Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
417 PM EDT Sat Mar 26 2022

Valid 00Z Sun Mar 27 2022 - 00Z Wed Mar 30 2022

...Great Lakes/Central Appalachians...
Days 1-2...
An amplified longwave trough will remain positioned over the
eastern U.S. through Monday before a ridge begins to shift east
across the Great Lakes on Tuesday.  The continuance of deep
cyclonic flow with embedded energy aloft will contribute to
additional lake effect/enhanced showers before diminishing in the
lee of the northern Great Lakes early Monday and then tapering off
later in the day downwind of the eastern Great Lakes.   With
contributing moisture from Lake Huron and wraparound moisture from
a consolidating low over the Gulf of St. Lawrence/Atlantic Canada,
the heaviest amounts from this evening into Monday are expected to
line up along the higher elevations southeast of Lake Erie.  For
the 48 hour period ending 00Z Tuesday, WPC probabilities indicate
that accumulations of 8 inches or more are greater than 50 percent
in the upslope areas of northwestern Pennsylvania and western New
York.  Locally heavy amounts are also possible in the Tug Hill
region, although veering winds are expected to result in less
favorable conditions. 

Additional snows are likely in the upslope regions of the central
Appalachians as well, with at least a couple more inches of
accumulation likely this evening/overnight along the Allegheny
Mountains.

...California to the Rockies...
Days 2-3...
An anomalously deep upper low developing over the eastern Pacific,
west of California, is forecast to impact the region by early
Monday.  Deep southwesterly flow ahead of the approaching low,
along with left-exit region upper jet dynamics, will contribute to
the development of heavy snow along the higher elevations of the
central and southern Sierra Nevada.  Snow is expected to continue
into Monday night as the low moves across the region.   Widespread
snow accumulations of 4-8 inches are likely, with locally heavier
amounts expected, especially for areas above 7000 ft.  Locally
heavy accumulations are also possible across the higher peaks of
the Southern California Transverse Ranges.

As the low continues east, high elevation snows are forecast to
develop over portions of the Great Basin, Arizona, and the central
Rockies.  Heavy accumulations are most likely across the San Juan
Mountains in southwestern Colorado, where deep southwesterly flow,
along with favorable upper forcing are expected to once again
contribute to heavier rates.

Meanwhile to the north, widespread but generally light
accumulations associated with a northern stream trough can be
expected late Monday into Tuesday across the northern Rockies into
the northern Plains.

Pereira