Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
341 AM EST Fri Nov 7 2025

Valid 12Z Fri Nov 07 2025 - 12Z Mon Nov 10 2025

...Washington Cascades through the Northern Rockies...
Day 1...

Upper low over Washington State early this morning will shift east
to central MT by midday on a strong westerly jet. Snow levels drop
to around 4000ft under the low with precip rates decreasing in the
wake. Day 1 snow probabilities for >6" additional after 12Z are
50-80% for the highest WA Cascades, ranges in and south of Glacier
NP, and the Tetons to the Wind River Range.


...Northern Plains through the Interior Northeast...
Days 1-3...

...Strengthening low from North Dakota to the Northeast...
A potent shortwave pivots southeast from eastern Montana
this evening and digs to Iowa through Saturday. A reinforcing
trough dives south over the Upper Midwest Saturday night before
developing into a deep low over the Great Lakes Sunday night. The
surface low rapidly develops over the eastern Great Lakes Saturday
night downstream of the reinforcing trough. The low then mainly
tracks along/north of the St. Lawrence in eastern Canada.

While this feature is progressive over the northern Plains, it
will create a stripe of snowfall across ND (where Day 1.5 snow
probabilities for >2" are 30-50%) with lesser amounts over eastern
SD, down along the MN/IA border. However, forcing intensifies
across lower Michigan where mesoscale analysis indicates a moderate
threat for CSI due to impressive fgen overlapping the DGZ and
driving ascent into a region of theta-e lapse rates of 0C/km
Saturday night. Day 2.5 snow probabilities for >2" are 30-50% over
central lower Michigan.


...Lake Effect Snow beginning Sunday...
The deepening and amplifying mid/upper level trough over the
central Great Lakes Sunday that develops into a deep low Sunday
night will bring Strong CAA and a winter-like air mass to the
region, headlined by 850mb temperatures between negative 10 and 15
degrees C. This injection of unseasonably cold air (near or below
the 10th climatological percentile) over top the warm Great Lakes
(temperatures of +10 to +15C) will result in an impressive
convective environment with model soundings revealing steep lapse
rates and deep mixing heights to near or above 700mb. Given delta
Ts of 20 to 30C, the environment appears more than supportive of
lake effect/enhanced snow production.

North-northwest to northerly surface winds along with increasingly
unidirectional winds aloft will act on the instability and support
the development of a few prominent north-south lake effect snow
bands, particularly downwind of Lake Superior Sunday and Lake
Michigan Sunday night. The U.P of Michigan bands will be rather
stable which leads to Day 3 WPC probabilities for >6" in the
60-90% range east of the Keweenaw Peninsula and around 30% for the
Porcupine Mtns. There is increasing confidence on Sunday night into
Monday snow banding from Lake Michigan over northern Indiana where
Day 3 snow probabilities for >6" are now 40-60%. This area, along
with downstream snow banding from Lake Erie will need to continue
to be monitored for the heavy snow banding threat.


The probability of significant ice across the CONUS is less than
10 percent.


Jackson