Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
349 AM EDT Mon Sep 20 2021

Valid 12Z Mon Sep 20 2021 - 12Z Wed Sep 22 2021

...Strong to locally severe thunderstorms are possible from the upper
Mississippi Valley and Great Lakes to the Ozarks on Monday...

...Elevated to critical fire weather conditions expected to continue
across portions of Northern California through Monday into Tuesday...

...Heavy rainfall and localized flash flooding possible across portions of
the Tennessee Valley, southern Appalachians, and the Southeast Monday and
Tuesday...

A strong cold front will continue to advance east from the northern and
central Great Plains into the upper and mid Mississippi Valley on Monday. 
Ongoing showers and storms along the front are expected to weaken by late
morning before redeveloping with the return of daytime heating later in
the afternoon.  These storms may become strong to locally severe during
the afternoon and evening hours, impacting areas from the upper
Mississippi Valley and Great Lakes to the Ozarks. In addition to locally
damaging winds, there is the potential for heavy rainfall and isolated
flash flooding.  The front is forecast to continue to push east across the
Great Lakes and east of the mid Mississippi Valley into the lower Ohio and
Tennessee valleys on Tuesday.  Although the recurrence of severe
thunderstorms appears unlikely, heavy rainfall with localized flash
flooding is possible -- especially for parts of the lower Ohio Valley
northward into Lower Michigan.

Back to the west, unseasonably cool temperatures will spread across the
Great Basin and northern Rockies -- supporting high elevation snows across
portions of the northern Rockies on Monday and Freeze Watches and Warnings
for parts of Wyoming and Colorado Monday night into Tuesday morning.

High pressure is expected to build across the West -- supporting dry
conditions for most areas west of the Rockies through midweek.  Dry, gusty
northerly to northeasterly winds are expected to support elevated to
critical fire weather conditions, with Red Flag Warnings in effect for
portions of Northern California through Monday into Tuesday.

Moisture and the upper level circulation associated with the remnants of
tropical cyclone Nicholas will continue to pose a heavy rainfall and flash
flooding threat, especially for portions of the Tennessee and lower Ohio
valleys and the southern Appalachians on Monday.  Meanwhile, onshore winds
along the Southeast coast will reinforce the already rich tropical airmass
in place -- supporting heavy rains and localized flash flooding,
especially along the southern South Carolina and Georgia coasts on Monday,
before shifting farther north along the northern South Carolina coast into
southeastern North Carolina on Tuesday.

Pereira

Graphics are available at www.wpc.ncep.noaa.gov/basicwx/basicwx ndfd.php