FOUS11 KWBC 220720
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
320 AM EDT Sat Mar 22 2025

Valid 12Z Sat Mar 22 2025 - 12Z Tue Mar 25 2025


...Pacific/Interior Northwest to Central Rockies...
Days 1-3...

Shortwave over eastern WA this morning will continue east-
southeastward today across the Rockies. Light snow via onshore flow
will continue over the Cascades while light to modest snows are
expected for northwestern MT/northern ID into WY and northern UT/CO
before ending from NW to SE this afternoon and evening. WPC
probabilities for at least 6 inches of additional snow are >50%
above 5000ft (north) to 8000-10,000ft (south). The next system into
the PacNW D2 will be much milder due to increasing mid-level
ridging with snow levels rising from 4000-5000ft late tonight to
over 8000ft Sunday evening. Any initial snow over the passes will
change over to rain with significant snow at the highest peaks. By
D3, upper ridging will remain in control with light snow for the
high elevations as snow levels settle to between 7000-9000ft.


...Upper Midwest/Great Lakes/Northeast...
Days 1-3...

The upper-level trough exiting the Northern Rockies/western High
Plains this afternoon will push into the Upper Midwest tonight into
early Sunday. Multiple vort maxima will lie beneath the poleward
exit region of the modest jet over MO, providing broad vertical
ascent aloft from the Dakotas to Minnesota. Surface low pressure
over South Dakota will deepen and move into MN, with WAA driving
snow (and some mixed precip/light icing) to its northeast (MN into
WI). On Sunday, sharpening upper pattern will and a slight negative
tilt aloft will help increase snow on the NW side of the low in a
modest but still progressive deformation axis. Wraparound snow amid
dynamic cooling and low-level convergence/enhancement on the west
side of Lake Superior will help to maximize snowfall there, from
near/northeast of Duluth northeastward to Grande Portage. A modest
snowfall is expected elsewhere from central MN across northern WI
and into the U.P. of Michigan near and to the north of the track of
the sfc low pressure (and north of any subsequent secondary low
pressure development out of the Corn Belt).

By late Sunday into early Monday, frontal boundary will continue
to arc eastward, pushing precipitation across the Appalachians into
northeastern PA and into NYS, where cold surface temperatures may
support some snow and light icing as WAA invades from the
southwest. Limited cold air will confine most snowfall to areas
north of I-90, but with a sfc low track remaining in Canada, many
areas may change over to rain except for northern NH into
northwestern Maine. Back to the west, colder air across the Great
Lakes will spur some lake-effect snow into the U.P. and western
Lower Michigan as 850 temps briefly drop to -10C or so. The entire
system will wind down late Monday with only some lingering lake-
effect snow by early Tuesday.

WPC probabilities for at least 4 inches of snow through the period
are highest (>70%) over northeastern MN and especially over the
eastern Arrowhead (where probabilities for at least 8 inches of
snow are >50%), northern WI and the entire U.P. of Michigan,
northwestern Lower MI, and into the Tug Hill Plateau.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso

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