473
FXUS02 KWNH 290632
PREEPD

Preliminary Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
231 AM EDT Tue Sep 29 2026

Valid 12Z Fri Oct 02 2026 - 12Z Tue Oct 06 2026


...Major Multi-day South-Central to East-Central U.S. Excessive
Rainfall/Flooding threat this week with tropical connections...


...Guidance/Predictability Assessment...

Guidance overall remains agreeable on the synoptic split pattern
over the nation comprised of an energetic and progressive northern
stream and an impactful southern-stream upper-low/surface systems
set to slowly work over the south-central U.S. this week. Forecast
spread and predictability seem improved with lastest guidance.
Favor a broad model/ensemble/machine learning guidance composite
that should tend to mitigate lingering smaller scale variances as
consistent with individual predictability. The main upper-low will
begin to weaken/transition into an open wave and become absorbed
within the northern stream as a potent cold front catches lead wavy
frontal boundaries over the south- central U.S.. Moderating frontal
surges early and later period will impact the transition of an
expected prolonged period of heavy rainfall from the south-
central to eastern U.S. this week and then the suppressing and
confinment of heavy rain focus to the southern/southeast U.S. into
next week. The 01 UTC NBM seemed to provide a good compromise QPF.

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

A closed upper trough/low with wavy frontal systems will shift
slowly eastward over the South-central U.S. later week in southern
stream split flow. Widespread excessive rainfall/flooding threats
over the South-central U.S. will slowly shift across the East-
central/Southern U.S. as further focused by Gulf/Southeast Coast
frontal genesis. This event will be fueled by a tropical moisture
connection from current East Pacific Hurricane Polo set to weaken
with landfall/track across Baja California and Northwest Mexico.
There will also develop an increasingly deep and protracted lead
Gulf inflow pattern with tropical influence. This expansive multi-
day threat should prove slow to progress late week wedged between
upper ridges over the Southwest and Southeast U.S.. Activity focus
will then slowly work downstream into the East. Expansive WPC
Excessive Rainfall Outlook Marginal Risk areas with embedded Slight
Risk areas cover the Southern Plains through the Tennessee Valley
and Central Gulf Coast states then into the Appalachians and
vicinity for the Day4/Friday and Day5/Saturday periods.

Meanwhile, systems within a more progressive/zonal mean northern
stream flow will support passage of a series of wavy frontal
systems across the U.S. northern tier of the nation from the
Northwest through the Northeast this week. These will act to
provide a northern rainfall shield focus and over-running for
lifting moisture/clouds and deliver moderating post-frontal fall
temperatures to spread/sink southward with high pressure settling.
This scenario will also act to focus/confine a lead heavy rainfall
main threat axis to The South and the Southeast early next week.

Accordingly, the WPC Excessive Rainfall Outlook (ERO) offers
anomalously large Marginal and Slight Risk areas from the South-
Central to East-central U.S. on Day4/Thursday and Day 5/Friday. The
Day 4 also includes a Southern Plains Moderate Risk. Activity will
progress slowly from the East-central U.S. to the East later
period with the greatest confidence in additional heavy rainfall
shifting from the Southern Plains/Middle Miss Valley to the
Tenn/Lower Miss Valleys, as well as possibly into the northern Mid-
Atlantic. These EROs and supporting WPC Hazards Outlook areas are
all linked below.

Upper-ridging will lead to a period of above-average temperatures
over the western U.S. including highs into the 90s and low 100s
for central/southern California and the Desert Southwest. Some heat
may reach hazardous levels for southern California this weekend.

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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