532
FXUS02 KWBC 181956
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EST Tue Nov 18 2025

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

...Overview...

A closed upper low will dig into the Southwest late this week into
the weekend and eject an upper low/shortwave across the Central
U.S. towards the Mid-Atlantic. Locally heavy rainfall will be
possible across the Ohio and Tennessee Valleys as the shortwave
moves overhead, and a trailing cold front will extend shower and
thunderstorm chances south into the Lower Mississippi Valley as
well. The closed low will slowly shift towards the southern Plains
early next week, bringing heavy rainfall potential to the region on
Sunday and Monday. Meanwhile, a couple of upper level troughs will
swing across the northern tier of the nation, resulting in periods
of precipitation for the Northwest and Northeast.


...Guidance/Predictability Assessment...

Model guidance continues to show increasing agreement on the timing
of the closed upper low moving from the Southwest to the southern
Plains. The general consensus from the available deterministic
models favors a slower solution, which is consistent with the
previous WPC forecast. Though agreement has increased, there was
still some spread in the 00Z/06Z guidance. The 00Z ECMWF was on the
slower end of the spread, probably keeping the low over the
southern Plains too long next week, the 06Z GFS was on the faster
side with a slightly more progressive evolution, and the 00Z CMC
fell in between the ECMWF and GFS.

Given pretty good agreement with a reasonable amount of spread, a
general blend of the deterministic models provided a good starting
point for the afternoon forecast. The forecast placed slightly more
weight on the ECMWF to reflect a slower evolution of the Southwest
low, and ensemble means were added in increasing amounts for the
second half of the period to help smooth out model differences.


...Weather/Hazards Highlights...

An upper level low/shortwave will eject across the Central U.S.
towards the Mid-Atlantic late this week and will be accompanied by
a surface frontal system that will trigger widespread showers and
thunderstorms from the central/southern Plains to the Mid-Atlantic.
Locally heavy rainfall will be possible in the vicinity of the
surface low as it tracks across the Ohio and Tennessee Valleys, and
locally heavy rainfall may also be possible along a trailing cold
front moving across the Lower Mississippi Valley, though the
progressive nature of the cold front will likely limit flood
potential. Accordingly, the day 4 (Friday) Excessive Rainfall
Outlook depicts a Marginal Risk area for the Ohio and Tennessee
Valleys.

Meanwhile, a digging Pacific system will close off and offer some
enhanced precipitation chances to the West Coast on Friday. Given
the sensitivity of southern California after a few recent rain
events and the slower motion of the upper low and surface low
pressure system, there will be a Marginal Risk of excessive
rainfall for portions of southern California on Day 4 (Friday).
Light to moderate precipitation should spread across the Southwest
this weekend, and the potential for heavier rainfall amounts looks
to return to the south-Central U.S. Sunday into Monday. There are
signals that this could be a significant rainfall event, and this
potential will continue to be monitored.

Periods of precipitation will also be possible in the Northeast and
Northwest as a series of quick-moving upper troughs/shortwaves
sweep across the northern tier of the nation. There is still some
uncertainty with the amplitude and timing of a stronger upper
trough slated to dig into the Northwest 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. late this week and will include some
record temperatures, including some overnight minimum temperatures
10-20+ degrees warmer than normal, with moderated warming shifting
to the East late this week into the weekend. The north-Central
U.S. can also expect above average temperatures, especially this
weekend into Monday. Meanwhile, rounds of troughing in California
and over the West/Southwest will lead to below average highs about
5-10+ degrees below normal.


Dolan/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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