Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Thu Sep 21 2023

Valid 00Z Fri Sep 22 2023 - 00Z Sun Sep 24 2023

...Potential tropical cyclone Sixteen is forecast to become a tropical
storm, spreading heavy rain up the East Coast and tropical-storm-force
winds near/along the coast...

...Bouts of strong to severe thunderstorms are expected to impact portions
of the central U.S. as heavy/excessive rainfall develops across the
northern Plains toward the Midwest...

...Colder than normal conditions will expand across the western U.S. as
high-elevation snow and wet snow gradually taper off across the
Intermountain region...

Potential tropical cyclone Sixteen became the spotlight this morning as
the National Hurricane Center began issuing advisories on this developing
system off the coast of southeastern U.S.  This system is forecast to
intensify as it tracks generally northward, edging toward the Mid-Atlantic
coast through the next couple days.  As the core of the system moves over
the warm Gulf Stream underneath a cold upper trough while interacting with
a frontal zonal near/off the East Coast, heavy rain is forecast to
gradually overspread the Mid-Atlantic region later on Friday and Friday
night, and then farther north into southern New England on Saturday.  The
core of the system will be prone to further acquire tropical
characteristics as it moves over the warm waters off the southeast U.S.
through Friday night.  This will allow the system to gain strength through
Friday night and make landfall potentially as a tropical storm over
eastern North Carolina early on Saturday.  Squally heavy rain is forecast
to intensify along the Mid-Atlantic coast through Friday as the storm
approaches.  The center of the storm could potentially track further up
the Chesapeake Bay later this weekend, spreading heavy rain and gale 
force wind farther inland as well as up the East Coast as general 
weakening is forecast to begin.

Meanwhile, a potent upper level trough over the northwestern U.S. will be
responsible for an abnormally cool temperature regime throughout the
second half of the work week. Temperatures were cold enough that parts of
southern Oregon and northern California are under Frost Advisories and
Freeze Warnings this morning. Winter Weather Advisories remain in effect
for parts of the northern Rockies through this evening where a few inches
of snow are possible in the highest elevations. Daytime high temperature
anomalies will range between 15 to 25 degrees below normal from the
northern Rockies to southern California. The storm system traversing the
Intermountain West will also trigger showers and storms into parts of the
Intermountain West into Friday before tapering off on Saturday as the
storm moves out into the Plains. On the flip-side, gusty and dry
conditions are key cogs in an Elevated Fire Weather risk in parts of
northern California through this evening.

The aforementioned upper low in the Northwest will also play a role in
what looks to be a wet and stormy end to the week over a good portion of
the central U.S.. A pair of frontal boundaries; one across the Southern
Plains and the other across the Northern Plains are going to help spark
widespread heavy showers and storms. There are a pair of Slight Risks for
Excessive Rainfall and severe weather over portions of the Southern and
Northern Plains. By Friday, as the upper low tracks a little farther east,
the Excessive Rainfall and severe weather threat will likely overspread a
good portion of the northern Plains. From a severe weather standpoint,
large hail and damaging wind gusts are the primary concerns, although some
severe storms could also produce tornadoes. In the southern Plains,
summer-like heat remains in the forecast as daytime highs routinely reach
the 90s throughout the vast majority of Texas through Friday. The Storm
Prediction Center (SPC) has also issued an Elevated Threat area for fire
weather in the southern High Plains on Friday.  By Saturday, the focus of
heavy rain will likely shift farther east and southeast from the northern
Plains down toward eastern Oklahoma ahead of an elongated low pressure
system that is forecast to consolidate over the central U.S.  Severe
weather concerns will likewise be embedded within this general corridor,
and especially later in the day when instability is increased by solar
heating.

Kong/Mullinax


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