Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
242 AM EST Fri Jan 26 2024

Valid 12Z Fri Jan 26 2024 - 12Z Mon Jan 29 2024

...Pacific Northwest...
Days 1-2...

Pacific system will push toward/into the region later today, with
the parent low well north of the area into the Gulf of Alaska.
Warm front will bring in much milder air, raising snow levels well
above pass levels by early Saturday. An inch of two of snow is
likely at the higher passes today before the changeover to rain.
Within and east of the Cascades, as warmer air aloft first pushes
northeastward, freezing rain is likely in sheltered valleys that
remain below freezing into Saturday before above freezing
temperatures overtake inland areas. WPC probabilities for at least
0.10" ice are generally 20-50% through parts of the Columbia Gorge.


...Southern Rockies & Central High Plains...
Days 1-2...

Mid-level closed low over northeastern NM this morning will
continue eastward, allowing heights to rise in its wake over CO/NM
later today. Surface low pressure will slowly move away from
northeastern NM as well, with wrap around snow near the upper low
diminishing by midnight. A few additional inches of snow are
likely, mainly in the Sangre de Cristos and into the Raton Mesa.


...Northeast...
Days 1 & 3...

For D1, today into early Saturday, low pressure currently over
northeastern OH will weaken as it moves toward the Southern Tier
of NY. A new area of low pressure along the warm front will become
the dominant center as the entire system then quickly slips
eastward tonight. Surface high pressure over southern Canada will
continue to supply sub-freezing temperatures into much of northern
NY and central/northern New England today, battling the southerly
WAA from the south aloft. This will set up a mixed precip zone
generally north of I-90 to the Canadian border, with the exception
of much of Maine which will be deeper into the colder air. There,
WPC probabilities for at least 4 inches of snow are moderate
(40-70%). Over much of VT/NH, freezing rain is likely through the
day, with modest (20-50%) chances of at least 0.10" icing,
especially over parts of the Green and White Mountains.

The system exiting the southern Rockies today will progress
through the lower MS Valley on Saturday and then turn the corner
into the Upper Ohio Valley as a closed mid-level circulation with
the parent surface low heading into eastern Ohio/WV. By 12Z Sun,
the triple point low will start to take over as the dominant
center (Miller-B evolution), and help guide the system eastward
along 40N overnight into early Monday. Weak high pressure over
Canada Saturday will retreat/dissipate as the precipitation shield
advances into the Mid-Atlantic and Northeast, resulting in a
snow-to-rain changeover for some areas with snow preferred at
higher elevations. Much of the precipitation will fall during the
daytime on Sunday, limiting some accumulation as well. Models show
a fair amount of spread with respect to the extent and amount of
overall QPF, in addition to the thermal structure and depth of
cold air, which is marginal. WPC probabilities for at least 4
inches of snow are tied to the higher elevations of the Catskills,
Berkshires, and Worcester Hills, with values between 30-60%. The
broader NY/PA region between I-90 and north of I-80, especially
along the NY Southern Tier/I-86/Rt 17 corridor, and eastward
across MA has a low-end (10-40%) chance of at least 4 inches of
snow. Spread between the 10th and 90th percentile spans anywhere
from 0-8" of snow, so there is room for refinement in future
forecast iterations.

Fracasso