418
FXUS02 KWBC 020644
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
144 AM EST Fri Jan 2 2026

Valid 12Z Mon Jan 05 2026 - 12Z Fri Jan 09 2026

...Additional rounds of rain and mountain snow for California
early next week...

...Overview...

With troughs off both coasts, flow across the CONUS itself should
be pretty zonal to start the period on Monday, though with a couple
of north-central to northeastern U.S. clipper systems. Troughing
off the West Coast may close off into an upper low off California
before it moves inland by mid-week. This likely brings additional
rounds of possibly heavy rains and mountain snows for California.
This shortwave/low should shift inland across the Southwest and
eventually the central states as additional energy dives down the
West Coast late week. This next wave should allow for a fairly
amplified pattern to end the work week, with strong ridging along
the East Coast and deeper troughing moving through the West. This
brings an increase in precipitation coverage across the Central
U.S. for late week, and well above normal temperatures for the
East.

...Guidance/Predictability Assessment...

Model guidance generally shows good agreement on the large scale
pattern, but with significant uncertainty still in the details and
timing of individual systems. Beginning of the period for the
northern tier should be dominated by shortwaves. There are some
timing differences with these, which do impact surface low/frontal
placement and temperatures, but it is difficult to pick out
outliers in such shallow flow. A multi-model blend should handle
this aspect of the forecast.

The main forecast concern and source of uncertainty for the medium
range will be with troughing off the West Coast on Monday, which
shows some increasing agreement may close off an upper low off
California. Timing difficulties become evident as early as Tuesday,
with the UKMET and ECMWF still on the faster side of the guidance
envelope (though the new 00z run did come in slightly slower). The
GFS is slower, but the new 00z run tonight did trend faster than
the previous run. Prefer a solution for now closest to the ECMWF
and CMC, which has support from the AI guidance and the ensemble
means.

WPC trended quickly towards the ensemble means for the latter half
of the period as this system translates inland and troughing
becomes reestablished across the West with the next wave. There is
a lot of uncertainty in the details with the evolution of this and
also how strong the initial shortwave is as it pushes through the
Central U.S. and the Midwest.

...Weather/Hazards Highlights...

Shortwaves rounding the eastern Pacific/western U.S. trough will
provide support for possibly a few rounds of weak to moderate
atmospheric rivers and precipitation in the West into next week.
With one moisture plume exiting the region at the very end of the
short range, the next one should move into California by Monday.
Guidance continues to focus mostly on northern to central
California for better rainfall potential, but some moderate QPF may
make it as far south as the sensitive Transverse Ranges. Thus,
continue to show a marginal risk on the Day 4/Monday Excessive
Rainfall Outlook from northern California to the Transverse Range.
Heavy snow is likely for the higher terrain of the Sierra. More
modest precipitation amounts are expected farther north in the
Pacific Northwest and farther east into the Intermountain West.
Precipitation is forecast to continue into Tuesday across the
Southwest, while a northern stream wave leads to increasing Pacific
Northwest precipitation as well.

Elsewhere across the country, a couple of clipper systems are
forecast to track from the Upper Midwest to the Great Lakes and
then the Northeast during the period. These relatively weak systems
could produce a swath of mainly light snow and perhaps some mixed
wintry precipitation along the southern portion of its track. Also
by midweek, troughing tracking into the Rockies/High Plains from
the West could tap into Gulf moisture and lead to increasing rain
chances (and perhaps some thunderstorms) across southern/central
parts of the Plains and Mississippi Valley into the Mid-South.
Coverage and amounts remain highly uncertain given differences in
the larger pattern.

Temperatures are likely to be much warmer than average across a
wide expanse of the country into much of next week, especially
across the Plains, where temperature anomalies of 15 to 30 degrees
above average will be common. Daily records for warm lows and highs
could be set across the Intermountain West and Plains.
Unseasonably warm temperatures will gradually expand and spread
eastward through the week, bringing anomalies of +15 to +25 degrees
to the Mississippi Valley and eventually +10 anomalies to the East
Coast, after a colder than average start to the week across the
Northeast. The West/Southwest should remain near or below normal
much of the week as the pattern turns more amplified and troughing
develops.


Santorelli


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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