508
FXUS61 KBGM 171721
AFDBGM

AREA FORECAST DISCUSSION
National Weather Service Binghamton NY
1221 PM EST Mon Dec 17 2018

.SYNOPSIS...
Lake enhanced snow showers behind a cold front will bring minor
snow accumulations to Upstate New York through early Tuesday.
High pressure will yield drier conditions for Tuesday and
Wednesday.

&&

.NEAR TERM /THROUGH TUESDAY/...
1040 AM update...

Lake enhanced snow showers continue to stream into Northern
Onondaga and Western Oneida counties. We made minor adjustments
to the precipitation grids to account for the radar trends.

Otherwise, the forecast remains in good shape. New grids are
published.

310 AM Update...
We are transitioning back to colder weather at least for the
near term period. Main concerns are gusty northwest winds and
lake enhanced snow showers that develop later today through
tonight, which will both then diminish into Tuesday.

At this moment, very weak flow exists between low pressure
departing well to our northeast, and an amplified wave with
associated shot of cold air advection now dropping over northern
Lake Huron. There is abundant low level moisture, but aloft a
temporary ridge exists and thus the saturated layer below is
shallow. Weak flow will prevent it from mixing out, so we are
pretty much stuck with low clouds and patchy fog early this
morning, and temperatures are confined to the low to mid 30s.

Changes get underway late morning onward, as upper wave and
associated cold front punch into the region. Immediately behind
the front, winds will pick up considerably out of the northwest
15-20 mph with gusts easily 25-35 mph this afternoon into
evening; a few spots could even touch 40 mph. The front will
heavily rely on the lakes for help in terms of moisture, because
by itself there will not be a whole lot. However, with lapse
rates becoming steep under strong cold air advection, lake
enhanced snow showers will indeed get going behind the front.
Initially, upstream Georgian Bay connection may contribute to
moisture already offered by Lake Ontario, to a degree more than
previously figured. Eventually, however, boundary layer flow
veers too much for this connection late evening onward which
will cut back snowfall rates later tonight into early Tuesday.

Expectations are for 2-4 inches of snow accumulation east-
southeast of Lake Ontario, with highest amounts in the terrain
south of the NY Thruway including southern portions of Cayuga-
Onondaga counties, as well as Madison-Cortland-Northeast
Tompkins-Northwest Chenango counties. Lighter lake enhanced
accumulations may extend through Otsego-Delaware-Oneida
counties, and 1-2 inches could also occur into western Yates-
Steuben counties via help from Lake Erie. Accumulations for the
remainder of the Twin Tiers to Catskills will generally be an
inch or less from scattered snow showers and flurries. Very
little if any will make its way to the Scranton-Poconos areas.

The snow amounts above of course are not at all unusual for our
area. However, combined with gusts 25-35 mph, areas of blowing
snow could easily cause slick roads for some locations late
today through early Tuesday. Tuesday itself, other than
lingering morning flurries, will present the typical forecast
challenge of northwest flow and stratocumulus competing with a
dry air mass. Areas southeast of Lake Ontario will take a long
time to lose the cloud deck, but generally speaking we should
see gradual erosion of that deck from all sides resulting in at
least partial sunshine with time.

Temperatures at first today will move very little, with midday
highs about 33-39 and then falling behind the front this
afternoon. Continued overspreading of cold air mass results in
lows of mid teens to mid 20s tonight, and little recovery
Tuesday with highs of 20s-lower 30s. Though not quite as much
wind, we will probably still see gusts in 20-30 mph range
Tuesday. All told, the breeze will send wind chills late tonight
through midday Tuesday into the single digits-lower teens.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
3 AM Update...
Tuesday night as high pressure at all levels builds in and the
low clouds exit, temperatures will fall into the teens. Skies
won`t completely clear as upper levels shift to west bringing
high clouds in ahead of the next system. These clouds will lower
some Wednesday night. Wednesday highs from upper 30s northeast
to low 40s west. Increased dewpoints will let temperatures only
fall into the 20s Wednesday night.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
3 am update...
Little change to this period. Still have a warm rainy period
Thursday night and Friday. Lingering wraparound rain showers
behind the storm will slowly change to snow Saturday night. Snow
then continues into Monday. Another inch of rain possible
before much lighter rain and snow accumulations on the weekend.
Temperatures above normal throughout but falling to near normal
highs of low and mid 30s Monday.

previous discussion...
Thursday through Friday night: Low pressure will develop over
the deep south on Thursday then track northward into thew region
on Friday. Yet another surge of warm air advection will come
northward into the region. Ahead of a warm front associated with
this system moisture will overrun the front leading to
widespread rain Thursday night through a good portion of Friday.
Modeling has slowed the start time a bit, so have backed off
any rain chances till later Thursday afternoon with this
forecast. We will have to watch for a heavy rain threat as wet
closer to the event. Daytime temperatures should rise into the
40`s Thursday. However, temperatures at night are likely to rise
with the warm front approaching the region as well through the
40`s and getting into the low 50`s Friday in spots. Blended
model and ensemble guidance is likely too cool in this timeframe
and we have gone a little warmer with the forecast package than
the blended guidance.

As the low moves north of the region Friday night, temperatures
should fall back into the 30`s and 40`s with a transition to more
showery precipitation.

Saturday through Sunday: A west or northwest flow will setup as the
system which moves Friday continues to pull away. Another round of
lake effect snow showers is a potential result with more winter like
temperatures Saturday night and Sunday. Temperatures may still be
warm enough for rain on Saturday.

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...

Widespread MVFR ceilings are forecast through this evening as
low clouds and scattered snow showers move through NY into PA.
Ceilings will generally be between 1500 and 3000 feet.

In addition, lake effect snow showers will cause IFR-MVFR
visibility restrictions at KSYR and KRME through sunset, with
IFR ceilings possible at KRME for the next 3-6 hours.

Clouds will begin to break up tomorrow morning.

Winds will be westerly at 10 to 20 knots with gusts of 20 to 30
knots.

Outlook...


Tuesday afternoon through Thursday...VFR.

Thursday night through Friday...Large system impacts area with
restrictions and rain.

&&

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

&&

$$
SYNOPSIS...DJP
NEAR TERM...DJP/MDP
SHORT TERM...TAC
LONG TERM...MWG/TAC
AVIATION...DJP

NWS BGM Office Area Forecast Discussion

Random Fact

Snow

Snowflakes generally fall from the sky at speeds between one and five miles per hour.