Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Sun Mar 03 2024

Valid 12Z Sun Mar 03 2024 - 12Z Wed Mar 06 2024

...West Coast & Northern/Central Rockies...
Days 1-3...

Expansive and broad troughing over the Northeast Pacific eastward
to the Rockies this morning will finally start to ease its grip
over the West, allowing heights to rise over the next few day.
However, with the upstream upper ridge axis still over western
Alaska, the vorticity highway will remain open from the
Yukon/British Columbia as shortwaves and PVA move into the Pac NW,
maintaining an unsettled period. For D1, upper jet will slice
across NorCal and northern NV/UT, placing the northern Sierra in
the RRQ of the jet and bringing another round of at least modest
to locally heavier snow for the region. Onshore flow will favor
the Cascades, particularly the OR Cascades, into the NorCal ranges
with downstream terrain enhancement over the Wasatch into the CO
Rockies. WPC probabilities for at least 12 inches of snow today
are high (>70%) in the northern Sierra, and moderate (40-70%) over
the OR Cascades and Klamath/Shasta/Siskiyous. Into D2, upper jet
will lift northward into southern OR, moving the focus for heavier
snow squarely into the OR Cascades and Klamath/Shasta/Siskiyous.
There, WPC probabilities for at least 12 inches of snow are >60%.
Additional snowfall will also be possible across the central ID
ranges in response to the lifting jet. By D3, upper pattern
becomes a bit more muddled, with a shortwave moving into the Pac
NW and a Pacific system approaching the NorCal coast. Upper jet
will weaken across the region, but westerly flow will still favor
the OR/CA border terrain eastward across Idaho and into western WY
beneath the best PVA. WPC probabilities for at least 8 inches of
snow are >60% in the far northern Sierra into the
Shasta/Siskiyous, then ENEward to the central ID ranges and
western WY (Tetons and Wind River Range).


...Northern High Plains...
Day 1...

A sharpening mid-level vort over southeastern MT this morning on
the eastern side of the much larger upper trough will become more
negatively-tilted through today in response to upper jet buckling
over Canada as a jet streak over the Rockies extends eastward to
the Corn Belt by this evening. An already potent surface low
around 990mb will lift through ND/MN this afternoon with an
impressive albeit short-lived TROWAL on its NW side across
northern ND and especially into southern Canada, supporting
moderate to occasionally heavy snow along the surface trough and
beneath an axis of lower level FGEN. Frontal boundary across the
Upper Midwest will lift northward today in response to increasing
southerly flow, promoting an area of mixed precip across eastern
ND into northwestern MN where a few hundredths to a tenth of an
inch of ice is possible (WPC probabilities around 10% for at least
a tenth of an inch). The highest snowfall will likely be across
northern ND along the Canadian border, where WPC probabilities for
at least 4 inches are high (>70%). Lesser amounts are likely
farther south through ND, trending to about 10% just north of
Bismarck. Snow will exit the region this evening as the low
steadily pulls away into Canada.


Fracasso