Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
330 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 from the southern Plains through the Tennessee Valley today. 
Areas of heavy rain together with the possibility of severe thunderstorms
could result in flooding issues today across these areas as a low pressure
wave develops along 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 slides 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.  Farther to the
south, well above average temperatures from the Deep South to the East
Coast will gradually return to seasonal levels behind the cold front.

After a break in the precipitation today across the Pacific Northwest,
moisture from the next Pacific system is forecast to arrive on Saturday. 
Moderate to heavy rain near the coast along with mountain snows will once
again overspread the region throughout the weekend.  Over the northern
Rockies, an Alberta clipper dipping toward the southeast will bring a
round of modest snowfall followed by a strong and gusty cold wind from the
north and northwest across the northern Rockies into the northern to
central High Plains today.  The clipper will then dissipate as it merges
with the intensifying low pressure wave over the Ohio Valley on Saturday. 
By Saturday night, another Alberta clipper is forecast to form as snow
lingers across western Montana into northern Idaho.

Elsewhere, modestly dry and breezy conditions promoted by downslope winds
will allow elevated fire risk to continue today in the central High Plains.

Kong


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