Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Tue Nov 21 2023

Valid 12Z Tue Nov 21 2023 - 12Z Thu Nov 23 2023

...Active weather expected to impact pre-Thanksgiving travels for much of
the U.S. east of the Mississippi River but should exit the East Coast just
in time for Thanksgiving...

...Severe weather threat will progress from west to east across the
central Gulf Gulf states into the Southeast...

...Heavy rain expected to move through the interior Mid-Atlantic tonight
with some snow and freezing rain over interior New England into
Wednesday...

...Snow is forecast to develop over the northern Rockies to northern High
Plains to begin Thanksgiving holiday...

A developing low pressure system roughly centered over the Mississippi
Valley early this morning will continue to bring an expanding area of
inclement weather through much of the eastern half of the country as we
head toward the peak of the pre-Thanksgiving Day travel period. 
Precipitation associated with this system is already rather expansive
early this morning, stretching from the central Gulf Coast up through the
Tennessee and Ohio Valleys, into the Midwest and the southern part of the
Great Lakes.  Thunderstorms are expected to be most intense early today
across the lower Mississippi Valley with severe weather excepted before
cooler and drier air arrives behind a dynamic cold front.  Farther north,
rain heavy at times, with embedded thunderstorms, is forecast to quickly
overspread the Appalachians and the interior Mid-Atlantic by this evening,
with rainfall totals locally a few inches possible.  Nearly all of these
regions have had much below average precipitation over the past several
weeks, with areas from the lower Mississippi Valley into the Tennessee
Valley in Severe to Exceptional drought conditions.  Given these recent
dry conditions, stream flows and soil moisture are below average, which
should decrease the threat of flash floods.  However, isolated flash
flooding still possible given the heavy rainfall threat, especially across
urban areas.

Still farther north across New England, trapped cold air will support snow
and areas of freezing rain beginning Tuesday evening over upstate New York
as the moisture from the low pressure system arrives from the southwest. 
A few inches of snow is possible across interior New England before
tapering off from west to east later on Wednesday.  By the morning on
Thanksgiving Day, much of the Eastern Seaboard should clear out just in
time for holiday festivities as the storm should begin to move out to sea.
 However, much of the Northeast will likely contend with blustery
conditions as the storm is forecast to deepen quite rapidly just offshore.

Much more tranquil weather is expected across most regions to the west of
the Mississippi River to the West coast over the next few days.  Much of
this region will be dry, save for the Pacific Northwest where a slow
moving front will bring light to moderate precipitation amounts by tonight
into early Wednesday.  A large dome of high pressure will promote very
gusty Santa Ana winds over southern California today given a tight
pressure gradient in place.  By Wednesday night into Thursday morning, the
moisture in the Pacific Northwest is forecast to join force with colder
air arriving from western Canada to develop an expanding area of snow to
enshroud the northern Rockies into the northern High Plains to begin
Thanksgiving Day.

Above average temperatures are expected the next couple of days from the
West Coast, across the Rockies and into the Northern to Central Plains. 
Much colder temperatures expected across the Northern Plains beginning
late Wednesday into Thanksgiving as a strong cold front pushes southward
out of central Canada. 

Kong/Oravec


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