Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
347 AM EST Thu Feb 15 2024

Valid 12Z Thu Feb 15 2024 - 12Z Sun Feb 18 2024

...Northwest to North-Central Rockies and North-Central Great
Plains...
Days 1-2...

Low pressure will remain over western WA today as it is trapped
south of a high centered over the Yukon while a shortwave trough
pushes east over the Great Basin on westerly flow. The presence of
this low and shortwave trough will provide plenty of lift and
Pacific moisture over a lingering stationary front over the
northern Intermountain West. This will continue a long-duration
snow through tonight over the OR Cascades and ID/WY ranges where
Day 1 PWPF are high for >12" and lingers into Friday for WY and
northern CO ranges where Day 2 PWPF are over 40% for >6".

The shortwave trough crossing the Great Basin today crosses the CO
Rockies by this evening, allowing lee-side cyclogenesis over the
southern High Plains to combine with 1038mb high pressure centered
over northern MT to enhance convergent flow, producing snow bands
over the Black Hills, southern SD, into IA this afternoon/evening.
Day 1 PWPF are 30-50% for >6" through this swath.


...Great Lakes to New England...
Days 1-3...

Surface low pressure ahead of a mid-level shortwave trough over MN
early this morning will shift east over southern WI/MI this
morning before crossing Upstate NY and central New England
tonight. Dynamics increase today as northern and southern stream
shortwaves merge/interact over southern Ontario as the upper jet
increases over the Southeast. Combination of upper divergence and
incoming height falls/PVA as the combined shortwave tries to close
off over northern New England will promote an expanding area of
snowfall from the Great Lakes eastward, initially tied to a
modest/strong area of FGEN over northern Lower Michigan where Day
1 PWPF for >4" of snow are 50-80%. Snow will be at least locally
heavy with 00Z HREF mean rates of 1-2"/hr cross the central
portion of the L.P. this morning. Low pressure will slip steadily
eastward through NY into New England this evening before
translating to the Gulf of Maine early Fri. Again, WAA/FGEN into
northern NY and New England will support modest snows with
embedded heavier bands (around 1"/hr per the HREF) though the
quick movement will limit amounts somewhat. Day 1.5 PWPF for >6"
are 40-80% over much of the Tug Hill/Adirondack region and into
the Green/White Mountains in VT/NH with some probs in southern
coastal Maine as well.

LES kicks off in the wake of this low today which is then enhanced
by the next wave to the south Friday night. Day 2 PWPF are 30-60%
for >4" in WNWly snow belts over the U.P. and around Grand
Traverse Bay and again on Day 3 for Wly snow belts in MI and also
Upstate NY. 


...Central Appalachians/Mid-Atlantic...
Day 2...

The shortwave trough over South Dakota this evening also
intensifies with increasing dynamics as it shifts east late
tonight through Friday night. Snow bands cross northern MO and
southern IL/IN to the eastern OH Valley Friday beneath a
ballooning upper jet (wide expanse of >150kt from the Mid-South to
Bermuda with a jet max approaching 200kt over VA). Day 2 PWPF for
>4" are 10-30% over a swath north of St. Louis. Low pressure is
expected to quickly move east from eastern TN across southern VA
Friday night with a strong thermal gradient to the north cold
enough for snow over the central Appalachians and the central
Mid-Atlantic. Day 2 PWPF for >4" are 40-60% for the western slopes
of the Appalachians in WV/MD with 10-30% probs in a stripe from
northern VA along the Mason-Dixon line into central NJ.


...West Coast...
Day 3...

The next low approaches the Pacific Northwest Friday night as a
strengthening ridge axis begins to drift inland. Strong southerly
flow raises West Coast snow levels to around 6000ft as precip
moves inland Saturday night. Day 3 PWPF for >6" are 40-80% for the
Sierra Nevada, Shasta/Siskiyou, and higher OR Cascades.


Jackson