Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Fri Dec 17 2021

Valid 12Z Fri Dec 17 2021 - 12Z Sun Dec 19 2021

...Heavy rain and potentially severe thunderstorms near a meandering front
expected from the southern Plains to the Mid-Mississippi Valley through
Saturday morning...

...Moderate to heavy snow across northern New England later this weekend
with freezing rain over central New England...

...Showers and thunderstorms will gradually move across the Deep South and
into the East Coast during the weekend ahead of a cold front...

The trailing cold front associated with a deep low pressure system moving
farther away into eastern Canada is forecast to meander across the
Mid-South today.  Ample moisture returning from the Gulf of Mexico will be
lifted along the front resulting in an axis of enhanced rainfall to extend
eastward through the Tennessee Valley today where areas of heavy rain
could result in flooding issues.  In addition, instability will enhance
the possibility of severe thunderstorms to occur across portions of the
southern Plains today as a low pressure wave develops along the the
meandering front.  The front is forecast to begin moving more steadily
toward the east later tonight, pushing the rain and thunderstorms eastward
across the Deep South on Saturday and into the East Coast Saturday night
into Sunday morning.  Meanwhile, the low pressure wave is forecast to
intensify as it tracks across the Ohio Valley on Saturday and then slide
off the New England coast early on Sunday.  With cold air in place across
the Northeast, moderate to heavy snow is forecast to spread from west to
east from upstate New York eastward through northern New England later
this weekend while a swath of freezing rain can be expected farther south
across central New England.  Well above average temperatures from the
Southern Plains to the Northeast will gradually return to seasonal levels
behind the cold front.

In the Southern High Plains modestly dry and breezy conditions are
forecast to persist over extremely dry fuels through Friday morning, while
similar conditions are expected to arise Friday morning to Saturday
morning over the Central High Plains. Given the fact these conditions are
conducive to fire spread, the Storm Prediction Center has issued an
Elevated Risk of Fire Weather for the Southern High Plains through
tomorrow morning and the Central High Plains Friday morning through
Saturday morning. Red Flag warnings are currently in effect for portions
of southeast Colorado.

Elsewhere, a stationary boundary meandering through the Northern and
Central Rockies will support heavy snowfall over the regions' high
elevation mountain ranges through Friday morning. The eastward progression
of shortwave instability at the surface will guide this snowfall out of
the mountains and into the Northern Plains on Friday where light to
moderate accumulations are expected. In the Pacific Northwest, a system
moving onshore Saturday is forecast to bring rainfall to the coast and low
elevation areas, while heavy snow is expected over Olympics and northern
Washington Cascades before spreading east into the Northern Rockies
Saturday evening.

Temperature-wise, unseasonably warm record-breaking weather is forecast to
persist from the Southern Plains to the Northeast into the weekend. With
today's daily highs sitting 20 to 30 degrees above normal, 56 daily high
temperature records throughout the eastern half of the country have
already fallen. A handful of tomorrow and Saturday's daily high
temperature records will also be put to the test as highs are forecast to
reach a modest 10 to 20 degrees above normal. In stark contrast to the
east, temperatures out west have dropped moderately to 5 to 10 degrees
below normal. An even larger departure from normal is expected over the
Northern High Plains, where daily highs could drop to as low as 20 degrees
below normal on Friday.

Kong/Zavadoff


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