Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Fri Dec 10 2021

Valid 12Z Fri Dec 10 2021 - 12Z Sun Dec 12 2021

...There is an Enhanced Risk of severe thunderstorms over parts of the
Middle/Lower Mississippi, Ohio, and Tennessee Valleys through Saturday
morning...

...There will be heavy snow across the Upper Midwest...

...There is a Marginal Risk of excessive rainfall over parts of the Lower
Mississippi, Ohio, and Tennessee Valleys through Saturday morning...

A rapidly deepening area of low pressure over the Central High Plains will
move northeastward to the Upper Great Lakes by Saturday morning. The low
will move into Southeastern Canada by Saturday evening, as the associated
front moves off the East Coast overnight Saturday. The storm will produce
snow over parts of the Northern/Central Rockies into parts of the
Southwest on Friday morning.  By Friday afternoon, heavy snow will develop
over parts of the Northern/Central Plains into the Upper Mississippi
Valley, expanding into parts of the Upper Great lakes by Friday evening. 
The heavy snow will wind down over the Upper Great Lakes on Saturday into
Sunday morning.  The snow will result in reduced visibility and hazardous
driving conditions.

Moreover, showers and thunderstorms will develop along and ahead of the
cold front, mainly during the late afternoon into Saturday morning.  Some
of the thunderstorms will be severe.  Therefore, the SPC has issued an
Enhanced Risk of severe thunderstorms over parts of the Middle/Lower
Mississippi, Ohio, and Tennessee Valleys through Saturday morning. The
hazards associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a few tornadoes.  Furthermore, there is
a 10% or greater probability of EF2-EF5 over the region. The threat for
severe thunderstorms decreases slightly on Saturday into Sunday morning.
However, the SPC has issued a Slight Risk of severe thunderstorms over
parts of the Ohio and Tennessee Valleys on Saturday into Sunday morning.
The hazards associated with these thunderstorms are frequent lightning,
severe thunderstorm wind gusts, hail, and a few tornadoes.

In the meantime, the thunderstorms will contain areas of heavy rain.
Therefore, the WPC has issued a Marginal Risk of excessive rainfall over
parts of the Lower Mississippi, Ohio, and Tennessee Valleys through
Saturday morning. The associated heavy rain will create localized areas of
flash flooding, affecting areas that experience rapid runoff with heavy
rain. The Marginal Risk of excessive rainfall will move slightly south and
eastward to include parts of the Southern Appalachians, Ohio/Tennessee
Valleys into the Lower Mississippi Valley on Saturday into Sunday morning.
Likewise, the associated heavy rain will create localized areas of flash
flooding, affecting areas that experience rapid runoff with heavy rain.

Meanwhile, onshore flow will aid in producing rain and higher elevation
snow over the Pacific Northwest on Friday.  On Saturday, a front will come
onshore over the Northwest as rain, heavy at times, and higher elevation
snow moves into Northern California. As a result, there is a Marginal Risk
of excessive rainfall over parts of the Northwest into Northern California
on Saturday into Sunday morning. The associated heavy rain will create
localized areas of flash flooding, affecting areas that experience rapid
runoff with heavy rain.  Additionally, heavy snow will develop over the
Cascades through Sunday morning.

Ziegenfelder


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