Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 150834
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
334 AM EST Fri Dec 15 2017

.SYNOPSIS...
Outside of some weak lake effect snow bands, mainly north of the
thruway, early this morning be dry and cold, across central New
York and northeast Pennsylvania. Another fast moving, clipper
type storm, will bring some light snow showers and flurries from
Friday afternoon into the weekend. A round of lake effect snow
is likely, mostly north of the Thruway, late tonight into
Saturday.

&&

.NEAR TERM /THROUGH SATURDAY/...
250 am update...

Weak lake effect snow continues in central NY in the far north
from Lake Ontario and far west from Lake Erie. This is lifting
north out of the area by sunrise as the flow shifts to the
southwest. Another large and strong short wave is dropping
southeast into the area with an upper level trough today. A
stacked low moves slowly east across southeast Ontario today and
tonight. This could spread some light snow into the far
northern zones this afternoon and evening. Amounts will be light
but lake moisture will increase as the flow shifts to WNW late
tonight into Saturday. More details on CNY later.

A short wave in the southern Plains will move northeast to NJ
this evening. A weak surface low will form ahead of it and
spread light snow into NEPA and the southern Catskills this
afternoon. Amounts will be an inch or less of snow with the
highest in the Poconos. This is a quick shot of light snow and
moves out of the area by 7 PM.

As a weak front moves slowly across the area some snow with lake
enhancement starts in central NY late today. Behind the front
late tonight the lake effect will become stronger with a band
off the east end of Lake Ontario brushing northern Oneida
County. A lake Erie band will extend across the western southern
tier into the Finger Lakes and central southern tier. Late
tonight there will be weak caa and better low level wind
alignment. The Lake Ontario band will be fairly stationary late
tonight but mostly north of our CWA. Saturday morning it will
shift south into Oneida County but become disorganized by midday
as the flow shifts to 300 and the moisture drops from 10k ft to
5k ft. Put up a Winter Weather Advisory for northern Oneida
County for 3 to 6 inches of lake effect late tonight and
Saturday morning. The Lake Erie band will do the same. For
Saturday a chance of light snow showers and flurries in all but
the Scranton/WB area and Poconos.

Temperatures slowly warm from this mornings single digits. Highs
in the low and mid 20s today warm to mid 20s from the Mohawk
Valley to the Catskills to around 30 for Elmira to Scranton with
more sunshine. Lows in the teens tonight. Less clearing of the
clouds so should stay out of the single digits. Still below
average.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
230 pm update... The aforementioned clipper is progged to track
across southern Ontario and Quebec Friday night, and into
northern New England and the Canadian maritime provinces by
Saturday. As it does so, light and patchy warm advection driven
precipitation much of Friday night, will only amount to
scattered snow showers and flurries in CNY/NEPA.

However, as the flow veers into a more westerly orientation
towards daybreak Saturday, and a low-level surface trough also
approaches from the north, dynamic support will increase for a
W-E oriented Lake Ontario snow band, which could become fairly
intense for a brief time early Saturday. At this time, although model
consensus keeps the brunt of the snow with this band just north
of Oneida county (across Oswego and southern Lewis), it may be
a close call. For now, we`ll mention potential for a period of
lake-effect snow across northern Oneida in our hazardous weather
outlook.

During the day Saturday, as the previously mentioned surface
trough drops southward across CNY/NEPA, it will carry some snow
showers with it. However, early indications are that these snow
showers will lose their punch with southward extent, keeping any
accumulations on the light side. Temperatures on Saturday will
moderate a bit ahead of the trough, with afternoon highs
ranging from the mid 20s-lower 30s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
300 PM Update...Not alot of changes to the extended forecast
period. After some lingering snow showers Saturday night into
early Sunday AM, much of Sunday should be dry but mostly cloudy.
Did bump up PoPs into the 40-50 percent chance range areawide
for a period of light snow Sunday night, as the 12z ECMWF/CMC
are in agreement that a weakening wave will track up the Ohio
Valley and into our area, bringing a period of light warm air
advection precip...the 12z GFS weakens the wave faster, and it
never quite makes it to CNY/NE PA.

Monday and Tuesday will feature a moderation of temperatures
as the area remains under a mild southwest flow, with highs
reaching 35-45 both Monday and Tuesday. Weak waves will move
through, bringing chances for rain and higher elevation snow
showers. Models are still in good agreement that a rather strong
cold front will push through the area Tuesday night...dropping
850mb temperatures back down to around minus 10-12C. This
colder air-mass will combined with a moist northwest flow regime
to bring renewed chances for lake effect snow and snow showers.
There is the potential for some significant snow accumulations
in the favored lake effect areas of Central NY.

The model guidances then begins to struggle/diverge heading into
the end of next week as a deep low pressure system and
associated warm front move toward the region. Precipitation
type, amounts, and overall temperatures are very uncertain for
this period. These will strongly depend on the ultimate track
of the surface low and frontal position. The 12z GFS actually
pushes the low further south as it runs into a very cold air
mass in southern Canada...meanwhile the 12z ECMWF and CMC allow
the low to strength and move well to our west, through the Great
Lakes. This type of track would place our CWA in the warm sector
of the storm system, with much higher temperatures. With all of
the uncertainty in this period, decided to make only very minor
changes...mainly to slightly raise temperatures and PoPs.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
1230 am update...

Lake effect band giving local IFR conditions to RME will end
around 08z but MVFR will continue until around 11z. More lake
effect clouds around 3k ft are affecting ITH but that should end
by 08z. Rest of sites have VFR ceilings which will continue
through the rest of the morning.

A weak system will bring lower conditions and light snow to AVP
in the afternoon. 17z MVFR vsbys then at 20z IFR vsbys and MVFR
cigs until 00z when VFR.

Lake effect will also affect RME starting at 22z and SYR at 03z
with mostly MVFR conditions. Flow is WSW so should stay north of
rest of sites.

Winds early this morning will be light west or calm shifting to
south or southwest at 12z. During the day wins increase to 4 to
8 kts and remain there through the evening.

Outlook...

Friday overnight and Saturday...Periodic restrictions possible
in snow showers, especially KSYR and KRME.

Sunday...VFR.

Monday and Tuesday...Possible restrictions in rain or snow
showers.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...Winter Weather Advisory from 10 PM this evening to 1 PM EST
     Saturday for NYZ009.

&&

$$
SYNOPSIS...TAC
NEAR TERM...TAC
SHORT TERM...MLJ
LONG TERM...MJM/RRM
AVIATION...TAC



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