Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
358 PM EDT Sun Sep 28 2025

Valid 12Z Wed Oct 01 2025 - 12Z Sun Oct 05 2025


...Overview...

As there is better consensus for Imelda to curve east away from the
U.S. before midweek, attention turns to other forecast aspects
during the medium range period. A relatively slow-moving and blocky
pattern will set up across the U.S., with mean troughing in the
West promoting frontal passages with cooler temperatures and rounds
of precipitation, while an upper ridge sets up from the Southwest
northeastward into the Midwest promoting warm temperatures and
mainly dry conditions. Southern stream energy and a possible
frontal boundary atop the Gulf Coast/Florida could allow for rounds
of rain and storms there.


...Guidance/Predictability Assessment...

The early part of the medium range period (starting Wednesday)
shows reasonably good agreement on the large scale with the pattern
described above. Initial troughing will be quickly lifting out of
the north-central U.S. while a primary upper low is forecast just
offshore British Columbia and supports troughing atop the eastern
Pacific and Northwest. In the East, most upper troughing will be
exiting midweek but could leave some energy behind around the Gulf
Coast or so that would meander through much of the week south of
the agreeable ridge axis. The most uncertain part of the forecast
is how troughing in the West evolves. GFS runs from 00Z/06Z
maintained a closed low for longer as it slowly pushes into the
Northwest compared to the faster/open troughing of the ECMWF, CMC,
and most EC-based AI models by Thursday-Friday. The newer 12Z GFS
has jumped to an open trough, more like consensus, with a possible
shortwave farther in the Central Rockies or so on Saturday. The
evolution also depends on additional upstream energy dropping
through western Canada. For the most part the newer 12Z model suite
shows this energy being stronger as it moves into the Northwest
next weekend, and pushing the first shortwave east more quickly.
Will see if these trends continue.

The WPC forecast used a multi-model blend of deterministic
guidance early in the forecast period. As the period progressed,
increased the proportion of GEFS and EC ensemble means, reaching
half means for Days 6-7 amid increasing spread.


...Weather/Hazards Highlights...

A weak atmospheric river is forecast to push across the Pacific
Northwest into California Wednesday with a cold front ahead of the
upper trough. Rain totals generally under an inch or two do not
appear to cause hazardous conditions in the coastal mountain areas
that are accustomed to seeing multiple inches of rain. Rain could
continue in the West Coast states through Thursday with another
front. Rounds of precipitation will be likely across parts of the
Intermountain West/Rockies through multiple days this week, and the
higher elevations can expect snow. Moisture levels will be above
normal, but the rain seems unlikely to cause flooding concerns with
not much instability in place, limiting rain rates. Precipitation
chances should increase later week into next weekend across the
north-central U.S. once the frontal system emerges in the Plains.

After Imelda tracks east away from the Southeast U.S., some weak
energy aloft in the southern stream could stall south of the
northeastward oriented trough, which along with a frontal boundary
and sufficient moisture could lead to scattered showers and storms
across Florida and for the Southeast, especially along the Gulf
Coast. Through Wednesday and Thursday rain amounts and rates look
to stay below Marginal Risk ERO thresholds, but moisture and
instability look to increase by next weekend. Meanwhile most areas
under the upper trough stay dry through the latter half of the week
into the weekend, including the Southwest/southern Plains
extending into the Ohio Valley and the Northeast/Mid-Atlantic.

With upper ridging building overhead, warmer than seasonal average
temperatures are expected across the central U.S., most anomalous
for the Northern Plains to Upper Midwest. Highs of 10 to 20 degrees
above normal will be common in those areas through late week, with
highs of 80F reaching to the Canadian border by Wednesday. 90s are
likely to continue for early October into the Desert Southwest and
Texas. By next weekend, warmer than average temperatures could
shift a bit east and cover the Great Lakes region and Northeast.
Meanwhile, below normal temperatures especially for highs are
likely across the West due to upper troughing and rainy/cloudy
conditions.


Tate


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
356 PM EDT Mon Sep 29 2025

Valid 12Z Thu Oct 02 2025 - 12Z Mon Oct 06 2025


...Overview...

Through late week into early next week, much of the lower 48 will
be in a relatively slow-moving and blocky pattern. Rounds of
renewing upper troughing are likely in the West, with multiple
frontal passages bringing cooler temperatures and rounds of
precipitation. Meanwhile, an upper ridge will stretch from the
Desert Southwest into the Midwest promoting warm temperatures and
mainly dry conditions. Southern stream energy and a possible
frontal boundary atop the Gulf Coast/Florida could allow for rounds
of rain and storms there.


...Guidance/Predictability Assessment...

