Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
311 AM EDT Tue Oct 28 2025

Valid 12Z Fri Oct 31 2025 - 12Z Tue Nov 04 2025


...Overview...

Models continue to advertise an amplified upcoming medium range
pattern which features mean troughing over the eastern U.S. and a
building ridge out west. An initial upper low will be exiting the
Northeast by the start of the period on Friday, as another
shortwave drops southward from the Upper Midwest bring renewed
amplified troughing (or a cut off closed low) over the East once
again by early next week. The Northwest will start the period
wetter and more active Friday and Saturday ahead of a shortwave
moving into the region, with upper ridging building back in after.
Another shortwave may approach the coast next Tuesday.


...Guidance/Predictability Assessment...

Models are pretty agreeable that the initial upper low over the
Northeast on Friday will lift northward and into eastern Canada by
Saturday, dragging a strong surface low with it. Some minor timing
inconsistencies continue with this, but a general model blend works
as a good starting point for now. The main forecast concern though
is with the next shortwave as it drops southward from the Upper
Midwest on Friday. At this point, the consensus would say this
shortwave just acts to reinforce troughing over the East into the
weekend, but there is some guidance suggesting a cut off low
developing over the South/Gulf Coast being slower to exit the
region. Some of the new 00z guidance (including the GFS and ECMWF)
have trended this direction too, so it is definitely worth
watching. For now, the WPC forecast was based more on the ensemble
means showing a general eastward progression of the upper trough
into early next week. Out West, the guidance shows plenty of
uncertainty on the timing of the next shortwave into the West on
Day 7, so trended towards the ensemble means.


...Weather/Hazards Highlights...

With the first low, heavy rain looks to be moving through Maine
Friday morning and then exiting the Northeast, though lake effect
rains are likely behind the primary system. By the weekend, upper
level energy and frontal systems could lead to rounds of light
precipitation, primarily rain, in the Midwest, Great Lakes,
Ohio/Tennessee Valleys, and possibly reaching the central Gulf
Coast.

Heavy precipitation is likely Friday into Saturday for the Pacific
Northwest as a moderately strong atmospheric river takes aim at
the region ahead of a larger northeast Pacific low. There is a
Marginal Risk in the Day 4/Friday ERO for this region. Most
precipitation is forecast to stay rain other than snow in the
highest peaks of the Olympics through Friday, with perhaps more
snow in the Cascades. The region should trend drier Sunday with
possibly another increase in precipitation for Monday. Elsewhere,
the Southwest to the Plains should stay mostly dry through the
period under the ridge aloft.

Much of the West can expect warmer than average temperatures
underneath upper ridging through the period, expanding into the
Central U.S. by Sunday and beyond. Meanwhile, the eastern U.S. will
be mainly near or below normal temperatures underneath mean upper
troughing.


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