Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
424 AM EDT Sun Apr 12 2020

Valid 12Z Sun Apr 12 2020 - 12Z Wed Apr 15 2020


...Central Plains to the Upper Great Lakes...
Days 1-2 (12Z Sun-12Z Tue)...
A southern stream shortwave ejecting from the Southwest is
expected to lift northeastward out of the southern Plains ahead of
a northern stream trough amplifying over the northern Plains on
Sunday.  As the southern stream wave begins to assume a negative
tilt, a rapidly deepening surface low is forecast to track from
the lower Ohio valley to the Great Lakes Sunday night into early
Monday.  Northwest of the developing low, strong upper jet forcing
in combination with low-to-mid level frontogenesis will likely
support a stripe of moderate to heavy snows from the central
Plains to the upper Great Lakes.  Several members of the overnight
HREF guidance indicated strong potential for moderate to heavy
banded snow, producing QPF amounts of 0.10-0.30 in/hr, that is
forecast to move northeast from northeastern Nebraska and
southeastern South Dakota, across northwestern Iowa and southern
Minnesota into central and northern Wisconsin on Sunday.  WPC PWPF
shows high probabilities for snow accumulations of 6-inches or
more across this area.  Heavier amounts are expected farther to
the northeast over the western U.P. of Michigan, where strong
northerly winds will support lake enhancement Sunday night into
Monday.  WPC PWPF continues to show high probabilities for snow
accumulations of a foot or more across much of the western U.P. of
Michigan.

...Central Rockies...
Days 1-2 (12Z Sun-12Z Tue)...
Upslope flow behind a strong cold front plunging south through the
central Rockies and High Plains, along with modest upper forcing,
will support several inches of snow along the Front Range, with
lighter amounts farther east across the High Plains.  Heaviest
accumulations are expected to occur on Sunday, with some lighter
amounts continuing into Monday.  WPC PWPF shows high probabilities
for storm total amounts of 12-inches or more along the Front Range.

...Southwest to the Southern High Plains...
Days 1-2 (12Z Sun-12Z Tue)...
Mid level energy moving into the base of the base of a broad upper
trough, along with a developing upper jet couplet is expected to
support a stripe of organized precipitation, including high
elevation snows, across northern Arizona and New Mexico Sunday and
Monday.  While widespread heavy amounts are not expected, there is
the potential for locally heavy snow totals, including along the
Sangre de Cristo Mountains where WPC PWPF is indicating that local
amounts of 8-inches or more are likely.  As the better lift moves
east of the Rockies, cold air in place over the southern High
Plains will support accumulating snows over northeastern New
Mexico and southeastern Colorado into the Texas and Oklahoma
panhandles and southwestern Kansas Tuesday morning.

For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Pereira