Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
348 AM EST Tue Dec 21 2021

Valid 12Z Tue Dec 21 2021 - 12Z Thu Dec 23 2021

...Low pressure system expected to bring locally heavy rain/thunderstorms
across Florida and the Southeast coast today...

...Another low pressure system will spread snow across the northern tier
states today into tonight and then a quick round of snow for Maine later
on Wednesday...

...Unsettled weather spreads farther south from the Pacific Northwest into
California as well as farther inland across the northern Rockies...

A low pressure system moving through the Gulf of Mexico is forecast to
make landfall and traverse the Florida Peninsula this afternoon.  This
system has been ingesting plenty of moisture from the Gulf water and is
forecast to bring a quick round of moderate to heavy rain across northern
Florida today.  To the south of the low track, thunderstorms ahead of a
cold front could become severe this morning.  Some of the heavy rain and
thunderstorms may result in instances of flash flooding.  In addition, a
period of gusty winds can be expected as the low center moves over the
Florida Peninsula this afternoon.  The heavy rain and severe weather
threat will quickly diminish by this evening for all of Florida as the low
moves out into the Atlantic.  On the other hand, some of the heavier
rainfall will brush the Southeast U.S. coastal areas tonight into
Wednesday morning as the low turns northeastward and tracks along the Gulf
Stream.  By  Wednesday night, the low pressure system should track far
enough offshore to allow fine weather to return to the East Coast.  Colder
air will then overspread the entire eastern U.S. into Thursday behind a
reinforcing cold front and as a high pressure system takes over.

Meanwhile, an clipper type low pressure system is expected to bring a
quick round of light to moderate snow across the northern tier states
today.  The warmer waters of upper Great Lakes should help deliver
somewhat higher snowfall amounts on the lee side of the lakes.  On
Wednesday, some snow or wintry mix is expected to develop in Maine ahead
of this low and the snow should continue into Wednesday eveing.  By
Thursday morning, the wintry weather in Maine should taper off to flurries
as cold blustery winds rush in from the west.

More active weather will move into the West Coast during the next couple
of days as a large cyclone spins offshore and waves of low pressure
converge toward the Pacific Northwest.  Moisture will first reach northern
California today ahead of an offshore cold front before a surge of
moisture reaches the Pacific Northwest tonight ahead of a low pressure
wave digging down the west coast of Canada.  Snow will once again become
heavy over the mountains as rain will become heavy near the coast and
lower elevations later on Wednesday and into Thursday morning.  The
precipitation will also become progressively more widespread further south
into California and into the Sierra Nevada.  The moisture will also work
its way inland and bring mixed precipitation across the Great Basin and
mountain snows for the northern Rockies during the next couple of days.

For much of the central U.S., dry and mild weather is in store through
midweek as below average temperatures remain confined to the Northern
Plains.  Parts of the High Plains will begin to see an increasing risk of
fire weather where dry conditions are forecast to persist.

Kong


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