964
FXUS02 KWBC 180752
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
252 AM EST Tue Nov 18 2025

Valid 12Z Fri Nov 21 2025 - 12Z Tue Nov 25 2025


...Guidance/Predictability Assessment...

Model guidance is reasonably consistent with an upper low pivoting
out from the Southwest to over the south-central U.S. Friday along
with an associated surface low pressure system. A little more
spread develops regarding the timing of weakening of this shortwave
over the weekend as it pushes east as well as overtop for embedded
shortwave timing differences within a mean northern stream upper
trough over the Great Lakes/Northeast. A GFS/ECMWF blend seemingly
provides reasonable system details consistent with predictability.

Upstream, recent models have been much less consistent with the
next upper trough in emerging southern stream flow likely forming
an upper low near California. Guidance now seems to be converging
in showing a just offshore position Friday into Saturday before
moving east, with a continued trend towards slower solutions. The
primary AI models have wavered some with this feature, but recent
CMC runs in particular have offered an outlier faster phased
trough, even compared to CMC ensembles. However, the latest 00 UTC
CMC model has finally jumped to the slower camp, bolstering
forecast confidence. To a lesser degree, the 00 UTC ECMWF/GFS
models continue to trend a bit slower. The earlier released WPC
forecast was mainly based on the GFS/ECMWF models Friday/Saturday
before transitioning Sunday and onward to slower camp and best
compatible GEFS/ECMWF ensemble mean guidance. WPC continuity was
reasonable and manual adjustments were applied to 01 UTC National
Blend of Models guidance to focus weighting on the slower plan.

...Weather/Hazards Highlights...

Amplified upper trough energy within separated southern stream
flow will eject from the Southwest to the south-central U.S. by
Friday. Height falls and lead moisture and instability return flow
into wavy frontal system and mesoscale features favors emergence of
a growing area of heavy rains and possibly strong thunderstorms
over the south-central U.S. into late week, shifting with reduced
impact with eastward progression into the weekend. Accordingly,
the Day 4/Friday the main low and frontal system should progress
faster and thus lead to lower rain totals, but a Marginal Risk
still seemed warranted for isolated flooding across the Lower
Ohio/Tennessee Valleys and also with trailing convection down
across the Lower Mississipi Valley back towards Houston prior to
frontal passage whose arrival over The South also moderates heat.

Meanwhile upstream, a digging east Pacific system will close off
and offer some enhanced precipitation chances to the West Coast
into Friday. Given the sensitivity of southern California after a
few previous rain events recently and the slower motion of the
upper low/resulting surface low pressure system, have maintained
a Marginal Risks for the Day 4/Friday ERO. Light to moderate
precipitation should spread across the Southwest this weekend and
potenmtial for heavier amounts may return back in to the south-
central U.S. particularly into Sunday/early next week to monitor.

There is also amplitude and timing uncertainty with a farther
upstream system slated to dig from the Gulf of Alaska to the
Northwestern U.S. into early next week. However, favored ensemble
means offer a compromise solution that still has a dynamic upper
trough/surface system that spreads some moderate to heavy
precipitation into the Northwest to include enhanced mountain
snows inland to the Rockies later period with progressive flow.

Pre-frontal temperatures will linger much warmer than average for
portions of the southern U.S. into late week will include some
record temperatures including some overnight minimum temps 10-20+
degrees warmer than normal, with moderated warming shifting to the
East late week/weekend. The north-central U.S. also can expect
above average temperatures especially this weekend into Monday.
Meanwhile, rounds of troughing in California to the West/Southwest
will lead to below average highs about 5-10+ degrees below normal.

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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