Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
153 PM EST Sun Jan 19 2025

Valid 12Z Wed Jan 22 2025 - 12Z Sun Jan 26 2025

...Bitterly cold temperatures to continue through about Thursday
for parts of the East and the South...


...Overview...

Troughing over the Eastern Seaboard to start the period should
shift east helping to gradually moderate bitterly cold temperatures
to start the period. Reloading of the trough is expected though as
another amplified pattern develops upstream across the Central to
Eastern U.S. Thursday-Friday. Ridging over the West should shift
quickly inland late week as an amplified shortwave into the
Northwest drops down the coast and produces positively tilted
troughing with possible southern stream closed low development over
southern California/the Southwest into next weekend. Much of the
early period precipitation should be light in nature and confined
to the northern tier, Florida, and perhaps the coastal parts of the
East. The developing trough atop the West is expected to lead to
some light to moderate precipitation across the West Coast to the
Great Basin and Rockies late week into next weekend, while moist
inflow returns to the Mid-South for rain potential next weekend and
some possible snow toward the Great Lakes.


...Guidance/Predictability Assessment...

Model guidance shows generally good agreement on the large scale
pattern through the entire extended range period, but uncertainty
on the details remains. A multi-model blend worked well for upper
troughing deepening across the Plains/Mississippi Valley around
Thursday and moving east late week. With lows offshore in the
western Atlantic that may produce precipitation along the East
Coast, the 00Z CMC seemed to be a western outlier compared to
consensus and spread more precipitation into New England, but the
12Z CMC shifted much farther offshore.

Models are in better agreement today compared to a day ago with
the track and timing of the next trough digging into the Northwest
around Friday and shifting south. Its evolution into the weekend is
still in question though, as guidance varies with how much energy
may separate into the southern stream. As of the 00Z/06Z model
runs, most trended away from producing a closed low atop the
southwestern U.S. by Sunday, other than the CMC. The AI/ML models
were steady with a closed low though. The incoming 12Z
GFS/CMC/ECMWF now all show a closed low so expect the next forecast
to trend back that direction, but it may take additional time for
models to completely stabilize before settling on a solution.
Regardless, with the reasonable agreement in the overall pattern,
maintained a majority of deterministic models in the blend through
the period but with some inclusion of the ensemble means.


...Weather/Hazards Highlights...

Bitterly cold temperatures moving into the central U.S. and the
Midwest early this week should moderate by the start of the period
Wednesday and become near to slightly above normal. Much colder
than normal temperatures by 20-30 degrees will continue for parts
of the East and South and could set daily record low max and min
temperatures. Though still chilly Thursday and Friday, temperatures
will gradually moderate in the South and East, reaching near
normal this weekend. Meanwhile, California to the Great Basin can
expect warmer than normal temperatures through the rest of the
workweek before the West cools underneath the upper trough next
weekend.

Precipitation across the lower 48 during the medium range period
should be relatively quiet. Some modest rains are possible across
Florida associated with lingering frontal boundaries Wednesday and
Thursday, with rain or light snow up the Southeast to Mid-Atlantic
to Northeast coast with weak surface lows lifting northward. A
couple rounds of light precipitation are forecast from the Northern
Plains to Midwest/Great Lakes and Ohio Valley as cold frontal
clipper systems move through. More widespread rain and mountain
snows will move into the West by Thursday-Friday and shift south
with time, hopefully providing some much needed rain to Southern
California next weekend. Farther east, moisture return into the
Lower Mississippi Valley to Tennessee/Ohio Valleys is expected into
next weekend for some modest rain amounts, with snow possible
farther north across the Great Lakes.


Tate/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