Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
328 AM EST Tue Jan 23 2024

Valid 12Z Tue Jan 23 2024 - 12Z Fri Jan 26 2024

....Central Plains to the Northeast...
Days 1-3...
An upper level ridge is forecast to remain in place over the
southeastern U.S., directing a series of shortwaves from the
southern Plains to the Northeast.  Ongoing warm advection
precipitation associated with a leading wave that is now moving
across the mid Mississippi Valley will continue to spread east
from the Great Lakes into the Northeast.  Ahead of the system,
cold low level dry air associated with a high centered over
southeastern Canada remains in place over the Northeast.  Warm air
aloft and subzero surface wet bulb temperatures will support a
wintry mix spreading from the southern Great Lakes region into the
Northeast this morning.  Freezing rain is expected across northern
Pennsylvania into the Catskills, with the WPC PWPF still
indicating probabilities above 50 percent for ice accumulations of
0.10 inch or more across north-central to northeastern
Pennsylvania and the Catskills on Day 1.  Within the deeper cold
air to the north, light snow accumulations are expected from
northern Lower Michigan to southern New England.  Overall, snow
accumulations are expected to be an inch or two at the most, with
WPC PWPF less than 10 percent for accumulations of 4 inches or
greater.  Meanwhile, a wintry mix is expected to develop within
the system's deformation band, producing light ice and snow
accumulations from eastern Kansas and Nebraska to southern
Wisconsin and northern Illinois this morning, before shifting into
Lower Michigan during the afternoon.

Another shortwave will move quickly on the heels of the first,
lifting from the mid Mississippi Valley to the Great Lakes
Wednesday morning.  A wintry mix along the northern edge of
deformation band is expected, resulting in some light ice
accumulations as it lifts north across the lower Missouri and mid
Mississippi valleys Wednesday morning.  Mostly rain is expected
ahead of this next system across western to central New York and
Pennsylvania.  However, some pockets of freezing rain are possible
as precipitation spreads back into the region on Wednesday.  A
greater threat for additional accumulating ice is expected across
the Catskills and Adirondacks into the Green and White mountains. 
With precipitation expected to transition over to rain for much of
these areas as well, the probabilities for ice accumulations of
0.10 inch or more are less than 50 percent for much of the region
on Day 2.

The series of shortwaves will continue, with another wave moving
across the Great Lakes Friday morning.  While rain is expected for
most areas, a cold air wedge associated high pressure sliding east
into Atlantic Canada will support a wintry mix across Maine and
northern New Hampshire Friday morning.

...Western U.S....
Days 1-3...
An amplifying trough will bring high elevation snow to the
Southwest as it moves across the region today.  Generally light
accumulations are expected along the Mogollon Rim, with locally
heavy accumulations forecast across the southeastern Arizona and
southwestern New Mexico mountains, especially for areas above 7000
ft.

Meanwhile, shortwave ridging will support dry conditions across
much of California and the Northwest late Tuesday into early
Wednesday before a closed low moving across the northeastern
Pacific and its associated frontal band impact the region
beginning later in the day.  Precipitation amounts will be
relatively light as this progressive system quickly dissipates
while it moves inland.  Snow levels will be rising on Wednesday,
further limiting the threat for widespread heavy snows.  However,
several inches are possible across the higher elevations of the
Cascades and Sierra Nevada.    

Energy associated with this system will dig southeast, amplifying
a trough and bringing generally light snow across the Great Basin
into the Four Corners region on Thursday into Thursday night.

Pereira