Winter Weather 23/24

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Area Forecast Discussion
National Weather Service Burlington VT
650 PM EST Thu Jan 25 2024

NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 634 PM EST Thursday...

* Winter Weather Advisory is in effect for all of northern New
York and Vermont tonight through Friday


* Primary concern is for localized power outages in the St.
Lawrence Valley due to ice loading from cumulative freezing
rain events and increasing winds


* Difficult travel is likely due to ice and/or snow for most
locations during the morning commute, as well as the evening
commute, especially northern areas.

No significant changes to the forecast this evening. The
challenge will be overnight temperatures as many areas are
hovering right around freezing. Beyond that, the forecast looks
on track. Previous discussion follows...

A complex and impactful weather event is expected tonight
through tomorrow as yet another wave of low pressure moves
through the region. Overall, there was a slight shift towards
colder conditions with this forecast cycle, with enough coverage
and probability of freezing rain/drizzle to issue a Winter
Weather Advisory areawide. Similar to the previous event, the
areas most susceptible to sub-freezing temperatures and more
than just a trace of ice are in the St. Lawrence Valley,
northern portions of the western Champlain Valley, and
along/east of the Green Mountains.


Precipitation will fall throughout much of the day, with storm
total liquid amounts mainly ranging from 0.3" to 0.6". This
system has less deep moisture than the last one, but it makes up
for it with better dynamics as low pressure deepens approaching
central New York tomorrow morning. The gradient flow between
this system and high pressure to our northeast will bring cooler
air in from the east, helping change freezing rain/rain to
snow, particularly east of the Green Mountains in the northern
half of Vermont and in much of Clinton County, New York.
These
areas will see precipitation gradually change to snow beginning
with the mid-morning hours with 1 to 3" of wet snow possible.
Elsewhere, strong warm air advection at 850 millibars will
ensure precipitation is again primarily rain and freezing rain,
with insufficient cooling to get more than a brief period of
light snow before ending. Northeast winds down the St. Lawrence
Valley will keep precipitation mainly freezing rain where storm
total ice is expected to again approach 0.4", although southern
portions of the region may see plain rain during the afternoon.

One note for tonight: the aforementioned high pressure area,
currently to our north, has helped maintain chilly northerly
flow this evening in the eastern Champlain Valley. Along with
patchy fog/drizzle, with temperatures so close to freezing, be
prepared for areas of black ice this evening into the overnight.

As the low pressure system departs tomorrow night, lingering low
level moisture and little change in temperature (still hovering
near freezing) may cause slick conditions to persist even after
steady precipitation ends. Winds, after picking up a bit
tomorrow morning, will tend to relax by tomorrow night.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
As of 330 PM EST Thursday...Have increased pops and qpf on Sat
associated with embedded 5h s/w and ribbon of favorable 850 to 500mb
moisture. QPF and snow accumulations wl be light, given the limited
available moisture and forcing, so have utilized the light
descriptor. Have placed 30 to 50% pops in the grids, but feel some
low likely wl be needed, especially mtns of northern NY into VT. Bl
temps are marginally cold enough to support snow in the valleys, but
mtns above 1000 feet should see a light dusting to maybe an inch of
snow on Saturday.
Progged 925mb temps btwn -1C and -3C support highs
upper 20s to mid 30s most locations, did undercut NBM guidance by
several degrees. Sat night clouds prevail with temps falling back
into the 20s to near 30F locally here in the CPV. Sounding data
indicates varying amounts of moisture trapped below thermal
inversion around 850mb and limited favorable rh within the snow
growth region, so patchy drizzle/freezing drizzle is possible,
especially above 1500 ft. Given the time frame and uncertainty in
the depth of moisture and areal coverage have not mentioned in fcst
yet.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 330 PM EST Thursday...Strong mid/upper lvl trof crntly acrs the
southern Rockies wl eject into the southern Plains by the weekend
and track into the Ohio Valley/Mid Atlantic States by Sunday. A very
fast confluent flow aloft persists acrs the NE CONUS as sfc high
pres is nosing south from Hudson Bay and low pres is tracking
northward from the MS River Valley. This synoptic scale scenario
results in a sharp south to north moisture and qpf field setup acrs
the NE CONUS for our next system. Latest 12z guidance has trended
further north with regards to deeper moisture and higher qpf into
central/southern VT,
while 1000 to 500mb rh >70% extends to the
International Border. Based on this have increased pops by 20 to 30%
for our central/southern cwa with low likely, while placing schc
near the border. Would not be surprised based on water vapor
presentation of s/w energy and mid/upper lvl trof, this system is
stronger than modeled and is slower to shear apart in the fast
confluent flow aloft
acrs the NE CONUS, resulting in a slight
northward trend in pops/precip on Sunday into Monday. At this time,
best potential for a snow accumulation would be along and south of
Interstate 89 acrs central/southern VT, into Essex County NY. Temps
on Sunday/Monday are in the upper 20s to mid 30s with very mild
overnight lows in the 20s to near 30F.
 
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