Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
417 PM EST Mon Feb 24 2020

Valid 00Z Tue Feb 25 2020 - 00Z Fri Feb 28 2020


...Northern High Plains to the Central Plains...
Day 1...
Models continue to show a well-defined northern stream shortwave
dropping southeast along the northern to the central Rockies and
High Plains.  In addition to the favorable upper forcing, strong
low-to-mid level convergence along a developing low and lingering
inverted trough is expected to support light to moderate snows
across portions of the northern High Plains, from eastern Montana
and southwestern North Dakota to eastern Wyoming and western South
Dakota Monday evening into the overnight.  Orographic enhancement
is expected to enhance totals across the Black Hills region, where
locally heavy amounts are most likely.

Farther to the south, models have trended upward -- indicating a
stronger signal for at least light to moderate precipitation
developing, with rain changing to snow, along a narrow axis of
strong low-mid-level forcing extending north-south across central
Nebraska early Tuesday and northwest-southeast across northeastern
Kansas by late morning and continuing into the afternoon.


...Mid Mississippi Valley to the Upper Great Lakes...
Days 1-2...

Shortwave trough dropping southeast into the central Plains
Tuesday morning, is forecast to pivot northeast across the mid
Mississippi valley toward the western Great Lakes late Tuesday
into early Wednesday, with a band of moderate to heavy snow
expected to develop in the low-to-mid level frontogenesis and
deformation zone.  The daytime model runs continued the ongoing
trend toward a more southerly axis, with the 12Z GFS showing a
significant shift farther south.  Latest model consensus now shows
the heaviest amounts centering from far northeastern Missouri to
southern Lower Michigan.  Models are still showing the potential
for some lake enhanced, heavier amounts along the southeastern to
southern shores of Lake Michigan beginning Tuesday and continuing
into Wednesday.


 Northeast...
Day 3...
As the upper trough crosses the Great Lakes, an upper jet maxima
is forecast to move along the spine of the Appalachians, with a
well-defined 300 mb divergence maxima crossing PA/NY into interior
New England Thursday morning.  This will combine with low-mid
level warm advection to produce widespread precip across the
northern mid Atlantic to the northeast on Thursday.  The
combination of synoptic lift and upslope flow into the NY
Adirondacks, the VT Green Mountains, and NH White Mountains to the
ranges of interior Maine will support the potential for several
inches of snow at these locations.  Meanwhile, expect warm
advection will likely limit snowfall potential at lower
elevations, including the major cities.

For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Pereira