Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Sun Nov 21 2021

Valid 12Z Sun Nov 21 2021 - 12Z Tue Nov 23 2021

...Heavy rain and isolated instances of flash flooding possible across
portions of eastern Florida and South Texas today...

...Widespread showers to track across the eastern third of the country
today and early Monday due to a sweeping cold front, colder temperatures
return with lake effect snow possible in its wake...

...Elevated to Critical fire weather conditions in Southern California;
warming temperatures in the Rockies and Plains early week; wet weather
return to the Pacific Northwest late Monday...

The weekend concludes on a wet and stormy note in the southern most
reaches of the Lower 48. Southeast Florida continues to experience onshore
flow that is responsible for training showers and thunderstorms, prompting
a Marginal Risk for Excessive Rainfall on Sunday. In South Texas, an
approaching cold front will trigger showers and thunderstorms capable of
producing Excessive Rainfall rates atop overly saturated soils. Both areas
should trend drier by Monday as a pair of cold frontal passages usher in
drier and cooler conditions the first half of Thanksgiving week.

Speaking of "cold frontal passages", a pair of cold fronts will sweep
across the eastern third of the U.S. to kickoff Thanksgiving week.
Unsettled weather is anticipated ahead of the fronts with much colder
temperatures rushing in behind the fronts today and Monday. The leading
front is responsible for numerous showers from the Northeast and Ohio
Valley on south to the South-Central U.S. today and into Sunday night.
Meanwhile, a secondary cold front is guiding a cold Canadian air-mass
through the Upper Midwest on Sunday and eventually into the Great Lakes
Sunday night. Lake effect snow bands are expected to breakout over the
Upper Great Lakes Sunday night into Monday morning. Snowfall accumulations
will be highest in the eastern half of the Upper Peninsula of Michigan
where snowfall in excess of 6" is likely, while several inches are
possible in northern Michigan and downwind of Lakes Erie and Ontario. By
Monday morning, the cold fronts race across the Northeast and
Mid-Atlantic, forcing temperatures to fall and drier conditions to return
the second half of the day. December-like temperatures look to engulf much
of the East as high pressure builds in Monday night into Tuesday morning.

Farther west, a ridge of high pressure leads to an expansive area of dry
conditions and warming temperatures from the Great Plains to California.
The strong high pressure over the Great Basin and surface troughing off
the California coast will lead to Santa Ana winds in the higher elevations
of Southern California and even to the coastal areas. This has resulted in
the issuance of Red Flag Warnings and a Critical Risk for fire weather
today. An Elevated Risk for fire weather is forecast to persist in
Southern California on Monday. As upper level riding moves into the
Rockies and Great Plains on Monday, warmer temperatures will push into the
Heartland by Tuesday. Meanwhile, a storm system in the northeast Pacific
delivers another round of precipitation to the Pacific Northwest late
Monday into Tuesday. Coastal and valley locations can expect periods of
rain while mountain ranges such as the Olympics and Cascades receive
several inches of snowfall.

Mullinax

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