Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
304 AM EST Wed Dec 29 2021

Valid 12Z Wed Dec 29 2021 - 12Z Fri Dec 31 2021

...Bitterly cold wind chills in the northern Rockies and High Plains
today, more heavy mountain snow from the Sierra Nevada to the central
Rockies...

...Slight Risk for Excessive Rainfall in Southern California today and
Thursday; urban and flash flooding possible...

...Spring-like weather to stick around in the South; Enhanced Risk for
severe storms and a Slight Risk for Excessive Rainfall posted in parts of
the Deep South today...

The continental U.S. remains under the influence of prolonged troughing in
the Intermountain West and ridging in the Southeast. Beneath the troughing
pattern in the West, chilly temperatures are most common with dangerously
cold wind chills located in the Northern Plains. Wind Chill Warnings and
Advisories were issued from Montana and parts of the Dakotas to northern
Minnesota where wind chills will range anywhere from -30 to -50 degrees.
In addition to the cold, accumulating snowfall throughout the mountain
ranges of the West are expected with heavy accumulations for some. The
heaviest snow totals are forecast from the southern Sierra Nevada and the
Transverse range of southern California to the Wasatch and central
Rockies. Snow totals in the highest peaks of these regions will be
measured in feet, which combined with whiteout conditions in these areas
will result in hazardous and, at times, impassable travel conditions.
Closer to southern California, a storm system rounding the base of the
upper trough in the West is funneling Pacific moisture into the Los
Angeles and San Diego metro areas. Excessive rainfall potential is high
enough to warrant a Slight Risk, meaning there is a threat for flash
flooding today and into Thursday. Lastly, High Wind watches were posted
for southern Wyoming this Thursday as strong cross winds could make for
hazardous travel conditions for light weight and high profile vehicles.

Farther east, the anchored ridge atop the southeastern U.S. shows no sign
in relinquishing its spring-like regime in the South and East-Central
U.S.. Numerous record warm lows and highs are anticipated from the
Southeast coast to the Rio Grande of South Texas today. More of the same
is expected in the Southeast on Thursday with highs in the 70s and lows
that are 20 to 40 degrees above normal. An Elevated Risk for fire weather
is also in place for portions of the southern High Plains today. In terms
of precipitation, moist southerly flow and increasing instability levels
will lead to an increasingly favorable environment for severe weather. The
Storm Prediction Center has issued an Enhanced Risk (threat level 3/5) for
parts of the Lower Mississippi Valley, while a Slight Risk (threat level
2/5) stretches from southern Arkansas to the southern Appalachians. Highly
anomalous moisture content also supports the threat for Excessive
Rainfall, thus leading to the issuance of a Slight Risk for the Tennessee
Valley today due to a heightened chance for localized flash flooding.
Scattered showers and thunderstorms will remain possible across a broad
portions of the South on Thursday, but the severe and flash flood threat
will be lower compared to today's threat. Meanwhile, a little farther
north, light rain and snow showers across the Lower Great Lakes Wednesday
evening. A coating to 2 inches is possible from southern Iowa to the
northern Illinois and Indiana with a light but treacherous glaze of ice
possible from northeast Missouri to central Illinois and Indiana.

Mullinax


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