Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Mon Jan 09 2023

Valid 12Z Mon Jan 09 2023 - 12Z Wed Jan 11 2023

...Two major episodes of heavy precipitation expected to impact California
today and Tuesday...

...Periods of mountain snow spread across the Intermountain West and into
the northern and central Rockies...

...Well above average temperatures build into the southern Plains...

Two major episodes of heavy rain and heavy mountain snow are expected to
impact California in quick succession during the next couple of days in
association with two of the more energetic and moisture-laden parade of
cyclones that are aiming directly for California.  The heavy precipitation
episode currently streaming into central California is expected to be the
more robust of the two, resulting in heavy rainfall totals of 3-5 inches
near the coast.  The second episode will quickly arrive on Tuesday with
amounts slightly less heavy, but impacting locations farther south into
southern California.  The Sierra Nevada will likely see heavy snow
exceeding 6 feet across the higher elevations before the snow tapers off
Wednesday morning.  The cumulative effect of successive heavy rainfall
events will lead to additional instances of flooding. This includes rapid
water rises, mudslides, and the potential for major river flooding.
Susceptible terrain and areas near recent burn scars will be most at risk
for debris flows and rapid runoff. For the higher terrain of the Sierra
Nevada, extremely heavy snow and intense snowfall rates are anticipated to
make travel very dangerous to impossible at times, including the potential
for road closures. The amount of additional accumulating snow on top of an
already well built snowpack is likely to increase the threat of avalanches
and strain infrastructure. Gusty winds are also expected to spread onshore
with the approaching system and could lead to the threat of downed trees
and power outrages. The combination of saturated soil and gusty winds
could exacerbate the tree damage threat. Residents and visitors across
this region 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.

Elsewhere, excess moisture associated with the two heavy precipitation
episodes is forecast to reach well inland across the Intermountain West
and central Rockies. Widespread mountain snow, locally heavy, can be
expected to reach the northern Great Basin later today, before more
mountain snow expands farther south across the Great Basin toward the
central Rockies on Tuesday into early Wednesday. For the eastern U.S., a
weak system with a light wintry mix across the northern Mid-Atlantic and
showers near the Eastern Seaboard this morning will quickly exit into the
Atlantic.  Tranquil weather is anticipated for the remainder of the
country today, as much above average temperatures begin to establish
across the southern Plains on Tuesday, where high temperatures into the
60s and 70s are forecast from the southern Plains to the Deep South, upper
70s and 80s across Texas.  By early on Wednesday, a low pressure wave
could deliver a period of snow across the northern Plains into the upper
Midwest.

Kong/Snell


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