S., but could eventually affect
the Canadian Maritimes as it transitions to an extratropical
system. The WPC forecast continues to follow the official forecast
track from the National Hurricane Center.


...Weather/Hazards Highlights...

An area of low pressure near the lower Ohio Valley will produce
rainfall, heavy at times, which shifts from the Mid-South/Southern
Appalachians on Wednesday into the Mid-Atlantic and Northeast
Thursday into Friday. The negatively tilted trough looks to draw in
some tropical moisture and modest instability, while the forcing
and divergence with the coupled jet will be particularly
impressive. Areas along and ahead of the low track could see
locally heavy rain rates, and isolated flooding concerns are
possible. A Marginal Risk is in place on the Day 4/Wednesday ERO
centered over the southern Appalachians and surrounding areas, and
then across parts of the Mid-Atlantic and Northeast for Day
5/Thursday. Timing and placement differences in the low track could
certainly lead to future changes in these risk areas. Rainfall
should clear New England over the weekend, but some lake effect
rains are possible on the backside of the system. The
Ohio/Tennessee Valleys may see some rain with another frontal
system over the weekend, though this is uncertain.

Most rain and higher elevation snow will be lessened in the
Northwest by Wednesday into Thursday. But renewal of precipitation
that could be heavy is possible late week into the weekend, ahead
of a larger northeast Pacific low. The Southwest to the Plains
should stay mostly dry under the ridge aloft.

The southwestern U.S. can expect warmer than average temperatures
underneath upper ridging for much of the week with spotty areas of
Moderate HeatRisk near the Los Angeles/San Diego area on Wednesday.
The area of above normal temperatures will expand through the week
and overspread much of the West into the Central U.S. by next
weekend. Meanwhile, the southeastern quadrant of the lower 48
should see below average temperatures through much of the week
under the upper low with daytime highs only into the upper 50s/low
60s in much of the Southeast, around 10-20 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