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

Valid 12Z Wed Dec 27 2023 - 12Z Sat Dec 30 2023

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

The fully matured cyclone over Missouri this morning will continue
eastward and weaken over the next couple of days. Generally light
snow is forecast near the track of the upper/sfc low, especially
over east central Missouri where 2-day WPC probabilities of at
least 4 inches of snow are around 10-20%. By day 3 (Fri), the
system will reach into the Ohio Valley, with height falls into the
central Appalachians. Cooler air will steadily work its way
eastward, changing rain to snow at higher elevations over WV,
western MD, into the Laurel Highlands by Friday morning and into
the afternoon. Limited upslope will still wring out a few inches
of snow for favored areas, with WPC probabilities of at least 4
inches around 10-30%.

...Northern New England...
Days 1-3...

A frontal boundary will meander around Maine for the next couple
of days, with modest moisture ahead of the central CONUS upper low
streaming in from south of New England. Precipitation will
generally be light and intermittent, with snow to the north near
the Canadian border and mix of sleet and mostly freezing rain over
interior Maine today. A more cohesive area of precipitation will
move into the area by Friday night as a result of an area of low
pressure moving along the East Coast and lifting toward the Gulf
of Maine. For day 3 (Fri into early Sat), inverted trough may set
up briefly across the region, enhancing some snowfall via
lower-level convergence generally away from the coast with some
locally higher amounts in the mountain peaks. Total snowfall may
only be a few inches, as the approaching upper low will help kick
out Gulf of Maine low and refocus another low off the
Mid-Atlantic. WPC probabilities for at least 4 inches of snow,
mostly on day 3, are low (10-20%) over far interior and northern
Maine. Southern portion of the wintry precipitation will likely be
freezing rain, and persistence may allow for a slow accretion of
ice during the 3-day period. WPC probabilities for at least 0.10"
ice are as high as around 40% for the 3-day period.


...Pacific Northwest and Northern California...
Days 1-2...

A couple shortwaves moving northeastward through the Northeast
Pacific will bring weakening fronts into the West Coast the next
couple of days. First system today will focus into the NorCal
ranges, but snow levels remain high (above 6000-6500ft). Next
system will final bring its cold front into the West by late day 3
(early Sat), perhaps in split form as the upper trough takes
shears northeast/southeast. Light snow is forecast for the
Cascades and through the Sierra into early Saturday, but the
Sierra may see more appreciable snow into day 4 as the system
brings more moisture to the region.


Fracasso