668
FXUS02 KWBC 100800
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri Oct 10 2025

Valid 12Z Mon Oct 13 2025 - 12Z Fri Oct 17 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 is forecast to continue to lift slowly
northward up the East Coast into early next week. This coastal low
may bring strong onshore winds causing coastal flooding, rip
currents, beach erosion, and heavy rain to the Mid-Atlantic and
Northeast. Meanwhile, upper troughing in the West will draw
tropical moisture and remnant tropical energy northward and bring
potentially widespread heavy rain and some flash flooding into the
Southwest early next week. This trough and another round with a closed
low/trough into the West will maintain cooler than average
temperatures as well as heavy precipitation chances with focus over
California to include higher elevation Sierra snows. Upper ridging
should prevail farther east in the central U.S., allowing for
unseasonably warm temperatures, and 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 bolstered
with respect to the stubborn main flow, significant variances and
cycle to cycle continuity issues remain within individual models,
ensemble members and machine learning guidance to focus impacts of
the main embedded systems, especially the difficult East Coast
storm. Accordingly, the WPC medium-range product suite was
primarily derived from a composite of overall best clustered
guidance of the 12 UTC ECMWF/Canadian, GEFS/ECMWF ensemble means
and compatible 01 UTC National Blend of Models along with WPC
continuity. The 00 UTC GFS trended more in line with this favored
composite over time compared to the 18 UTC GFS.

...Weather/Hazards Highlights...

A dangerous coastal storm will offer a wide array of threats up
the East Coast early-mid next week. Heavy rain focus may lift from
the Mid-Atlantic toward the Northeast with main focus slated into
Tuesday 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. Given
uncertainty and local Excessive Rainall outlook collaboration,
opted to maintain a WPC Day 4/Tuesday Marginal Risk for the coastal
Mid-Atlantic to Northeast. 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.

Early next week, another round of tropical moisture and energy is
forecast to enter the Southwest as newly formed Raymond in the
Pacific follows in the wake of Priscilla. Precipitable water values
are likely to be near max values for this time of year, and PWs of
1.5 inches would even be in the 75th-90th percentile during the
typical peak of monsoon season in early-mid August. The Southwest
should also be 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. Thus continue to hold off on any Moderate Risks at this
time, but Slight Risks are in place across portions of Arizona and
New Mexico for the Days 4-5 (Sunday and Monday) Excessive Rainfall
Outlooks, and WPC will continue to monitor for potential upgrades,
with the greatest current threat appearing to center across
southeastern Arizona.

Elsewhere, the rounds of upper troughing in the West will promote
precipitation, including higher elevation snow. Moderate to heavy
snow is likely for the Cascades/northern Rockies Sunday, and then
moving into the Sierra Nevada Monday-Tuesday. Lighter snow is
possible for the Intermountain West/northern Rockies with a second
amplified/closed trough upstream. Additionally, a moisture
plume/atmospheric river is forecast to shift southward across
California early next week ahead of a cold front. While it could
be relatively fast-moving, some instability could be present and
rainfall rates could reach an inch per hour, so have a Marginal
Risk of excessive rainfall drawn up for parts of California for the
WPC Day 4/5 EROs centered on Monday/Tuesday. Farther east, rounds
of precipitation are possible in the Plains to Upper Midwest and
Great Lakes region with downstream system/energy translations next
week out from the West/Rockies as lead moisture and instability
pool with genesis of several wavy frontal systems on the northern
periphery of a warming south-central U.S. upper ridge.

It still remains generally the case that cooler than average
temperatures are forecast particularly for highs in the West
through next week underneath renewing troughing. Meanwhile, upper
ridging in the central U.S. will lead to warmer than average
temperatures. Highs in the 70s reaching as far north as the Dakotas
Sunday will be 15-20 degrees above average. Temperatures there
should cool behind a cold front into the workweek, but temperatures
of 10 to 15 degrees above normal will last several days farther
south, as unseasonably warm highs in the 90s continue for Texas and
Louisiana. Warmer than average temperatures are forecast to
stretch into the Midwest. Some cool highs along the East Coast
early week should moderate close to normal as the week progresses.


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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