Area Forecast Discussion
Issued by NWS Binghamton, NY

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338
FXUS61 KBGM 241719
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1219 PM EST Fri Nov 24 2017

.SYNOPSIS...
A storm system will pull warm air and a few showers into NY and
PA toward sunrise on Saturday. A cold front behind the storm
will set off light lake effect snow showers and flurries for
Sunday, before milder air returns for early next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
1115 AM update...

Skies have cleared nicely across the region and temperatures are
quickly climbing, with the high elevation BGM station already
sitting at 40 degrees.

We ammended temperatures slightly for today. Otherwise the
forecast is in great shape. Light winds and plenty of sun are
expected for the remainder of this afternoon.

3 AM update...

High pressure over the mid Atlantic region will give the area a
mild southwest flow of dry air. Current satellite imagery
already shows the low clouds lifting from southwest to northeast
under increasing flow. Skies will become mostly sunny early
this morning with high temperatures ranging from the middle to
upper 40s.

Tonight...Southwest flow regime will continue overnight as high
pressure moves off the east coast and a surface trough drops
through the central Great Lakes. Low temperatures will remain
above freezing across much of the area with areas primarily east
of I81 dropping into the lower 30s. Readings in the lake plain
will remain around 40.

Saturday...Model trend the past few days has been to slow the
frontal system on Saturday and this trend continues with the
latest suite of guidance. Model consensus indicates frontal
passage between 15Z-21Z along with a leading short wave.
Boundary lacks moisture and significant forcing with model
rainfall forecast only a few hundredths of an inch. Lowered
pops into the chance category. Precipitation type will be just
rain as high temperatures generally range in the middle to upper
40s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
For Saturday night, upper level trough axis swings across NY and Pa
as strong low-level cold air advection continues on a 290-300 degree
flow initially between 00z and 06z. The flow as per the NAM12 and
GFS veers a bit to between 310 and 320 degrees between 06z and 12z
Sunday and the settles back to around 290-300 degrees for Sunday
morning. 850 mb temperatures drop to about -10C or so by 12z Sunday
which leads to a 20C or so Lake Ontario temperature to 850 mb
temperature differential. This by itself is decent instability for
lake effect snow. The inversion initially is about 700 mb between
03z and 09z Sunday when it is too warm for accumulating snow in most
areas of north central NY. Then, as the colder air rushes in, the
inversion rapidly falls from the subsidence with the passage of the
upper level trough. The inversion is around 850 mb to 825 mb or so
from about 10z-16z Sunday as drier air also sneaks in at the lowest
levels. The top of the inversion is below the maximum ice crystal
growth layer. This all occurs as it is finally cold enough for snow
which will limit accumulations to below advisory levels downwind of
Lake Ontario Sunday. Subsidence and drying continues all day Sunday
and with boundary layer temperatures in the low to mid 30s
accumulations will be generally an inch or less in the lower terrain
and maybe 1-2 inches high elevations of north central NY downwind of
Lake Ontario. The rest of the forecast area will see mostly cloudy
skies and a few light snow showers or flurries with little to no
accumulations.

The low-level flow will back to more westerly late Sunday into
Sunday night as another short wave ripples southeast from the Great
Lakes region. Models all show some warm air advection ahead of this
wave Sunday evening that quickly goes to cold air advection. The
flow rapidly veers to northwest during the day Monday and then
settles back to southwest by Monday night. The 850 mb temperatures
drop to about -9 to -10C for a short window. Moisture is limited as
well. Hence we have slight chance to chance for snow showers and
flurries downwind of Lake Ontario in central NY and far northeast
Pa. By Monday afternoon, the flow turns enough to more westerly for
most of the region to be dry with some light showers of rain and
snow in our far northern counties. Otherwise, Monday will be mostly
cloudy and breezy with highs near 40 most areas.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
A ridge of high pressure builds across all of NY and PA Monday
evening and then shifts east off the coast. This will lead to a mild
southwest flow of air later Monday night and Tuesday. Tuesday looks
to be a dry and mild day as a result with highs approaching 50
degrees in some areas. Then for Tuesday night and Wednesday, a cold
front will drop south and weaken as 500 mb heights remain fairly
high over our area. Precipitation with this front will be scant and
in the form of rain showers and sprinkles. By Thursday, models are
in fair agreement that a surface low and south winds will track
through the Great Lakes region leading to some potential for light
showers and continued mild weather.

&&

.AVIATION /17Z FRIDAY THROUGH TUESDAY/...

The models continue to produce drier solutions for Saturday with
fewer restrictions. Our latest TAF package includes the
potential for LLWS overnight at KBGM, KELM, and KSYR. A few
showers will occur tomorrow, but due to the spotty coverage we
couldn`t justify a tempo group.

A VFR ceiling will fall to between 2000 and 3500 feet late
Saturday morning as widely scattered showers advance out of
Western NY.

Outlook...

Saturday night into Monday...Lake effect snow showers likely
causing at least some restrictions, mainly KSYR and KRME.

Most of Monday and Tuesday...VFR.

&&

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

&&

$$
SYNOPSIS...DJP
NEAR TERM...DJP/RRM
SHORT TERM...DJN
LONG TERM...DJN
AVIATION...DJP



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