941
FXUS02 KWBC 280707
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
307 AM EDT Mon Sep 28 2026

Valid 12Z Thu Oct 01 2026 - 12Z Mon Oct 05 2026


...Major Multi-day South-Central to East-Central U.S. Excessive
Rainfall/Flooding threat fueled by moist tropical connections...


...Guidance/Predictability Assessment...

Guidance shows a reasonably similar larger scale pattern evolution.
Forecast confidence is above average for the development of a
multi-day heavy rainfall/flooding event with tropical moisture
connections into this period with a focus to slowly work from the
South-central through East-central U.S.. However, there remains
ample smaller scale embedded system timing, convective rainfall and
tropical moisture focus/interactions issues that grow over time,
especially by next weekend. Accordingly favor a blend of still well
clustered model and ensembles later week before increasingly
embracing the still compatible ensemble means by next weekend. This
plan seems in well in line with with uncertainty growth and best
allows for consistent threat messaging and forecast products.

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

A closed upper trough/low with wavy frontal systems will shift
slowly eastward from the Southwest U.S. to the South-central U.S.
mid-later week in southern stream split flow. Widespread excessive
rainfall/flooding threats over the Southwest/Southern Rockies
states during the short range will then focus over the South-
central U.S. then 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 forecast to weaken with landfall/track across Baja California
and Northwest Mexico over the next couple of days. 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/next weekend wedged
between upper ridges over the Southwest and Southeast U.S..

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 additional heavy rainfall threats likely. These EROs
and supporting WPC Hazards Outlook areas are all linked below.

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.


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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