Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
314 AM EDT Sat Sep 18 2021

Valid 12Z Sat Sep 18 2021 - 12Z Mon Sep 20 2021

...A strong cold front and accompanying atmospheric river will bring windy
conditions and heavy rains to the Northwest through the weekend...

...Very warm, windy, and dry conditions will support widespread elevated
to critical fire weather conditions from the Sierra Nevada to the northern
High Plains through Saturday...

...Post-Tropical Cyclone Nicholas is dissipating but will still bring
pockets of locally heavy rain and flash flooding to portions of the Gulf
Coast states this weekend...

A strong cold front and accompanying plume of deep moisture associated
with an atmospheric river will continue to impact the northwestern U.S.
through the weekend.  As the front continues to slide southwest through
the region, heavy precipiation is expected across western Oregon into
northwestern California on Saturday.  This rainfall may produce localized
areas of flash flooding.  Burn scar areas are especially vulnerable to
flash flooding and debris flows.

Ahead of the system, dry, warm, and windy conditions -- supporting
elevated to critical fire weather conditions -- will continue from the
Sierra Nevada northeastward to the northern High Plains on Saturday.  Red
Flag Warnings have been raised for much of the region that extends from
the Sierra Nevada to the western Dakotas.  Along the northern High Plains,
daytime temperatures are forecast to climb well into the 90s on Saturday
-- more than 20 degrees above normal in some spots. 

As the system continue to progress, the warm air is forecast to shift east
on Sunday, with temperatures expected to climb well-above normal across
much of the northern Plains and Midwest.  Showers and storms are expected
to develop along the front as it moves across the northern Plains on
Sunday, with some potential for severe weather across the eastern Dakotas
into Minnesota late in the afternoon into the evening.  Meanwhile behind
the front, below-normal temperatures will spread across the Northwest into
the northern Rockies and Great Basin on Sunday, before spilling out into
the High Plains on Monday.  High elevation snow is expected for portions
of the northern Rockies on Sunday into early Monday.

Although Post-Tropical Cyclone Nicholas continues to weaken, plenty of
moisture remains in place -- supporting additional showers and
thunderstorms that may produce locally heavy rains from the central Gulf
Coast into the lower Mississippi and Tennessee Valleys and portions of the
Southeast through the weekend.  Southerly winds ahead of the system that
is moving across the central U.S. will begin to carry some of this
moisture farther to the north -- introducing an increasing change for
showers and thunderstorms into the Ohio Valley by late Sunday.

Tropical Storm Odette, which has developed well off the Mid-Atlantic Coast
is expected to remain well offshore as it tracks northeast over the coming
days.  However, swells generated by Odette are impacting portions of the
Mid-Atlantic coast and are forecast to spread northward to portions of the
Northeast coast during the weekend.  These swells are likely to cause
life-threatening surf and rip current conditions.   

Pereira

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