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Area forecast discussion 
National Weather Service Binghamton New York
401 am EST Monday Dec 22 2014

Synopsis...
it will remain cool today with some sunshine possible. A low
developing over the northern Midwest in combination with a low
moving up the East Coast will bring a brief period of light mixed
precipitation tonight...followed by rain Tuesday through
Wednesday. Gusty winds are expected Christmas day...with lingering
rain showers mixing with snow showers.

&&

Near term /through tonight/...
4 am update...
low clouds have finally eroded over western PA and west central
PA. While high clouds may filter the sunshine from time to time,
today will mark the best chance for sunshine that we have seen in
2 weeks. Sunshine chances will be highest west of I-81, decreasing
points east. Late in the day clouds thicken up again ahead of our
next weather system.

Tricky call tonight in terms of mixed precipitation potential.
Arrival of precipitation should be between 23z and 03z, northeast
PA/Sullivan County NY, 03z to 06z southern tier of NY, after 06z
elsewhere.

Through 03z, a mixed bag is expected over nepa and Sullivan
County. In the higher populated areas of the Wyoming Valley
(wilkes-Barre/scranton) a rain/snow mix is expected at the start
but with surface temperatures above freezing and warming aloft, a
transition to all rain will quickly happen with no ice or snow
amounts expected. A 1 to 3 hour period of freezing rain is
possible in the Poconos but even here temperatures rise above freezing
fairly quickly and it would take an early onset of precipitation to cause
any problems. After coordination with philly and NYC, decided
against a Freezing Rain Advisory here given such an expected short
duration. This matches up well with the lack of ice in wpc
guidance.

After 03z, most areas again may see a brief period of wet snow or
sleet at the onset mixed with rain before quickly changing to
rain. However where the colder air is known to hang tough, at
least a few hours of freezing rain are possible from north central
Wayne County PA northeast through Sullivan, Delaware and Otsego
counties. Confidence is highest here we will eventually need a
Freezing Rain Advisory given climatology matching current model
output. Based on collaboration with Albany will let the day-shift
take one more look at things with precipitation here arriving near
or after 03z tonight. Even here a change to all rain is expected
after 08z.




&&

Short term /Tuesday through Thursday night/...
340 am update...
wet period as a large low pressure system impacts the area...with
gusty winds as well by Christmas day as colder air moves in and
mixes lingering rain showers with snow showers.

Temperatures will rise into the low to middle 40s Tuesday...with any
lingering threat of light freezing rain in the Catskills quickly
ending around or shortly after dawn. SW to south-southwest flow will have
multiple waves embedded within it...but for Tuesday moisture will
be very limited. Rain chances higher towards Poconos-
Catskills...but all rain Tuesday will be quite light.

Deeper moisture arrives Tuesday night into Wednesday...with
precipitable water values around 4 Standard deviations above
normal by late Wednesday. Waves will be able to harness the
moisture in the form of batches of light to moderate rain.
Wednesday morning in particular currently looks like a broad few
to several tenths of an inch of rainfall. Speed of individual waves
at this point though appears unlikely to produce enough rainfall
for water problems.

Negatively tilting showery cold-occluded front to blast through
late Wednesday night-early Christmas morning. Prior to
that...stable low levels will prevent much wind from mixing to the
ground...but after frontal passage will be a different story as
cold air advection makes things unstable. GFS is most bullish on wind
in regards to strong pressure rises Thursday...and strong gradient
winds capable of mixing down...yet the European model (ecmwf) also exhibits classic
negative tilt to the upper wave which is also suggestive of gusty
winds. I have placed 30-40 miles per hour gusts in the forecast...highest in
Finger Lakes to central New York to western Catskills...but
advisory level gusts /frequent gusts above 40 miles per hour/ are not out of
the question. This potential will be assessed further with
upcoming model runs.

Model trend of decreasing magnitude of Post frontal cold air mass
continues. In the lingering shower activity /best coverage in
central New York with little if any in northeast PA/ behind the front
Thursday into Thursday night...925-850mb temperatures are not as
cold as in prior runs. Thus many areas especially lower elevations
mainly rain showers Christmas day...gradually mixing with snow
showers with little accumulation if any into Christmas night.

&&

Long term /Friday through Sunday/...
cold fnt swings through Friday night and returns the area to more typical
early winter weather. Continued cold air advection will gradually lower temperatures through the period
incrsg the chance of le snow showers. Sheared flow initially bhd
the fnt will limit the amount of le...while the deeper cold air aits
to just beyond the period late sun and early Monday.

Temperatures will average near normal through the period.

&&

Aviation /09z Monday through Friday/...
MVFR ceilings through the end of the taf period. With a ceiling around
1200 feet now at kbgm, some IFR is possible here toward daybreak.

Precipitation overspread the southern terminals early tonight as a
rain/snow mix. Some ice pellets possible New York terminals. For now I
left out any mention of freezing rain. Some of this is possible
mainly at kbgm, but too low confidence to include just yet.

Winds light southeast to east 5 to 10 kts.

Outlook...

Tuesday to Thursday...restrictions with developing light mixed
precipitation early Tuesday...then periods of rain Tuesday- Thursday.

Friday...VFR.

&&

Bgm watches/warnings/advisories...
PA...none.
New York...none.

&&

$$
Synopsis...heden/mdp
near term...dgm/djp
short term...mdp
long term...dgm
aviation...heden

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