318
FXUS61 KBUF 212346
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
646 PM EST Thu Nov 21 2024

.SYNOPSIS...
Strong low pressure will continue to spin over the Northeast US
through Friday night, producing low elevation rain and high
elevation wet snow across the region. The highest elevations will
see locally moderate accumulations across the Southern Tier and Tug
Hill Plateau, with no accumulation for lower elevations. A few
leftover rain and wet snow showers will continue Saturday through
early Sunday before mainly dry weather returns later Sunday.

&&

.NEAR TERM /THROUGH FRIDAY/...
Radar imagery showing widespread, synoptic scale precipitation from
the Genesee Valley east across Central NY and the eastern Lake
Ontario region. Most of this is rain, except for the highest
elevations of the Tug Hill Plateau and Finger Lakes where wet snow
is falling. Meanwhile across Western NY, a disorganized area of lake
effect is persisting over Lake Erie in a light flow regime, with a
few of the showers drifting onshore in Chautauqua and Southern Erie
counties. This is mostly rain, although some graupel may be mixing
in.

A large and deep mid/upper level low over the upper Ohio Valley this
evening will continue to move east to the Mid Atlantic by later
Thursday. At the surface, the primary low over the western Great
Lakes continues to weaken and give way to secondary cyclogenesis off
the east coast.

Tonight, the surface low off the coast of New Jersey will deepen and
retrograde northwest into the Catskills, continuing widespread lower
elevation rain and high terrain snow. Forecast thermal profiles will
be ever-changing with time due to milder air from the east being
pulled into the low, supporting a difficult higher terrain snow
forecast. The coldest column temperatures are through the first half
of tonight, and then start to warm slightly late tonight. While
temperatures will cause a difficult precipitation type forecast,
moisture will be plentiful due to moisture being advected in to the
area from the Atlantic and support a large precipitation shield
backing westward over the region tonight.

This all being said, the lower elevation lake plains will stay
almost all rain, with no snow accumulation and temperatures
remaining in the upper 30s. Thermal profiles will support colder
temperatures across higher elevations, with some minor accumulations
showing up above about 1000-1200 feet, and moderate accumulations
above 1500 feet across the Southern Tier, western Finger Lakes, and
Tug Hill region. Expect slushy, wet totals of 3-7" for the highest
terrain in these areas, while the valleys below see far less.

Winter Weather Advisories have been issued for the ridges of
Wyoming County, higher terrain of the western Southern Tier and Tug
Hill tonight through Friday morning.

The surface low will then move southward into eastern Pennsylvania
Friday, causing dry air to filter into the forecast area and
precipitation to begin to dwindle down from east to west during the
afternoon. However, due to northwest winds supporting orographic
lift and limited lake enhancement western New York, especially the
western Southern Tier showers will continue. Temperatures will
gradually warm both surface and aloft Friday as somewhat warmer
Atlantic air is wrapped back west by the system, resulting in a
change back to rain in most areas, even across higher terrain.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
P-type might become a bit of a challenge by Friday night as drier
air begins to wrap in around the departing low. While precipitation
will `likely` continue in the liquid form below 1000 feet, above
that elevation there will be a transition gradually over to snow.
That said...there is one caveat, as was mentioned drier air moving
into the mid-levels may produce just drizzle. This is indicated in
BUFKIT sounding profiles with a pronounced dry layer in the DGZ (-10
to -20 layer). Additionally...the airmass circulating in across the
Lower Lakes is not all that cold, with 850T`s only down to -3C to
-4C) aloft. Therefore...have limited snow accumulations to under an
inch Friday night into Saturday morning across the S. Tier. The
higher terrain of the Tug/Western Dacks it will be matter of how
much precipitation lingers as the low pulls further away overnight.
Even so...we are only looking at nuisance accumulations of an inch
or less there too.

As the low moves further out to sea Saturday it will then draw
Atlantic moisture back eastward across the forecast area. A cool WNW
flow (850H temps still around -2C/-3C) with the increase in moisture
will lead to a reinvigorated lake response causing showers to expand
across much of the area. The main lake enhanced/upslope areas east
and southeast of the lakes will see the most activity, though the
warmer daytime temps will `likely` support rain as the dominant p-
type for all locales. Temps cooling overnight Saturday night may
support some wet snow across the higher terrain areas.

