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Area forecast discussion 
National Weather Service Binghamton New York
258 PM EST Tue Dec 6 2016

Synopsis...
a storm system will impact the region tonight, with a mixture of
rain and snow. Most of the accumulating snow will be confined to
the higher elevations. After dry conditions most of Wednesday, a
strong cold front will cross the region on Thursday. Much colder
temperatures will follow Friday and Saturday, along with potential
lake-effect snow, for parts of central New York.

&&

Near term /through Wednesday/...
115 PM update... clouds will continue to lower and thicken this
afternoon. Based on radar extrapolation, surface obs, and the
latest model output, we still expect mixed rain and wet snow to
begin overspreading portions of the central southern tier in New York
and northeast PA from 5-7 PM.

The models remain consistent in bringing a 6-9 hour band of steady
light precipitation through the forecast area tonight. A good
moisture fetch from the Atlantic, forcing from a mid-level short-
wave, and some upper jet dynamics are the main forcing mechanisms.
The primary detractors are marginal boundary layer temperatures
and relatively fast system movement, with dry slotting aloft
coming in towards daybreak.

Bottom line, most of the accumulating snow should occur over the
higher terrain, with a general 1-3" snowfall anticipated at most
locations near and above 1500 feet. This includes the Pocono
plateau, the western Catskills, the higher terrain across the twin
tiers and south of Syracuse, and the Allegheny Highlands west of
Elmira and Corning. For the valley cities, like Syracuse, Elmira,
Corning, Binghamton, Wilkes-Barre, and Scranton, only a coating
to a slushy inch is foreseen.

When steadier, heavier precipitation is falling tonight,
temperatures will be at their lowest (due to dynamic cooling from
above; mainly 31-35 degrees). Towards daybreak, readings may
begin to inch upward.

Wednesday, after some lingering light rain/drizzle/flurries early
in the day, expect a mainly cloudy, but dry day. A few breaks of
late day sun are possible in the western Finger Lakes. There is
little to no cold air advection behind tonight's system, so
expect temperatures Wednesday afternoon back into the upper 30s-
mid 40s.

&&

Short term /Wednesday night through Friday night/...
245 PM update...
main focus will be the potential for significant lake effect
snows across part of our area and cold weather for everybody.

Wednesday night will be dry, and the first half of Thursday also
looks fairly quiet with a deep southwest flow ahead of an
approaching 500 mb trof keeping any lake effect activity north and
west of our area. However with the approaching trof combined with
synoptic moisture will be enough for a chance of a few snow
showers or scattered flurries just about anywhere Thursday.

Up north as the 500 mb trof moves through early Thursday afternoon, a
250 to 260 wind flow will veer slightly toward 270 to 280 around
18z Thursday and remain that way through 08z Friday. 850 temps
around -18c over lake waters well into the 40s will create
moderate instability over the lake, with inversion heights above
10,000 feet! We do have a bit of shear in the lower levels with a
west to west- southwest flow at the surface and a west-northwest
flow around 10,000 feet. This shear however may act to make the
band wider than what you would normally expect on a 270-280 flow,
so confidence is higher that the band will actually make it into
northern Oneida County. Accumulations here of a foot or more are
possible so a lake effect snow watch has been issued.

By daybreak Friday a secondary trof will move through and our flow
will veer toward 300/310 and will remain that way through Friday
night. Inversion heights do lower somewhat, but are still
respectable around 6 to 7,000 feet. In addition we have excellent
moisture and lift in the snow growth region (think high flake
production/snow ratios). Lastly upstream trajectories from hysplit
on the 12z GFS show that we should have an upstream connection to
Georgian Bay Friday and Friday night. Model quantitative precipitation forecast seems to have an
OK idea of where the band will be but based on what I just wrote,
are way too underdone in my opinion. While the devil is always in
the details and adjustments to placement and amounts will likely
be made, confidence is greater than 50% that significant snows of
a foot or more are likely over a good part of central New York that a
lake effect snow watch has been issued. I have the start time at
23z Thursday to match up with National Weather Service Buffalo and help out the
Syracuse and Utica media markets. The heavier snow through in
these areas is more likely toward daybreak Friday, and through
Friday night. Please refer to our latest briefing at
weather.Gov/bgm and click on weather hazard briefing at the bottom
for our first snowfall forecast. Again this will likely be
adjusted somewhat both in coverage and amounts.

Lastly, if the upstream connection is verified. With deep moisture
an the upstream contribution, heavier snow amounts likely are to
extend inland through Cortland, Chenango, Otsego, and Delaware
counties. However with these areas on the southern edge of the
bands, confidence is not high enough just yet to include them in
any watches. If you live in these areas however, keep in mind
heavy snow is still possible and please check back for updates as
we are still more than 48 hours away.

For the rest of US cold will be the big story. With highs in the
20s to near 30 and somewhat of a breeze, wind chill values in the
teens likely during the day.




&&

Long term /Saturday through Monday/...
250 PM update...

The main focus was on the lake effect snow earlier in the week.
With that said we remain with a moist, northwest flow through
Saturday. Inversion heights increase again and we still have an
upstream connection progged by the models. Bottomline snow squalls
likely to continue through Saturday. A zonal flow early next week
keeps our weather unsettled. We remain cold enough for mainly snow
but with storm tracks to our west and daily temps above freezing
in some spots, kept rain/snow mix for some of the lower terrain.

&&

Aviation /20z Tuesday through Sunday/...
VFR conditions will continue this afternoon.

Steady rain/snow will develop this evening, then persist overnight.
MVFR restrictions are expected to settle in from 23-02z at most
terminal sites, with at least periodic IFR anticipated overnight
into Wednesday morning, especially at kbgm, where snow may be more
prevalent.

Slow improvement is foreseen Wednesday, with residual IFR ceilings
improving to MVFR first, then perhaps to VFR towards midday at
kelm and kith.

S-southeast winds will average 5-10 kt tonight and early Wednesday,
before shifting to the west and SW by midday.

Outlook...
Thursday...possible restrictions in lower ceilings and scattered
rain/snow showers, especially ksyr and krme.

Friday-Saturday...restrictions likely at ksyr and krme in lake-
effect snow, with possible restrictions in snow showers/flurries
down to kelm, kith, and kbgm. Kavp should be mainly VFR.

Sunday...although residual restrictive conditions are possible at
ksyr and krme, a general improvement to VFR is foreseen at this
early juncture.

&&

Bgm watches/warnings/advisories...
PA...none.
New York...Lake effect snow watch from Thursday evening through late
Friday night for nyz017-018-036-037.
Lake effect snow watch from Thursday morning through Friday
morning for nyz009.

&&

$$
Synopsis...mlj
near term...mlj
short term...heden
long term...heden
aviation...mlj

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