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FXUS61 KBGM 181045
AFDBGM

AREA FORECAST DISCUSSION
National Weather Service Binghamton NY
545 AM EST Fri Jan 18 2019

.SYNOPSIS...
Light snow will finish moving across the area this morning, as a
weak low exits. Scattered lake effect snow showers and flurries
will continue in parts of Central New York this afternoon and
evening. A major winter storm will impact the area Saturday
afternoon into Sunday as a powerful low moves up the east coast,
followed by frigid air and very low wind chills into Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
310 AM Update...
Just some nuisance light snow or flurries today and quiet
tonight, before the major winter storm impacts the region over
the weekend.

A weak low will continue lifting across roughly Lake Ontario
this morning, and down the Saint Lawrence this afternoon.
Only limited lift exists, with what is initially a decent
amount of moisture but that diminishes quickly as associated
upper shortwave zips to our east. Thus light snow in progress
from overnight, through this morning, will end up generally only
an inch or two; even under an inch in many cases at lower
elevations. Main batch of light snow lifts out by midday, but
flow will also veer northwesterly allowing for scattered snow
showers/flurries in much of Central New York from lake effect
this afternoon through evening.

After starting off in the 20s, highs will be lower to mid 30s
today, but with cold air advection getting going this afternoon
through evening. This will drop temperatures to lows of teens to
around 20 tonight; even single digits to about 12 from Cortland-
Norwich-Cooperstown northward, especially north of the Thruway.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
4 AM Update...


Major Winter Storm Expected This Weekend...

A winter storm warning is now in effect from noon Saturday until
4 PM Sunday for much of the forecast area; except a winter storm
watch remains in effect for Luzerne, Lackawanna, S Wayne and
Pike Counties where the highest uncertainty in snow/ice amounts
remains.

Confidence increasing on storm total snow amounts between about
10 to 20 inches for most of the area...with the heaviest stripe
of snow now looking to set up from about Corning, northeast to
Cortland, Norwich and Cooperstown (17-22+ inches here).

Further south is the area with the least confidence on precip
type. Sleet and freezing rain will cut down the snow amounts.
The sleet looks to perhaps make it as far north as far southern
Bradford and Susquehanna counties in PA; then across all of
Sullivan County in NY. The highest chance to see a period of
freezing rain mixing in late Saturday night will be along and
south of I-84, then into the Wyoming Valley south of Scranton.
The good thing is it falls in the middle of the event after
several inches of snow already has fallen. A few areas in
southern Pike, far southeastern Luzerne and Lackawanna counties
could end up with close to a quarter inch of ice from freezing
rain. With gusty north-northwest winds on Sunday, this could
cause scattered power outages in these areas.

Still some model disagreement. The big factors are how far north
the mid level warm layer gets changing snow to a mix, and how
much phasing of the northern and southern jets there is. All
models have some sleet and freezing rain into the far south from
Luzerne County PA to Sullivan County NY. The GFS has now come
around to be in better line with the rest of the guidance as far
as mixing potential and temperatures aloft. This warm air moves
in just ahead of the surface low late Saturday night and Sunday
morning. Other uncertainties include total precipitation
amounts. The GFS is now lighter bringing about 0.90", meanwhile
the ECMWF and NAM are heavier...bringing about 1.1 to 1.4" of
precipitation. Followed a blend of WPC, superblend, ECMWF and
NAM for the official forecast, which gives about 0.90" north,
with 1 to 1.25" QPF central and south. WPC and the NAM are
hinting at a heavy deformation zone of snow snow setting up near
the I-88 corridor later Saturday night and into Sunday morning.
If the NAM/WPC guidance is right, snowfall rates of 2-4" per
hour would be possible within this band. Very strong mid-level
frontogenesis is evident around this time, as the mid level
circulation also moves into Central NY...so these very heavy
rates cannot be ruled out. Nudged up snow/QPF amounts in this
area between 06-12Z Sunday, but not as extreme as the 00z and
06z NAM would indicate. Temperatures will be very cold Saturday
night, with a dry/powdery snow expected in most areas. Snow
ratios of 12-18:1 are forecast. Overnight lows drop into the
upper single digits to mid-teens across NY, and between 15-22 in
NE PA. Northeast winds 8-15 mph will start to blow/drift the
snow around later Saturday night. Travel will be extremely
hazardous, if not impossible.

