Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EDT Fri Nov 01 2019

Valid 12Z Fri Nov 01 2019 - 12Z Mon Nov 04 2019


Days 1-3...

...Great Lakes...

Day 1...A brief of snow showers in the post frontal cold advection
is expected in the Tug Hill to western Adirondacks today.  The
models show loss of lift plus drying tonight so the limited
duration should result in light accumulations.

Day 2...
The next cold front progresses across the Great Lakes.  The models
show possible boundary layer west winds across Lake Erie,
supporting potential for snow showers in favored terrain east of
Lake Erie.  A few high res models show as much as a half inch
liquid equivalent QPF, supporting potential for 4 to 6 inches of
snow. A few snow showers are expected in modest low level enhanced
convergence and relative humidity off Lake Superior and Lake
Michigan.
Warmth from the lake may keep the precip from being all snow,
particularly in near shore areas. The event winds down Sun as a
ridge approaches from the Ohio Valley, with drying aloft and loss
of lift leading to less activity. 


...Northern Rockies...

Day 3...
On Sunday night to early Mon morning, confluent flow aloft leads
to a 300 mb jet maxima extending south from Canada into MT.  The
confluent flow enhanced relative humidity over time to moisten the
column.  Flow coming into terrain of southern MT turns upslope,
resulting in likely show showers developing there. The NAM
shortwave is more amplified than the GFS, ECMWF, and UKMET, with
higher amounts resulting in the Beartooth Range. 

The probability of significant icing (0.25 inches) is less than 10
percent all 3 days.

Petersen