811
FXUS61 KBUF 090730
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
230 AM EST Tue Dec 9 2025

.SYNOPSIS...
Two waves of low pressure will pass by our region, with the first to
arrive this afternoon in the form of widespread, but light, synoptic
snow. Southwest winds behind this wave will deposit several inches
of lake effect snow downwind of Lake Erie on a southwest flow this
evening and into tonight, with a few inches of snow also falling
through the Saint Lawrence Valley off Lake Ontario tonight. A more
potent storm system will arrive later tonight, with snow and gusty
winds, with this snow mixing with rain late tonight and Wednesday
across lower terrain, while hills tops may remain as just snow
through the event, with this snow heavy at times.

&&

.NEAR TERM /THROUGH TONIGHT/...
Regional radars this early morning display light lake effect snow,
on a low level wind convergent boundary, with this activity expected
to drift northward through the morning as deeper southerly flow
develops. Accumulations will be a fresh coating of snow. Otherwise a
cold start to the day with many locations in the single digits, to
double digits below zero east of Lake Ontario.

Attention then turns to the west where a shortwave trough is passing
across the Western Great Lakes. This feature will being widespread,
but light, snow across our region this afternoon. Considering the
better low level lift will remain well to our west along the track
of the surface low through the Central Great Lakes and the
progressive nature of this shortwave trough, just a 3-4 hour window
of light to moderate snow is expected for our region, with just an
inch or two of snow accumulation.

The exceptions will be northeast of the eastern Great Lakes where a
southwest flow this late afternoon and through the evening, combined
with 850 hPa temperatures around -8C and lake induced equilibrium
levels around 5K will bring a band of lake effect snow. This snow
may be slow to develop off Lake Erie, with plenty of dry air in the
snow DGZ, but a return of ambient moisture by the evening hours
should allow for several inches of snow to accumulate northeast of
Lake Erie, mainly north of a line from Buffalo to Batavia. A more
favorable moisture profile off Lake Ontario, with a more southerly
component to the flow likely to keep this band north of
Watertown...with a few inches of snow accumulating through the SLV.
A southerly flow will carry such lake effect snowbands northward
into Canada...this as the next storm system bears down upon our
region later in the night. More on that in the short term section
below.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
Model consensus is to track a slowly deepening storm system just to
the north of Lake Erie and near the northern shoreline of Lake
Ontario late tonight and through the day Wednesday.

Vertical accent ahead of a stronger shortwave trough, combined with
convergent lift along a 40 to 50 knot LLJ will bring a period of
precipitation across our region, starting just past midnight tonight
for the Southern Tier and then by daybreak east of Lake Ontario.

Thermal profiles display precipitation likely to start as all snow,
but a warm front carried northward by this strong LLJ and advancing
shortwave trough will transition the snow to plain rain, first
across the lower elevations near Lake Erie late tonight, and then as
the warm front expands northward across our region Wednesday, all
regions except for the hills tops of SW NYS and the Tug Hill will
likely see a transition to plain rain for a period of time.

While thermal profiles display low chances for freezing rain during
this transition, there is increasing concern that a lag time in a
frozen road surface to warm above freezing, that an icy glaze may
occur on untreated roads, bridges and other sheltered areas.

Overall rain amounts around a quarter to a third of an inch will
ripen the snowpack, but flooding concerns will be low.

Higher terrain thermal profiles display precipitation likely to
remain all snow. This will allow several inches to accumulate on the
higher terrain of SW NYS, while a longer duration, slightly higher
SWE of the snow and upslope enhanced QPF effects east of Lake
Ontario will potentially allow for snow to accumulate more than 7
inches. Will continue a winter storm watch for areas east of Lake
Ontario, while issuing a winter weather advisory for SW NYS
counties.

The other concern Wednesday will be strong wind gusts. With this
system passing so close to our region, models still have slight
variations of the placement of the axis of the LLJ, with the NAM
tracking the low slightly farther to the north and deepening the
surface low the greatest, allowing the stronger wind field to reach
northward into our region. The GFS, ECMWF and Canadian are not as
deep with the surface low, and track the low just slightly southward
of the NAM, with the track of the low along the northern Lake
Ontario shoreline with a slightly weaker wind flow aloft. For now
will continue with wind gusts up to 45 mph northeast of Lake Erie,
with slightly weaker gusts inland and northeast of Lake
Ontario...though the possibility of stronger gusts remain if the NAM
with its stronger wind field verifies.

A cold front will push across our region during the late afternoon
and evening hours, with cold air advection changing mixed
precipitation back to plain snow, with lake effect snowbands then
forming on a west-northwest flow. There is the typical uncertainty
with wind direction as models still have slightly different tracks
of the departing surface low and orientation of the remaining low
level winds, but at this time expect the potential for moderate snow
accumulations across the western Southern Tier off Lake Erie, and
near or just east of Rochester to Oswego County off Lake
Ontario.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Another reinforcing shot of colder air and round of lake effect snow
on tap for Thursday in the wake of the cold frontal passage. A gusty
west to west-northwest flow will direct lake effect plumes east and
east-southeast of the lakes. Moderate accumulations still look
plausible with the highest accumulations off Lake Erie across
southern Erie, Chautauqua, and Cattaraugus counties...while off Lake
Ontario the highest accumulations are expected east of Rochester
over to Oswego County, and across Tug Hill where upslope snows will
help boost totals there. Temperatures will plunge back below average
with daytime highs around 10 degrees below average.

