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077
FXUS61 KBGM 051745
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1245 PM EST Thu Dec 5 2019

.SYNOPSIS...
A trough of low pressure exits with scattered snow showers and
flurries early this morning, though lake effect snow continues
today through this evening southeast of Lake Ontario with a few
inches accumulation in the most persistent bands. A clipper
system will pass through Friday with additional snow, especially
in Central New York. Mainly dry weather expected this weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
1230 PM Update...

No real changes with this latest update. For the rest of the
day, the snow chances should continue to shift largely to areas
to the east and east- southeast of Ontario, generally along the
I-90 corridor. In fact, hi - res model reflectivity continues to
agree on pretty much a single band wobbling back and forth
around I-90, and have increased how eastward it is able to
permeate eastward. the spatial extent of snow showers has been
adjusted accordingly.

Previous discussion continues below.

645 AM Update...
Main forecast issues are details of lake effect snow southeast
of Lake Ontario today through this evening, and then a clipper
system which will bring a light coating of snow to most of the
area Friday.

A trough is finishing its trek through the area, with scattered
snow showers and flurries. However, with 850mb temperatures now
dropping, lake effect snow is organizing. As flow veers to
west-northwest behind the trough, this will press lake effect
snow showers as far south as Ithaca-Whitney Point-Delhi today.
The dendritic growth zone will not be in the middle of the
saturated layer; more like at the top, which will limit
accumulations to light dustings to maybe a fluffy inch or so.
However, high resolution models are suggesting that for a time
there will be a Lake Huron to Lake Ontario connection with
Georgian Bay late morning into afternoon which will increase the
depth in a more enhanced band or couple bands for at least
Onondaga-Madison-far southern Oneida counties; perhaps into
Otsego-far northern Chenango counties. The band or bands will be
narrow with some moving/shifting, but locally 2-4 inches looks
pretty doable for parts of that area. This includes
Baldwinsville to Syracuse (especially north side) to
Chittenango-Canastota and over to Clinton-Waterville and Utica
(especially south side). An advisory will not be issued unless
confidence for greater than 4 inch amounts increases. However,
anyone in those areas this afternoon can at least anticipate
untreated roads to become slick in spots, along with rapid
changes in visibility as the lake effect bands shift.

Temperatures are currently lower to mid 30s, and with cold air
advection through today, there will be very little movement to
the readings. Higher terrain may even dip a few degrees.
Meanwhile, low level lapse rates will steepen with mixing up to
about 750mb. This will cause west-northwest winds, already
increasing from pressure gradient, to become rather brisk with
gusts frequently in the 20-30 mph range. Wind chills will be
mainly mid teens to lower 20s.

The primary lake effect is expected to shift back to the north
to roughly along the NY Thruway late this afternoon into
evening as the winds back westerly; even west-southwest tonight.
Most of the area gets a break in the snow showers tonight as
the 850mb ridge builds across the region. However, our next
system will already be en route. Lows tonight will be upper
teens to mid 20s; actually creeping up slightly towards dawn as
the next system approaches.

Models have consolidated more on the nature of a clipper system
that will quickly move through the region Friday. NAM tracks
the low roughly WNW to ENE along the NY-PA border; GFS and ECMWF
are just slightly north of that by a row or so of counties.
This detail will be rather important for the Twin Tiers zones
since it could make the difference between a slushy less-than-
half inch, or more like 2 inches due to more moisture and cooler
air north of the track. To the south, not only will there be
less precipitation, but also temperatures will get warm enough
for a mixing with or changing over to rain and thus little if
any snow accumulation especially at lower elevations. Further
north; that is from Penn Yan-Ithaca-Whitney Point- Sidney-Delhi
northward, confidence is high for a widespread 1-2 inches of
snowfall from the clipper Friday with localized amounts up to 3
inches especially north of the NY Thruway with lake enhancement
getting involved late in the day as the system pulls away. Some
rain could still briefly mix in for lowest elevations of the
Finger Lakes, which would cut back on snow amounts there.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As the above mentioned clipper system departs the area Friday
evening, lake effect snow showers are expected in Central New
York, especially across the Syracuse area into the Finger Lakes
region, before tapering off Saturday morning as a strong and
cold high pressure system builds into the area. Additional
snowfall will likely range from 1-2 inches in the most
persistent lake effect snow showers to less than an inch
elsewhere in Central New York. Lows Friday night will mainly be
in the teens to lower 20s, with single digits expected in
northern Oneida County.

