Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
307 AM EST Thu Dec 29 2022

Valid 12Z Thu Dec 29 2022 - 12Z Sat Dec 31 2022

...Heavy rain and mountain snow to enter the West today and continue
through the end of the week...

...Increasing shower and thunderstorm chances across parts of the Gulf
Coast and lower Mississippi Valley...

...Well above average temperatures forecast throughout the central and
eastern United States...

A series of fronts will move onshore the West Coast and track through the
West and exit across the Plains spreading moderate to heavy precipiation
across the West Coast and for portions of the Deep South. An initial wave
of moisture will make its way inland over the Pacific Northwest and parts
of California today with a potent atmospheric river following on its heel
for the end of the week. Moderate to heavy precipitation is expected along
with heavy mountain snow. Most of the potential impacts are anticipated
across central/northern California and parts of southwest Oregon where
rainfall amounts of 3 to 6 inches are forecast through early this weekend.
These amounts may lead to scattered instances of flash flooding,
especially near recent burn scars where terrain is most susceptible to
rapid runoff. WPC has identified an area having a Slight Risk (level 2/4)
of Excessive Rainfall for these regions in order to further highlight the
flash flood threat. Heavy snow is possible across the higher elevations of
the Cascades and Sierra, with storm total snowfall amounts up to several
feet are possible. Most of the snow will be confined to the highest
terrain as warm Pacific air pushes snow levels very high and generally
above pass level. Moisture will also spread into the Intermountain West
along the strong Pacific jet stream, with moderate to heavy snow possible
across northern Nevada by Friday night.

East of the Rockies, an upper-level trough will pass through the Plains
while high pressure over the East Coast shifts eastward. As this occurs a
steady plume of warm and moist air begins to surge northward out of the
Gulf of Mexico. A quick-hitting swath of snowfall is possible to the north
of a developing low pressure system as it progresses from Kansas to the
Upper Midwest today. The best chances for over 4 inches of snow is
currently expected to remain confined to central High Plains of Colorado.
Farther east, shower and thunderstorm activity is anticipated to develop
across parts of eastern Texas and the Lower Mississippi Valley through
Friday as atmospheric moisture content increases ahead of an approaching
cold front.  There is the potential for some of these thunderstorms to
turn severe with damaging wind gusts the primary risk. A few instances of
flash flooding are also possible. The active weather is expected to shift
east by the end of the week and produce locally heavy rainfall from the
central Gulf Coast to parts of the Ohio Valley.

Temperatures across much of the nation will undergo a drastic warm up in
comparison to those near the start of the week. As mild air surges
northward around the high pressure system pushing into the western
Atlantic, highs into the 50s and 60s  will be common for the eastern
states. Daily minimum temperatures may reach record warm territory
throughout the Great Lakes and Interior Northeast by Friday, where
overnight lows are not expected to drop below the upper 30s. This equates
to over 20 degrees above average compared to climatology.

Campbell/Snell

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