Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EST Sun Dec 18 2022

Valid 12Z Sun Dec 18 2022 - 12Z Tue Dec 20 2022

...Wintry and exceptionally chilly temperatures across much of the
northern U.S. through early week...

...Heavy showers and thunderstorms to track along the Gulf Coast Monday
and into early Tuesday...

...Potential for high impact storm system during the middle to latter half
of the upcoming week leading up to the holiday weekend...

With one week to go until Christmas Day, it is beginning to look a lot
like Christmas for much of the northern tier of the continental U.S.
through the first half of the week. This is due to a strong dome of Arctic
high pressure bleeding south through western Canada and into nation's
midsection through Tuesday. The winter storm that brought heavy snowfall
and ice to the Northeast the last couple days is still close enough to New
England to produce more measurable snowfall over northern Maine today.
Latest WPC snowfall probabilities show a large footprint of high chances
(70-90%) for >4" of snowfall throughout most of northern Maine today.
Downwind of Lakes Superior and Erie, lake effect snow bands will continue
to generate heavy snowfall rates with similar probabilities for >8" of
snowfall today. In addition, an Arctic front slowly pushing south through
the Northwest and Northern Rockies is also expected to produce measurable
snowfall. The Lewis Range of western Montana, the Bitterroots, and the
Cascade Range all feature 60-80% probabilities of receiving >6" of
snowfall today and into early Monday. Another round of heavy snow arrives
on Tuesday as an influx of Pacific moisture arrives from the West. The
coldest temperature departures will be found in the Northern Rockies and
Northern High Plains where daily average temperatures are forecast to be
20 to 35 degrees below normal each day. Abnormally cold temperatures have
also engulfed much of the eastern half of the Lower 48 in wake of a series
of strong cold frontal passages over the last couple days. In terms of
potential hazards, there are a handful of Freeze Warnings and Watches
along the Gulf Coast, freezing fog advisories in the Northern Plains, and
Wind Chill Advisories in central Montana.

Farther south, a more organized wave of low pressure will form in the
western Gulf of Mexico on Monday. A southerly fetch of anomalous Gulf of
Mexico moisture will stream north ahead of the storm system and lead to
heavy showers and thunderstorms from the Upper Texas coast to the central
Gulf Coast. WPC has issued a Marginal Risk for Excessive Rainfall in this
area for Monday due to the potential for some localized flash flooding.
North of this storm system, the aforementioned fetch of moist southerly
flow will run into a subfreezing air-mass in the Central Plains and Upper
Mississippi Valley. WPC probabilistic snowfall forecast show as much as a
30-40% chance for snow totals >2" in parts of eastern Kansas. Farther
north, where temperatures are even colder, snow will be heavier as this
same stream of moisture becomes ingested by a developing wave of low
pressure tracking into the northern Great Lakes Monday night. Periods of
snow, falling heavily at times, is anticipated with latest WPC snowfall
probabilities showing 20-40% odds of snowfall amounts >4" in the Minnesota
Arrowhead and along the northern coast of Michigan's Upper Peninsula.

By early Tuesday morning, the large and strong dome of Arctic high
pressure continues its descent through the Canadian Prairies and into the
Nation's Heartland, introducing an even more frigid air-mass into the
Lower 48 the second half of the week. The tandem of bitterly cold
temperatures and an intensifying storm system over the Rockies and Central
Plains by mid-week, will mean treacherous travel for many locations along
and east of the Rockies leading up to the holiday weekend. Please monitor
the forecast closely in the coming days as high impact weather; from
strong wind gusts and heavy snowfall to heavy rain and thunderstorms, will
likely mean numerous travel headaches the second half of the upcoming
week.


Mullinax


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