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000
FXUS61 KBGM 070248
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
948 PM EST Fri Dec 6 2019

.SYNOPSIS...
Lake effect snow will be southeast of Lake Ontario tonight into
early Saturday. Mainly dry weather is expected this weekend,
followed by rain for Monday and Tuesday.

&&

.NEAR TERM /THROUGH SATURDAY/...
945 PM Update...Increased PoP overnight across Onondaga County
as lake effect band is now starting to form and snow appears
highly likely. Also, just made some minor changes to hourly
temperatures to align with current observations and trends.

625 pm Update...Water vapor imagery shows upper trough dropping
into Central NY and into the Southern Tier. Forcing is enough to
make snow shower activity more widespread than previously
forecast, so have increased PoP for the next few hours across
Central NY. Also, some of the showers have been quite heavy, so
localized amounts of a quick half inch to possibly an inch will
be possible.

330 PM Update:

No real changes with this update apart from minor adjustments to
taper rain chances off a little sooner in NE PA, with most of
the precipitation now north of the PA border ahead of the cold
front.

Previous discussion:
The forecast remains largely on track this afternoon, with much
of the precipitation north of the southern tier of NY. A few
rain/snow showers are being seen across the southern Tier, with
any precipitation across PA looking like hit and miss periods of
light rain. Otherwise, light snow continues mainly north of a
line from Oneonta-Ithaca-Dansville, with a rain/snow mix in the
lower elevations. Still looking like a general 1 to 2 inches
from that line, increasing to around 3 to 4 inches of snow
heading northward towards the I-90 corridor and the western
Mohawk valley before snow associated with this clipper system
winds down tonight.

Overnight, a shift to NW flow will bring in another round of
snow downwind of Ontario. The main changes with this update have
been to increase the coverage of snow to allow for better
chances for a few snow showers to develop across Oneida county.
However, the thinking still stands that our best chances will be
for bands to set up and extend across Onondaga, Cayuga, and
northern Cortland counties, extending downwind into Chenango
and Otsego counties with healthy NW flow and a connection to the
Georgian Bay. Additional totals up to 2 to 4 inches will be
possible across the I-90 corridor and western Mohawk valley
with lesser totals below an inch elsewhere. With higher amounts
still not looking likely, will hold off on any advisories.

Otherwise, lingering lake effect snow showers wrap up into
Saturday afternoon with a ridge building in and our flow turning
lighter. Temperatures drop generally back into the teens to low
20s tonight with the passing cold front, peaking in the 20s
Saturday afternoon with a colder airmass in place.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
306 pm update...
Main concerns in the short term remain centered around a
drastic shift in the weather pattern Sunday night into Monday
with much warmer temperatures and a transition from a
quick/light wintry mix to rain.

Will also be watching the potential for minor flooding, mainly
along the smaller tributaries of the Upper Susquehanna and Upper
Delaware river basins, and near the Lackawanna river in ne
PA...where there is around an inch of snow water equivalent and
where the heaviest rain is expected.

Weather conditions Saturday night and most of Sunday will be
very quiet with high pressure sliding to the east. The primary
concern Saturday night will be the potential for very cold
temperatures as a good portion of the area will be under mostly
clear skies with strong raditional cooling. Lows are expected to
drop into the single digits above zero and teens.

The high will shift to the east as the next system begins to
move into the Ohio Valley/srn Great Lakes Sunday evening. A
tight surface pressure gradient will develop across the
Northeast/mid Atlantic which will allow for strong southerly
flow to begin Sunday night. A strong stream of warm moist air
from the southern Atlantic coast will advect north into PA/NY
Monday morning and spread precipitation north to the south
through the area. Thermal profiles and subsequent p-types will
be challenging during this time as the cold air near the
surface...around 30 deg...gets trapped under a rapidly warming
air mass aloft. The initial push of precip will be light on the
front end Monday morning, with a slight chance of sleet and
freezing rain...but should change to all rain as the boundary
layer warms above freezing and increase in intensity and cover
through the late morning. A strong inversion just above the
surface will likely also produce an abundance of low clouds and
fog.

The axis of moisture on Monday will ride up along the I-95
corridor during the day and likely brush the Poconos and
Catskills with a solid half to 1 inch of rain. The rain will
likely shift further east Monday night, but persist in the form
of light rain showers into Tuesday morning. The surface low will
track from the sern Great Lakes into srn Quebec by early Tuesday
morning with a drawn-out slow moving cold front extending south
along the Appalachian Mtns. Along and ahead of this front will
be the focus for an extended period of light rain Monday night
into Tuesday where there should be sufficient time and heating
to melt a good portion of the snowpack. Surface dewpoints in the
40s will aid in the melting of snow during this time. Latest
modeled snow water equivalent across the region is roughly 1-2
inches in central NY and along the nrn tier of PA. The
combination of the initial push of mdt- hvy rain on Monday,
combined with an additional quarter of an inch or so of rain and
an inch of snow melt may put enough water into some area basins
to rise smaller streams and creeks to bankful, and possibly
cause minor flooding for the usually sensitive
areas...especially the Upper Susquehanna and Upper Delaware.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
306 pm update...
Rain showers continue early Tuesday before the back edge of the
precip moves through wrn NY and the front edge of the cold
Arctic air moves in later in the day. The cold front will start
to make strong progress east later Tuesday into Tuesday night
with the upper trough catching up and kicking the system out to
sea. The onset of much colder and drier air will arrive Tuesday
afternoon/evening with any remaining rain showers transitioning
to snow showers quickly as temperatures go from the lower 40s to
the upper 20s in a short period of time. The focus then shifts
to the potential for accumulating lake effect snow, mainly north
of the Thruway Tuesday night through Thursday. Strong cold air
advection and a persistent west wind will put the focus across
the northern counties. There are still a lot of details to be
worked out with respect to the LES potential, but the air mass
will definitely be cold enough...850mb temps around -15 to -20
C...for heavy lake snow in some areas downwind of Lake Ontario.

Much colder temperatures are on tap for the middle part of next
week...with highs in the 20 and 30s...and overnight lows in the
teens.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
630 pm update...
Lake effect snow has expanded across CNY early this evening with
even some sprinkles at AVP. IN general MVFR conditions tonight
improving to VFR Saturday.

With the northwest flow AVP should only have MVFR cigs with
mixed precipitation the first 2 hours then VFR.

ELM mainly VFR too with the first 4 hours with a MVFR tempo in
snow showers. RME will be east of the bulk of the snow showers.
Up to 04z also a tempo for MVFR. As the flow shifts a little to
the west late tonight a return to MVFR 9 to 15z.

ITH fuel alternate MVFR to continue all night with some IFR up
to 04z. Return to high end MVFR at 12z then VFR at 19z. BGM
similar with fuel alternate MVFR all night improving to high end
MVFR at 13z then VFR at 20z.

SYR is expected to have the steadiest snow tonight. MVFR all
night with possibly some IFR from 07 to 11z. VFR at 18z.

Northwest winds tonight around 6 kts. West to northwest winds at
8 kts Saturday.

Outlook...
Saturday night through Sunday evening...VFR.

Monday and Tuesday...Restrictions likely with a broad area of
rain across the region.

Wednesday...Restrictions possible in lingering snow showers.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

$$
SYNOPSIS...BJG/HLC
NEAR TERM...HLC/MPK
SHORT TERM...BJT
LONG TERM...BJT
AVIATION...TAC