Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
407 AM EST Wed Jan 22 2020

Valid 12Z Wed Jan 22 2020 - 12Z Sat Jan 25 2020


Days 1-3...

...Pacific Northwest...
A warm front lifting north along the coast on Wednesday, followed
by an upstream cold front on Thursday, will bring periods of
organized heavy precipitation to western Washington and Oregon. 
Snow levels are expected to increase through Wednesday and remain
high on Thursday into Friday, limiting the potential for heavy
accumulations away from the higher peaks of the northern Cascades.

...Ozarks/Midwest...
A complex upper pattern consisting of several shortwaves moving
through a broad upper trough is expected to bring widespread, but
generally light winter precipitation to the region over the next
few days.

Ongoing precipitation over the central Plains will continue to
extend northeast as a low to mid level wave moving through the
base of the trough lifts northeast from the central Plains to the
Upper Midwest on Wednesday.  Overall snow and ice accumulations
are expected to be light, however WPC PWPF does show some low
probabilities for accumulations of 4-inches or more from
southeastern Minnesota to eastern Upper Michigan late Wednesday
into early Thursday.

Meanwhile, additional energy moving into the base of the trough
will support redeveloping precipitation over the southern Plains
into the Ozarks and lower Mississippi valley on Wednesday.   There
remains a good signal for significant ice accumulations over
portions of southern Missouri and northwestern Arkansas where WPC
PWPF shows locally high probabilities for ice accumulations of
0.10-0.25 inch Wednesday into early Thursday.

This energy is expected to lift north and phase with a upper low
closing off over the lower Missouri to mid Mississippi valleys
late Thursday to early Friday.  This is expected to produce
widespread light snows, with the potential for locally heavier
accumulations across the mid Mississippi valley.  The overnight
models presented a good deal of spread.  While there it the
potential for locally heavy amounts, model uncertainty is
reflected in the low probabilities for accumulations of 4-inches
or more.

The upper low is forecast to move east through the Ohio valley on
Friday, with light snows expected to spread across the Upper Great
Lakes.  By early Saturday, models show a secondary surface low
beginning to develop to the east, with organized heavier
precipitation moving north along the southern to central
Appalachians and Mid Atlantic.  Thermal profiles suggest a wintry
mix, with light snow/ice accumulations expected along the southern
to central Appalachians.

Pereira