864
FXUS02 KWBC 031948
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
348 PM EDT Fri Oct 3 2025

Valid 12Z Mon Oct 06 2025 - 12Z Fri Oct 10 2025


...General Overview...

Upper ridging over the Eastern Seaboard will shunt south and shift
west over the Gulf Coast Monday through Tuesday where it will
persist through next week. Meanwhile a more transient upper pattern
continues over the central/northern states with a deep trough
swinging through the Great Lakes Tuesday into Wednesday. A cold
front and Canadian surface high pressure follows this trough with
cooler than normal temperatures tracking from the northern Plains
Tuesday to the Northeast by late week. Farther south, tropical
moisture interacting with a lingering stationary front may produce
heavy thunderstorms over Florida, Georgia, and into South Carolina
Monday. Finally, deep upper troughing looks to amplify along/off
the Pacific Northwest coast later next week.


...Guidance/Predictability Assessment...

Updated deterministic and ensemble guidance is well clustered for
the first part of the period early next week. A transition looks to
occur from mean ridging over the eastern U.S. and mean troughing
over the central/western U.S. to a trough/ridge/trough pattern from
the East to West Coasts. Guidance begins to diverge mid-week as
the ECMWF and ECens mean remain more progressive with the upper-
trough moving through the eastern U.S. as well as with an upper-
trough approaching the western U.S. from the northeastern Pacific.
Both pieces of guidance are also more positively tilted with this
upper-trough, whereas the GFS/CMC and their centers respective
means are more meridional and feature a stronger ridge building
north over portions of the western U.S. while retaining the upper-
trough/low father west either just along or offshore the West
Coast. This was a trend that has continued from the prior WPC
forecast. They also suggest the low will cutoff from the mean flow,
with the deterministic guidance a bit more aggressive with this
solution than the ensemble means. Interestingly, the suite of AI
guidance from the EC also generally leans towards the
GFS/CMC/respective means with most solutions differing from the
ECMWF/ECens. This also includes the progressive nature of the
eastern trough as well. One other layer of uncertainty will be the
potential for short-wave energy under the central U.S. ridge and
associated precipitation chances, though these features naturally
have lower predictability at this timeframe. The ECMWF is less
aggressive with this energy, with the means not surprisingly less
pronounced as well. The updated 12Z guidance generally continued
all noted trends.

The updated WPC forecast began with a composite blend of the 00Z
ECMWF/CMC and 06Z GFS guidance given the noted good clustering.
Thereafter, the ECens mean was swapped for the ECMWF given a less
notable difference compared to the other guidance while a
contribution from the GEFS mean was also added as uncertainty
increased with respect to shortwave energy over the central U.S.
The blend for the latter part of the period relied heavily on the
GEFS mean, with an additional contribution from the CMC ensemble
mean, which leans towards the more meridional guidance and also
represented some of the solutions from the AI guidance good as
well. This also helped keep some continuity from the prior WPC
forecast by not shifting even further west/more amplified as the
GFS/CMC.

Guidance has also continued a trend in showing stronger ridging
and less QPF not only for SC/GA but also along portions of the
Florida Coast. While tropical moisture may lead to some heavier
rainfall, trended downward with the broader numbers in the updated
QPF forecast compared to the NBM considering all guidance was
indicating lower amounts.


...Weather/Hazards Highlights...

Despite a downward trend in Southeast QPF Monday/Tuesday, the Day
4 ERO remains Marginal with some shifts south and inland. The
moisture anomalies are now generally focused over the FL Peninsula
into GA/AL, so this area will continue to need to be monitored for
excessive rain. Thunderstorm activity looks to linger across the
region through much of the week.

A cold front ahead of a powerful trough pivots over the central
Plains into the Midwest Monday. The risk of repeating heavy rain
warrants maintenance of a Marginal Risk for Day 4/Monday from
central KS through the IL/WI border. Additional storms are expected
ahead of the front across the Interior Northeast southwest into
the Ohio Valley Day 5/Tuesday. Despite what should be somewhat
limited instability, moisture pooling ahead of the front will
support the chance for some heavier rainfall and at least an
isolated risk for flash flooding for more sensitive areas across
the Upper Ohio Valley/Appalachians vicinity, so a Marginal Risk has
been included here as well.

Moisture anomalies increase over New Mexico Tuesday from continued
surges of moisture from the western Gulf onto a frontal wave that
is stalled over northern NM. Introduced a Day 5 Marginal Risk for
much of NM. A Slight Risk was considered, but given the notable
run- to- run changes in guidance a Marginal will suffice for now. A
lot of uncertainty remains with the potential for an influx of
tropical moisture from the Pacific into the Desert Southwest mid-
to late next week, but at least some increase in thunderstorm
activity should be expected. An upper-trough approaching from the
northeastern Pacific will bring increasing precipitation chances to
the Pacific Northwest by mid- to late next week as well.

Temperatures will be below normal under troughing over the
Intermountain West Monday with that cooler trend shifting east with
a cold front over the Northern Plains Tuesday, the Midwest
Wednesday, and the Eastern Seaboard for Thursday/Friday. Meanwhile,
ridging over the Gulf Coast will maintain above normal
temperatures over Texas and Louisiana through next week.


Putnam/Jackson


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


















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