Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EST Wed Nov 20 2019

Valid 12Z Wed Nov 20 2019 - 12Z Sat Nov 23 2019

...Mountain West onto the Central Plains...
Days 1-2...
High elevation heavy snow event will continue into Thursday night.

A cold core low over the south-central CA coast this morning will
merely drift east across the Four Corners region through Thursday
night. Snow levels drop to as low as 6000ft just ahead of this
low. With ample moisture streaming ahead of this low prolonged
high terrain snows are expected across the Desert SW and across
the central and southern Rockies. Widespread moderate to high
probabilities for 12 inches on Days 1/2 exist above 6000 ft from
the Mogollon Rim across the Wasatch to the Unitas, the San Juans,
Sangre De Cristos, and CO/southern WY Rockies. More moderate 8
inches probabilities extend across the Great Basin ranges, and
ranges and just into the high plains of southern WY/CO/northern
NM.

Two main swaths farther onto the central Plains are expected.
Tonight, light to moderate snow extends east from southern WY to
the NE Panhandle as a surface low develops over the lower central
Plains. The main upper low ejects across the southern Rockies
Friday with a swath of low probabilities for four inches extending
east from Raton Pass, along the CO/NM border and into the OK
Panhandle and southwest KS.


...Northern Great Plains to Lake Superior...
Days 1-2...
A positively tilted northern stream trough extending northeast
from MT will drift east, maintaining a cold/stationary front over
the northern Plains into Thursday. Meanwhile a trough ejecting
northeast from the Sea of Cortez will cross the central Plains
tonight. The associated surface low will develop over the central
Plains tonight and cross the Upper Midwest Thursday. The swath of
light to moderate precip currently shifting east from northern MT
to ND will merge into the northern end of the comma head of this
central Plains tonight and allow moderate to locally heavy snow
bands to form tonight over the Arrowhead of MN as gulf-sourced
moisture streams ahead of the surface low and across the cold
front. WPC probabilities are for 6 inches are in the likely range
(around 60 percent) in the Arrowhead for Day 1.


...New England...
Days 2/3...
The developed low from the Upper Midwest will cross interior
Quebec Friday with prefrontal southerly flow lifting over a cold
surface and causing light freezing rain over northern New England
Thursday night and across northern Maine Friday morning. Wrap
around snow on the back side of the system looks to produce mainly
light snow in the same areas of northern New England Friday
afternoon through Friday night. WPC probabilities for Day 3 are
moderate for two inches in far northern VT/NH/Maine.

Jackson