Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
317 PM EST Thu Dec 30 2021

Valid 00Z Fri Dec 31 2021 - 00Z Sun Jan 02 2022

...More heavy mountain snow to overtake much of the Intermountain West to
close out 2021; bitterly cold wind chills to stick around in the Northern
Rockies and Northern Plains; Slight Risk for Excessive Rainfall in
Southern California today...

...Record breaking Spring-like temperatures in the South to reach the
portions of the East Coast; Slight Risks for severe storms and Excessive
Rainfall on Friday...

...Both winter weather and severe weather possible to kick off the new
year this weekend...

The continental U.S. remains under the influence of prolonged troughing in
the Intermountain West and ridging in the Southeast. The next
weather-making system embedded within the large-scale trough has pushed
inland over the Pacific Northwest this afternoon, which will focus another
moderate-to-heavy snow chances throughout much of the Intermountain West
today and tomorrow as it dives toward the Great Basin. Further south, a
developing storm system off the California coast will continue to usher
Pacific moisture into Southern California and the Southwest today and
Friday. Locally heavy rainfall rates supporting 1-2 inches of rainfall
could cause isolated to scattered flash flooding in Southern California
(Slight Risk today in the Los Angeles metro area) and south-central
Arizona (Marginal Risk for Excessive Rainfall on Friday), while also
ushering in a round of moisture into the southern Rockies. This combined
with the arrival of another Arctic air-mass makes for another period of
heavy mountain snow Friday night. By Saturday morning, mountain ranges
such as the Cascades, Sawtooth, Wasatch, and both the central and southern
Rockies can expect 1 to 2 feet of snow with totals exceeding 3 feet in the
highest elevations of Utah and Colorado. A myriad of winter weather
alerts; from Warnings and Watches to Advisories, have been issued in these
areas. Precipitation aside, another injection of frigid Arctic air causes
temperatures to plummet throughout the West on Friday and into Saturday
morning, with sub-zero temperatures expected from the Upper Mississippi
Valley to the Northern Rockies. Wind Chill Warnings and Advisories remain
in effect for the far North Central U.S. through Saturday, with more
bitterly cold wind chills anticipated through New Year's weekend.

Farther east on the warm side of the front, abnormally warm and humid
conditions will stick around in the Southeast with considerably milder
conditions spreading as far north as the Northeast by New Year's Day.
Numerous record warm lows and highs are expected from the Gulf Coast to
the northern Mid-Atlantic through Saturday morning. Moreover, the
troughing in the West and the strong ridge of high pressure over the
Southeast are working together to funnel rich Gulf of Mexico moisture into
the Mid-South late Friday. A Slight Risk for severe weather and a Marginal
Risk of Excessive Rainfall over parts of the Southeast today, but the next
developing storm system in the Plains will set the stage for another
active day of severe weather from North Texas to the southern Appalachians
on Friday. Ample moisture and instability is also present to support high
rainfall rates, making flash flooding a concern in the Middle Mississippi
and Ohio/Tennessee River Valleys. As a result, Slight Risks have been
issued for both severe storms and flash flooding in these regions on
Friday, with concerns for nocturnal severe weather and localized flooding.

As the storm system responsible for Friday's potential severe weather and
flash flooding event emerges into the South Central U.S. Saturday morning,
the New Year is forecast to start off in wintry fashion as measurable
snowfall and an icy wintry mix are expected to paint a swath of widespread
hazardous travel conditions New Year's Day from the Central Plains to the
Great Lakes. Several inches of snowfall are likely with this impending
storm, with 6-8+ inches of snowfall possible within heavier snowfall
bands. All the while, significant mixed precipitation is possible south of
the heavy snow activity, leading to widespread moderate potential winter
storm impacts over the Central Plains and Midwest per the WPC Winter Storm
Severity Index. Meanwhile, within the storm's warm sector, another busy
day of severe weather and Excessive Rainfall is likely in the Mid-South,
with another round of severe weather and Excessive Rainfall Slight Risks
hoisted from the Ohio/Tennessee River Valleys southwestward toward
ArkLaTex. Residents in these regions are encouraged check for the latest
forecasts from their local NWS offices and National Centers as a plethora
of weather hazards strike to kick off 2022.

Asherman/Mullinax


Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php