Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
444 AM EDT Sat Oct 17 2020

Valid 12Z Sat Oct 17 2020 - 12Z Tue Oct 20 2020


...Northern Rockies to the Black Hills...
A sheared mid-to-upper level shortwave drops southeast across BC
to eastern MT today with surface high pressure building into the
northern High Plains through tonight is expected to support heavy
accumulating snow across much of west-central MT...the Big Horns
of WY and the Black Hills through tonight. As a lingering boundary
and upper level jet support continues to support periods of snow
across this region into Monday. Days 1 and 2 snow probabilities
for 6 or more inches are moderate to high for much of the higher
elevations of west-central and southern MT.


...Northern Minnesota...
Day 1...

The clipper system forecast track has dipped south a bit across MN
and WI today. Low-to-mid level frontogenesis supporting a stripe
of accumulating snow across northern Minnesota including upslope
flow on the North Shore of Lake Superior this morning.  While the
progressive nature of the system should limit the potential for
widespread heavy accumulations, mesoscale banding is expected to
produce periods of moderate and potentially locally heavy
accumulations. Day 1 snow probabilities for 4 or more inches are
around 40 percent just above Minnesota's North Shore.


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

In response to a negatively-tilted upper level shortwave moving up
the Northeast surface low pressure is expected to deepen and move
north along the New England coast this morning, before crossing
eastern Maine and New Brunswick this afternoon. While all rain is
expected for most areas, a change to wet snow is expected for the
mountains of northern England. While mostly minor amounts are
expected, the highest elevations, including the Presidential Range
in northern New Hampshire, could see several inches of
accumulation.


For Days 1-3, the probability of significant ice accumulations is
less than 10 percent.

Jackson