FOUS11 KWBC 050906
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
406 AM EST Wed Mar 5 2025

Valid 12Z Wed Mar 05 2025 - 12Z Sat Mar 08 2025

...Upper Midwest through the Great Lakes and into the Northeast...
Days 1-3...

...Powerful storm to bring blizzard conditions to portions of the
Upper Midwest...

The powerful winter storm continues to produce heavy snow and
blizzard conditions in some cases from northwestern Missouri
through the Upper Mississippi Valley this morning. This deformation
axis of snow, placed beneath the TROWAL and the right-entrance
region of a robust 250mb jet streak over southern Canada, will
support a band of snow generating 1-2"/hr snowfall rates. The
storm will track over the Wisconsin/Illinois border through late
morning with the swath of snow moving across most of Wisconsin and
the Michigan U.P.. Persistent NErly flow over Lake Superior will
keep periods of snow in the forecast across the Michigan U.P.
through Wednesday evening, but snow should finally taper off by
Thursday morning. Note that some periods of snow are expected on
the backside of the storm on Thursday downwind of the usual snow
belts of Lakes Erie and Ontario, as well as down the spine of the
Appalachians. Light snow totals will linger into Friday as well,
especially in the Tug Hill, Adirondacks, and the Whites. Most 
snowfall amounts in these areas are likely to range between 1-4" 
with some localized amounts approaching 6" in the Tug Hill. 

WPC probabilities show moderate-to-high chances (50-70%) for
additional snowfall totals >12" in the Huron and Porcupine
Mountains along the Michigan U.P. Meanwhile, there are high chance
probabilities (>70%) for additional snowfall totals >4" from
northern Iowa to southeastern Minnesota and western Wisconsin. Some
additional localized amounts of 4-6" are possible in west-central 
Iowa on the back side of the storm through this morning. Expect
hazardous travel conditions in these affected areas, especially in
areas under blizzard warnings where visibilities may be near zero.
 
...California, Great Basin, Southwest, and central Rockies... Days 1-3...

An approaching upper trough 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 
>400 kg/m/s over portions of the Desert Southwest that are topping
the 99th climatological percentile by 00Z Thursday. This IVT will
introduce rich subtropical moisture into the Great Basin and
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, developing another 700mb low in lee of the
Wyoming Front Range by Thursday afternoon. the track of the 700mb
low places much of Nevada, southern Idaho, and Wyoming in a
favorable position for heavy snow, especially from the Absaroka,
Tetons, and Wind River ranges to the Medicine Bow, Big Horn, and
Laramie Mountains. As the 700mb low stalls over the Tetons and Bear
River Range, a secondary shortwave trough revolving beneath the
longwave trough over the West will sustain a >200 kg/m/s IVT
directed at the southern Rockies. In addition to the upper-level
ascent out ahead of the upper trough, falling heights and lowering
snow levels will support periods of mountains snow along the
Mogollon Rim, the San Juans, the Sangre de Cristo, and the Front
Range of the Colorado Rockies. The snow in the Front Range and
Sangre de Cristo is a byproduct of upslope flow with low pressure
developing over the southern Plains and high pressure over the
northern Plains.

WPC probabilities show high chances (>70%) for snowfall exceeding
12" in the Sierra Nevada above 6,000ft, the >7,000ft ridge lines in
the Nevada, the Wasatch, Uinta, Tetons, Wind River, Laramie, and
San Juan ranges. Some portions of the Sierra Nevada, Wasatch, and
Uinta sport moderate-to-high chances (50-80%) for snowfall >24"
through Friday. Mountains of southern Idaho, the Absaroka, and the
Big Horns also have high chances (>70%) for snowfall >8" through
Friday. Much of the Mogollon Rim above 6,000ft are forecast to see
any where from 6-12" of snowfall. Some of the valleys in Wyoming 
can also expect as much as 6-12" of snowfall through Friday 
morning. The WSSI range from Moderate to Major Impacts with the 
Major Impacts confined to the highest elevations of the mountain 
ranges listed.

...Central Plains... Days 2-3...

By Thursday, as the upper trough in the West aids in the
development of low pressure in lee of the Rockies, strong 700mb WAA
will foster 700mb FGEN over southeast Wyoming and Nebraska. A band
of heavy snow will stretch across these areas, including the Black
Hills and Sand Hills Thursday afternoon. Snow in these areas will
continue Thursday night and should taper off by Friday morning. 
Some measurable snow may make it as far south as northeast Colorado
and possibly into the Midwest Thursday night into Friday, but 
guidance suggests milder boundary layer temperatures may make it 
tougher for much more than minor snowfall totals. WPC probabilities
show moderate-to-high chances (50-70%) for snowfall >6" in the
eastern Wyoming High Plains, the Black Hills, and northwest
Nebraska. Low chances (10-30%) for >4" of snowfall extend as far
east as east-central Nebraska. 

Mullinax

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

https://www.wpc.ncep.noaa.gov/key_messages/La...

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