327
FXUS01 KWBC 122012
PMDSPD

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Tue Nov 12 2024

Valid 00Z Wed Nov 13 2024 - 00Z Fri Nov 15 2024

...Heavy coastal rain and high-elevation mountain snow expected to
reach the Pacific Northwest and northern California this evening...

...Showers and thunderstorms will bring locally heavy rainfall,
some strong thunderstorms and isolated flash flooding concerns to
the Tennessee and Mississippi as well as the lower Ohio Valleys on
Wednesday...

...Above average temperatures continue for much of the central
U.S. and Gulf Coast states while colder air moves into the
Northeast and the West...

A low pressure system developing over the central High Plains will
quickly move across the north-central U.S. tonight.  Light to
moderate lower-elevation wintry mix and higher-elevation snow
associated with the low pressure system across the northern
Rockies and Great Basin will move into the central Rockies this
evening and then gradually taper off tonight.  Meanwhile, another
Pacific frontal system and accompanying Atmospheric River will
approach the West, bringing a wave of Pacific moisture and
triggering increasingly heavier lower elevation/coastal rain and
higher elevation mountain snow by this evening. The system will
move swiftly inland, bringing an expanding area of lower
elevation/coastal rain and high elevation mountain snow to
northern California and a wintry mix into the northern Rockies and
Great Basin through Wednesday. Favorable upslope regions along the
coastal ranges and Cascades will see locally heavy rainfall and
the threat of some isolated flooding today, expanding southward
into coastal northern California on Wednesday. By Wednesday night
into Thursday, the precipitation coverage across the West will
gradually decrease with time as the main energy of the system
continues to progress east into a dry ridge of high pressure in
the Rockies.  The rain will continue to linger into Thursday
afternoon near the coast of the Pacific Northwest along with some
high-elevation snow over northern Idaho.

Across much of the eastern U.S., fine and colder weather is
expected to overspread the region for the next couple of days as
an expansive high pressure system takes control behind an exiting
low pressure system.  Meanwhile, a cold front trailing south from
the developing low pressure system over the north-central U.S.
will push eastward against the expansive high pressure system in
the East.  Moisture returning from the Gulf of Mexico will then
interact with the cold front and produce a couple of expanding
areas of moderate to heavy rain with embedded thunderstorms--one
near the central Gulf Coast states, and another across
north-central U.S. ahead of the cold front.  The rain and
thunderstorms over the central Gulf Coast is associated with the
remnants of Hurricane Rafael which has been meandering over the
central Gulf of Mexico for the past couple of days.  These two
areas of expanding rain and thunderstorms are forecast to merge
near the mid-Mississippi Valley on Wednesday to produce widespread
moderate to locally heavy rainfall across the lower Ohio and
Tennessee Valleys, Mid-South, and into the lower Mississippi
Valley.  Some isolated flash flooding is possible especially given
wet antecedent conditions from recent rainfalls. More light to
moderate rainfall is likely over the Great Lakes with lower
instability and available moisture. The system will push eastward
into the Appalachians Wednesday night into Thursday morning with
moderate to possibly locally heavy rain. By Thursday afternoon,
the rain will reach into the Mid-Atlantic and into the Carolinas
as a low pressure system develops along a coastal front just off
the coastline of the Carolinas.

Much of the central and eastern U.S. will continue to see above
average high temperatures of 5-15 degrees over the next couple of
days. Forecast highs range from the 40s in the Great Lakes, 50s in
the northern Plains, 60s for the central Plains, 70s for Texas and
the Southeast, and 80s along the Gulf Coast. Colder air will move
across the Great Lakes into the Northeast while more seasonable
temperatures will come to the Carolinas and Southeast on
Wednesday, with highs dropping into the upper 50s to mid-60s. Rain
will keep temperatures cooler up the East Coast on Thursday. The
multiple frontal systems will keep temperatures cooler across most
of the West as well, with highs Tuesday mostly in the 40s and 50s
for the Pacific Northwest and interior locations, 60s for coastal
California, and 60s and 70s for the Desert Southwest. Conditions
will moderate by around 5-10 degrees on Wednesday and into
Thursday.

Kong/Putnam


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