Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
354 PM EST Sat Nov 09 2019

Valid 00Z Sun Nov 10 2019 - 00Z Wed Nov 13 2019

...Northern Plains and Rockies...
Days 1-2...
An Arctic high currently centered over the Yukon will dive south
behind a surface cold front currently pushing into MT from Canada
with a positively tilted upper trough in between. The particularly
cold air, upslope post-frontal flow from the high and upper level
support will promote moderate to locally heavy snow mainly over
north-central MT and eastern slopes of the Rockies in MT through
Sunday night. In addition, a stripe of light to moderate snowfall
oriented NW to SE from near Glacier NP into Iowa can be expected
tonight into Monday night as the right entrance region of a jet
streak tracks along the trough. Pockets of heavy snowfall are
likely in the terrain of central MT and northern WY, as well as
into the Black Hills of SD, where WPC probabilities are moderate
for 4 inches.

Since much of the upper level forcing shifts east across the
northern tier of the CONUS, the threat for heavy snow decreases as
the upslope flow pushes south from WY Sunday night into Monday.

...Great Lakes...
Days 1-3...
An upper level trough swinging across the Great Lakes Sunday night
through Tuesday will bring another round of lake effect snow,
heaviest Monday through Monday night. Ongoing cold air advection
will increase behind the upper trough and promote more NNW to SSE
band orientation off Lakes Superior and Michigan. Locally high
amounts are possible given the instability over the relatively
still warm lake surface.

...Northeast...
Day 3...
A wave of low pressure developing along a cold front currently
over the northern Great Plains will shift northeast across the
Midwest to the Northeast Sunday night through Tuesday. The exact
surface low track will determine where mixed precip and the
heaviest snow sets up. For now a slightly inland track that favors
snow for inland portions of New York and New England is preferred.
The ECMWF continues to be farther inland than the GFS/NAM, so
progress of this track will need to be closely monitored.
Cyclogenesis of the low along the front will promote comma head
development and prolonged duration in snow north of the track. The
heaviest snowfall is likely in the highest terrain where upslope
enhancement is likely, and WPC probabilities are moderate for 6
inches in 24 hours for the Adirondacks, as well as the highest
terrain of VT and NH. Further SE into the foothills and towards
the coast, WAA will make the column too warm for snow until the
low pulls away and CAA commences. Some light freezing rain is
possible before changeover to snow occurs, but accumulations of
snow and/or freezing rain are expected to be light at this time.

The probability for significant icing is less than 10 percent all
3 days.

Jackson