Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
405 PM EST Fri Jan 12 2024

Valid 00Z Sat Jan 13 2024 - 00Z Tue Jan 16 2024

...Great Lakes and Interior Northeast...
Days 1-3...

A powerful storm now centered over the mid Mississippi Valley will
intensify further as it continues to lift northeast, with the
model consensus showing a consolidated surface low dropping into
the mid to upper 970s as it tracks across southeast Lower Michigan
into Lake Huron overnight. 

Heavy synoptically-driven snow on the the northwest side of the
low will continue to translate north across northern Lower
Michigan during the evening.  Lake enhanced snow over the upper
Great Lakes will transition to intense lake effect that will
develop across all the Great Lakes by late Saturday as the low
lifts into Quebec and much colder air begins to sweep across the
still relatively-warm lakes. 

Further to the east, cold air in place over the interior Northeast
will retreat in the face of southerly flow ahead of the low's
advancing cold front.  Snow at the onset will transition to a
wintry mix before changing over to all rain in many locations as
the cold air erodes.

For Day 1, ending 00Z Sunday, WPC PWPF shows high probabilities
(greater than 70 percent) for additional snow accumulations of 8
in or more across northern Lower Michigan and in the Upper
Michigan snow belts.  Within this area, the PWPF shows high
probabilities for accumulations of a foot or more, with the
highest in the Huron Mountains, where north to northwest flow is
expected to accentuate totals.  In the Northeast, heavy snow
amounts are expected to be more localized, with the higher
probabilities for accumulations of 4 inches or more confined
mainly to the Adirondacks and the northern New England mountains
from the Greens to northern Maine.

For Day 2, ending 00Z Monday, as strong westerly flow and cold air
spreads across the lower Lakes, the probabilities for locally
heavy snow develop in the Buffalo Metro area and near and north of
the Tug Hill region.  The WPC PWPF shows high probabilities for
amounts exceeding 8 inches in these areas.

Then on Day 3, ending 00Z Tuesday, as the low tracks farther to
the north and then backs to the west over Hudson Bay, the heavy
lake effect potential is expected to diminish as winds become more
west-southwesterly across the Lakes.

...Mid-South/Lower MS Valley/eastern TX...
Day 3...

Sharp trough/splitting shortwave over the northern/northeastern
Pacific this evening will swiftly dive southeastward and move
through the Southwest/Four Corners Sunday. Thereafter into day 3,
strengthening upper jet across the Mid-South will support an
expanding area of snowfall over the southern Plains Sunday night
into Monday in the right entrance region. Surface cold front will
have plunged to the Gulf Coast, allowing cold arctic air to invade
the region as Gulf moisture returns on southerly flow at 850mb.
Through Monday, snow will expand eastward across eastern OK and
through AR but also southward over southeastern TX. In the deeper
cold air, generally north of I-20, frontogenetic banding may
enhance some totals over AR, but models differ on placement.
Formed a consensus with a nudge toward the wetter, but not
wettest, side of the QPF, resulting in an area of >4" over a broad
region. WPC probabilities for at least 2 inches of snow are
moderate (40-70%) from eastern OK eastward to middle TN, and
northward to southern MO/KY and southward to around the ArkLaTex
eastward to northern MS. Within this area, WPC probabilities for
at least 4 inches are moderate (40-70%) across central AR eastward
to western TN (including northwestern MS) through 00Z/16 (Monday
evening) with the event continuing thereafter.

Farther south and southwest, cold surface temperatures beneath a
warm nose aloft supports an area of freezing rain from the TX Hill
Country eastward across northern LA and southern AR into western
MS. Ensemble ptype guidance shows some probabilities of all four
types but with a dominant signal for ice vs sleet (though each or
both are quite possible), though the models always struggle with
near-surface sub-freezing layers and the evolution of the warm
nose. Overlap of the higher ZR probs and higher QPF (closer to the
TX/LA border) may result in more significant icing. As of now, WPC
probabilities for at least 0.10" ice are low (generally 10-40%)
from near I-35 near AUS east-northeastward into northern LA along
and south of I-20. Again, uncertainty in both ptype and QPF
amounts will likely make for a changeable forecast for at least
the next day or so. The probability of any icing exists from the
Hill Country eastward through the I-10 corridor, northeastward to
northern AL.

Fracasso/Pereira