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

Valid 00Z Sat Dec 18 2021 - 00Z Mon Dec 20 2021

...Flash flooding likely and severe thunderstorms possible near a
meandering front extending between the Southern Plains and Ohio Valley...

...Moderate to heavy snow expected across northern New England beginning
on Saturday with pockets of freezing rain located over the Interior
Northeast and southern New England...

...Heavy snow to impact the Cascades and far Northern Rockies this
weekend...

The majority of the active weather this evening and into early Saturday
will be found along a quasi-stationary boundary extending from the
Mid-Atlantic to the Southern Plains. Showers and thunderstorms are
expected to focus along this front and ahead of a developing wave of low
pressure. Repeating rounds of moderate-to-heavy rain is likely across
parts of eastern Oklahoma, northern Arkansas, and southern Missouri.
Multiple inches of rain in a short period of time could result in areas of
flash flooding. WPC has issued a Moderate Risk (level 3/4) of Excessive
Rainfall for tonight that extends from northeast Oklahoma to north-central
Arkansas, with a larger Slight Risk (level 2/4) extending from northeast
Texas to southwest Indiana. Flash Flood Watches have also been issued for
parts of this region. Otherwise, a few severe thunderstorms are also a
possibility this evening from far northeast Texas to southeast Oklahoma.
As the aforementioned wave of low pressure pushes northeast on Saturday
and into the Ohio Valley, the attached cold front is forecast to push into
the Deep South and shift the marginal heavy rain/severe thunderstorm
threat into the Gulf Coast States.

By this weekend, cold air located across New England and southeast Canada
is expected to interact with approaching precipitation, resulting in an
area of sleet, freezing rain, and snow throughout the Interior Northeast
and New England. Light freezing rain may lead to a glaze of ice from
northern Pennsylvania to western Connecticut and Massachusetts. Even light
amounts of freezing rain can lead to treacherous travel; therefore,
residents are advised to check road conditions before venturing out.
Farther north, heavy snow (greater than 5 inches) is possible from the
Adirondacks of New York to eastern Maine between Saturday afternoon and
Sunday morning. Winter Weather Advisories and Winter Storm Watches have
been issued.

Elsewhere, after a quiet day today, a surge of moisture is forecast to
enter the Pacific Northwest tonight and extend into Saturday. 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.

Snell


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