335
FXUS02 KWNH 300702
PREEPD

Preliminary Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 AM EDT Wed Sep 30 2026

Valid 12Z Sat Oct 03 2026 - 12Z Wed Oct 07 2026


...Major South/Southeast U.S. Excessive Rainfall/Flooding threat
with tropical connections this weekend and early-mid next week...


...Guidance/Predictability Assessment...

Guidance forecast spread continues to improve through medium-range
time scales, again bolstering confidence. A favored composite of
overall compatible model, ensemble mean and machine learning
guidance seems to offer a solid forecast base for consistent threat
messaging and products mainly in line with the National Blend of
Models. Greater uncertainty remains with smaller scale convective
interaction and local focus. The composite will tend to mitigate
variance as consistent with individual feature predictability.


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

A main upper trough and wavy/wet frontal system will shift slowly
eastward from the South-central U.S. into the weekend in separated
southern stream flow. Leading excessive rainfall/flooding threats
working into the South/Southeast will be fueled by tropical
moisture from the remnants of Hurricane Polo and an increasingly
deep and protracted lead Gulf inflow pattern with tropical
influence. WPC Excessive Rainfall Outlook Marginal Risk areas with
embedded Slight Risk areas cover from coastal Texas through the
Gulf Coast states and Tennessee Valley/southern Appalachians then
the Southeast for Day4/Saturday and Day5/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 will act to provide a northern rainfall
shield focus and over-running boundary for lifting moisture/clouds
before delivering a post-frontal fall temperatures/drier airmass
southward with high pressure settling. This will act to shift
southward and confine the lead focus for heavy rainfall/flooding
threats down over the South/Southeast through early-mid next week
to monitor given the ample repeat activity threat.

Elsewhere, 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/early next week.


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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