The surface low lifts northeast out of the Tennessee Valley
Saturday morning. This is pushed by a strong short wave and
deep upper level trough. Warm air advection ahead of the storm
will push snow into our area late Saturday morning across the
western zones. Snow intensities pick up late in the day and
evening. Snowfall rates should be 1 to 2 inches an hour and
maybe more between about 7PM Saturday until 7-10 AM Sunday.
Moisture is very deep. The dendrite zone is also deep between 10
and 15k ft. Lift is very good through most of the saturated column.

The storm slows some as it hits the coast Sunday morning but
the trough keeps it positive tilt to keep the storm going. As
the low level winds shift to the north some lake enhancement is
possible into the Finger Lakes Sunday afternoon and evening.
The steady snow exits the area late Sunday morning or midday
west to east. Temperatures fall on the back side and winds
increase. Blowing and drifting snow likely in the afternoon.

Sunday night and Monday will continue to be windy with Arctic
air over the area. Temperatures continue to fall below zero.
With winds of 15 to 25 mph with higher gusts. A short fetch and
air that is too cold and dry will limit the lake effect snow.
Only a few inches possible in CNY. Flakes will be small with no
dendrites. Blowing and drifting snow will continue to be an
issue through the day Monday. Dangerously cold wind chills are
also forecast Sunday night into Monday...between 15 to 25 below
in NE PA, and mainly 20-30 below in Central NY. Wind chill
watches, warnings and/or advisories will likely eventually be
needed for this period. High temperatures Monday afternoon range
from 5 below north to 10 above in the Wyoming Valley.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...

High pressure will try to build in Monday night to decrease the
already weak lake effect snow showers/flurries. Monday night
back below zero but winds drop to below 10 mph.

Not a lot of changes to the rest of the extended forecast.
Lowered PoPs under slight chance for Tuesday as an upper level
ridge moves overhead. Then, bumped PoPs up to high chance or
lower end likely Tuesday night and Wednesday as the next weather
system and frontal boundary moves in. Temperatures warm aloft,
looking to rise above 0C at 850 mb Tuesday night. At the same
time low level cold air (sub-freezing) remains in place over the
area Tuesday night and Wednesday morning. Added in a chance for
a wintry mix along with snow considering the above set up.
Looks like precip changes to mainly rain by Wednesday afternoon,
but some snow or mix could still linger.

Will be watching closely to see if another low pressure system
will impact the area toward Thursday, as the aforementioned
front stalls along the East coast. For now stuck close to
Superblend/WPC PoPs and temperatures Thursday and beyond.

After a very cold start to the extended period, temperatures
warm above freezing by mid-week. Then, it appears temperatures
fall back into the 10s and 20s late next week.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
A weak low will finish moving across the area this morning, with
occasional light snow and fuel alternate required ceilings
and/or visibility. Gradually lifting of ceilings into higher
MVFR or even VFR will occur this afternoon through evening.
However, intermittent snow showers or flurries may still occur
for KSYR-KRME and perhaps briefly KITH-KBGM. Variable or light
southeast to south winds, will veer to west/northwest with time
yet under 10 knots except for a few higher gusts.

Outlook...

Late Friday night through Saturday morning...VFR expected.

Saturday afternoon through Sunday...Major storm causing restrictions
in snow, heavy at times. Blowing snow also Sunday. Sleet or
freezing rain may mix in KAVP late Saturday night-early Sunday.

Sunday night through Monday...Occasional snow showers
restrictions and perhaps blowing snow, mainly NY terminals.

Tuesday...Mainly VFR, but a few restrictions still possible
KSYR-KRME central NY possible due to snow showers.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Winter Storm Warning from noon Saturday to 4 PM EST Sunday for
PAZ038>040-043.
Winter Storm Watch from Saturday afternoon through Sunday
afternoon for PAZ044-047-048-072.
NY...Winter Storm Warning from noon Saturday to 4 PM EST Sunday for
NYZ009-015>018-022>025-036-037-044>046-055>057-062.

&&

$$
SYNOPSIS...MDP
NEAR TERM...MDP
SHORT TERM...MJM/TAC
LONG TERM...MJM/TAC
AVIATION...MDP
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