FOUS11 KWBC 250813
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
413 AM EDT Mon Mar 25 2024

Valid 12Z Mon Mar 25 2024 - 12Z Thu Mar 28 2024

...Southern Rockies... Day 1...

An inverted 500mb trough over the Southern Rockies will be the
focus for additional heavy snow today. The Sangre De Cristo and
eastern San Juans both sport high chances (>70%) for additional
snowfall totals >8" with the tallest peaks of the Sangre De Cristo
in northern New Mexico even having moderate-to-high chances
(50-70%) for >12" snowfall accumulations through Monday afternoon.
The axis of moisture and lift associated with this upper trough
will even result in heavy snow over the Gila Mountains in eastern
Arizona. WPC PWPF shows moderate chances (40-60%) for snowfall
accumulations >8" through Monday evening. The 500mb trough will
eject east into the Southern Plains Monday night, thus all but
concluding the lingering periods of snow by Tuesday morning.

...Northern Plains & Upper Midwest... Days 1-2...

The major winter storm will be well underway with the worst impacts
being felt from the central High Plains on north to north-central
Minnesota. The deformation axis on the northern and western flank
of the storm will be capable of producing 1-2"/hr snowfall rates to
go along with wind gusts that are exceeding 40 mph in northwest
Kansas, central Nebraska, and southeast South Dakota. Farther east,
the impressive 850mb WAA in the Upper Mississippi Valley that was
in part responsible for the heavy snowfall overnight will lead to
a burgeoning warm nose at low levels that causes snow to
changeover to a wintry mix this morning in southern Minnesota,
northern Wisconsin, and the Michigan U.P. By this afternoon, any
lingering wintry mix is expected to transition over to plain rain.
Meanwhile, the storm will continue its trek northeast into the
Upper Mississippi Valley Monday evening with heavy snow enveloping
eastern South Dakota, northern Minnesota, and the Minnesota
Arrowhead.

Snow will continue to fall heavily over north-central Minnesota
Monday night with some residual snow as far south as eastern
Nebraska and northern Kansas as a TROWAL pivots overhead. By
Tuesday morning, the low will be tracking into northern Wisconsin
with heavy snow across northern Minnesota and a mix of heavy
snow/wintry mix along the Minnesota Arrowhead. The storm will then
move over the U.P. of Michigan Tuesday afternoon, then finally into
southern Ontario Tuesday night. Snow will continue to fall across
northern Minnesota and portions of far northern Wisconsin and the
western Michigan U.P. Heavy snow will effectively come to an end by
Wednesday morning with just lingering snow showers along the
Minnesota/Canada border and along the northern coast of the
Michigan U.P..

WPC PWPF shows moderate-to-high chances (50-70%) for additional
snowfall >6" from north-central Nebraska and eastern South Dakota
to far southeast North Dakota, northern Minnesota, and the
Minnesota Arrowhead. South-central South Dakota and the Minnesota
Arrowhead even show low chances (10-30%) for additional localized
snowfall amounts >8". Farther southwest, WPC PWPF shows moderate-
to-high chances (50-70%) for additional snowfall totals >4" in
southwest Nebraska, northwest Kansas, and southeast Colorado.
Nebraska and northwest Kansas, in particular, could contend with
blizzard conditions due to prolonged high wind gusts and
significantly reduced visibilities.

...Pacific Mountains Ranges... Days 2-3...

Outside of some diurnally driven snow showers and weak onshore
flow in the Pacific Northwest through Tuesday night, little in the
way of heavy snowfall is likely to occur for many of the mountains
ranges along the West Coast. That finally changes by early
Wednesday morning as the next Pacific storm system approaches and
directs a slug of Pacific moisture first at the Pacific Northwest,
then into the Northern California ranges and interior Northwest
ranges Wednesday night. The IVT is a quick mover but a fairly
potent IVT sporting values >400 kg/m/s just off the California
coast. Overall, the peak of the IVT tracking into northern
California Wednesday afternoon is likely to top the 97.5
climatological percentile, supplying not only abundant moisture to
the region but strong upslope enhancement (especially in the Sierra
Nevada). Snow levels in the Sierra Nevada will initially start out
as high as 6,500ft, but gradually fall to 5,000ft by Thursday
morning as the cold front pushes through. Farther north, snow
levels will start out around 5,000ft in the northern California
ranges (Salmon/Siskiyou/Trinity) and closer to 4,500ft in the OR/WA
Cascades, but those too will fall an additional 2,000ft by
Thursday AM. Latest WPC PWPF shows high chances (>70%) for snowfall
amounts >8" in the Northern Sierra Nevada >6,000ft and in the
northern California ranges, while only the volcanic peaks of
southern Washington and the Olympics sport similar high chances
for >8" of snowfall through early Thursday morning. Some snow will
spill over into the Blue Mountains and the Boise/Sawtooth late
Wednesday night into Thursday with low-to-moderate chances (30-50%)
for snowfall totals >6" through early Thursday morning.

Mullinax


***Key Messages for Plains-Upper Midwest Winter Storm***

--A high-impact winter storm unfolding

A powerful storm system will impact the Northern/Central Plains
into the Upper Midwest through Tuesday. Periods of snow and gusty
winds will continue from the Central Plains to northern Minnesota,
along with some sleet and freezing rain in parts of the Upper
Mississippi Valley.

--Widespread heavy snow expected

Snow accumulating at rates of 1-2"/hr in heavier bands are
expected from central Nebraska and eastern South Dakota to northern
Minnesota. Additional snowfall totals between 6-12" are forecast
from central Nebraska to northeastern Minnesota.

--Hazardous impacts due to snow, snow load, and wind

Heavy snow and gusty winds approaching 50 mph will produce
blizzard conditions with near zero visibility into Tuesday morning.
Travel could be nearly impossible at times. Power outages and tree
damage are likely in some areas due to the heavy and wet snow
combined with icing and strong winds.


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