Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Fri Dec 10 2021

Valid 00Z Sat Dec 11 2021 - 00Z Mon Dec 13 2021

...A robust low pressure system will spread moderate to heavy snow across
the upper Midwest tonight, severe thunderstorms across the mid-Mississippi
to Ohio Valleys and record warmth into the Mid-Atlantic on Saturday...

...A heavy precipitation event will overspread the Pacific Northwest into
the northern Rockies tonight into Saturday, reaching northern California
on Sunday...

A low pressure system currently over the central Plains will continue to
intensify as it tracks northeastward to the central Great Lakes by
Saturday morning.  Cold air already in place across the northern U.S. will
support a swath of moderate to heavy snowfall from the northern Plains
through the upper Midwest into tonight.  The snow is forecast to continue
into Saturday across the upper Great Lakes along with increasingly
blustery winds as the low continues to intensify and move into Canada
later on Saturday.  Meanwhile, warm and moist air from the Gulf of Mexico
will converge ahead of a pre-frontal dry line to result in strong to
severe thunderstorms along the Mississippi Valley tonight.  The best
chance of severe thunderstorms will likely be from the mid-Mississippi
Valley to Ohio Valley tonight into Saturday morning.  Some of the
thunderstorms will likely accompany with heavy downpours that could result
in local flooding issues.

The low pressure system will become quite large on Saturday as it pulls
very warm air into much of the Eastern Seaboard.  In fact, many locations
over the Mid-Atlantic region will likely see record high temperatures
Saturday afternoon under a brisk southwesterly winds.  Northern New
England could see a brief period of wintry precipitation Saturday morning
before it changes over quickly to rain with the passage of a warm front. 
By Saturday night, a strong cold front trailing from the deep storm in
eastern Canada will sweep across the entire East Coast, bringing sharply
falling temperatures and sudden onset of blustery winds.  In fact, high
winds will be mostly likely downwind from the lee sides of the lower Great
Lakes Saturday evening, possibly spreading through northern New England
Saturday night before the front moves out to sea on Sunday as a high
pressure system settles across the entire eastern U.S.

Meanwhile, a heavy precipitation event will overspread the Pacific
Northwest into the northern Rockies tonight and into Saturday before
reaching northern California on Sunday.  Plenty of moisture associated
with an amplified upper-level trough and an associated front will likely
bring big snowfall totals down the spine of the Cascades through Saturday,
and then into the higher terrain of northern California during the day on
Sunday.  Coastal sections will likely see up to a few inches of heavy rain
along with strong and gusty winds as this event unfolds.  The moisture
will also spread farther inland across the northern Rockies with areas of
heavy snow over the higher elevations of Idaho through the weekend.  Parts
of northwestern Montana and eastern Wyoming can expect strong downslope
winds to develop during the weekend where a strong pressure gradient
emerges.

Kong


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