Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Mon Dec 27 2021

Valid 12Z Mon Dec 27 2021 - 12Z Wed Dec 29 2021

...Significant snowfall to continue for portions of West Coast mountain
ranges and the Intermountain West; record cold for parts of the West
Coast...

...A pair of storm systems to bring snow and an icy wintry mix to the
Upper Midwest, Great Lakes, and Northeast; Marginal Risk for Excessive
Rainfall from the mid-Mississippi Valley to the Ohio Valley on Tuesday...

...Record warm temperatures expected for broad areas of the South;
dangerously cold wind chills in the northern High Plains, Elevated Risk
for fire weather in the High Plains...

The unrelenting troughing pattern over the West Coast finally makes its
way a little farther east to kick off the final week of 2021. This results
in an increasingly active storm track in the East as storm systems
originating out West track through the eastern half of the Lower 48 this
week. The first storm is unfolding in the Upper Midwest this morning with
its associated shield of precipitation stretching from northern Minnesota
to the northern Mid-Atlantic. Periods of snow in parts of the Upper
Midwest and northern Great Lakes will generally lead to light
accumulations, but totals over 6 inches are possible in the Minnesota
Arrowhead. Farther east, warmer air aloft will support the potential for
an icy wintry mix in the central Great Lakes and northern Mid-Atlantic.
Travel delays due to icy conditions are possible in these regions, both on
the ground and in the air. As this storm system weakens Monday evening,
the next storm system already causing heavy mountain snow along the West
Coast on Monday will track across the Intermountain West Monday night and
into Tuesday morning. The Sierra Nevada are expected to receive another 1
to 2 feet of snow with totals up to 3 feet possible in the highest
elevations. From the Wasatch to the Colorado Rockies, mountain snow totals
appear to be on the order of 8 to 12 inches with localized amounts up to 2
feet. This next western U.S. storm system then heads into the Plains by
Tuesday where a strengthening low pressure system is primed to bring
another round of wintry weather to the Upper Midwest with anywhere from a
coating to 6 inches possible. Light but still potentially travel
disruptive ice accumulations, from a glaze to a tenth of an inch, may
ensue from Iowa and the central Great Lakes Tuesday morning, to the
interior northern Mid-Atlantic by Tuesday evening. Look for periods of
rain and even some thunderstorms to breakout across the Ohio Valley and
into the Mid-South. Excessive Rainfall could lead to localized flash
flooding, prompting the issuance of a Marginal Risk from southern Missouri
to the Ohio Valley on Tuesday.

Temperature-wise, the slight eastward push of the upper trough in the West
allows for more Canadian air to spill in behind it throughout the western
third of the country. The coldest temperatures for the period will be
focused in the northern High Plains where daytime highs in Montana and
North Dakota will struggle to get above zero. Blustery conditions will
also lead to dangerously cold wind chills ranging as low cold as -30 to
-50 degrees, leading to the issuance of Wind Chill Warnings and
Advisories. Some record cold lows and cold max temps are possible up and
down the West Coast today, including the Pacific Northwest where metro
areas such as Seattle and Portland may not get above freezing today.
Meanwhile, the southern and eastern U.S. continue to be under the
influence of upper level ridging over the Southeast, causing very warm
southerly flow to keep much above normal temps in the forecast through
mid-week. Parts of the South Central U.S. will soar into the 70s and 80s
once again this afternoon, with temperatures becoming warmer across much
of the Deep South by Tuesday. Numerous record warm highs and lows are on
tap Tuesday and should continue into Wednesday. The abnormally warm
conditions, mixed with dry conditions and gusty winds keeps Elevated Risks
for fire weather in the fold across portions of the central and southern
High Plains today and Tuesday.

Mullinax


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