Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 PM EST Wed Dec 27 2023

Valid 00Z Thu Dec 28 2023 - 00Z Sun Dec 31 2023

...Mid-Mississippi Valley to the Central Appalachians...
Days 1-3...

Core of massively occluded low centered over central MO this
afternoon will continue to allow snow bands to develop around this
core over eastern MO/southern IL tonight and a second round for
this area wrapping around the core from northern IL Thursday
afternoon/night. While moderate rates are expected to be the
limit, the two waves could make for some notable amounts even with
the marginal thermal conditions going into tonight. The Day 1.5
probs for >2" snow are 40-70% over western IL to eastern MO.

This backside band weakens as the low fills a bit more into
Friday. However, the resulting westerly flow/upslope to the
western slopes of the central Appalachians allows for snow
enhancement Friday afternoon into Saturday. The Day 2.5 snow probs
for >4" over central WV into western MD are 20-40%. 


...Northern New England...
Days 2-3...

The sprawling occluded low centered over the Midwest meanders east
through Friday with a mid-level lobe with coastal low pushing up
the Northeastern Seaboard Thursday. As the low reaches to the Gulf
of Maine Thursday night, precip lifts into northern New England
where dynamic forcing and sufficient antecedent cold air allows
snow to fall. Rates are not expected to be heavy. However,
sufficient overrunning of Atlantic sourced air over the colder
surface air west of the low track should allow a wintry mix with a
fair percent going to freezing rain. Day 2 probs for >0.1" ice are
20 to 40 percent over north-central Maine.


Pacific Northwest...
Day 1...

A shortwave trough rounding a sprawling low well west of BC will
cross the OR/WA coast this evening, maintaining moderate precip
rates with snow levels around 5000ft. Only the higher Cascades and
Olympics will see impactful snow which could reach 2' above 6000ft.


...California...
Day 3...

A digging trough becomes full-latitude as it reaches the West
Coast Friday night with a southern stream lobe crossing SoCal
Saturday. Precip pushes inland Friday night with snow developing
along the Sierra Nevada ahead of the height falls. Snow levels dip
below 6000ft Friday night/Saturday over the Sierra Nevada where
there are 30-70% probs for exceeding 6" on Day 3.


Jackson