Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
643 PM EST Mon Jan 23 2023

Valid 00Z Tue Jan 24 2023 - 00Z Fri Jan 27 2023

...Northeast...
Day 1...

In the wake of the departing coastal system, another shortwave
will roll through the Great Lakes and into NYS by Tuesday morning
with a broad area of light snow and light lake effect snows. With
a brief favorable alignment off Lake Ontario with the frontal
passage, some enhancement into the Tug Hill is likely with several
inches possible. WPC probabilities for at least 4 inches of snow
are moderate (>40%).


...Southern Rockies, Southern Plains, & Ozarks...
Day 1-2...

Deep upper low moving through southeastern AZ/southwestern NM this
evening (500mb heights around -3 sigma) will weaken just a bit as
it moves across Texas Tuesday the lifts through the Mid-MS Valley
Wednesday. Paired upper jets over the Southwest and exiting
northern stream jet streak will promote broad lift over the
NM/OK/TX as a modest moisture surge (PW anomalies around +1 sigma)
out of the western Gulf advects from the southeast. Surface low
will track out of northern Mexico and through the TX Hill Country
Tuesday with a marginal thermal environment over northern TX into
OK and deeper cold air over the TX Panhandle into NM. As the upper
shortwave or nearly closed low passes through, the column will
cool and rain will change to snow from west to east with the
potential for several inches over OK eastward and twice that
farther west where ptype will be all snow. Moderate to heavy snow
is likely over the Sacramento and San Mateo Mountains over NM. WPC
Snowband Probability Tracker indicates potential for 1-2"/hr
snowfall rates over the southeastern NM terrain and across the TX
Panhandle into central/southern OK, given sufficient cooling of
the column there (heavier rates would support increased
accumulations). A large spread in the ensembles exists over OK as
it is partially dependent on rates; e.g., 0-12" range in the
ensembles at some locations. WPC probabilities for at least 4
inches are greater than 50% in this area but over 80% over the
eastern NM terrain into the TX Panhandle.

Into Wednesday, the upper and sfc low will track northeastward
over and just southeast, respectively, of the Ozarks with the
diffluent right-entrance region over much of eastern OK and into
the Middle MS Valley. Moisture surge will progress eastward with
moisture transport up and over the surface warm front and 850
boundary to the north/northwest. Boundary layer temperatures will
be coldest over the Ozarks but precipitation will fall in the form
of snow beneath the deformation axis as it tracks from eastern OK
into southern MO and southern IL. Hourly snowfall rates ranging
between 1-2"/hr are likely here per the Snowband Tool. WPC
probabilities of at least 4 inches of snow are moderate to high on
D2 from northwest AR into IL, and are moderate (>40%) for at least
8 inches of snow.

...Lower Great Lakes, Midwest, northern Mid-Atlantic, &
Northeast...
Days 2-3...

Mid-level system and surface low will move into the lower OH
Valley D2 with a brief surge of milder air in advance of the cold
front. Advancing upper jet into the Great Lakes will provide for a
large area of lift as the system approaches from the
south/southwest. In-situ cold boundary layer and approaching
700-mb frontogenesis band will push through parts of Indiana/Ohio
Wednesday morning, with potential for several inches before a
changeover to rain and/or a dry slot (farther east, at least) move
in before the low passes. Deformation axis on the NW side of the
low will lift northeastward in tandem with the low, from MO into
IL and IN before weakening Wednesday afternoon. These areas on the
northwest track of the 850mb low are likely to witness the best
snowfall rates with a sufficiently cold thermal layer and very
saturated DGZs. NAEFS shows >90th climatological percentile values
of mean specific humidity in the 500mb layer throughout the region
by 06Z Wednesday and within the deformation axis, supporting
heavier rates. WPC probabilities for at least 4 inches of snow D2
are high (>70%) over much of southern/southeastern MO
northeastward into central/northern IN, northwestern/western OH
and southeastern Lower MI. Farther east, WAA-driven snow may come
in quite hard over central PA and into the Poconos on Wednesday,
but milder air may eventually change many places to a mix or plain
rain until the front comes through. Some light icing is possible
down the Appalachians as well.

The robust synoptic-scale ascent via dueling jet streaks at 250mb
makes its way into the Northeast Wednesday afternoon and into the
overnight hours. Similar to the northern Mid-Atlantic, strong
850-700mb WAA will result in periods of moderate to heavy snow
throughout the northern Appalachians (upstate/central/western NY
into the North Country and into central/northern New England).
Significant snow is possible over portions of New England (esp.
NH/Maine), contingent upon formation/deepening/track of a coastal
low (Miller-B type evolution) early Thursday. WPC probabilities
for at least 4 inches of snow are high (>70%) over much of central
PA and areas north of I-90 in northern NYS as well as much of
NH/VT/ME. In addition, WPC probabilities of at least 8 inches are
moderate (>40%) D2-3 over the Adirondacks, Green Mountains, and
across eastern NH into much of interior Maine. 


Fracasso/Mullinax

...Key Messages for Jan 23-26 Winter Storm...

--A large-scale winter storm will move into the southern Plains
Monday night and Tuesday, producing areas of heavy snow from
eastern New Mexico through Oklahoma.

--The storm is expected to strengthen and track northeastward from
the lower Mississippi Valley to the Great Lakes Tuesday night and
Wednesday, and produce a stripe of moderate to heavy snow from the
Ozarks to the Great Lakes.

--A wintry mix is expected to develop across portions of the
central Appalachians, with areas of heavy snow across portions of
the interior Mid-Atlantic on Wednesday.

--Heavy snow is forecast to spread across the interior Northeast
as a second area of low pressure develops along the coast
Wednesday night.

--Snow-covered roads and reduced visibility will make travel
difficult across impacted areas.  Gusty winds and heavy snow may
result in downed trees and power outages.