The extended period begins with a reasonably well clustered
pattern. Positively tilted upper ridging will be in place from the
Southwest to Northeast; however there will be lingering energy for
the Gulf region to the south of the ridge axis. Farther west, a
primary upper low near British Columbia is expected to usher in
troughing to the Northwest/Intermountain West. The timing of this
trough moving in late week remains somewhat questionable. The
trough track is generally slower than a day ago, but will depend on
an upstream shortwave dropping south from the northeast Pacific.
The 00Z CMC was an outlier in having a stronger upstream shortwave
farther south by Friday, but the 12Z CMC has trended closer to
consensus. The 00Z UKMET was farther west and stronger with this
upstream shortwave, but kicks out the initial troughing more like
most models from a day ago, and was not favored. New 12Z model runs
are generally even slower across the West around Saturday,
especially the ECMWF. This should generally pivot east while the
second shortwave continues to develop troughing in the Northwest,
but there are timing differences in the shortwaves affecting
sensible weather. By next Monday most guidance indicates energy
pulling away to create possibly closed upper low development atop
California and vicinity. This appears to be in good agreement Day 7
but the variations in the Days 4-6 forecast limit confidence.

Given initial reasonable agreement, the WPC forecast began with a
blend of the 06Z GFS, 00Z ECMWF, and lesser amounts of the 00Z CMC
early in the forecast period, with increasing proportions of the
ensemble means to 60 percent Days 6-7.


...Weather/Hazards Highlights...

Shortwaves within the Western trough and associated surface fronts
will promote rounds of precipitation especially for the Rockies
and Intermountain West. The higher elevations can expect snow under
the upper trough. Moisture levels will be above normal, but the
rain seems unlikely to cause flooding concerns with not much
instability in place, limiting rain rates. The Pacific Northwest
could see precipitation especially Thursday. Rain chances are
forecast to expand into the north-central U.S. late week into the
weekend as a couple of frontal systems emerge into the Plains.

Some weak energy aloft in the southern stream could stall south of
the southwest to northeast oriented trough, which along with a
frontal boundary and sufficient moisture could lead to scattered
showers and storms across Florida and for the Southeast, especially
along the Gulf Coast. Rain accumulations and hourly rates seem to
be below the threshold for excessive rainfall at this time, but
will continue to monitor for flooding concerns especially in urban
areas that tend to be more sensitive. Moisture and instability
could lift north into Georgia and the Carolinas over the weekend.
Meanwhile most areas under the upper trough stay dry through the
latter half of the week into the weekend, including the
Southwest/southern Plains extending into the Ohio Valley and the
Northeast/Mid-Atlantic.

Warmer than seasonal average temperatures are expected for a vast
majority of the central U.S., most anomalous for the Northern
Plains to Upper Midwest. With the building ridge, daily high
temperatures will average 15 to 25 degrees above normal through
late week, well into the 80s even to the Canadian border. 90s are
likely to continue for early October into the Desert Southwest and
Texas. By the weekend, warmer than average temperatures could shift
a bit east and cover the Great Lakes region and Northeast, while
the northern Plains cools. Meanwhile, below normal temperatures
especially for highs are likely across the West due to upper
troughing and rainy/cloudy conditions.


Tate/Campbell


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
359 PM EDT Tue Sep 30 2025

Valid 12Z Fri Oct 03 2025 - 12Z Tue Oct 07 2025


...Overview...

Deep upper troughing is forecast to progress through the West to
erode a strong ridge initially dominating the eastern two-thirds of
the country. This shift in the synoptic pattern will bring the
first frost/freeze of the season into the lower elevations from
the northern Rockies to the northern Plains after record warmth in
the upper Midwest. Tropical moisture interacting with a stationary
front could deliver heavy rain and thunderstorms along the east
coast of Florida and along portions of the central Gulf Coast.


...Guidance/Predictability Assessment...

Overall, there is decent model agreement on the aforementioned
evolution of the large scale pattern across the U.S. Strong upper
ridging initially extending from the Southwest to Northeast will
be gradually eroded by deep upper troughing forecast to advance
through the western U.S. By early next week, models show good
agreement for an upper low to detach from the main positively-
tilted upper trough over the Southwest. Across the northern tier
states, model consensus shows a sightly faster eastward progression
of the cold front and the positively-tilted upper trough by early
next week.

The WPC medium-range forecasts began with a general consensus of
40% from the 06Z GFS/GEFS, 40% from the 00Z ECMWF/EC mean, and 20%
from the 00Z CMC/CMC mean, with higher proportions from the
ensemble means for Days 5-7.


...Weather/Hazards Highlights...

