Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 PM EST Mon Feb 17 2020

Valid 00Z Tue Feb 18 2020 - 00Z Fri Feb 21 2020

...Great Lakes and Northeast...
Days 1-3...

Phasing mid-level energy MN/WI this evening will support a
deepening surface low shifting from northern MO to the LP of MI
tonight. Low-to-mid level frontogenesis along with favorable upper
jet forcing (right entrance region of a jet streak) is expected to
support a stripe of light to moderate snows on the northwest side
of the low track (mainly central WI to northern MI tonight). Day 1
snow probabilities are moderate to high for four or more inches in
a stripe northeast from both sides of Green Bay WI and across
northern MI.

The surface low will shift northeast from MI Tuesday, tracking on
the north side of the St. Lawrence through Tuesday night. Warm
advection precipitation will spread quickly east from the Great
Lakes across the Northeast on Tuesday.  With high pressure over
the Northeast moving rapidly offshore, thermal profiles continue
to show some snow at the onset before changing to rain across much
of northern Pennsylvania, western to southern New York and
southern New England. Farther north however, expect snow to remain
the dominant precipitation type, particularly from the Adirondacks
into northern New England, with at least a few inches likely along
the favored terrain. Day 1.5 snow probabilities for four or more
inches are moderate to high for the southern Adirondacks, the
highest Green Mtns in VT, the White Mtns of NM/western Maine and
much of far northern Maine.

...Central Rockies and High Plains...
The combination of back-to-back mid-level troughs that keep a mean
positively-tilted trough over the northern Rockies and a deep
surface high spreading southeast across the northern Great Plains
will promote an upslope flow and low level convergence from the
central High Plains into the mountains of eastern Colorado. The
first round is tonight through Wednesday over southeastern CO and
western KS with to 20 to 30 percent probabilities for four or more
inches over the eastern CO High Plains (roughly across the Palmer
Divide) on Day 1. The second and more significant round is early
Wednesday through Wednesday night over western NE, spreading south
to southeastern CO. Day 2 snow probabilities are 20 to 30 percent
for four or more inches over west-central NE and Day 2.5 snow
probabilities are moderate for four or more inches over the
southeastern CO High Plains and western KS with high probabilities
for eight or more inches for the Sangre de Christos in southern
Co.

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

Jackson