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

Valid 12Z Thu Dec 30 2021 - 12Z Sat Jan 01 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 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 upper level
disturbance to round the base of this trough is set to enter the
Northwestern U.S. this morning, providing another round of
moderate-to-heavy snow throughout much of the Intermountain West.
Meanwhile, a developing storm system in the East Pacific ushers Pacific
moisture into Southern California and the Southwest today into Friday.
Locally heavy rainfall rates could cause 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) but
it also supplies another 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. As previously mentioned, another injection of frigid
Arctic air causes temperatures to plummet through out the West on Friday
and by early Saturday morning, sub-zero temperatures are 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. today for the
present frigid air-mass, but expect more bitterly cold wind chills Friday
and into Saturday.

Farther east, the atmosphere continues to believe the calendar has skipped
winter all together and entered spring. 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. The troughing in the
West and the strong ridge of high pressure over the Southeast are working
to funnel rich Gulf of Mexico moisture into the Mid-South late Friday.
There is a Marginal Risk for both severe weather and Excessive Rainfall in
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. Ample moisture and instability
is also present to support Excessive 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 with concerns for nocturnal severe weather and
localized flooding.

As the storm system responsible for the severe weather and flash flood
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 hazardous travel
conditions New Year's Day from the front range of the Rockies to the
Midwest and Great Lakes. Meanwhile, within the storm's warm sector,
another busy day of severe weather and Excessive Rainfall is likely in the
Mid-South. Residents in these regions should check for the latest forecast
from their local NWS offices and National Centers as a plethora of weather
hazards; from bitterly cold wind chills and travel-disruptive snowfall
totals to severe storms and flash flooding will make for a treacherous
start to the 2022.

Mullinax


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