Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Sun Jan 08 2023

Valid 12Z Sun Jan 08 2023 - 12Z Tue Jan 10 2023

...Two major episodes of heavy rain and mountain snow expected to impact
northern and central California amid a relentless parade of cyclones
moving across the Pacific...

...Scattered showers and thunderstorms moving across the Deep South
today...

...Light rain and a wintry mix expected to track through the Midwest today
followed by the northern Mid-Atlantic Sunday night into early Monday...

The West Coast remains under the target of a relentless parade of cyclones
that form and intensify over the Pacific Ocean while moving directly
toward the North American continent.  Two major episodes of heavy rain and
mountain snow are expected to impact northern and central California
during the next couple of days.  The first episode is currently associated
with the energetic and moisture-laden fronts that are swinging rapidly
toward the West Coast ahead of a large cyclone.  Heavy rain and mountain
snow have already overspread much of northern California while expanding
further south into central California.  Meanwhile, heavy snow has reached
the interior mountains including the Sierra Nevada.  A lull in this latest
episode of heavy precipitation is expected by tonight as the storm system
is forecast to weaken quickly over land.  However, a more potent surge of
moisture associated with the next system in line is forecast to once again
impact northern California by Monday morning, shifting further south into
central California by Monday night before starting to taper off early on
Tuesday.  Heavy new snow along the Sierra Nevada could exceed 5 feet with
this onslaught of moisture.  The heavy snow loads will increase the threat 
of avalanches and damage to infrastructures.  With terrain already saturated 
from previous rainfall, additional bursts of heavy rain will lead to a 
heightened threat of flash flooding and rapid rise of river levels.  The 
longevity and intensity of rain, combined with the cumulative effect of 
successive heavy rain events dating back to the end of December, will lead 
to widespread and potentially significant flood impacts.  In addition, strong 
and gusty winds are expected to accompany the passages of the energetic fronts,
which could result in downed trees and scattered power outages.  Residents
and visitors are advised to check their local forecast, never drive across
flooded roadways (Turn Around Don't Drown!), and have both an emergency
kit and evacuation plan in place.

For the central and eastern U.S., a relatively weak low pressure system is
forecast to track eastward across the mid-Mississippi and Tennessee
Valleys today before reaching the East Coast tonight.  Showers and
thunderstorms moving across the Deep South ahead of the trailing cold
front this morning are expected to head further northeast for the rest of
today with diminishing intensities.  On the northern side of this system,
a light wintry mix and cold rain moving across the Midwest should reach
the northern Mid-Atlantic/central Appalachians tonight into Monday morning
which could cause locally slick roads.  The light precipitation will then
exit the East Coast later on Monday as a low pressure system intensifies
and moves out into the Atlantic.  Meanwhile, tranquil weather is expected
for the rest of the mainland U.S. with temperatures generally milder than
average.

Kong/Snell


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