Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 031738

Area Forecast Discussion
National Weather Service Binghamton NY
1238 PM EST Sat Dec 3 2016

Chilly air passing over the Great Lakes will allow occasional
rain and snow showers to continue today through tonight in the
Twin Tiers to especially Central New York. After a quiet Sunday,
a passing disturbance will bring a quick light coating of snow
Sunday night, followed by spotty mixed rain and snow showers
Monday. The weather pattern will remain unsettled this week.


300 AM...NW flow in place with cold air advection as low pressure
sits well to the east with high pressure to the west. 850 mb temps
dropping to -6 to -9 C range and with lake temps in the 40s this
is enough differential to result in lake effect rain/snow showers
across the area. Expect these to continue early this morning and
generally trend toward being mainly snow showers. The boundary
layer flow near 310 will favor multi bands tending to focus in on
the higher terrain areas south of Syracuse through southern
Onondaga, Cortland, Chenango, and Madison Counties. These higher
terrain areas will be mainly snow with a couple inches of
accumulation possible by morning. Elsewhere, accumulation should
be limited to a coating up to a half inch or so.

Heading into the day today, not a lot of change. Conditions will
be mostly cloudy, breezy, and cool with lake effect continuing,
mainly over central NY. Early in the day, this should fall as
mainly snow showers. However as high temps rise into the mid to
upper 30s, lower elevation areas will tend to see snow showers
becoming mixed with rain at times. Another inch or so of snow will
be possible across the higher terrain areas south of Syracuse
mentioned above with little to no snow accumulation across the
lower elevations since temps will be a little too warm.

For tonight, high pressure will begin to finally advance toward
the area with the trend being for lake effect to weaken and
diminish with time but also change back to all snow showers.
Overnight lows will be mainly in the upper 20s to low 30s.


330 AM Update...
Main feature of interest will be a negatively tilted trough which
will bring a quick coating of light snow Sunday night-early Monday
morning. While not much, the timing of it may potentially cause
slick conditions for the Monday morning commute.

Before that, other than lingering morning flurries in parts of
Central New York, Sunday itself will be a fairly quiet day with
the passage of high pressure at the surface and ridging aloft.
The last of the stratocumulus may take awhile to break but all
areas should see at least partial sunshine, before high clouds
begin to stream in from the west ahead of the next system.

With model agreement increasing and the trend being consistent,
confidence continues to also increase that the negatively tilted
wave and associated area of weak warm air advection aloft Sunday
night will provide the lift necessary for a broad area of light
snow to overspread the region. Though the dendritic growth layer
will be above 10 kft agl, this feature will be accompanied by a
period of deeper moisture and lift within that layer where
temperatures are in the teens below zero Celsius. Thus fluffy
light snow appears likely to develop, especially in the pre-dawn
hours of Monday morning. At this point a quick coating of an inch
or two is expected for most of the area. Lower elevations in the
Susquehanna-Wyoming-Delaware valleys of Northeast PA-Sullivan
County NY may struggle initially to collect and thus may fall
short of an inch, but at least a little accumulation is still
likely. Overall we are not talking about a lot of snow, but the
timing is not favorable to those commuting early Monday morning.
Roads for a time could be a bit slick.

Deeper moisture will shift northeast Monday, though a weak
embedded shortwave could still zip through. Light snow, mainly
east of I-81 after dawn, will diminish to spottier mixed rain and
snow showers during the day with perhaps just a little help from
Lake Ontario in Central New York. Any additional amounts should be
very light considering how shallow moisture becomes. Also, 850mb
temperatures will be about 4-6 degrees below zero Celsius, which
will produce a very muted lake response if any.

As for temperatures, highs will be mainly mid to upper 30s Sunday
and then up 2-4 degrees for Monday. Lows both Sunday-Monday
nights will be upper 20s-lower 30s.


430 AM Update...
Forecast adjusted for latest model trends but not much change
overall. GFS-ECMWF-GEM continue to differ on details of the busy
pattern this week, including thermal profiles and precipitation
type. However, they are in general agreement on where things end
up. That is, come around Friday-Saturday, we will be on the south
side of a large cold upper low with 1000-500mb thicknesses around
510 decameters. The arctic air mass could be the coldest so far
this season, and the lakes may become active.

Well before then, there is also significant disagreement on how
quickly precipitation develops with that next wave Tuesday. The
NAM is by far the fastest; the remainder of models center more on
Late Tuesday-Early Wednesday. Precipitation type will be tricky,
including at least a little possibility for brief ice in our
northeast zones if a period of cold air damming sets up against
the Catskills-Poconos. It is not in the forecast yet due to level
of uncertainty for both precipitation timing and thermal profiles,
but this potential will need to be further assessed in coming
model runs.

Previous discussion...
Weak high pressure builds in at the surface behind the departing
wave to the northeast as ridging aloft amplifies over the wrn
Great Lakes ahead of the next s/w expected to move in from the sw
again...but slowly phase with a much colder and deeper trough
digging into the Upper Midwest/Great Lakes early Wed. The broad
large scale lift and strong dynamics aloft will work with the much
colder temperatures in the mid levels and steep low level lapse
rates to produce showers across the region. There is still some
uncertainty with regard to the thermal profiles...which will prove
important in deciding p-type. Will go with mainly a rain/snow mix
during this time...but lean more toward the cooler, snow solution.
Snow and/or rain amounts should be relatively light through
Thursday as the air mass will be lacking any significant deep
layer moisture. There may be a lake component involved too...which
will again depend on the thermal profiles and if the real arctic
type air mass moves in quicker than expected at this point.


Ceiling heights will fluctuate between fuel alternate required and
VFR...but predominately hover in the MVFR category the rest of
today through Sunday morning. The lake effect clouds will remain
in place and continue to pulse up and down numerous lake snow
bands that will bring IFR or lower conditions to KSYR, KITH and
KBGM. KRME, KITH and KBGM may see another round of fuel alter cigs
early Sun morning before the drier air begins to push in and the
lake clouds lift and mix out at all terminals closer to 18Z

Winds will remain WNW around 10 knots today with gusts of 15 to 10
knots this afternoon. Winds will subside but remain nwly tonight.


Sunday PM...Mainly VFR.

Sunday Night-Monday...Restrictions possible as weak system brings
light snow Sunday night, then spotty rain-snow Monday.

Monday Night-Early Tuesday...Mainly VFR.

Tuesday Afternoon-Wednesday...Restrictions in wintry mix or rain.




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