Area Forecast Discussion
Issued by NWS Binghamton, NY

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493
FXUS61 KBGM 032346
AFDBGM

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

.SYNOPSIS...
Chilly air passing over the Great Lakes will allow occasional
snow showers to continue through tonight in central New York and
the endless mountains of northeast Pennsylvania. Some patchy light
freezing drizzle is also possible tonight in these same areas.
After a quiet and dry Sunday, a quick light coating of snow is
likely Sunday night, which may make the Monday morning rush hour
slippery. Unsettled weather continues most of this week with
chances for both rain and snow.

&&

.NEAR TERM /THROUGH SUNDAY/...
6 PM update...
only major change was to up the cloud amounts to cloudy. Moisture
will remain most of tonight as the northwest flow weakens. Some
clearing will start from the far southeast late tonight and work
north Sunday but mid and high clouds will quickly move in from the
west ahead of the next system.

Rest of grids in good shape. Precipitation amounts will be very
light tonight. Most of radar returns under 20 dbz.

300 PM Update...
Main concerns in the near term remain focused around the lake
effect rain and snow showers this afternoon...transitioning to all
snow this evening and tonight with only light slushy accumulations
expected mainly in the higher elevations.

Large upper low over far eastern Canada and large amplitude ridge
axis in central Canada this afternoon drawing down a cold air mass
across most of the the Great Lakes into the Northeast. Weak upper
waves embedded in the cold flow combining with 850mb temps -7 to -9
deg C today and tonight will allow the light lake effect rain/snow
bands to continue. Steep low level lapse rates and a shallow layer
of moisture in the boundary layer should be enough to allow the
showers to persist...although there will be a gradual decrease in
coverage and intensity of the showers through this evening as
heights rise aloft and a slightly drier air mass builds in from the
west.

Area observations indicating a mix of rain and snow across the
region with the remaining lake effect bands...and as the evening
progresses and near-sfc temps cool should see a change over to all
snow. There may also be patchy freezing drizzle as the moist layer
becomes shallow and any liquid in the column becomes super-
cooled...falling into a sub-freezing layer all the way to the
ground. So, have added mention of patchy freezing drizzle to the
forecast. Roads and overpasses may become slippery tonight and
Sunday morning.

Conditions should dry out through the morning hours Sunday, with low
and mid level clouds mixing out, leaving a likely shield of high
clouds in advance of the next system which will begin to move in
later Sunday. There will be a fairly strong push of warmer air in
the mid levels Sunday afternoon...but the cold air near the surface
will likely get trapped, and keep afternoon highs only in the low
30s in the higher elevations and in the mid and upper 30s in the
lower elevations.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
300 PM Update...

An area of snow is still likely Sunday night and while not a big
snowstorm by any means, the timing will make the morning commute Monday
morning slick. Some general timing differences with the arrival of
the snow Sunday evening, with the GFS being the fastest and the
EURO slower. Despite these onset issues, a model blend gives us
widespread QPF amounts between a tenth (far south) to as much as
two tenths of an inch across Central NY by mid Monday morning.
Snow ratios start off around 15:1 Sunday evening, but do drop
toward or even under 10:1 by Monday morning as warmer air comes
into the area. Putting this all together expect a general 1 to 2
inches by mid Monday morning. The best chances for near or just
above 2 inches will be in the hills between Binghamton and
Syracuse, along with up I-88 toward the higher terrain between
Binghamton and Albany. The least amount of snow looks to be in the
Wilkes-Barre/Scranton area with up to an inch in the higher
elevations just outside the valley, but generally under an inch
in the metro areas themselves. Again it will be the timing that
will cause issues as a good amount of the snow will fall prior to
and through the rush Monday morning. Beyond Monday morning enough
warm air may move in for a bit of rain before the precipitation
comes to an end. With highs well above freezing Monday, we may
loose much of our morning snow by late in the day.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
300 PM Update...

After a mainly dry Tuesday, our next disturbance now over the
Gulf of California, will bring another round of precipitation.
Again overall agreement amongst the models is good in that it is
highly likely we will see a period of precipitation during the
Tuesday evening into early Wednesday period. Timing differences
exist on the front end (GFS has precip prior to dark, while the
other models are mainly dry through sunset Tuesday) and thermal
profiles. A blend of model QPF values is a bit higher than our
event going into Sunday night, or generally between .15" and .30".
Unlike Sunday night we are a bit warmer aloft and at the surface,
so the potential to mix with and change to rain may be faster,
especially in the lower elevations and the farther south and west
you live. With the uncertainty in the precipitation type I
continued to mention a rain or snow mix through mid Wednesday
morning. I did increase chances for precipitation to 80% as our
confidence is high we will see precipitation.


After precipitation diminishes later Wednesday, our next focus in
our active pattern will be the potential for more rain and snow
Thursday, along with much colder air arriving Thursday night into
Friday. By Friday we should be into the heart of the cold air with
850 temps into the teens below zero. This should be more than
enough with a west-northwest wind for lake snows downwind of Lake
Ontario. In general used a model blend which kept chances for
precip in the 30 to 50% range, but I did increase chances by
Thursday night into Friday downwind of the lakes given the
impending colder surge of air.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
630 pm update...

Ceiling heights will fluctuate between MVFR and VFR this evening.
BGM/ITH could have ceilings as low as fuel alternate MVFR.
Ceilings across central NY will fall to high end MVFR this evening
then remain there until between 13 and 16Z Sunday. Moisture
advection will weaken tonight and Sunday as winds become light out
of the northwest off of the Finger Lakes and Lake Ontario. Sunday
afternoon high clouds will lower to 10k ft. AVP will remain VFR
tonight and Sunday.

Winds will remain NW at 5 to 10 knots tonight into Sunday morning.
sunday afternoon winds will become light and variable.

OUTLOOK...

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

Monday Night-Early Tuesday...Mainly VFR.

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

&&

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

&&

$$
SYNOPSIS...Heden/TAC
NEAR TERM...BJT/TAC
SHORT TERM...Heden
LONG TERM...Heden
AVIATION...TAC



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