Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
325 AM EST Sat Dec 18 2021

Valid 12Z Sat Dec 18 2021 - 12Z Mon Dec 20 2021

...Heavy rain and severe thunderstorm threat this morning from the
southern Plains to Ohio Valley...

...Moderate to heavy snow expected across northern New England this
evening into Sunday; freezing rain from upstate New York to central New
England...

...Heavy snow to impact the Cascades and far Northern Rockies today,
lingering into Monday...

A low pressure wave developing over the Mid-Mississippi Valley is forecast
to intensify as it tracks toward the New England coast tonight.  Areas of
strong to severe thunderstorms near a meandering front will keep rounds of
moderate to heavy rain this morning from eastern Oklahoma through the Ohio
Valley where up to a moderate risk of flash flooding is forecast.  As the
low pressure wave moves quickly through the Ohio Valley today, the front
will be guided eastward more quickly, thereby diminishing the heavy rain
threat over the Mid-Mississippi Valley by later today.  The trailing
portion of the front will move more slowly across the western Gulf Coast
where a threat of heavy rain is forecast for this evening.

In the mean time, with cold air in place across New England, the
intensifying low pressure wave will bring a round of snow and some mixed
precipitation across the lower Great Lakes today.  By tonight, moderate to
heavy snow is forecast to overspread northern New England from west to
east as the low pressure wave intensifies and tracks near the southern New
England coast.  Areas from upstate New York to central New England should
see sleet, freezing rain, and/or snow tonight before the low quickly exits
out to sea on Sunday.  Much of the wintry precipitation should come to an
end later in the afternoon on Sunday.  Farther south, showers and
thunderstorms are expected to move steadily through the East Coast and the
Southeast during the weekend.

Another surge of moisture is entering the Pacific Northwest ahead of a
Pacific low pressure system.  A few inches of coastal/lower elevation rain
is expected, with heavy snow found in the Cascades.  Snowfall amounts may
add up to over 2 feet in the highest peaks of the northern Cascades.  The
system will settle a bit southward into Oregon on Sunday and then will
start to push back northward Sunday night into Monday as a cyclone is
forecast to expand and push northward off the West Coast.  Some of the
heavier precipitation will then spread northward from Oregon into
Washington by Monday.  Meanwhile, snow is also expected to spread further
east into parts of northern Montana and Idaho this weekend, where
widespread snowfall amounts over 10 inches are possible.  Colder air will
enter the northern Plains Sunday night into Monday behind an Alberta
clipper.  Snow associated with the cold front is forecast to be light.

Elsewhere, rain chances are expected to increase across southern Texas
later this weekend as a low pressure system is forecast to develop along a
meandering front in the western Gulf of Mexico.

Kong


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