Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
326 AM EDT Mon Oct 27 2025

Valid 12Z Thu Oct 30 2025 - 12Z Mon Nov 03 2025

...Heavy rain likely for the Mid-Atlantic and Northeast Thursday
into Friday...

...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 will be over the Mid-South by the start of the period on
Thursday, and will lift northward across the interior East as its
easterly movement gets blocked by a strong ridge over the Atlantic.
This brings a risk for heavy rainfall to parts of the Mid-Atlantic
and Northeast Thursday into early Friday. Another shortwave on the
backside of the upper low will drop southward next weekend
renewing amplified troughing over the East once again early next
week. The West will trend wetter and more active Friday and
Saturday ahead of a shortwave moving into the region, with upper
ridging building back in after.


...Guidance/Predictability Assessment...

Compared to the past few model runs, guidance shows much better
consensus on the upper low over the Mid-South into the East
Thursday-Friday. There remains some question on the details and
timing of the front/surface low up the East Coast, but there does
seem to be a slightly faster trend in the last few runs. A general
consensus of the deterministic guidance served as a good starting
point for this system. Behind this, a shortwave drops into the
northern U.S. by the weekend, acting to reinforce troughing over
the East for the second half of the period. There is considerable
uncertainty on the strength and consequently timing of this, with
some pieces of guidance showing another possible closed low
in/around the Mid-South with coastal low development up the East
Coast too. The consensus though at this point is just amplified
troughing that shifts eastward with time and this is the preference
for the WPC progs today too, which were more weighted towards the
ensemble means for the latter half of the period.

Out West, there is good agreement on the initial shortwave as it
moves into the Pacific Northwest late week, but increasing
uncertainty at the end of the period for another system just off
the coast. The WPC progs favor a blended approach with increasing
ensemble mean weighting Days 6 and 7.

Regarding Hurricane Melissa, guidance continues to show increasing
agreement that this system will get picked up by the departing
Eastern U.S. trough later this week and not be a direct impact to
the Eastern U.S.. It could however, eventually affect the Canadian
Maritimes as it transitions to an extratropical system next
weekend.


...Weather/Hazards Highlights...

Strong surface low pressure shifting from the Mid-Atlantic into
the Northeast Thursday into Friday will draw tropical Atlantic
moisture into it, creating a threat for moderate to heavy rainfall
in this region along and ahead of the low track and associated cold
front. With modest instability in place, and sufficient forcing
and divergence within the coupled jet, locally heavy rain rates are
possible with isolated flooding concerns. A Marginal Risk is in
place on the Day 4/Thursday ERO over parts of the Mid-Atlantic and
Northeast, as well as back into the central Appalachians and
eastern parts of the Ohio Valley as moisture gets drawn well
inland. Timing and placement differences in the low track could
lead to future changes in these risk areas. For Friday, much of the
rain will have cleared the Northeast but the rainfall along the
front as it moves northward through Maine supports a Marginal Risk
for northern Maine. Some lake effect rains are possible on the
backside of the system as well. The northern Plains/Upper Midwest
and into the Ohio/Tennessee Valleys may see some rain with another
frontal system over the weekend, though more uncertainty associated
with this one. Rain may expand in coverage across the Gulf Coast
and east-central U.S. early next week ahead of the next deep
trough.


Thursday should be a relatively quieter day for the Pacific
Northwest but renewal of precipitation that could be heavy is
possible late week into the weekend, ahead of a larger northeast
Pacific low. A Marginal Risk was raised for the Day 5/Friday ERO
tonight across this region. Elsewhere, the Southwest to the Plains
should stay mostly dry through the period under the ridge aloft.

The southwestern U.S. can expect warmer than average temperatures
underneath upper ridging for much of the period, expanding through
much of the West into the Central U.S. by the weekend. Meanwhile,
the southeastern quadrant of the lower 48 should see below average
temperatures late this 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,
with temperatures returning back closer to normal by early next
week.


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