Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 210914

Area Forecast Discussion
National Weather Service Binghamton NY
414 AM EST Tue Nov 21 2017

It will be sunny today, with mild temperatures and a southwest
wind. A cold front will cross the area late tonight into early
Wednesday, accompanied by some rain showers briefly changing to
snow showers, especially at higher elevations. Wednesday will be
breezy and colder, with lingering lake effect snow showers and
only very minor accumulations in parts of Central New York.


245 AM Update...
After a sunny mild day, a cold front will move through the
region late tonight followed by lingering lake effect snow
showers and colder air on Wednesday. Precipitation amounts
however will be quite light.

The sky has cleared out, with strong southwest flow and warm air
advection just above the surface inversion. Temperatures have
been more-or-less steady or slowly rising in the 20s and 30s
overnight, with coldest readings in the most radiational cooling
prone valleys east of I-81 in Central NY, such as Sidney and
Norwich, as well as Monticello and Cortland.

Full sunshine this morning to early afternoon, will only
gradually give way to increasing thin high clouds by mid-to-late
afternoon. This along with warm air advection well ahead of
approaching cold front will help temperatures reach upper 40s to
mid 50s today; or 6 to 8 degrees above climatology for highs. 50-60
knots of flow will exist just above the 850mb level, but with
warm air aloft thankfully keeping the thermal profile quite
stable, we are only figuring on surface gusts in the 20-30 mph
range. Highest elevations could hit 35 mph.

Models are in pretty good agreement on moisture-limited front
sweeping through the area late tonight into early Wednesday
morning. Upper trough will be digging into the Central Great
Lakes, which will enhance right entrance region of a jet aloft.
this will cause forced ascent along and just behind the front
for a time, though this support will become more muddled by dawn
Wednesday. So while it is highly likely that rain will move
across Finger Lakes-Twin Tiers-Mohawk Valley, moisture and jet
support will both become more lacking as the front progresses
east. However, since this will be a bit of an ana-front in terms
of precipitation occurring behind the boundary, cold air
advection will start to convert rain over to a brief period of
wet snow before ending, especially at higher elevations.

All that being said, the limited moisture and weakening support
will mean precipitation amounts only coming to one-two tenths of
an inch liquid equivalent for Finger Lakes to Mohawk Valley;
perhaps not even a tenth an inch for Twin Tiers; and just a few
hundredths of an inch if any further south. Snow accumulations
if any will be nominal and mainly at higher elevations.

As colder air pours in Wednesday, there will be a brief window
for potential lingering lake effect snow showers Wednesday as
850 mb temperatures fall to around 10 to 12 below zero Celsius
with westerly flow. However, much drier air and a quickly
lowering inversion will cut off lake effect as moist layer drops
below dendritic snow growth zone by mid-afternoon. Thus we are
only expecting snow accumulations of around an inch or so in
higher elevations of Northern Oneida County. Wind gusts will
peak in 25-35 mph range, which along with steady or falling
temperatures will make for a brisk day.


Upper level trough is well east of the region by Wednesday night
as high pressure builds east from the Ohio Valley. Both
Wednesday night and Thanksgiving will be dry with highs on
the holiday ranging from the middle 30s to around 40.

Thursday night, a weak surface trough moving through eastern
Canada could bring a snow shower to the far northern forecast
area but nothing of any significance. Lows will range in the
middle to upper 20s.


Friday will be mild and partly sunny with a moderating
southwest flow as high pressure is over the mid Atlantic and the
next surface trough drops through the western Great Lakes. High
on Friday will generally range in the lower to middle 40s.

Friday night through Sunday, an upper level trough will swing
through the Great Lakes region as a surface cold front moves
through on Saturday. Will continue with chance pops across the
area during the period with likely pops downwind of Lake
Ontario. Significant cold air advection begins Saturday night
with the airmass cold enough for lake effect snow late Saturday
night into Sunday night. The precipitation will fall primarily
as rain showers through the day on Saturday then change to snow
showers Saturday night. Saturday night steering flow for lake
snows are mainly westerly so will advertise likely pops in the
far north then Sunday into Sunday night the flow veers more
northwest impacting the Finger Lakes region and parts of the
southern tier. The snow showers will diminish on Monday as upper
level heights rise and surface high pressure builds in from the
Ohio valley. Tuesday should remain dry with high pressure in
the vicinity. Temperatures will run 5 to 10 degrees below
seasonal normals Sunday through Tuesday behind the cold front.


VFR conditions for 06Z Tuesday through 06Z Wednesday. Mostly
clear sky exists, yet just off the surface a 35-40 knot
southwesterly low level jet is surging in milder air into the
region. This will maintain low level wind shear for all
terminals to at least mid morning, until surface winds increase
out of the south-southwest to 9-12 knots with gusts of 17-22
knots. Winds will slacken again in the evening, which could
present LLWS for some terminals, though that has not yet been
added into the TAFs until confidence increases since it will be
borderline. High thin clouds will start to move in late
afternoon, thickening and lowering 00Z-06Z as cold front
approaches yet still in VFR category. Precipitation and
restrictions will wait until just after 06Z Wednesday.


Late Tuesday night through midday Wednesday...Some restrictions
in rain showers changing to scattered snow showers.

Late Wednesday through Friday...Mainly VFR.

Friday night through Saturday...Possible restrictions in rain
or snow showers, especially Saturday.




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