Clipper system pulls away from the area Thursday night, with low
level westerly flow lessening through Friday. Lake snows will wind
down through the overnight with another inch or two possible across
these same areas. High pressure sliding by to the south will try to
dry things out for the end of the work week, however a cold westerly
flow may keep some nuisance light snow showers going east of the
lakes Friday.

Another Clipper will slide east, just north of the upper Great Lakes
Friday night before shearing out across Quebec on Saturday, with
just some light lake effect snow showers continuing east and east-
northeast of the lakes. Mainly dry weather expected outside of LE to
start the weekend.

Models continue to advertise another system in the Clipper pipeline
moving southeast toward the lower Great Lakes region for late
Saturday and Sunday with potential synoptic and/or lake effect snow
possible depending on the track of the system. Northwest flow LE
snow showers may persist into Monday, however model guidance
diverges considerably heading into the start of next week. Better
confidence lies with temperatures during this timeframe, with fairly
good chances of another shot of arctic air invading the lower Great
Lakes and Northeast for the finish of the weekend and start of the
new work week.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
High pressure sliding east of the area will keep mainly VFR flight
conditions intact through midday/early Tuesday afternoon. Exception
will be remainder of tonight into the first couple of hours Tuesday
morning east of Lake Ontario as a weak band of localized lake effect
snow off the southeast end of Lake Ontario with limited inland
extent will continue to weaken and move north across the Lake
Ontario region. VSBYs around 3SM in -SHSN and marginal MVFR CIGS
have been observed at KFZY. If this band holds together, a brief
period of marginal MVFR/low VFR CIGS will be possible in and around
KART from around 10Z-13Z, however any snow shower activity should be
very light.

Flight conditions will then rapidly deteriorate from early/mid
afternoon Tuesday through the end of the TAF period as a warm front
extending south from a weak Clipper system approaches, then moves
across the area. Expect MVFR CIGS into western NY by mid afternoon,
spreading east to the eastern Lake Ontario region by around early
evening. A brief period of light snow will also be possible along
and ahead of the boundary. This may bring a brief period (1-3 hours)
of MVFR/IFR VSBY with timing mirroring the aforementioned onset of
MVFR CIGS. A period of localized lake effect snow is then expected
to develop in the wake of the warm frontal passage with intermittent
MVFR/IFR VSBYs northeast of Lake Erie possibly impacting KBUF and/or
KIAG Tuesday evening into the early overnight.

Southerly to southwesterly flow will ramp up for Tuesday afternoon
and evening as well, with gusts mainly in the 20-25 knot range,
however a few gusts to 30 knots is not out of the question.

Outlook...

Tuesday night...Mainly MVFR/IFR with snow potentially mixing with
rain late in the night.

Wednesday...VFR/MVFR with rain and snow showers. Breezy, with gusts
20-30kts in many areas. Gusts to 35kts possible at KBUF/KIAG.

Thursday...VFR, with MVFR/IFR in scattered to numerous snow showers.

Friday and Saturday...MVFR/IFR east of the lakes with snow showers
likely. MVFR/VFR outside the main lake effect areas.

&&

.MARINE...
The offshore flow will increase and begin to turn southwesterly this
morning as high pressure exits to the east and a weak system moves
through the eastern Great Lakes, which will then be followed by a
more potent area of low pressure on Wednesday.

A deepening area of low pressure will pass by just north of Lake
Erie, though very close to Lake Ontario such that the strongest wind
fields with this second storm system will maintain gales to just
Lake Erie. Have upgraded the gale watch to a warning with this
product issuance.

Behind this second low, a persistent west to northwesterly flow
below gale force will ensue Wednesday night and through much of the
remainder of the week with small craft conditions on both Lakes
right through the week...if not through the weekend.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Watch from late tonight through Thursday morning
     for NYZ006>008.
     Winter Weather Advisory from 1 AM to 10 PM EST Wednesday for
     NYZ012-019>021-085.
MARINE...Small Craft Advisory from 1 PM this afternoon to 4 AM EST
         Thursday for LEZ020.
         Small Craft Advisory from 7 AM this morning to 4 AM EST
         Wednesday for LEZ040-041.
         Gale Warning from 4 AM to 7 PM EST Wednesday for LEZ040-
         041.
         Small Craft Advisory from 3 PM this afternoon to 10
         AM EST Friday for LOZ042.
         Small Craft Advisory from 9 PM this evening to 6 PM EST
         Saturday for LOZ043>045.

&&

$$

SYNOPSIS...Thomas
NEAR TERM...Thomas
SHORT TERM...Thomas
LONG TERM...JM
AVIATION...JM
MARINE...Thomas