Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
359 PM EST Sat Mar 05 2022

Valid 00Z Sun Mar 06 2022 - 00Z Wed Mar 09 2022

...Western U.S....
Days 1-3...

The upper low currently dropping southeast across California and
the southern Great Basin will move east through Sunday across the
Four Corners region. Locally strong forcing associated with the
height falls coupled with favorably moist upslope flow will result
in areas of heavy snow for areas of the Wasatch and the central
Rockies. The heaviest accumulations are expected to be over the
southwest facing slopes of the San Juan Mountains in southwest
Colorado where amounts locally in excess of a foot are expected.
The Wasatch and Uinta Range of Utah, and the Wind River Range of
western Wyoming are likely to see totals of as much as 6 to 12
inches. For Sunday night and Monday, a new upper trough digging
down from the northern Rockies will help to gradually eject the
upper low/trough crossing the Four Corners out into the Plains. A
combination of the departing energy and the arrival of new energy
will support a few inches of new snow, and especially the Colorado
high country for this period.

Meanwhile, a new and broad upper trough will impinge on the
Pacific Northwest and the northern Rockies Monday night through
Tuesday, and a cold front will be seen dropping southeast from
Alberta and Saskatchewan. Relatively moist deep layer northwest
flow over the Washington Cascades and the northern Rockies along
with embedded shortwave energy should result in the development of
orographically driven snow showers. Meanwhile, low-level
post-frontal upslope flow especially into the east-facing slopes
of the northern Rockies and far northern High Plains will be in
place by late Tuesday, and this will also couple with the moisture
and energy aloft for areas of northwest and central Montana to see
expanding areas of moderate to locally heavy snow. Snowfall
accumulations of as much as 4 to 8 inches are expected for these
areas with locally heavier totals approaching a foot by the end of
the period.


...Midwest to the Northeast...
Days 1-3...

Surface low pressure crossing the Upper Midwest this evening along
with an associated mid-level trough will advance through the Upper
Great Lakes overnight and then quickly into southeast Canada on
Sunday. An axis of snow, sleet, and freezing rain is expected
along the northwest flank of the low track. Much of the additional
freezing rain threat will extend from areas of central Minnesota
through northwest Wisconsin and across the U.P. of Michigan, and
this will tend to occur as the low-level flow begins to back
around and bring some low-level cold air back south as the low
center passes just to the south of the region. Locally heavy
precipitation will be expected as the core of the mid-level
energy/trough crosses this evening and overnight, and some of
these areas will likely see sufficient dynamic cooling arrive for
any areas of sleet and freezing rain to changeover to a period of
snow before ending Sunday morning. In fact, there is enough model
support for a swath of 2 to 3+ inch snowfall amounts from eastern
South Dakota through central Minnesota and far northwest Wisconsin
as the aforementioned upper-level support lifts northeast across
the region. Farther downstream across areas of northern New
England, and especially northern Maine, this system as it
approaches tonight will be encountering a retreating cold airmass,
but there is expected to be a burst of some accumulating snow
Sunday morning on the front end of the nose of strong warm air
advection. A brief changeover to some sleet and freezing rain is
expected too with some light icing possible before the system
gradually pulls away Sunday evening.
 
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 northern Illinois east-northeastward through
southern lower Michigan and the interior of New York and northern
New England. To the northwest of this axis, sufficiently deep
enough cold air will in place for a swath of light snow with 2 to
3+ inch amounts expected from areas of northeast Iowa, southern
Wisconsin and northern lower Michigan. Some light snow
accumulations will also be expected for areas of northern New
England with this next wave before it exits the Northeast Monday
night.

Orrison