Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
258 PM EST Tue Jan 03 2023

Valid 00Z Wed Jan 04 2023 - 00Z Fri Jan 06 2023

...Heavy snow across parts of the Upper Midwest through Wednesday while
freezing rain and a wintry mix spreads into northern New England by
Thursday...

...Severe thunderstorms and instances of flash flooding likely across
portions of the Southeast tonight...

...Strong atmospheric river to produce heavy rain, damaging winds, rough
surf, and heavy mountain snow across much of California into southern
Oregon on Wednesday and Thursday...

Two major storm systems are anticipated to impact the Nation over the next
few days, with one currently situated over the central and eastern U.S.,
while another enters the West Coast by Wednesday. For the ongoing system,
an area of low pressure churning over Iowa is expected to very slowly
drift into the Upper Midwest through Wednesday before gradually
dissipating on Thursday. Heavy snow is likely to the northwest of this low
throughout central/southern Minnesota and into northern Wisconsin/U.P. of
Michigan, with light freezing rain amounts extending just to the south of
the better snow chances. Travel conditions could be treacherous at times
within intense snowbands and areas of light freezing rain. Snow should
decrease in intensity throughout this region by Wednesday night as the
robust influx of moisture shifts to the East Coast. An anomalous and
record-breakingly warm airmass surging up the eastern U.S. will allow for
precipitation to fall as rain outside of northern New England. For
portions of Upstate New York, Vermont, New Hampshire, northern
Massachusetts, and Maine, sleet and freezing rain is possible as cold air
lingers at the surface while much warmer air flows in aloft. Freezing rain
amounts up to at least a quarter of an inch are probable and could lead to
scattered tree damage and power outages.

With the extremely warm and moist airmass in place across the East Coast
and Southeast, heavy rain and severe thunderstorms are likely ahead of an
approaching cold front as it swings eastward tonight. The greatest threat
for heavy rain to produce flash flooding is forecast over parts of
central/southern Mississippi, where a Moderate Risk (level 3/4) of
Excessive Rainfall has been issued. Several inches of rain falling in a
short amount of time could lead to several flash floods, with some
potentially becoming significant. Residents are urged to plan ahead before
traveling and make a plan if located in a flood-prone region. Never drive
through flood waters! Additionally, severe thunderstorms are possible from
the central Gulf Coast to the southern Appalachians and Southeast through
early Wednesday. Damaging wind gusts, large hail, and tornadoes are
possible, with the threat gradually weakening as the showers and storms
push into Georgia and northern Florida.

The other major weather story is about to enter the picture as an intense
storm system over the eastern Pacific sends a strong atmospheric river
into California on Wednesday and Thursday. A plethora of hazards are
forecast, with heavy rain and strong winds expected to be the most
widespread impact. Widespread rainfall amounts of 3 to 6 inches are
anticipated, with locally higher amounts throughout the coastal ranges and
over northern California. These rainfall amounts would normally not lead
to widespread or significant impacts, but recent rainfall has left soils
saturated and susceptible to flooding and rapid runoff concerns. Sensitive
terrain will also have the potential for landslides. A Moderate Risk of
Excessive Rainfall has been issued for the northern and central California
coast, where flooding impacts are most likely. The heavy rain threat will
shift southward along a cold front by late Wednesday into early Thursday
into parts of southern California. However, by this point the area of
heavy rain should be rather progressive and limit major impacts, with more
scattered flooding concerns possible. Another aspect of this storm system
will be the widespread hazardous winds to move onshore. Wind gusts up to
70 mph are possible across coastal ranges, while valley locations see
gusts up to 50 mph. Power outages could become a more widespread issue
where heavy rain and saturated soils lead to more downed trees. Rough surf
is inherently likely along coastal regions as the high winds lead to
hazardous seas. Lastly, the high terrain of the Sierra Nevada is forecast
to experience extremely heavy snow rates above 3 inches per hour. These
rates are probable for areas residing above 5000 feet and will make travel
very dangerous to impossible at times. White out conditions will also be a
concern when combined with gusty winds. Residents and visitors located in
California over the next few days are advised to check their local
forecast and plan ahead for potentially hazardous weather conditions.


Snell

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