Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Thu Jan 25 2024

Valid 12Z Thu Jan 25 2024 - 12Z Sun Jan 28 2024

...Intermountain West...
Days 1-2...

A digging jet through CA along with a sharpening mid-level vort
will help drive a widespread light to modest snow over the Great
Basin into the central/southern Rockies today into Friday. A
modest moisture plume ahead of the height falls (PW anomalies
around +1 to +1.5 sigma) will compensate for the rather
progressive system, but most of the forcing will be from upslope
into the terrain. On D1, WPC probabilities for at least 6 inches
of snow are highest (>50%) over the Wasatch in UT and into the San
Juans in southwestern CO. Into D2, mid-level low will try to close
off over northern NM/southern CO as the upper jet swings around
into TX/OK, maintaining broad divergence over the Sangre de
Cristos and Raton Mesa where snow will continue on Friday. There,
WPC probabilities for at least 6 inches of snow are as high as
around 70% in the highest peaks. Farther east, the system will
move across the southern Plains with some wintry precipitation on
its northern side, including freezing rain across KS (if the
precipitation makes it that far north). Drier air to the north
could prevail, limiting any icing, but for now WPC probabilities
for at least 0.10" icing are around 10-20%.


...Northeast...
Days 1-2...

Frontal boundary draped across the region will slowly sink
southward, allowing some colder Canadian air to filter southward
over at least central/northern New England as the current system
exits the area. Later today, mid-level shortwave will lift through
the Ohio Valley, with a new surface low along a frontal boundary
moving toward the eastern Great Lakes by 12Z Fri. Exiting high
pressure over Quebec will try to maintain a supply of colder air
into the region as precipitation and milder air aloft on southerly
850mb flow overspread the area from the southwest, favoring
freezing rain over parts of northeastern NY, much of VT/NH, and
into western ME (also into northern MA). WPC probabilities for at
least 0.10" ice are moderate (40-70%) over the Green and White
Mountains, with lower probabilities over much of the rest of the
northern CT River Valley. By Friday afternoon, another low
pressure along the front will start to become the dominant center,
translating the system eastward and out to sea by Saturday.
Farther north, over central Maine, the cold air will be deeper and
favor snow, with several inches possible over the Central
Highlands. There, WPC probabilities for at least 4 inches of snow
are generally 20-40%.


...Pacific Northwest...
Days 1-3...

Shortwave will move through WA/OR today as onshore flow continues
into early Friday. Snow levels will remain below the Cascade
passes (at roughly 2000-2500ft) where several inches are likely.
WPC probabilities for at least 4 inches of snow are moderate
(40-70%) around 3500ft, with higher amounts in the highest
elevations. Some icing is possible near and east of the Cascades
in sheltered valley locations. Ridging will move into the region
by early Friday, helping to diminish the snowfall for a bit.
However, another Pacific system will move into the region by
Friday afternoon. Warm front will bring in much milder air to the
area, with rising snow levels to well above pass level
(6000-7000ft).


Fracasso