919
FXUS02 KWNH 110738
PREEPD

Preliminary Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
337 AM EDT Sat Oct 11 2025

Valid 12Z Tue Oct 14 2025 - 12Z Sat Oct 18 2025


...Strong coastal low with significant coastal flooding, beach
impacts, high winds and heavy rain lingers for the East Coast...

...Heavy rain and flash flooding remain a threat for the Southwest
early next week given anomalous tropical East Pacific moisture...

...California Heavy Rain Threat with early next week closed low...


...Overview...

A potent coastal storm looks to be a significant maritime hazard
from development this weekend through slow lift off the East Coast
into early-mid next week. Strong onshore winds also offer threats
of coastal flooding, rip currents, beach erosion, and heavy rain to
the Mid-Atlantic and Northeast. Meanwhile, upper troughing in the
West is drawing tropical moisture and remnant tropical energy
northward to fuel ongoing and widespread heavy rain and some flash
flooding into the Southwest and expect lingering activity through
early next week. This trough and additional rounds including closed
low/trough into/over the West will maintain cooler than average
temperatures as well as heavy precipitation chances with focus over
California to include Sierra to northern Rockies snows. Upper
ridging farther east over the south-central U.S. to east-central
U.S. next week meanwhile should allow for unseasonably warm
temperatures. Impulses and surface low/frontal system genesis and
fueling moisture with some rounds of rain in the north-central
U.S. directed around the ridge may increase later next week.

...Guidance/Predictability Assessment...

Models and ensembles offer reasonably similar mid-larger scale
pattern evolutions in an amplified and active weather pattern
across the lower 48. While forecast confidence is overall good with
respect to the sluggish main flow development and evolution,
significant variances and cycle-cycle continuity issues remain
within individual models, ensemble members and machine learning
guidance to focus impacts of the main embedded systems. This
includes for the difficult East Coast storm as early as short
range time scales as well as interations and details of the multi-
faceted mean upper trough impacting West. The WPC medium-range
product suite was mostly derived from a model composite for
Wednesday/Thursday before switching mainly to an ensemble mean
blend at longer time frames amid growing forecast spread. This
solution seems compatible with the National Blend of Models.

...Weather/Hazards Highlights...

A dangerous coastal storm will offer a wide array of threats up
the East Coast into early-mid next week. Into Tuesday/Wednesday,
a main heavy rain threat should gradually shift focus from coastal
Mid-Atlantic to Long Island and coastal New England. There remains
ample uncertainty with the inland extent of rain amounts given an
uncertain coastal storm evolution and ejection. There could be
potential heavy bands of rain, which combined with any urban area
could enhance flooding issues. In addition to heavy rain threats,
the combination of persistent and strong onshore winds, high surf,
and above normal tides may lead to significant coastal flooding
impacts along with strong rip currents and potential beach erosion.
See Key Messages being issued by WPC for the latest on this
system. The system may pull away from the coast into midweek.

Into early-mid next week, tropical moisture and energy is forecast
to work over the Southwest as Raymond lifts from the eastern
Pacific in the wake of Priscilla. Precipitable water values are
likely to be near max values for this time of year, with the
Southwest also in the right entrance region of the upper jet for
good dynamical support for heavy rain. However, a limiting factor
in terms of flash flooding could be somewhat limited instability
under widespread clouds and rain, which could limit rain rates.
Also, the current forecast shows the greatest rainfall totals to
the southeast of where the heaviest rain could fall in the short
range. WPC Excessive Rainfall Outlook Marginal Risk areas in place
for portions of Arizona and New Mexico/southern Colorado for Day
4/Tuesday may well linger near Arizona/Colorado Day 5/Wednesday.

Elsewhere, a moisture plume/atmospheric river is forecast to shift
southward across California early next week ahead of a cold front
to produce heavy rainfall and mountain snows for California. While
it could be relatively progressive, some instability could be
present and rainfall rates could reach an inch per hour, so still
have a Marginal Risk of excessive rainfall for parts of California
for the WPC Day 4 ERO centered on Tuesday. Enhanced to local heavy
mountain snows will also spread inland next week across the
north-central Intermountain West/Rockies associated with the mean
amplified upper trough. Farther east, rounds of precipitation are
possible in the Plains to Upper Midwest/Great Lakes region with
downstream system/energy translations next week as moisture and
instability pool with genesis of several wavy frontal systems on
the northern periphery of a warming south-central U.S. upper ridge.


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 (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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