FOUS11 KWBC 132116
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
416 PM EST Thu Feb 13 2025

Valid 00Z Fri Feb 14 2025 - 00Z Mon Feb 17 2025


...New York State and New England... 
Day 1...

Heavy synoptically forced snow shifts east of northern Maine tapers
off rest of this afternoon.

Westerly flow over Lake Erie is producing lake enhanced snow over
the Chautauqua Ridge in spite of Erie being nearly frozen over per
GLERL. However, as flow shifts WNWly this evening, flow over
Superior, Georgian Bay, and Lake Ontario will produce single
banding LES along the Oswego/Onondaga county lines through Friday
morning. Day 1 snow probs in that specific swath just north of
Syracuse for >8" are over 70% with localized totals over 12"
likely.


...Sierra Nevada, Pacific Northwest through the Rockies... 
Days 1-2...

...Heavy Sierra Nevada snow continues into Friday with heavy snow
over the central/southern Rockies into Friday night. Key Messages 
are linked below...

Upper low over northern CA is directing the AR over SoCal this
evening with continued onshore flow into Friday with instability
enhancing precip over the Sierra Nevada as the low opens into a
slow moving trough. Snow levels drop back to 5000-6000ft under the
trough axis tonight (Sierra) and around 4500ft (Shasta/Trinity)
helping add more wet snow. Day 1 snow probs for additional >18" are
60-90% along the High Sierra.

Cold air lingers over the PacNW lowlands with continued snow and
freezing rain, particularly around Portland (especially west of
town in the Coastal Range) tonight. Day 1 ice probs for an
additional >0.1" after 00Z are 20-30% there. 

Moisture continues to spread east through the Intermountain West 
through Friday evening ahead of the slow-moving trough axis. 
Snow rates peak tonight over the Wasatch and Tushar in Utah and
western CO Rockies slopes. Day 1 snow probs for >12" are over 80%
for these areas and around 50% for the OR Cascades, western
Sawtooths, Tetons, and Kaibab Plateau.

Day 3...

The next upper low approaches western Washington Sunday with snow
levels around 3000ft for the northern Cascades. Day 3 snow probs
for >8" are 30-60% for this higher terrain.


...Upper Midwest/Great Lakes/Northeast... 
Days 2-3...

Shortwave trough ejecting from the western trough crosses the
central Plains Friday with an inverted trough spreading up through
Wisconsin Friday night. Thump of snow with this inverted trough is
on warm air advection, but sufficient cold air is there to allow
heavier snow with >10:1 SLRs over much of WI Friday night. Day 2
snow probs for >4" are 50-80% across southern and eastern WI and
the northern 2/3 of the L.P. of MI. There are >6" probs inn the
40-60% with the key here the rates Friday night. 

Starting Friday night, the SWly jet from the southern Plains
through the Northeast intensifies to over 150kt by 00Z Sun. Snow 
expands across the Northeast on continued WAA ahead of the 
deepening upper trough Saturday/Saturday night. Day 3 snow probs
for >4" are 40-90% over Upstate NY and northern New England with 50
to 70% probs for >8" over the Adirondacks up through the northern
NY border, Greens, Whites, and much of Maine. Much like the system
ending today, there has been some shifts north with the low, so the
swath of heavy snow is yet to be determined. The rapidly deepening
low Sunday will add wind impacts over Northeast.

Jackson

...Winter Storm Key Messages are in effect for a winter storm
impacting the west into Saturday before intensifying over the
Northeast Saturday night and Sunday...

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

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