After any lingering lake effect snow showers end Saturday
morning, the remainder of the day will likely be dry with partly
to mostly sunny skies. Clouds may hang on a bit in Central New
York into the early afternoon, before breaking up as drier air
takes over. Highs will likely be in the lower 20s to lower 30s.
Then partly cloudy and cold conditions are expected Saturday
night with lows likely in the single digits to upper teens.

Temperatures moderate on Sunday as the high pressure system
moves east of the area, bringing a more southerly flow around
it. Highs will likely be in the mid 30s to lower 40s. After a
partly to mostly sunny start to the day, clouds will be begin
to increase from west to east as the day progresses as the next
system approaches the area.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Overall a very active pattern will be in place during much of
the long term period.

Return flow around the departing high pressure system located
well off the New England coast will bring in enough moisture for
precipitation beginning late Sunday night/early Monday morning
as a strengthening low pressure system moves from the Plains to
the Great Lakes. Temperatures will be cold enough Sunday night
for the form of precipitation to be initially a mixture of rain
and snow, especially at higher elevations, before transitioning
to all rain by mid-morning on Monday. Lows Sunday night will
likely be in the lower to mid 30s across much of the area,
although temperatures will remain steady or even rise a few
degrees overnight as warm air advection moves in.

A steady rain is likely on Monday across the entire area as the
above mentioned low pressure system moves over the Great Lakes,
along with a moist southerly flow. Temperatures will be becoming
quite mild for this time of the year, with highs on Monday
expected to be in the mid to upper 40s. Rain will likely
continue Monday night, with perhaps a brief lull in Northeast PA
into the Southern Catskills. Temperatures will likely not drop
very much, with lows only bottoming out in the lower to mid 40s.

More rain is expected on Tuesday as the low pressure system
moves into Canada, bringing a cold front through the area. Due
to the cold front passage, highs will likely be reached during
the morning hours, mainly in the mid 40s to lower 50s, before
dropping to the lower 30s to mid 40s by sunset. As a result,
rain will likely mix with and eventually change over to snow by
the late afternoon/early evening in portions of Central New
York.

Main overall concern with this system is the long duration
steady to potentially even locally heavy rainfall along with
rapid snowmelt. As a result, flooding will be possible, although
it is too early to pinpoint any specific threats. We will
continue to watch this flooding potential as we get closer.

As winds shift to a more west-northwesterly direction Tuesday
night and Wednesday behind the cold front passage, lake effect
snow showers will be possible, mainly in Central New York. It
will also become chilly with lows Tuesday night likely getting
down to the upper teens to upper 20s. Highs on Wednesday will
likely not rise much, with highs expected to be in the lower to
upper 20s.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
We continue to see restrictions in lake effect snow showers
southeast of Lake Ontario this afternoon, with generally fuel
alternate to IFR visibility and ceilings over the next several
hours across RME-SYR and ITH-BGM. Snow showers shift mainly to
the I-90 corridor into the evening, and while RME and SYR may
continue to see some snowflakes this evening through the night,
these are not expected to lead to much by way of restrictions.
Ceilings this evening lift to around 2500 to 3500 ft across the
central NY terminals, while AVP continues to see mainly VFR.

Tonight into Friday, a clipper system will bring in additional
snow showers from west to east, beginning by 12Z. Ceilings drop
to around 1500 to 2500 ft - again, with the exception of AVP,
where ceilings are expected to stay around 3000 to 5000 ft. MVFR
restrictions in snow across central NY may drop to IFR in the
heaviest of snow, most likely across SYR and RME.

Otherwise, west to northwest winds this afternoon will continue
to gust up to 20kts, dropping back this evening. Winds start to
shift to the south or southwest into friday, but then low level
wind shear will become a possibility across ELM BGM and AVP
after 13Z.

Outlook...


Friday night...Lake effect snow showers/occasional restrictions
for KSYR-KRME; possibly briefly extending to KITH-KBGM.

Saturday through Sunday evening...VFR.

Monday and Tuesday...Restrictions likely with a broad area of
rain spreading through the region.

&&

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

&&

$$
SYNOPSIS...MDP
NEAR TERM...HLC/MDP
SHORT TERM...BJG
LONG TERM...BJG
AVIATION...HLC/MDP