Multiple rounds of precipitation is forecast for the West and
Intermountain West as shortwaves within the western U.S. upper-
trough and associated surface fronts track eastward, especially
for the Rockies and Intermountain West. The higher elevations can
expect snow with the passage of the upper trough. Moisture levels
will be above normal, but the rain seems unlikely to cause flooding
concerns with not much instability in place, limiting rain rates.
The Pacific Northwest could see precipitation. Rain chances are
forecast to expand into the north-central U.S. late week into the
weekend as a couple of frontal systems emerge into the Plains.

Tropical moisture interacting with a stationary front will lead to
heavy showers and thunderstorms lurking near or just off the Gulf
Coast and off the Southeast U.S. A Marginal Risk of excessive
rainfall is maintained for Day 4 and Day 5 along the eastern coast
of Florida as urban areas tend to be more sensitive. A couple of
weak
low pressure centers may form on the front and could lift north to
enhance rainfall near the central Gulf Coast, and from the east
coast of Florida up into the Georgia coast over the weekend.
Meanwhile, most areas under an expansive deep-layer ridge stay dry
through the latter half of the week into the weekend, including
the Southwest/southern Plains extending into the Ohio Valley and
the Northeast/Mid-Atlantic.

Warmer than seasonal average temperatures are expected for a vast
majority of the central U.S., most anomalous for the Northern
Plains to Upper Midwest. Under the deep-layer ridge, daily high
temperatures will average 15 to 25 degrees above normal through
late week, well into the 80s even to the Canadian border where
daily record high temperatures will most likely be challenged or
broken Saturday afternoon. Meanwhile, 90s are likely to continue
for early October into the Desert Southwest and Texas. By the
weekend, warmer than average temperatures could shift a bit east
and cover the Great Lakes region and Northeast, while the northern
Plains cools. Meanwhile, below normal temperatures especially for
highs are likely across the West due to upper troughing and
rainy/cloudy conditions.


Kong/Campbell


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

Extended Forecast Discussion...UPDATED
NWS Weather Prediction Center College Park MD
619 PM EDT Wed Oct 1 2025

Valid 12Z Sat Oct 4 2025 - 12Z Wed Oct 8 2025


...General Overview...

The overall weather pattern across the Continental U.S. will be
featured with a general upper ridge situated over the Intermountain
West, and a building upper ridge over the eastern half of the
nation. There will likely be a split flow pattern aloft, with the
southern stream showing increased potential for a closed upper low
to develop over California/Nevada by early next week. Meanwhile,
the northern stream will support an amplifying shortwave with an
attendant cold front, ushering in much colder temperatures across
the northern Rockies and northwestern Plains, and heavy snow for
the higher mountain ranges of Wyoming and Montana. Farther south,
tropical moisture interacting with a lingering stationary front
will likely produce periods of heavy rain and thunderstorms along
the east coast of Florida, and also portions of the central Gulf
Coast for the upcoming weekend.


...Guidance/Predictability Assessment...

The 12Z model guidance suite features good overall synoptic scale
agreement through the upcoming weekend, with a general
deterministic model compromise used for fronts/pressures. The UKMET
is slightly faster with the large shortwave trough over the Four
Corners region, and recent runs of the GFS have been faster with
the passage of the cold front across eastern Canada and the Great
Lakes region early next week. By Monday and beyond,
the greatest model differences are mainly across south-central
Canada regarding timing of individual shortwaves. The AIFS
guidance generally has a broader upper trough situated over the
Great Lakes and southern Canada by Wednesday, whereas the
operational guidance favors more of a sharper trough. The ensemble
means were gradually increased to about 40% by next Wednesday as
mesoscale differences increased.


...Weather/Hazards Highlights...

Coastal portions of the central Gulf Coast and southeast Georgia
into Florida will remain in an active, wet pattern as tropical
moisture interacts with a stationary frontal boundary, and a
couple of weak low pressure centers may form on the front and
enhance the rainfall. A Marginal Risk of excessive rainfall was
maintained for both Day 4 and Day 5 along the eastern coast of
Florida, with urban locations most prone to flooding, and an
eventual Slight Risk area could be needed as the event gets closer
in time. The Day 4 Marginal remains for southeast Louisiana where
heavy showers and thunderstorms are expected along the coastline
and points inland for the southeast parishes. Locally, 3 to 4
inches of rain will be possible and may lead to isolated areas of
flooding. A new Day 5 Marginal Risk was also added for the central
Gulf Coast to account for this.

Multiple rounds of precipitation are forecast for the Western U.S.
as shortwaves within the upper trough and associated surface
fronts track eastward, especially for the Rockies and Intermountain
West. The higher elevations can expect moderate to locally heavy
snow
with the passage of the upper trough, especially for the higher
terrain of western Wyoming and southwestern Montana. Farther east,
moisture levels will be above normal, and even though instability
will not be all that high, areal QPF of 1-2 inches on Saturday
could be enough to lead to some instances of minor flooding in poor
drainage areas, and therefore a Marginal Risk area has been
introduced for the Day 4 period from the lower elevations of
northern Wyoming and southern Montana, eastward to the central
Dakotas.

