812
FXUS02 KWBC 012002
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
402 PM EDT Thu Oct 1 2026

Valid 12Z Sun Oct 04 2026 - 12Z Thu Oct 08 2026


...Lingering Gulf Coast/Southeast U.S. Excessive Rainfall/Flooding
threat Sunday into Monday...

...Long Duration Late Season Heat Wave Expected for California...


...Guidance/Predictability Assessment...

Predictability through the period continues to be above average as
as the deterministic/AI/mean guidance all remain well clustered on
the overall synoptic pattern. An amplifying northern stream upper-
wave over the eastern U.S. will help to drive two frontal
boundaries south towards the Atlantic/Gulf Coasts this weekend and
into early next week with a broad area of high pressure settling in
their wake. Meanwhile, an upper-ridge will remain in place over
the western U.S. Thereafter, another northern stream upper-
wave/surface frontal system will traverse the northern
tier/southern Canada bringing another cold front south through the
Plains, though with Gulf moisture suppressed by the frontal
boundaries to the south expect precipitation chances overall
outside of the southeastern U.S/Gulf Coast will remain limited.
Run-to-run continuity also remains good as the updated WPC forecast
only saw some small system progression-related adjustments. QPF
amounts/coverage across the southeastern U.S./Gulf Coast remains
the most uncertain part of the forecast. The deterministic/AI and
ECens mean have all trended faster with the front progression,
bringing the arcing axis of heaviest QPF to the Atlantic/Gulf
Coasts by late Sunday/early Monday compared to the GEFS mean that
has a broader precipitation shield further to the north and west
over the Southeast. This feature notably contributes to the NBM
forecast, so generally favor blending in a contribution from the
deterministic/AI guidance through at least the Sunday-Tuesday
timeframe for QPF. Thereafter, the heaviest QPF axis is more
uncertain but due to spread increase as well as a bi-modal
distribution between the NBM/means (favoring northern Florida) and
AI guidance (favoring South Florida), so feel the NBM is sufficient
as is for now. The rest of the updated WPC forecast package used a
composite blend of the deterministic/AI guidance through most of
the period given good clustering, with the ECens mean replacing the
time- limited UKMET at the end of the period. This preserved good
WPC forecast continuity.


...Pattern Overview and Weather/Hazards Highlights...

A main southern stream upper trough and wavy/wet frontal system
will shift slowly southward across the southeastern to south-
central U.S. this weekend. Leading excessive rainfall/flooding
threats will work south/southeastward as fueled by deepened Gulf
inflow. A WPC Excessive Rainfall Outlook Marginal Risk area from
coastal Texas through the Gulf Coast states and the Southeast for
Day4/Sunday also has an embedded Central Gulf Coast Slight Risk
area is in place lingering onshore into Monday. Day 5 Marginal
Risks include far south Texas as well as the central Gulf
Coast/Florida Panhandle Sunday. Meanwhile, systems within a more
progressive northern stream flow will support passage of a series
of wavy frontal systems down from the U.S. northern tier. These
fronts with stream phasing over time with northern stream
amplification will broadly deliver fall temperatures and a drier
airmass southward along with high pressure onset. This will further
act to shift southward and confine the lead focus for heavy
rainfall/flooding threats with slow/wavy frontal sag through the
Gulf Coast/Florida and more offshore into the Gulf next week.

Elsewhere, upper-ridging will lead to a period of above-average
temperatures over the western U.S. While these temperatures will
generally be pleasant despite being unseasonably warm for early
Fall for most of the region, much hotter temperatures into the 90s
and low 100s are expected for central/southern California and the
Desert Southwest. This prolonged heat wave will be dangerous to
anyone without adequate cooling hydration, specifically from the
Bay Area south to southern California. See WPC`s Key Messages for
the California October Heat Wave for additional information.

Putnam/Schichtel


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, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
are at:

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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