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

Valid 12Z Thu Sep 21 2023 - 12Z Sat Sep 23 2023

...Below-normal temperatures expected across much of the western U.S.,
with widespread precipitation over the northern Intermountain West and
Rockies...

...Strong to severe thunderstorms and excessive rainfall expected for
portions of the northern & southern Plains...

...Gusty winds, heavy rain, and high surf likely for portions of the
Southeast and southern Mid-Atlantic Friday and into the weekend..

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 are cold enough that parts of southern Oregon
and northern California are under Frost Advisories and Freeze Warnings
this morning. There are also Winter Weather Advisories in parts of the
northern Rockies that are in effect through Thursday evening where a few
inches of snow are  possible in the highest elevations. Daytime high
temperature anomalies today 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 today and Friday. On the flip-side,
gusty and dry conditions are key cogs in an Elevated Fire Weather risk in
parts of northern California today.

In the Nation's Heartland, 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. A pair of frontal boundaries; one in the Southern Plains and the
other in 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 today in the Southern and Northern Plains. By
Friday, as the upper low tracks a little farther east, the Excessive
Rainfall and severe weather threat becomes positioned over 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.

In the East, the spotlight shines brightest on a frontal system off the
Southeast coast that is forecast to direct a slug of rich subtropical
moisture from the Carolina Coast today to the coastal Mid-Atlantic on
Friday. A narrow Marginal Risk for Excessive Rainfall extending from South
Florida to southern South Carolina today grows on Friday to encompass most
of the heavily urbanized Mid-Atlantic on Saturday. There is a Slight Risk
in place from Myrtle Beach SC on north to the southern New Jersey shore on
Saturday. There still remains some uncertainty on storm track; a farther
inland track would bring heavy rainfall farther west into the central
Appalachians by the start of the weekend. The aspect of the forecast that
has greater confidence in causing detrimental impacts are gusty winds and
battering surf that may result in coastal flooding along the Mid-Atlantic
coast. This area of low pressure off the Mid-Atlantic coast has been
designated with a 40% chance for tropical development over the next 7
days. After a seasonally mild day today along the East Coast, the surge in
high-mid level clouds and periods of rain should lead to more October-like
temperatures from the Mid-Atlantic to New England this Friday and into the
upcoming weekend.

Mullinax


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