Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
352 AM EST Sat Jan 08 2022

Valid 12Z Sat Jan 08 2022 - 12Z Tue Jan 11 2022

...Mid-South through Midwest...
Day 1...

Return flow around high pressure centered over the Mid-Atlantic
and cyclonic flow from southern High Plains lee cyclogenesis will
direct warm air advection from the west-central Gulf Coast across
the Mid-South and into the Midwest through this evening. This warm
air will ride over particularly cold air this morning over the
Mid-South where low to mid 20s are currently across northern AR
and produce areas of light freezing rain before a changeover to
plain rain. Then later today this freezing rain spreads across MO
and into the Midwest where there are currently teens through
eastern MO/IL/IN and single digits in MI. Day 1 freezing rain
probabilities for over 0.01" are moderate through this swath from
the Ozarks to around Lake Michigan.


...Great Lakes...
Days 1-3...

An amplifying shortwave trough will dig across the Great Lakes
late tonight through Sunday. Strong cyclonic flow will develop
behind this trough and accompanying cold front. 850mb temps
plummet to the coldest of the season, falling below -20 to -25C,
over relatively warm/open lakes. The setup is favorable for an
extended period of heavy LES in the favored NW/W snow belts to
spread east across the lakes Monday through Monday night and
persisting into Tuesday for the eastern Lakes. Local soundings
suggest intense unidirectional flow and inversion heights over
10,000 ft with more than 500 J/kg of instability atop the Lakes.
Impactful heavy snow is likely for parts of the U.P. Sunday/Sunday
night, and in the Tug Hill area off Lake Ontario early Monday
through Monday night before flow becomes more northerly.


...Mid-Atlantic through central New England...
Days 1/2...

Cold high pressure centered over the central Mid-Atlantic with a
sfc ridge extending the length of the Eastern Seaboard today will
drift offshore tonight ahead of an approaching trough. Modest
return flow ahead of the mid-level trough and associated surface
front will spread WAA/precipitation across the central
Appalachians late tonight. The 850mb temps will climb well above
0C, but surface temps and surface wet-bulb temps will be below
freezing at precip onset and well into or through Sunday morning
across much of the central Mid-Atlantic northeast into interior
central New England. Day 1.5 probabilities for over 0.1" ice are
moderate to high from the northern Shenandoah Valley across
central and much of eastern PA, southern NY through the Berkshires
of MA and the Litchfield Hills of CT. East of this maximum axis is
likely light freezing rain accretion to a few hundredths of an
inch down to the the I-95 corridor from Washington, D.C. to
southern Maine including Boston, NYC, Philly, and Baltimore which
will cause travel concerns.


...Colorado Rockies...
Day 1..

A modest trough will push eastward across the Intermountain West
today while waves of embedded vorticity rotating through it,
providing good lift. Higher PWs will shunt south ahead of the
trough axis and focus moderate precip/snow on the CO Rockies where
Day 1 snow probabilities for 6+ inches are moderately high for
areas such as the Park and Sawatch Ranges.

Jackson