Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
343 AM EDT Sun Oct 26 2025

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

...Heavy rain possible for the eastern U.S. next 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 Southeast 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 next week. Meanwhile, weaker shortwaves into the
Pacific Northwest will keep that region wet, and may help to
reinforce deep troughing again over the East by next weekend.


...Guidance/Predictability Assessment...

Latest model guidance continues to show good agreement on the
large scale pattern, but a lot of uncertainty and run to run
variability in the details. At the start of the period on
Wednesday, the guidance shows two distinct upper lows -- one over
the lower to mid Mississippi Valley and another smaller one over
the Northeast. Recent runs have shown better consensus for the
Northeast low to retrograde westward and interact/combine with the
southern low. But latest 00z guidance for tonight (which was
available after the WPC forecast was generated) shows more
separation of these lows which results in a slower/more southern
track for the Mid-South low. Even with that, there are differences
in the north/south placement of the upper low center especially
late week and so trending the manual forecast towards the ensemble
means was prudent for the latter periods. The UKMET was a bit west
of consensus and was not used in the blend tonight.

Out West, a couple of weak shortwaves will move through the
Pacific Northwest. Eventually, this will help reamplify troughing
over the East behind the initially deep upper low as it departs
into Canada next weekend. The guidance agrees on amplified
troughing over the East again next weekend, but there are some
solutions that show another upper low over the Mid-South. The WPC
forecast was weighted more towards the ensemble means for next
weekend for this region.

Meanwhile, Hurricane Melissa in the Caribbean is forecast to be a
slow moving major hurricane at the start of the medium range period
near/over Cuba. Its track is also highly influenced by the
developing trough/low over the East next week. The bulk of models
now 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 lower probabilities that its energy/circulation could get
pulled back into 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...

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. A marginal risk is in place on the Day
4/Wednesday ERO, focused over the southern Appalachians region,
which tends to be more sensitive to flash flooding. Though
instability will be modest, forcing for ascent will be strong,
supporting just a marginal risk at this time. The swath of rainfall
lifts into the Mid-Atlantic and Northeast on Thursday, and a
marginal risk is in place for mainly locations along and just
inland from southeast Virginia to southern New England. Rainfall
will continue in the Northeast on Friday, clearing much of the
region (with the exception of some lake effect rains on the
backside) this weekend.


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 into the weekend, ahead of a
larger northeast Pacific low. Uncertain rain chances may return to
parts of the South later in the weekend depending on the evolving
pattern over the region.

The southwestern U.S. can expect warmer than average temperatures
underneath upper ridging for much of next 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 next 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 10-15 degrees below
average. These cool temperatures should moderate as the week
progresses as the low lifts through the East.


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