Sunday....a mid-level shortwave dropping southeast through the
region is advertised to bring a brief shot of colder air (850H temps
-4 to -8C) to the region. This will likely be just enough to
maintain at least a chance for showers (rain/wet snow higher
terrain) east/southeast of the lakes through the day. However, drier
air again filtering into the region should limit the lake effect
potential despite the injection of colder air.

Sunday night...continued drier air working into the region and then
warming mid-levels will slowly bring about an end to any lake
induced showers by Monday morning.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Surface high pressure will briefly ridge across the region Monday
morning, resulting in mainly fair and warm weather for the day.
After this, a mid level trough digging across the upper Great Lakes
will lead to surface low pressure developing and tracking across the
eastern Great Lakes Monday night into Tuesday. This will bring a
shot of widespread rain showers with modest rainfall amounts around
a quarter inch. It will also become windy and cooler Tuesday in the
wake of the passing surface low.

Consensus 850mb temperatures drop down to around -8C by late Tuesday
night, with a fairly moist cyclonic flow aloft. This will support
some lake effect precipitation, with it cold enough for some of this
to be snow. Westerly winds will direct most of the lake effect and
upslope enhanced precipitation across the typical snow belts east of
the lakes Tuesday night and Wednesday. Accumulating snows are
likely, with advisory level amounts (greater than 4 inches) possible
but far from a certainty. Due to the marginally cold air mass,
greater accumulations would be more likely across higher terrain
such as the Chautauqua Ridge and Tug Hill.

A more zonal flow aloft develops by Thursday, with some models
developing a wave of low pressure and tracking it to our south. This
possible system in addition to lingering lake effect may produce
some rain or snow showers.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
An expansive and strong upper level low will move from the upper
Ohio Valley towards the Mid Atlantic tonight through Friday. A
surface low over the western Great Lakes will continue to weaken and
give way to a strong east coast low, which will make a loop back
into southeast NY and eastern PA before moving out to sea Friday
night. This system will produce widespread lower elevation rain and
high elevation wet snow tonight through the first half of Friday,
before the widespread precipitation tapers off from east to west
later Friday afternoon and night.

VSBY will be VFR to MVFR in areas of rain, and IFR in snow tonight
through Friday. CIGS will deteriorate this evening as the low levels
saturate, with widespread IFR CIGS later tonight through all of
Friday in cyclonic northerly flow. It will become quite windy later
tonight and Friday, especially over and near the lakeshores where
gusts may approach 30 knots.

Outlook...

Saturday...VFR/MVFR with a few rain and wet snow showers.
Sunday...VFR/MVFR with a chance of a rain or snow shower.
Monday...VFR/MVFR with a chance of rain.
Tuesday...MVFR with rain and snow showers possible.

&&

.MARINE...
A surface low will rapidly deepen off the east coast tonight, then
make a cyclonic loop back into southeast NY and eastern PA late
tonight through Friday before moving back out to sea Friday night.
North winds will increase over Lake Ontario and Lake Erie as this
system deepens and moves closer, with higher end Small Craft
Advisory conditions on both lakes overnight through Friday before
winds diminish Friday night as the system moves back out to sea.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until noon EST Friday for NYZ008-012-
     019>021.
MARINE...Small Craft Advisory from 7 AM to 7 PM EST Friday for LEZ020.
         Small Craft Advisory from 10 PM this evening to 1 AM EST
         Saturday for LEZ040.
         Small Craft Advisory from 10 PM this evening to 7 PM EST
         Friday for LEZ041.
         Small Craft Advisory from 10 PM this evening to 7 PM
         EST Friday for LOZ043-044.
         Small Craft Advisory from 4 AM to 7 PM EST Friday for
         LOZ030.
         Small Craft Advisory from 10 PM this evening to 10 PM EST
         Friday for LOZ042.
         Small Craft Advisory from 10 PM this evening to 4 PM EST
         Friday for LOZ045.
         Small Craft Advisory from 4 AM to 4 PM EST Friday for
         SLZ022-024.

&&

$$

SYNOPSIS...Hitchcock
NEAR TERM...EAJ/Hitchcock
SHORT TERM...AR
LONG TERM...Apffel
AVIATION...Hitchcock
MARINE...EAJ/Hitchcock