Summer-like temperatures will hold on across much of the central
U.S. under the deep-layer ridge. Each day the maximum temperatures
will average 10-20+ degrees above normal going into Saturday, well
into the 80s even to the Canadian border where daily record high
temperatures will most likely be challenged or broken Saturday
afternoon. For the Desert Southwest and portions of Texas, 90s are
likely to continue for early October. By Sunday, warmer than
average temperatures affect areas to the east and cover the Great
Lakes region and Northeast, while the northern Plains gets much
colder behind the strong cold front. Meanwhile, below normal
temperatures especially for highs are likely across the West due to
upper troughing and rainy/cloudy conditions.


Hamrick/Campbell


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
355 PM EDT Thu Oct 2 2025

Valid 12Z Sun Oct 05 2025 - 12Z Thu Oct 09 2025

***Heavy rain likely for portions of the coastal Southeast U.S.
through the weekend into early next week***

...General Overview...

A general upper ridge will be situated over the Intermountain West
along with a building upper ridge over the eastern half of the
nation. There will likely be a split flow pattern aloft, with the
southern stream showing increased potential for a closed upper low
to develop over California/Nevada by early next week. Meanwhile,
the northern stream will support an amplifying shortwave with an
attendant cold front, ushering in much colder temperatures across
the northern Rockies and northwestern Plains, and heavy snow for
the higher mountain ranges of Wyoming and Montana. Farther south,
tropical moisture interacting with a lingering stationary front
will likely produce periods of heavy rain and thunderstorms along
the east coast of Florida, and also portions of the central Gulf
Coast for the upcoming weekend.


...Guidance/Predictability Assessment...

The 12Z model guidance suite features good overall synoptic scale
agreement through the upcoming weekend and into Monday, with a
general deterministic model compromise used for fronts/pressures as
a starting point. Noteworthy model differences become apparent by
Tuesday morning off the Pacific Northwest coast with a storm system
originating from the Gulf of Alaska, and by Wednesday this results
in big differences across the northwestern quadrant of the nation.
The ECMWF and to a lesser extent the CMC bring in the upper trough
faster than the GFS and the GEFS mean. Therefore, the GFS group of
solutions has more of an upper ridge across the northern Rockies in
contrast to the CMC/ECMWF which are well to the east with that same
ridge axis. The latest AIFS guidance suggests a solution that is
closer to the GFS/GEFS and delays the arrival of the northwestern
trough, and has the ridge axis generally between the GFS and ECMWF
solutions. The ensemble means were increased to about 2/3rds by
next Thursday given the higher model spread and below average
forecast confidence by this time.


...Weather/Hazards Highlights...

Coastal portions of the central Gulf Coast and southeast Georgia
into Florida will remain in an active, wet pattern as tropical
moisture interacts with a stationary frontal boundary, and a
couple of weak low pressure centers may form on the front and
enhance the rainfall. A Marginal Risk of excessive rainfall was
maintained for both Day 4 and Day 5 along the eastern coast of
Florida, with urban locations most prone to flooding. The Day 4
Marginal remains for southeast Louisiana where heavy showers and
thunderstorms are expected along the coastline for Day 3 and
continuing into Day 4 for the southeast parishes. Locally, a two
day accumulation may exceed 3 to 4 inches of rain and with
additional rain expected, a Marginal Risk of excessive rainfall
will remain in place.

Multiple rounds of precipitation are forecast for the Western U.S.
as shortwaves within the upper trough and associated surface
fronts track eastward, especially for the Rockies and Intermountain
West. The higher elevations can expect moderate to locally heavy
snow
with the passage of the upper trough, especially for the higher
terrain of western Wyoming and southwestern Montana. Scattered to
widespread showers and thunderstorms tracking through the Plains
may have locally heavy amounts from Kansas/Nebraska northeast to
the Wisconsin/Illinois border. A Marginal Risk area remains valid
on Day 5 for the potential for locally excessive rainfall and
isolated instances of flash flooding.

In the temperature department, it will be rather warm by early
October standards across the Upper Midwest and Great Lakes region
Sunday, and this anomalous warmth reaches the Ohio Valley and
Northeast states for the beginning of next week with both highs and
overnight lows running 10-20 degrees above average in many cases.
There may be a few daily records on Sunday across the Upper Midwest
ahead of the cold front. Readings will turn sharply colder behind
that same front for the northern Plains with highs returning to
slightly below average with breezy conditions. This boundary is
expected to reach the East Coast by this time next week with a
return to more seasonable conditions then.

Campbell/Hamrick


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