075
FOUS11 KWBC 272050
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
350 PM EST Thu Nov 27 2025

Valid 00Z Fri Nov 28 2025 - 00Z Mon Dec 01 2025

...Great Lakes...
Day 1...

Long duration lake effect snow (LES) event continues through
Friday with prolific snowfall totals in the favored snow belts for
NWly flow in northern MI and for WNWly flow off Lakes Erie and
Ontario.

Deep low remains over central Quebec through Friday before lifting
to Labrador. The mid level trough axis associated with the low is
currently over the eastern U.P. and will swing east over the
eastern Lakes tonight. Saturated DGZ zones will maintain efficient
snow production over the autumnally warm lakes. Ridging finally
spreads east over the region Friday night ending the LES.

For Michigan expect individual banding in NW flow over the eastern
U.P. with additional banding from added fetch from Lake Michigan
into the Tip of the Mitt will persist through Friday morning. Day
1 WPC snow probs for >8" additional are 40-70% in the same narrow
zones being impacted now.

Eastern Great Lakes see ideal multiple lake fetch in cyclonic flow as
seen in current radar mosaics with banding from Superior,
Michigan, Huron, and Ontario into the Tug Hill and fetch from
Superior, lower Michigan, and Erie into the Chautauqua Ridge of
western NY and east of Cleveland. WPC Day 1 snow probs for >8"
additional are 50-70% for these features, and over 80% on the
Chautauqua Ridge where probs for >12" are 50-70%.

Key Messages remain in effect for this system (link #1 below).


...Northern High Plains through the Midwest into the Northeast...
Days 1-3...

...Significant winter storm to impact large portions of the
Northern Plains, Midwest, and Great Lakes through this weekend...

A closed low along the WA coast this afternoon will shift southeast
tonight while opening, crossing the Northern Rockies Friday. This
wave is shunted on the southern trajectory from a northern stream
trough currently shifting south down the Canadian Rockies tonight.
This trough interaction and a strengthening upstream jet streak
will help spread moderate snow bands from Glacier NP through
northern MT tonight. Temperatures will be plenty cold for all snow
in the bands with some freezing rain potential on the southern
portions of precip over south-central MT overnight.

The frontogenetical banding quickly extends across the Dakotas
Friday morning, reaching western Iowa in the afternoon. This
banding is north of a developing lee-side low ahead of the merging
troughs that develops over eastern CO Friday and shifts east over
the KS/OK border as it further develops Friday night. This allows
the fgen band to transition into a deformation band around an
inverted trough extending from the surface low. Day 1.5 snow probs
for >6" are 30-60% from Northeast MT through central Iowa.

Thereafter, the system amplifies to become much more impressive
with expanding heavy precipitation through the central Midwest
Friday night through Saturday. The mid-level trough diving into the
Central Plains will sharpen, and as the vort swings into the base
of the longer wave trough it will force a negative tilt coincident
with the development of coupled jet streaks (one strengthening over
the Central Plains and another exiting the Great Lakes) to produce
strong ascent. This overlapping synoptic lift will help strengthen
a surface low developing in the lee of the CO Rockies and then
tracking east, and eventually northeast, from KS through IL and
into southern MI by 12Z Sunday.

Downstream of this surface low, warm and moist advection will
rapidly intensify as 850mb winds surging to above 50kts draw
elevated PWs northward from the Gulf, reflected by PW anomalies
surging above the 90th percentile according to NAEFS into KS/MO/IA.
This will be accompanied by a theta-e ridge lifting northward as
well, and although a true TROWAL is not currently progged, this
theta-e ridge will still promote additional moisture and some
elevated warm air to promote modest potential instability. This
intense WAA will help expand precipitation from the Dakotas and
Iowa Friday night, to encompass most of the Upper Midwest Saturday,
and then cross Lower Michigan Saturday night before surging up the
Interior Northeast Sunday.

Confidence continues to increase in the track of the low with a
preference for the northern end of the precip shield given to the
EC/GFS which are farther north (through central WI with 0.5" QPF) than
the CMC/UKMET. The broad precip shield and ample cold air will
result in pivoting heavy bands with the highest totals as of now
forecast over central IA where a foot is possible. As noted before
the DGZ depth will be a concern at times and with so much precip
from WAA, the ratios should be somewhat limited over IL/IN ahead of
the system.

Day 2/2.5 WPC snow probs for >8" are over 30% from far southeast
SD/northeast Neb across all but far southwest IA, southern MN,
central and southern WI, and northern IL. Day 3 probs for >8" are
20-40% for much of the L.P. of Michigan. Post-Thanksgiving travel
is likely to be extremely disrupted during this event.

Key Messages remain in effect for this system (Link #2 below).


...Cascades and Northern Rockies...
Days 1-2...

Low crossing WA tonight with snow levels in the Cascades around
5000ft. Pacific moisture surges inland ahead with snow levels over
the northern Rockies of 4000-5000ft which decrease after snow
tapers behind a northern stream trough descending from the Canadian
Rockies. Day 1 snow probs for >6" are 40% in the high WA Cascades
and 50-80% across all western MT ranges into northern ID.

A combined upper trough shifts down the Rockies Friday with Day 1.5
snow probs for >6" 40-70% in the Tetons, Absarokas, Bighorns, and
ranges of north-central C0.


Jackson



...Winter Storm Key Messages are in effect. Please see current
 Key Messages below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_2.png




$$