Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
326 PM EST Fri Mar 04 2022

Valid 00Z Sat Mar 05 2022 - 00Z Tue Mar 08 2022

...Western U.S. into the Central High Plains...
Days 1-3...

A shortwave trough currently traversing the Southwest will eject
northeast across the southern Rockies overnight and across the
central High Plains Saturday morning. This energy coupled with
favorably moist upslope flow will bring areas of heavy snow to the
higher terrain of the Mogollon Rim of northern and central
Arizona, and extending northeastward across the central Rockies.
Snow totals of as much as 6 to 12 inches are expected going
through Saturday morning, with isolated heavier amounts upwards of
18+ inches possible for the favored San Juan Mountains in
southwestern Colorado where stronger forcing and orographics will
result in heavier snowfall rates. As a result, WPC probabilities
for exceeding 8 inches are greatest in this area.

As this energy ejects northeast through through the central High
Plains, there will be developing low pressure over eastern
Colorado which will edge east into Kansas and being lifting
northeast toward the Midwest late in day on Saturday. This will
favor a favorable set-up for locally heavy snow for areas of
north-central Colorado, southeast Wyoming and into western
Nebraska. As much as 6 to 12+ inches is expected for the higher
terrain including the Medicine Bow and Laramie ranges, with as
much as 4 to 8 inches expected for the adjacent High Plains.
Correspondingly higher WPC snowfall probabilities are indicated
across these areas.

Meanwhile, a new upper low dropping southeast toward northern
California will be advancing inland across the southern Great
Basin on Saturday along with a reloading of a broad trough over
the Southwest by Saturday night. This will bring accumulating snow
tonight to the Modoc Plateau and Warner Mountains of northern
California, with snow also advancing gradually south through the
Sierra Nevada. More widespread coverage of snow along with heavier
totals are expected farther inland across the elevated plateau
areas of Nevada and the high terrain of southern Utah on Saturday.
Locally over a foot of snow is possible for these interior ridges
by Saturday evening.

For Saturday night and Sunday, the broader trough/closed low will
edge east into the Four Corners region and this will reload the
snow for the Wasatch and the central Rockies with sufficient
moisture and forcing for as much as an additional 4 to 8+ inches.
The heavier amounts should generally again be over the San Juan
Mountains. This energy will be advancing out across the central
Plains by Sunday night and Monday with snowfall tapering down in
this period.


...Midwest through the Great Lakes/New England...
Days 1-3...

Light to moderate precipitation falling in the form of a wintry
mix is again expected to develop across portions of the Upper
Midwest overnight into Saturday. The models show the first
ejecting Southwest U.S. shortwave advancing quickly across the
Midwest by late Saturday along with ejecting low pressure. The low
center will be deepening somewhat as it crosses the Upper Great
Lakes Saturday night through Sunday morning. A mixture of snow,
sleet, and freezing rain along the northwest flank of the low
track is expected and sufficiently deep enough cold air is
expected to foster locally a swath of 2 to 4+ inch snowfall
amounts from eastern South Dakota through central Minnesota and
far northwest Wisconsin. Much of the snowfall will tend to be on
the back side of the low center as a corresponding mid-level
deformation axis crosses favors stronger dynamic cooling for a
changeover of any wintry mix over to all snow.

However, just to the southeast, there will be a notable warm nose
aloft edging northeast and ahead of the low center with the warm
air advection pattern, and thus there will be an axis of sleet and
freezing rain extending from areas of especially eastern South
Dakota through central Minnesota, central/northern Wisconsin and
the U.P. of Michigan. Even on the back side of the low center, a
warm nose will still linger for some areas to foster plenty of ice
potential for the entire event. The greatest probabilities of
seeing over a 0.10" of ice are for northwest Wisconsin through the
western U.P. of Michigan. Some of the icing may be locally
significant across these areas with storm total ice in excess of a
0.25" going through Sunday.

As this system pulls way by late Sunday, additional energy
ejecting out across the central Plains will already be driving the
development of a new wave of low pressure across the middle
Mississippi Valley which will then very quickly move into Ohio
Valley by Monday morning and then New England by Monday evening.
Sufficient low-level cold air is expected to be in place to the
northwest of the low track to favor a swath of some light freezing
rain from parts of southeast Iowa, northeast Missouri, and
Illinois east-northeastward through southern lower Michigan and
the interior of New York and northern New England.

Orrison