Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 PM EST Mon Dec 11 2023

Valid 00Z Tue Dec 12 2023 - 00Z Fri Dec 15 2023


...Interior Northeast...
Day 1...

Amplifying, negatively-tilted trough lifting north from the
Mid-Atlantic spurs continued rapid deepening of surface low
pressure as it tracks north away from eastern New England this
evening. Lake effect snow in typical northwest flow snow belts off
Erie and Ontario will taper off while shifting westerly tonight
with additional accumulation of a few inches possible in the Tug
Hill.


...Michigan U.P. into the Tug Hill...
Days 2-3...

Upper-low will move from northern Manitoba across far northern
Ontario through Tuesday with the associated surface cold front
dropping through northern MN today, the western Great Lakes
tonight and eastern Great Lakes Tuesday. 850 temps will be notably
colder with this wave, dropping to around -12 to -15C (into the
DGZ) and supporting WNW to ESE bands post-FROPA tonight on the
U.P. and off Lake Ontario Tuesday night before slowly diminishing
into Wednesday. Day 2 WPC probabilities for >4" remain moderate to
high (40% to 80%) in eastern sections of the U.P. shoreline of
Superior. 

On Day 3, wind will veer from SW to W to WNW, favoring a
resurgence in lake effect single-band snow east of Ontario into
the Tug Hill as the cold front from the central Great Lakes passes
through. Day 2.5 WPC probabilities for >4" of snow have decreased
this forecast cycle to moderate to high (40-70%) in the Tug Hill.


...Southern Rockies...
Day 3...

A shortwave trough over the PacNW this evening gets ducted under
an amplifying northern stream ridge over western Canada through
tonight, with an arriving southern stream portion of the ridge
sending the trough south over Great Basin Tuesday. This trough
develops into an upper-low over Arizona Tuesday night and becomes
cut-off, drifting east across New Mexico through Thursday. Gulf
moisture shifts through West Texas in earnest by Tuesday night
with rain breaking out over the southern High Plains and an
easterly component sending it up the eastern slopes of the
southern Rockies (mainly the Sangre de Cristos Wednesday). Height
falls from the approaching upper-low and ample moisture (via
anomalous upslope flow) set up a terrain based heavy snow case for
the southern Rockies later Wednesday into Thursday. Day 3 snow
probs for >4" are moderate to high (40-80%) and for >8" are low to
moderate (10-40%), centered over the NM side of the Sangre de
Cristos through Raton Mesa.


Churchill/Jackson