Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Tue Jan 10 2023

Valid 12Z Tue Jan 10 2023 - 12Z Thu Jan 12 2023

...Another high impact heavy precipitation event today across much of
California with areas of thunderstorms and very gusty winds...

...Same storm system will bring widespread mountain snows across the
western U.S. followed by light snow across the central Plains and
thunderstorms across the South...

...Next Atmospheric River expected to impact northern California and the
Pacific Northwest beginning on Wednesday...

Just as the last episode of heavy precipitation across California is
beginning to wind down early this morning, another energetic low pressure
system is quickly gathering strength off the West Coast and heading once
again toward California.  In addition to being highly moisture-laden, this
rapidly intensifying system is also packing some thunderstorms.  The core
of the system will slam onshore with moderate to heavy rain resuming
across much of California today through tonight while several more feet of
snow is possible along the Sierra Nevada.  Nearly all of California has
seen much above average rainfall totals over the past several weeks, with
totals 400-600% above average values.  This has resulted in nearly
saturated soils and increasingly high river levels.  Today's heavy rain
will further exacerbate ongoing flooding while prolonging the risk of
flash flooding and mudslides especially across recent burn scar regions. 
By later tonight, the storm system will push rapidly inland, bringing
widespread mountain snows across the Great Basin as the heavy
precipitation across California begins to wind down.  However, an enormous
cyclone forming well off the coast of the North American continent will
bring yet another Atmospheric River toward the West Coast--this time
impacting areas further north from northern California northward up the
coast of the Pacific Northwest on Wednesday.  When all is said and done,
precipitation totals over the next few days will be in the 3-7 inch range
through the Transverse Range of southern California, northward along the
central to northern California coast ranges and through the Sierra. 
Widespread considerable flood impact is likely across large portions of
California into western Nevada.  The one good aspect of the recent heavy
rains has been relief from the persistent drought that has been plaguing
large portions of the West.  Much of California into the Great Basin have
seen 1 to 2 drought class improvements over the past month.  This much
above average precipitation is also being seen in reservoir levels across
California.  Many reservoirs are now above their historical average
levels, with water levels increasing rapidly during the past month.

The storm system associated with today's heavy precipitation in California
will quickly move through the western U.S. tonight and emerge into the
central Plains on Wednesday.  The system will be re-energized as it pulls
colder air from the north and warm air from the south.  The system will be
moisture-starved to begin with but moist air from the Gulf of Mexico will
eventually work its way northward into the system.  This will fuel some
thunderstorm developments over the Mid-South by Wednesday night ahead of a
strong cold front as the low pressure system intensifies and tracks
northeast toward the Mid-Mississippi Valley.  Some light snow is expected
across the central Plains along with increasing winds from the north and
northwest Wednesday night.  Farther north, some light snow and wintry mix
are expected to accompany a low pressure wave moving slowly across the
upper Midwest into the upper Great Lakes Wednesday and Wednesday night.

Kong/Oravec


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