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Upstate/Eastern New York


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Man. I hope you guys are ready out there in Western NY. This one has the potential to really bring the hammer. Someone will be getting hit pretty hard by wherever the TROWEL sets up. I think the Euro and NAM might be pinning down the placement of that feature in latest runs. Starting to think Upstate NY, somewhere, will see 20+" of heavy wet snow. That'll be fun, unless the power goes out....

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Kbuf 

The complexity of the weather system grows Thursday night, as the
northern stream and southern stream waves phase and start to dive
southeastward, while a close, negatively tilted low at 500 mb
develops over PA. The complexity of this interaction has lead to
some disagreement on the evolution of the surface low among the
global and regional models. The track of this surface low will be
largely important to how quickly colder air can be drawn southward
across the forecast area causing a transition from rain to snow. The
operational GFS remains right near the farthest north with its
track, stalling it almost over eastern Lake Erie or Buffalo. This
farther north track would severely limit snowfall amounts across the
forecast area, however this solution is also an outlier among its
own ensembles as well as the EC, NAM and Canadian models, as well as
the EC ensembles. The model consensus has certainly trended slightly
southward and slightly cooler over the last day or two, and given
the very marginal temperature profiles near the freezing mark, this
is enough to raise concerns about the possibility of a significant
snow event.

The colder air will lead to a transition from rain to snow Thursday
night into early Friday morning, with confidence increasing in
widespread accumulations. Precipitation efficiency will certainly be
high late Thursday night through Friday morning given an enhanced
deformation and trowal forcing wrapping back across western NY along
with a fetch of deep Atlantic moisture along the cold conveyor belt
of the storm. Exactly how this efficient precipitation process
translates to snowfall totals is a bit more complicated. The
boundary layer will be slow to cool, limiting accumulation
efficiency, but will be counteracted by the impressive dynamical
cooling overspreading the region underneath the upper level system.
A cooling northerly flow on the back side of the system will also
allow for some enhanced amounts from upslope.

Forecast models are also trending toward the snowfall linger longer
through the day on Friday, as the transfer of energy to the coast
is now forecast to result in a surface low making a cyclonic loop
near or just off shore from Long Island. By holding the secondary
surface low closer to the coast, there is more potential for
continued wrap around snowfall through the day Friday before
tapering off Friday night as the low finally drifts farther
offshore. This would also prolong the enhancement south of Lake
Ontario from frictional convergence and orographic ascent in the
northern Finger Lakes. However, lingering snowfall accumulations
into the day Friday will also struggle against marginal surface
temperatures (daytime highs +/- 32 degrees) especially for lower
elevations, and the higher sun angle even through the cloud cover
now that were getting into March. Lows Friday night will be back
into the mid 20s to near the 30 degree mark.

With regard to forecast snowfall amounts, there remains lower than
average confidence. A general 5 to 10 inches in the watch area is
currently forecast, with the highest amounts over the higher terrain
south of Lake Ontario. However it is extremely important to note
that the details in forecast snowfall will change as this storm
system approaches. Any changes which would allow for colder air than
currently forecast would result in higher snowfall totals, while any
changes with slightly warmer air could cut back on snowfall totals.
It is also quite possible that snow accumulations could vary widely
by elevation even for locations in otherwise close proximity, with
hilltops more likely to receive the higher amounts. In other words,
be aware of the wide range in possible outcomes, and monitor this
forecast closely as the storm system nears.
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nice write up from KBGM.

The general idea will be for an Ohio Valley low to lose definition
Thursday evening, while transferring energy to a coastal low
late Thursday night through Friday, which itself will get forced
ascent via left exit region of upper jet. Ohio Valley low will
become an inverted trough, with 700mb low tracking along the
Interstate 80 corridor. The trend has been for a slower moving
mid/upper level low which captures the deepening surface low
just off the NJ/NY coast during the day on Friday. The surface
low will rapidly deepen down to around 980mb by 18z Friday and
will likely do a small counter-clockwise loop near Long Island.
Meanwhile, a closed 850/700mb low will spin somewhere near NYC
(NAM) or south of Long island (ECMWF). Either way, plenty of
Atlantic moisture will wrap around the system and into our area.
The moisture feed will be enhanced by an 80kt easterly jet at
850mb over New England. Once this cyclone matures (becomes
vertically stacked) by around midday Friday indications are
that a strong deformation band of potentially heavy snow will
setup over much of the forecast area...and persist for at least
several hours well into Friday afternoon or evening. Exactly
where this band of heavy snow sets up is still uncertain
     however climatology would favor a scenario close to the ECMWF
solution, with the heaviest snow along the I-81 corridor and
east. A strong band of frontogenesis in the 850-700mb is evident
on the latest GFS starting around 12z Friday and persisting
through much of the day. Surface temperatures will be marginal
for heavy snow, especially in the lower elevations where temps
will likely be between 30-35 degrees...in the higher terrain
snow will accumulate more efficiently with slightly higher snow
ratios (closer to 10 or 12:1) as temps will be between about
28-33 degrees here. If models hold steady on the track and
strength of this system it certainly has the potential be bring
a significant snowfall to much of the area. Climatology would
favor a very snowy scenario with a strong, closed off mid-level
low sitting and spinning near NYC this time of year.
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