621 
FXUS61 KBGM 110000
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
700 PM EST Sun Dec 10 2017

.SYNOPSIS...
Scattered snow showers tonight, mainly in central NY, with a period 
of locally heavy snow in northern Oneida county. Quiet on Monday 
before a clipper system brings potentially significant accumulating 
snow Monday night through Tuesday. There will also be a period
OF lake effect snow Tuesday night through Wednesday night that 
could bring additional significant accumulations to Central NY.

&&

.NEAR TERM /THROUGH MONDAY/...
645 pm update

Adjusted the forecast based on the latest radar/hi-res model
trends for the lake effect snow tonight. Tried to tighten the
PoP gradient, indicating the highest chances for snow across
northern Onondaga and Oneida counties for the first half of
tonight. Then, late tonight or early Monday morning a subtle, 
low level arctic frontal boundary will cross Lake Ontario and 
move into the northern portion of our CWA. It is likely this 
feature will pick up the ongoing LES band over Lake Ontario and 
push it inland (south), toward Syracuse/Rome...at least briefly
early Monday morning. Winds will shift to the northwest behind 
this front over the northern third of the forecast area...the 
front will wash out and dissipate before reaching the NY/PA 
border. The snow shower activity could briefly make it south to
around Penn Yan, Ithaca and Cortland before tapering to 
flurries mid-morning Monday. Further south, it should remain dry
but mostly cloudy through the near term period. Snow 
accumulations tonight into Monday morning will range from 2-4 
inches in far northern Oneida County (where the winter weather 
advy for lake effect snow continues)...to 1-2 inches for 
Syracuse and Rome and less than 1 inch elsewhere. Overnight lows
dip into the lower to mid-20s areawide. Highs on Monday will be
in the mid to upper 20s north...with lower to mid-30s across 
our PA zones.


245 pm update... Main forecast concerns in the 
near term remain focused on the scattered snow showers across 
central NY and ne PA this afternoon and evening, and the return 
of a lake effect snow band off Lake Ontario into the Thruway in 
central NY tonight...tapering off Monday morning.

A Winter Weather Advisory for Lake Effect Snow remains in effect for 
northern Oneida county...through 7 am Monday morning.  

Conditions continue to be favorable for snow showers this afternoon 
as strong cyclonic flow in a very cold air mass persists. 
Intense LES bands downwind of Erie and Ontario continue as of 3 
pm this afternoon...and large scale, scattered snow showers 
linger over a good portion of central NY and far ne PA. Boundary
layer has become deep enough to entrain some dry air 
aloft...which is acting to mix some of the cloud cover out. As 
this occurs though, the BL is able to heat up and slowly 
becomes more unstable which produces more clouds and snow 
showers as a result. 

The flow is expected to back to the sw this evening and as that 
occurs, the LE bands will shift further to the north. The diurnal 
heating will weaken this evening as well with the loss of sun, and 
allow the scattered snow showers to taper off. So...most of the late 
evening and early overnight hours may be quiet and cool with temperatures
tonight falling into the low to mid 20s. 

Later tonight and Monday morning the flow will veer back to the w/nw 
and shift the Lake Ontario band back into central NY. As this
occurs though the inversion heights will fall below the 
DGZ...which will act to diminish the snow production 
significantly. The LES band will likely become diffuse and weak 
Monday morning before falling apart altogether. However, there 
will likely be a period tonight across portions of Oneida county
where the snowfall rates ramp up for a brief period of time and
drop an additional 1 to 3 inches on top of the 1 to 3 they 
already received earlier today. Other areas to the south will 
likely see an inch or less. 

The rest of Monday looks quiet and on the cool side with highs only 
into the upper 20s across the north, and the lower to mid 30s in ne 
PA.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
330 PM Update
Model guidance is showing increasing confidence in 
a low pressure system moving across NY Monday night into the day
on Tuesday. The latest guidance tracks the center of the 
surface low over Lake Erie, then to a position near Rochester by
Tuesday morning. Ample warm air advection precipitation(snow) is 
forecast to develop out ahead of this low pressure system, 
beginning late Monday evening for much of our forecast area. 
With the track of the low to our north, this will keep surface 
winds out of the south-southeast and breezy at times (10-20 
mph). This type of flow will keep some areas downwind of the 
higher Catskills and especially Poconos shadowed from the higher
precip/snow rates. By midday Tuesday the surface low begins to 
jump, and reform along the New England coast. This could allow 
for some enhanced wrap around snowfall to impact the far eastern
portion of our CWA during this time...but the snow will really 
pick up just off to our east...over far eastern NY and New 
England. Right now, storm total snowfall from this first system 
is forecast to range from about 1-3 inches for our NE PA 
zones...with 2-4 inches for our NY zones...except 4-8 inches in
Oneida County where the southerly flow upslopes in the Southern
Tug Hill plateau. Will hold off on any winter headlines at this
time, and let the evening/overnight shift take another look at 
the latest model guidance trends.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
330 PM Update...Closed mid/upper low moves overhead Tuesday 
night into Wednesday as strong cold air advection continues. 
This will bring lake effect/enhanced snows across much of the 
area with a northwest flow and deep moisture. Best chance for
potentially significant accumulations will be over over the 
higher ground of central NY, particularly the Finger Lakes but 
expect measurable snow down into NEPA as well. It is likely that
headlines will eventually be needed for parts of the area for
this event. Preliminary forecasts point to the potential for 3-6
inches of snow across most of our NY zones...with locally higher
amounts were the lake bands set up. Amounts during this time
will be lighter in NE PA, and could range from 1 to 3 inches, 
mainly in the higher terrain. Little change through Wednesday as
850 mb temps bottom out near -18C over the area and the NW flow
lake snows continues. 

Flow becomes more westerly and relaxes on Thursday so snow
showers will taper off. However, unsettled weather will continue
through Friday with trofiness aloft, a clipper moving into the
Great Lakes, and systems running up the coast to our east.
Confidence in forecast is low to moderate until Friday when 
global models diverge quite a bit on positioning and timing of 
disturbances diving around the base of the trof and interacting 
with the front along the coastal plain. Chance PoPs during this 
time and some moderation of temperatures with flatter flow and 
slight warm advection. Temperatures look to potentially warm
above freezing into the mid-30s to lower 40s by next Sunday, as
a storm system passes by well to our north. This system will
bring chances for rain and snow showers, and perhaps some mixed
precipitation.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Expect mainly VFR or MVFR conditions to persist through the
overnight hours with just a few flurries around. The exception
to this will be at KSYR and KRME, where periods of snow showers
will continue until Monday morning and will create MVFR to
occasional IFR CIGS/VIS. Snow will taper off between 13-16Z 
Monday morning at KRME and KSYR, with conditions returning to
VFR here after that time.

Winds will veer to the nw later tonight as a frontal boundary
drops down from the north. This wind shift will mainly be felt
at KSYR, KRME and KITH...but could also briefly make it south to
KBGM and KELM. Wind speeds will mainly be from 7 to 15 kts 
tonight into Monday morning. Monday afternoon winds become light
and variable, before shifting to the south-southeast Monday 
evening and increasing.

Outlook...

Monday afternoon...Generally VFR.

Monday night through Tuesday...A period of snow likely with 
restrictions as a clipper system moves through the region.

Tuesday night through Friday...Snow showers and associated 
restrictions, mainly NY terminals due to lake effect.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...Winter Weather Advisory until 7 AM EST Monday for NYZ009.

&&

$$
SYNOPSIS...BJT/MJM
NEAR TERM...BJT/MJM
SHORT TERM...MJM
LONG TERM...MJM
AVIATION...BJT/MJM