FOUS11 KWBC 040840
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EST Tue Mar 4 2025

Valid 12Z Tue Mar 04 2025 - 12Z Fri Mar 07 2025

...Central Rockies and High Plains to the Upper Midwest... Days 1-2...

...A powerful storm moving into the central U.S. will produce
multiple hazards through Wednesday, including periods of heavy snow
from the central Plains to the northern Great Lakes, as well as
blizzard conditions across parts of the central Plains and strong
winds throughout the much of the nation's heartland...

A powerful winter storm takes center stage today with periods of
snow and whipping wind gusts producing blizzard conditions in parts
of the central High Plains this morning. A clue to identifying how
powerful a storm is; reviewing the NAEFS/ECMWF situational
awareness tools and seeing each variable (temperatures, winds,
moisture, pressure, vapor transport) all either in the "max" or
"min" categories. By 12Z Tuesday, the storm's 700mb and 850mb
heights over western Kansas will be near the lowest in the observed
CFSR climatology, while mean specific humidity at the 500-700mb
layers are also above the 90th percentile. Periods of snow will
envelope portions of eastern CO (including as far west as the Front
Range and Palmer Divide), western and central Nebraska, and
western Kansas where wind gusts may exceed 70mph in some cases.
This will result in blizzard conditions that make travel by road
and air very difficult due to whiteout conditions. WPC
probabilities show low chances (10-30%) for snowfall >4" in
northwest Kansas and southwest Nebraska, but they jump up to
moderate-to-high chances (50-70%) over north-central Nebraska. Snow
should taper off by Tuesday afternoon but lingering strong wind
gusts are likely to linger through Tuesday evening.

As the storm marches west towards eastern Kansas Tuesday
afternoon, the mean 250-500mb trough axis will take on a negative
tilt that provides excellent diffluent flow aloft over the Midwest.
Plus, a classic "kissing jets" setup; denoted by the divergent
left-exit region of a jet streak over Texas and the divergent
right-entrance region of a jet streak positioned over the upper
Great Lakes. As strong 850-700mb warm air advection (WAA) pivots
north and west around the storm and anomalous moisture content
rotates around the 700mb low, a TROWAL will support intensifying
precipitation rates and lead to a narrow band of heavy snow that
originates over eastern Nebraska and northeast Kansas Tuesday
evening. The newest 00Z HREF guidance suggests the potential for

1"/hr snowfall rates within this band that could stretch as far

south as the Kansas/Missouri border. There are some hi-res
soundings do do show some elevated instability aloft that may lead
to thundersnow within this band. Farther north, the same slug of
moisture over northern Iowa, southern Minnesota, western and
norther Wisconsin, and the Michigan U.P. will also transition to
snow Tuesday night with >1"/hr rates possible there as well.
Combined with the strong wind gusts in excess of 40 mph, especially
along the Missouri River Valley on east into central Iowa,
blizzard conditions are possible in these areas Tuesday night. WPC probabilities shows western Iowa and directly along the Missouri
River on south to far northeast Kansas as having moderate chances
(40-60%) for snowfall >4". However, should the band pivot long
enough over the region, localized amounts of 6-8" are possible.

The heaviest snowfall is likely to occur from northern Iowa and
southeast Minnesota to northern Wisconsin and the Michigan U.P..
This is where the 850mb FGEN will be sticking around the longest,
while also being ideally placed beneath that 250mb jet streak's
divergent right-entrance region. Some lake-enhancement and upslope
component into the more elevated terrain of northern Wisconsin and
the Michigan U.P. will help to sustain periods of heavy snow into
Wednesday evening. The storm will be a quick mover and snow across
the Upper Midwest will be out of the picture by Thursday morning.
WPC probabilities now depict high chances (>70%) for snowfall total

12" from the Hurons of Michigan's U.P. on west to the Michigan

U.P.northern Wisconsin border. The Huron Mountains actually have
moderate chances (40-60%) for snowfall totals surpassing 24" for
the event. Farther southwest, WPC probabilities show moderate-to-
high chances (50-70%) for snowfall >8" from far northern Iowa to
the Mississippi river dividing southeast Minnesota and western
Wisconsin. With the combination of heavy snow and blustery winds,
there is the concern for heavy/wet snow weighing down tree branches
and power lines that could result in tree damage and power outages
from southeast Minnesota to the Michigan U.P..

...California, Great Basin, Southwest, and central Rockies... Days 2-3...

An approaching upper rough off the California coast will interact
with the subtropical jet in the East Pacific. This interaction will
produce a strengthening IVT that exceeds 400 kg/m/s and stretches
as far inland as the Lower Colorado River Basin. ECMWF SATs show
the >400 kg/m/s over portions of the Desert Southwest topping the
99th climatological percentile by 00Z Thursday. This IVT will
introduce rich subtropical moisture into northern Arizona, much of
Utah, and into the central Rockies. At the same time, the
approaching upper trough will induce strong vertical ascent over
the Intermountain West. By 12Z Thursday, a closed 700mb low over
southern Idaho will become elongated to the east and develop
another 700mb low in lee of the Rockies by Thursday afternoon. The
track of the 700mb low places much of Wyoming in a favorable spot
for heavy snow, especially from the Tetons to the Wind River,
Medicine Bow, and Laramie Ranges. This developing storm in the
central High Plains will generate strong WAA at low-levels that
cause 850-700mb FGEN from eastern Wyoming to as far east as the
Missouri River early Friday morning. Details on snow amounts east
of the Rockies are not as clear, but additional snowfall is growing
in confidence north of I-80 across the Sand Hills of Nebraska with
lighter amounts closer over the western Corn Belt.

When it comes to areas with the best odds of seeing >18" of
snowfall, the southern Sierra Nevada and peaks of the Wasatch are
the better bets. WPC probabilities show moderate-to-high chances
(50-70%) for >18" of snowfall at elevations above 9,000ft in the
southern Sierra Nevada, while the central and Sierra Nevada are
more likely to see 6-12" above 6,000ft. Farther east, mountain
ranges such as the Uinta, Bear River, Teton, Wind River, Medicine
Bow, and Laramie have moderate-to-high chances (40-70%) for
snowfall >12". Even the lower elevations of Wyoming, as low as
4,000ft in eastern Wyoming have high chances (>70%) for >4" of
snowfall through 12Z Friday.

Mullinax

...Winter Storm Key Messages are in effect. Please see current
Key Messages below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

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