126
FXUS02 KWBC 101952
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
252 PM EST Mon Nov 10 2025

Valid 12Z Thu Nov 13 2025 - 12Z Mon Nov 17 2025

...Atmospheric River to move south across California on Thursday
bringing a threat of heavy rain and mountain snows...

...Overview...

Lake effect precipitation on Thursday with the continues upper
troughing in the Northeast. Temperatures are marginal, but some
snow accumulation is likely in the higher terrain of upstate NY and
northern New England. Upper ridging in the West will shift to the
central part of the country which will usher in much warmer than
average temperatures into the weekend. By Thursday into Friday
troughing will move into the West directing an impactful
atmospheric river into California. This troughing subsequently
moves and transitions with lingering uncertainty to the
Southwest/Rockies and Plains over the weekend.

...Guidance/Predictability Assessment...

Large scale trough is expected to move into the West by the
weekend, however there remains significant uncertainty regarding
the exact evolution of this troughing as it moves into the
Southwest and eventually the Plains. Essentially there are two
possible outcomes...one being a more phased/stronger trough that
ends up more progressive in pushing a front and eventual strong low
into the Plains...and the other more of a split trough, with the
southern stream energy cutting off resulting in a slower eastward
progression. The previous WPC forecast leaned solutions that
indicated there would be a slower eastward progression across the
Plains. Today`s approach utilized the new NBM/EC/EC ensemble
means/CMC/CMC means/previous QPF forecast along with some GFS/GEFS
means. This helped reduce the waffling of location of the
impactful weather and provide a sense of continuity.


...Weather/Hazards Highlights...

An atmospheric river and cold front will be surging
onshore/southward through California Thursday with model consensus
supporting moderate to strong IVT values with this system, along
with strong convergence along the front and favorable upper
support. Portions of southern California have the potential to pick
up 1 to 3+ inches of rainfall and heavy, wet mountain snows at
higher elevations. Given the moisture influx and instability
expected there will be an elevated threat for flash flooding for
southern California and near the foothills, but that may be
limited with how progressive the front ends up being. A Marginal
risk for excessive rainfall will be maintained for Day 4 - an
upgrade to a Slight risk is a possibility for the favored terrain
of southern CA, especially if confidence continues to increase in
the heavy rain rate potential with further updates. It should also
be noted that a more offshore and slower evolution of the closed
low is still a possibility (albeit seemingly a lower probability
outcome at the moment), with the AIFS showing this evolution pretty
consistently. This evolution would prolong the rainfall and
increase the flood risk, so will need to continue to monitor
trends.

Confidence on specifics for this system this weekend and beyond
continue to be below average as the run to run vacillationwhether
it will be a quicker advancement through the Plains or a slower,
closed progression. Which in turn would have substantial impacts to
location of sensible weather and QPF amounts. The quicker
solutions would have supported a widespread convective threat from
the Plains into the MS Valley by Saturday, with rain spreading
into the OH valley and Mid-atlantic Sunday into Monday. The slower
and more closed off runs focus the convective threat over the
Southern PLains into the lower MS Vally later Saturday into Sunday.
These latter solutions would also likely result in more of a
significant weather threat, as the closed low has impressive large
scale forcing and is able to tap into moisture from the Gulf. Would
expect a stronger thunderstorm threat to exist in this scenario
with flash flooding a risk. The latest runs hint at leaning toward
favoring the slower, more closed off scenario.

Higher confidence persists in regards to above seasonal normal
temperatures from the Intermountain West into the Plains on
Thursday, spreading east across the Plains and into portions of the
MS and TN valley Friday into the weekend. Each day the maximum
temperatures are expected to reach 10 to 20 degrees above average.
The timing of the cold front bringing colder temperatures over the
West and eventually the Plains is of lower confidence and related
to the uncertainty with the troughing evolution.

Campbell/Chenard


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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