Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
226 AM EST Wed Nov 11 2026

Valid 12Z Wed Nov 11 2026 - 12Z Sat Nov 14 2026

...Great Lakes...
Days 1-3...

Troughing will dig southward from Ontario across the western Great
Lakes and into the Midwest/Northeast today, downstream of building
upper ridging over northern Canada. The surface cold front will
bring in northerly flow across the still mild lakes [Lake
temperatures +8 to +12C (Superior) and +10 to +15 (Michigan)] and
the incoming cold air is seasonably chilly (though much colder than
recent days). 850mb temperatures are forecast to dip to around
-5 to -10C (south to north) yielding a delta-T of around 15-20C,
 supporting lake effect precipitation. Surface temperatures will be
 coldest (and <32F) over the U.P. of Michigan where multi- banded
 snow on northerly winds will likely accumulate several inches
 starting late this evening into Saturday. Through 12Z Saturday,
 the probability of at least 4 inches of snow is >70% over the
 Huron Mountains (away from the warmer lake shore) with lighter
 snow over much of the rest of the Upper Peninsula and northern
 Lower Peninsula. Northerly flow down the long axis of Lake
 Michigan could spur a robust lake band of rain/snow into
 northwestern Indiana Thursday evening into Friday. Though
 temperatures are marginal, the potential exists for a narrow area
 of modest wet snow if rates are sufficiently high and temperatures
 cool just enough. There, the probability of at least 4 inches of
 snow is about 20-60%.


...Northeast...
Days 2-3...

An area of low pressure over the Corn Belt this morning will arc
through the Midwest later today and into the central Appalachians
overnight into early Thursday. From there, the models have
struggledwith how to eject this system and how far north to bring
its precipitation shield into the Northeast, with the most
uncertainty along the Canadian border. The physics-based models
were generally farther south while some of the REFS members were
quite far north. The AI-based models were generally farther south.
Though the trend has been for more precipitation overall, a
measured increased was implored. For ptype, with marginal cold air
incoming from the north/northeast, snow was focused over the
terrain with mostly rain for the valley locations but perhaps some
measurable amounts of snow <0.5" especially Thursday night into
early Friday. For areas above 1500ft or so, the probability of at
least 4 inches of snow is >50%, with some areas above 2500ft
possibly seeing at least 8 inches of snow (>40% chance).


...Central Appalachians...
Days 2- 3...

Post-FROPA cold advection in modestly moist northwesterly flow
will upslope into the western flank of the central Appalachians,
leading to continued precipitation production Thursday night into
early Saturday. Forecast model soundings show temperatures through
most of the column aloft falling below 0C by late Thursday night,
supporting a transition from rain to snow. Periods of light to
moderate snow will accumulate into the first half of the weekend,
especially above 3000ft. Probabilities of at least 4 inches of snow
are >40% (and as high as 90%), especially across the high terrain
of WV and along the border of TN/NC.


...Sierra Nevada...
Days 2-3...

A strong negatively-tilted upper wave swinging into northern CA
will direct a strong but weakening atmospheric river (IVT
diminishing to between 250-400 kg/(m s) by Friday night) into the
Sierra Nevada, leading to moderate to heavy upslope snow beginning
Friday afternoon and continuing just beyond this forecast period
(which ends 12Z Saturday). Snow levels will initially be around
8000ft at the start of precipitation before modestly falling to
between 6000 and 7000ft during the day on Saturday. The heaviest
snow will ramp up Friday afternoon, then gradually taper off
through the day on Saturday. The snow will likely be fairly wet and
heavy, with SLRs around 9-11:1 at best. Probabilities for at least
8" of snow are >50% above 6500-7000ft, and for at least 12" of
snow are >50% above 7000-7500ft. The heavy snow will likely make
for difficult travel across some mountain passes, leading to 40-90%
probabilities for moderate impacts per the probabilistic WSSI,
mainly above 7000-8000ft.


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


Fracasso/Miller