Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
337 PM EST Sun Mar 06 2022

Valid 00Z Mon Mar 07 2022 - 00Z Thu Mar 10 2022

...Western U.S.... 
Days 1-3... 
 
A new northern stream upper trough digging down from the northern
Rockies will help to gradually eject the current 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 tonight through Monday, and especially the
Colorado high country. This additional intrusion of northern
stream energy should then exit southeastward gradually out into
the Plains on Tuesday.

Meanwhile, a new and broad upper trough will impinge on the
Pacific Northwest and the northern Rockies Monday night through
Tuesday, and an Arctic 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, with
the cold front itself, there will be rather strong forcing and
sufficiently steep enough lapse rates/shallow instability for a
rather high chance of seeing snow squalls along and immediately
behind the frontal passage. Linear bands of snow squalls should
advance down from northwest to central Montana Monday evening and
will support some brief intense snowfall rates that could reach
1"+/hour. Low-level post-frontal upslope flow into the east-facing
slopes of the northern Rockies and northern High Plains will be in
place moving forward going through Tuesday, and this coupled with
the mid-level moisture fetch and energy aloft will favor an
expansion of areas of moderate to heavy orographically focused
snowfall across northwest and central Montana. As the overall
upper trough and focus of shortwave energy advances further south
into the Intermountain Region Tuesday and Tuesday night, there
will also be heavy snow spilling over into the Bitterroots,
Sawtooth and Blue Mountains as well. Snowfall accumulations of as
much as 4 to 8 inches are expected for the region with locally
heavier totals approaching a foot by early Wednesday for the
favored higher peaks.

On Wednesday, the upper trough will be broadening further down to
the south across the Intermountain Region and into the central
Rockies, and this will allow for areas of heavy snow to begin
focusing down across the favored terrain of western Wyoming,
northern Utah and northwest Colorado. This will include the
Tetons, Wind River Range, Uinta and Wasatch ranges. The northwest
Colorado high country will also see heavy snow arrive. Rather
divergent flow aloft associated the approach of the upper trough,
coupled with mid-level moisture and orographics will favor some
snowfall totals in the 4 to 8 inch range with isolated totals
approaching a foot by Wednesday night. Low pressure will also be
developing over the Colorado High Plains by early Wednesday as the
aforementioned cold front continues to settle southward.
Post-frontal east-northeast flow into High Plains of southeast
Wyoming including the Laramie Range and the ejecting energy from
the upstream trough will allow snow to develop and spread east
across these areas as well, with the snow advancing out into far
southwest South Dakota and much of central and western Nebraska.
Several inches of snow is expected by late Wednesday across these
areas with the Laramie Range likely seeing some amounts exceeding
8 inches.


...Central Plains to the Lower Great Lakes and New England...
Days 1-2... 
The mid-level closed low currently advancing east through the Four
Corners area will advance out across the central Plains this
evening and will generate a new area of low pressure along the
front across the middle Mississippi Valley which will then very
quickly move into Ohio Valley by Monday morning and then New
England by Monday evening. A nose of at least some modest elevated
instability coupled with strong forcing/vort energy associated
with the ejecting trough should foster an axis of convectively
driven precipitation across areas of the central Plains and lower
Missouri Valley this evening with snow, sleet and freezing rain
expected. This will include the Kansas City metropolitan area
where some brief heavy snow is expected and potentially a couple
of inches of accumulation. As the energy lifts northeastward
overnight and Monday, there should be a swath of 2 to 4 inch
snowfall amounts extending across northwest Missouri,
southern/eastern Iowa, southern Wisconsin, northern Illinois and
lower Michigan. Just to the south of this snowfall axis, but to
the northwest of the low track, the cold air will be more shallow
and these areas should see a swath of some sleet and light
freezing rain. As the low tracks into New England by Monday
evening, some light icing concerns will also be noted across parts
of western and northern New York, and northern New England. Some
snow is expected for areas of northwest Maine where the cold will
be a bit deeper, and locally several inches are expected here
going through Monday night.
 
Orrison