Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 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 likewise advance eastward more quickly, 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 more steadily through the East Coast and the
Southeast during the weekend.

Elsewhere, a surge of moisture is entering the Pacific Northwest and will
extend into Sunday. 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. Winter
Storm Watches have been issued here. Snow is also expected to enter parts
of northern Montana and Idaho this weekend, where widespread snowfall
amounts over 10 inches are possible.

Kong


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