Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
409 PM EDT Thu Oct 10 2019

Valid 00Z Fri Oct 11 2019 - 00Z Mon Oct 14 2019

Days 1-3...

...Major early season snowstorm spreading into the Northern
Plains...

...Northern Plains...

A powerful, early-season winter storm will continue to take shape
through the night, with heavy snow becoming more widespread as the
entire area spreads eastward across the Dakotas through Friday. 
Snowfall in the Dakotas is expected to linger into Saturday as the
system becomes occluded...resulting in heavy, potentially historic
accumulations for early October.

Overall...the 12Z suite of guidance remained in good agreement
with the large-scale features. Increasingly strong low to
mid-level frontogenesis will support banded precipitation and the
formation of a well-defined deformation zone...both of which will
result in enhanced snowfall rates.  While the system may have a
narrow band of mixed precipitation, the chances of multiple
precipitation types should be decreasing with time. The models are
also pointing to coupled left exit region and right entrance
region upper level jet streaks south and north of the eastern ND
respectively.

By Saturday, the mid/upper level circulation center continues to
drift out of the Dakotas and across northwest Minnesota to the
Canadian border. This will allow for snows to gradually taper off
across the Dakotas as drier air works in from the west. Farther
east, the risk of snows will start to be limited by a developing
dry slow as the entire system occludes.

70+ percent probabilities of exceeding 8" over through 12Z
Saturday encompass the eastern half of ND, while also clipping
north-central and northeast portions of SD. Probabilities of
exceeding 2 feet are now over 50% across a good chunk of eastern
ND, where quite a few models show spotty totals around or
exceeding 3 feet. The threat of heavy snowfall will be diminishing
considerably on Sunday.

The probability of significant icing is less than 10 percent Days
1-3.

Bann