Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 180855 AAC

Area Forecast Discussion...UPDATED
National Weather Service Binghamton NY
355 AM EST Sun Feb 18 2018

Lake effect snow showers will still be possible through the
morning along and north of the New York Thruway, otherwise
things turn out quiet today for Northeast Pennsylvania and
Central New York with increasing sunshine. Temperatures trend
milder Monday, followed by near record warmth Tuesday through
Wednesday with multiple chances for rain.


345 AM Update...
Light snow will exit quickly prior to dawn, but lake effect
snow showers will still be possible through midday along and
north of the New York Thruway. Other than that, passing high
pressure will ensure a fairly quiet day across NEPA-CNY with
increasing sunshine and temperatures recovering to a few degrees
above climatological averages.

Initial snow from coastal system already exited the area, but
the second piece in still just finishing up. This is from
forced ascent via left exit region of a jetmax aloft associated
with negatively tilted upper wave. 4AM expiration of Winter
Weather Advisory across parts of Northeast PA to Southern
Catskills will work out rather well, since light snow is just
wrapping up. Up north, 850mb temperatures will drop to 10-12
below zero Celsius with about 280 degree low level flow. This
should be enough to generate a brief lake effect response along
and especially north of the MY Thruway through the morning and
perhaps slightly into early afternoon while shifting further
north. The Canadian GEM model has been depicting this for
several runs now, and usually does a superior job with lake
effect compared to other models. About an additional half inch
to one inch of accumulation will be possible during daytime for
Oneida County, especially the northwest corner.

Clear evening will be followed by a few high clouds just
starting to get into the area late tonight. We will have a quick
radiational cooling this evening, then temperatures will level
off or even slightly rise due to strengthening warm air
advection just off the surface. Lows will be mostly in the 20
to 30 degree range, mildest in the Finger Lakes region.


For Monday, upper level jet streak rounds the base of a digging
western U.S trough, this will support the development of a low-level
cyclone that tracks up through the mid-west. This will lead to
strong warm advection and height rises across the eastern United
States. Associated with this, will be increasing upper confluence
over southeastern Canada with an anticylonically curved upper level
jet to our north. Strong upper level divergence will result over our
area as per all models which will lead to the development of a low-
level jet stream from eastern Texas to the Ohio Valley by Monday
18z. This low-level jet reaches into NY and PA between 18z Monday
and 00z Tuesday with an initial shot of warm air advection /
isentropic lift. The Gulf of Mexico will be wide open so there
should be sufficient moisture for rain showers to spread across
central NY and northeast PA Monday afternoon. All models indicate
this and thus have likely to categorical POPs for Monday afternoon
into the evening as this low-level jet streak and surge of moisture
and warm air advection / isentropic lift moves across the area.

By Monday evening into the overnight, with the amplification of the
upper level ridge in the east, the isentropes will be falling so
with continued positive isentropic pressure advection the lift will
dissipate for most of central NY and northeast Pa. The exception
will be our far northern counties where southwesterly flow and
associated upsloping will keep precipitation going longer. So we
have categorical to likely POPs mainly for Oneida County and far
northern Ononodaga County Monday night into Tuesday morning with
POPs for showers ramping down significantly farther south into south
central NY and northeast PA.

By Tuesday afternoon, most of the rain showers with the best
isentropic lift/ warm advection will be mainly north of our forecast
area. With a strong southwest flow we will see breaks in the clouds.
850 mb temperatures will become insanely mild for this time of year
reaching +10 to +12C on the Euro / GFS and NAM and +9C to +11c on
the CMC. Model guidance is showing widespread 60s the entire
forecast area with some locations especially along the Lake Ontario
plain potentially pushing 70F! Records for Tuesday at BGM are 58F on
the 20th in 2016 and 61 on the 21st in 1953. For SYR, 61 on the 20th
in 1951, and 68 in 1906. For AVP, 63 in 1951, and 67 in 1906. These
records could be challenged especially Tuesday.

Then for Tuesday night, southerly winds continue and equally
impressive will be night time minimums only down to the 50s with
dewpoints also in the low 50s. We are not expecting any significant
precipitation Tuesday night.

Then on Wednesday, a cold front will move into central NY during the
afternoon. This front reaches northeast Pa and southeast NY by the
evening. It will be another very mild day again with highs mainly in
the 60s. Once the front goes through most if not all of
precipitation will be behind the front in an anafrontal set-up as
the upper level jet streak stretches from the Great Lakes to eastern
Canada. Pa and NY will be in the jet entrance region which will
force a thermally direct circulation with lifting behind the front.
So we bring POPs in mainly after fropa Wednesday with the highest in
the Finger Lakes to north central NY in the afternoon. It looks like
the precipitation before 00z Thursday will be all rain as the air
will not be cold enough for snow at this time.


For Wednesday Night, front clears the region and precipitation will
begin to wind down over much of central NY as cold air advection
kicks in with significant drying. Best chance for precipitation will
be across northeast PA, However due to some timing differences and
model uncertainities we will maintain chance POPs all zones for rain
showers which mixes with snow showers in north central NY late
Wednesday night.

For Thursday, models begin to diverge with the Euro and CMC
suggesting front stalls across the Mid-Atlantic with another shot of
warm advection and hence a chance of rain/snow showers in the
morning with mainly a chance for rain showers in the afternoon. The
GFS is dry. So we maintain chance POPs in northeast Pa to south
central NY and slight chance in north central NY.

For Thursday night into Friday, the Euro and to a lesser extent the
CMC suggest another shot of warm advection and precipitation. Ptype
will be tricky if this occurs and there are hints that there could
be some freezing rain but the GFS is bone dry so our POPs are slight
chance Thursday night and chance on Friday so we added a slight
chance of freezing rain late Thursday night and Friday morning as
per WFOs PHI/OKX ISC grids.

For Saturday, we continue chance POPs for more rain and snow showers
as southwest moist flow continues with uncertainty related to the
thermal profiles.


A system will exit the region before dawn, but not before still
causing lingering light snow with MVFR-IFR visibility and/or
fuel alternate ceilings for a few to several hours after 06Z.
Initially variable to light southwest wind will also veer west-
northwest at 8-12 knots behind the system through midday, before
slackening and becoming variable late in the day. KAVP should
be VFR by 12Z, but the NY terminals will hold on to high end
MVFR ceiling a bit longer into the morning and then VFR for the
remainder of the TAF period.


Sunday night through Monday morning...VFR.

Monday afternoon through Wednesday...Occasional rain showers
and restrictions as disturbances move through the region.

Wednesday night...Chance of restrictions and mixed rain/snow

Thursday...Primarily VFR.




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