Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
429 PM EDT Fri Mar 31 2023

Valid 00Z Sat Apr 01 2023 - 00Z Tue Apr 04 2023

...Northern Plains and Upper Midwest...
Day 1...

Ongoing moderate to heavy snow, with strong gusty winds associated
with a deepening closed low centered over the northern Plains will
continue to extend east from South Dakota into southwestern
Minnesota this evening.  Strong upper upper jet forcing, along
with low-to-mid level frontogenesis, will continue to support
moderate to heavy precipitation developing and transitioning to
snow on the northwest side of the associated surface low as it
tracks northeast from Iowa into the upper Great Lakes tonight.  An
intense (2+"/hr), but narrow band of snow is forecast to translate
east-northeast from eastern South Dakota and southwestern
Minnesota to the U.P. of Michigan tonight.  WPC guidance indicates
accumulations of 8 inches, with embedded heavier totals, are
likely along a a narrow stretch extending from southern Minnesota
to the eastern U.P. of Michigan tonight into early Sat. Snow is
forecast to diminish from west-to-east and the winds relax as the
low begins to interact with a deep low to the north, with energy
shearing off to the northeast during the day on Saturday.  Please
see below the Key Messages for this storm.     

...Pacific Northwest to the Northern High Plains...
Days 1-3...

A well-defined mid-level shortwave/upper jet emanating from the
Gulf of Alaska are expected to dive southeast -- bringing the
threat for heavy mountain snow back into the Pacific Northwest
this evening.  As the mid-level shortwave/upper jet continue to
press east, favorable upper forcing, along with strong low-to-mid
level frontogenesis will support heavy snow moving east from the
Cascades into the northern Rockies on Saturday.  As the system
pushes east, snow levels are forecast to drop below 1000 ft across
western Washington and below 2000 ft from the northern Rockies
back into western Oregon.  By late Saturday, snow accumulations of
8 inches or more likely for most of the major Cascade passes, with
higher accumulations across the higher terrain.  Locally heavy
totals are also expected for the Blue Mountains, as well as parts
of the northern Rockies from northern Idaho to northwestern
Wyoming.

Periods of snow are forecast to continue through Sunday across the
Northwest into the northern Rockies as an upper low settling south
along the coast of British Columbia directs a steady stream of
energy across the region.  This energy will begin to carve out a
deeper trough across the region, with snow levels dropping below
1000 ft across much of the region behind a well-defined cold
front. Additional heavy accumulations are likely, especially for
the Cascades.

By late Sunday and continuing through Monday, a strong shortwave
will dig southeast through the broader scale trough, carving out
an anomalously deep trough centered over the Great Basin by late
Monday.  By late Monday, the model consensus shows -2.5 std dev
500mb height anomalies centered over Nevada-Utah.  Heavy snow and
strong winds are likely to develop along a strong baroclinic zone
following a impressive low developing over eastern Utah on Monday.
 This will mark the onset of what are expected to be heavy snow
accumulations along the Utah ranges.  Meanwhile, increasing ascent
and moisture advection will support snows east of the Rockies,
with amplifying low level easterly winds supporting heavy snows
developing over southeastern to south-central Wyoming.  By late
Monday, WPC probabilities indicate that snow accumulations of 6
inches or more will be common, with localized heavier totals
likely across the region. 

This system is likely to impact a large  portion of the northern
Plains and Upper Midwest next week.  Please see our Key Messages
below for additional details.

Pereira

...Key Messages for Mar 30 - Apr 1 Winter Storm...

--A combination of heavy snow rates (1-2â€/hr) and strong wind
gusts up to 50 mph will bring blizzard conditions to portions of
South Dakota and Minnesota through tonight.

--Across the Upper Midwest and Great Lakes, intense snow rates
(1-2â€/hr, locally higher) combined with strong winds may cause
extensive tree damage and power outages.

--Hazardous travel conditions are expected in impacted areas
including snow covered roads, near impossible travel from zero
visibility and whiteout conditions.

--On the warmer side of this system, a dangerous major severe
weather outbreak is increasingly likely across a large portion of
the MS Valley and into the lower OH and TN Valleys including
tornadoes, damaging winds, and large hail.

...Key Messages fpr Apr 3-5 Blizzard...

--A powerful storm system will track across the Intermountain West
and central Rockies early next week then through High Plains and
Upper Midwest the middle of next week.

--Confidence is increasing in a multi-hazard storm with
significant snowfall accumulations and strong winds. The
combination of heavy snowfall and strong winds could result in
blizzard conditions across the Plains.

--Widespread hazardous travel conditions and disruptions are
expected, including snow covered roads and reduced visibility,
particularly from Monday through Wednesday.

--In the wake of the storm system, much below normal temperatures
and wind chill readings near or below zero are likely, potentially
creating a dangerous situation for those who may become stranded
due to the heavy snow and strong winds.