Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
403 AM EDT Tue Oct 29 2019

Valid 12Z Tue Oct 29 2019 - 12Z Fri Nov 01 2019


Day 1...

...Central Rockies/High Plains...
An amplifying shortwave trough dropping into the Great
Basin/central Rockies is expected to bring another round of
moderate to heavy snows to the region on Tuesday into early
Wednesday, with heavy accumulations possible from the mountains of
central Colorado to the High Plains of northeastern Colorado.  In
addition to heavy accumulations across the mountains of northern
to central Colorado, overnight guidance continues to show low to
mid level frontogenesis supporting heavy accumulations farther
east across the High Plains east of the Denver metro.  As the
upper level trough begins to move east of the area on Wednesday,
snows are expected to diminish.

Days 2-3...

...Central Plains to the northern Great Lakes...
Even by early Wednesday, models continue to disagree on the timing
of the upper trough/low moving east of the Rockies.  Similar to
previous runs, the GFS is faster than the other models as the
system moves east across the central Plains.  By early Thursday,
as the system moves into the lower Missouri and mid Mississippi
valleys, the GFS is deeper and farther to the south than the
general model consensus - developing heavier precipitation as the
system pivots northeast into the Great Lakes region on Thursday. 
With respect to QPF/snowfall accumulations, WPC continued to
prefer a solution more similar to the ECMWF and its ensemble mean
- indicating mainly light snowfall amounts shifting northeast from
the central Plains to the Great Lakes on Wednesday into early
Thursday.  While the GFS is likely overdone, do feel there is some
potential for a band of organized heavier amounts to develop from
eastern Iowa to northern Illinois and southern Wisconsin on
Thursday.

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

Pereira