418
FXUS61 KBUF 030316
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1016 PM EST Thu Jan 2 2025

.SYNOPSIS...
An active wintry weather pattern will remain in place for the
foreseeable future...as a deep trough over eastern Canada will
maintain a flow of cold air southwards across the wide open lakes.
This will keep accumulating lake snows in place with the most
significant accumulations of several feet being found over Oswego
county and southern Tug Hill region. Temperatures from this weekend
THROUGH most of next week will average a solid 5 to 10 degrees below
normal.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
A somewhat phased -NAO / +PNA pattern over North America and the
North Atlantic has resulted in a large closed low over eastern
Canada. This pattern will maintain a feed of cold air southwards
across the Great lakes region...and with our lakes still wide
open...we can expect that the lake effect snow machines will remain
quite operational for the foreseeable future.

In regards to the accumulating lake snows east/southeast of the
lakes...

Off Lake Erie...

A westerly flow of -10C air will keep disorganized lake snows in
place tonight east of Lake Erie. Upslope flow will play an
important role in enhancing snowfall, with most of the heavier
snow focused across the higher terrain.

An approaching mid level shortwave, and a surface wave passing
through the Ohio Valley, will bring improved moisture late
tonight through Friday, which should allow for better organization
once again.

The west or WNW flow, and lack of stronger synoptic scale support
and moisture, both suggest the majority of the accumulating snow
will focus across the higher terrain inland from Lake Erie, rather
than along the shoreline and the NYS Thruway corridor. In general,
expect accumulations of 2-4" each 12 hour period tonight, and
Friday, then an average of 3-6" Friday night. Locally higher amounts
will be possible along the Chautauqua Ridge south of Cattaraugus
Creek. Snowfall rates through the three periods will average an inch
or less per hour.

Off Lake Ontario...

A longer fetch across Lake Ontario, and upstream connection to
Lake Huron, will support more organized lake snows over Oswego and
southernmost Lewis county tonight into Friday. Snowfall rates during
this period will average 1-3" per hour within the band. This
could result in nearly 18" of snow tonight across the higher
terrain of Oswego county to southernmost Lewis county (ie. southern
half of the Tug Hill). Given a cap over 10kft and a -10c level
of roughly 4kft...electrification is possible within the heart
of the band. Watch for echoes of 35 dbz or greater to suggest
the presence of graupel which correlates very well to lightning
generation.

The band should reach its northernmost position by late tonight and
Friday morning, likely across central or northern Oswego County and
far southern Lewis County. Note, followed closer to the farther
north Canadian GEM band position during this period. It will be a
very close call if the band makes it into Jefferson County or not,
and if it does, it would only be the extreme southern end of the
county.

Friday afternoon, a mid level trough will move southeast across the
eastern Great Lakes. This feature will produce a few snow showers,
and more importantly, veer boundary layer flow from west back to
northwest. This will begin to push the lake effect snow on Lake
Ontario back south across Oswego County, and the western end of the
band will likely move onshore as well, bringing a period of snow
showers to Rochester later in the day. The Lake Huron band may also
cross the Niagara Frontier and western Finger Lakes, producing a
period of snow showers and minor accumulation.

In the wake of a reinforcing short of colder air...the impressive
plume of heavy lake snow will then shift to the south across Wayne
and northern Cayuga county Friday night. Snowfall rates of an inch or
two an hour can be expected with overnight amounts of 5 to 8 inches
possible.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
The greatest impacts from the lake effect snow during the weekend
will be southeast of Lake Ontario from Wayne to Oswego counties.
Lake effect snows will intensify Saturday afternoon through Sunday
morning due to the passage of a shortwave and upstream lake
connections extending all the way back to Lake Superior. During this
time, snowfall rates of 2 to 3 inches an hour are likely, with
additional accumulations of 1 to 2 feet in most persistent snows.

Otherwise, lake snows will continue east of Lake Erie but will be
less intense since moisture contribution of upstream lakes will be
limited. Cyclonic flow aloft and 850mb temps around -14C will
support some lake snows across the Western Southern Tier Saturday
and Sunday, but these will mainly be across higher terrain where
upsloping will aid lift. On Sunday, the forecast adjusts band
placement to match wind fields rather than long range QPF fields.

Another factor will be gusty winds on Saturday and Saturday night,
with gusts 35 to 45 mph at times. This will combine with the snow
falling and on the ground to cause areas of blowing and drifting
snow. The greatest impacts from this will also be southeast of Lake
Ontario where the most snow will be in place and it will be ongoing.

Otherwise, there will just be snow showers outside of the steady
lake snows, with generally less than an inch accumulation in the
Buffalo and Rochester metro areas Saturday and Saturday night. The
passage of one final shortwave will shift winds from predominantly
west to the northwest during Sunday. This will push steady snows
south of Lake Ontario and across Niagara, Orleans, and Monroe
counties. Several inches of snow is possible with this.

Winds will diminish Sunday night as a weak surface ridge builds in,
and this will cause lake snows to taper off limited additional
accumulation. Temperatures will remain below normal during the
weekend with daytime highs in the 20s. This combined with gusty
winds will drop wind chills into the single digits during Saturday.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The phased -NAO/+PNA pattern across the Northern Hemisphere will aid
in maintaining the deep longwave troughing pattern across the
eastern CONUS through much of the week (and likely beyond). An
arctic sourced airmass within this trough will continue to flow
across the lakes through the period (850H temps well into the
negative teens), supporting a wealth of lake effect clouds and
chances for additional snow showers. With some exception, generally
WNW prevailing sfc-850H flow will continue to focus additional snows
east and southeast of the lakes.

Otherwise, there will be a couple of additional synoptic features to
watch this period...The first will come right on Monday as a potent
mid-latitude cyclone over the Mississippi Valley moves towards and
away from the Mid-Atlantic coast. The vast majority of the impacts
from this system are expected to be south of the forecast area,
though long range guidance has been in poor agreement on exactly how
far the northern edge of the main precip shield makes it. Confidence
remains low in the possibility in lighter synoptic snow making it
over the NY/PA border. Otherwise, this system will briefly cause the
steering flow over the lakes to shift northeasterly Monday,
redirecting any lingering lake effect activity more south to
southwest of the lakes. Thereafter, the later major feature of note
will come in the form of a sharp mid-level trough axis that will
pivot across the lakes between Wednesday and Thursday. This feature
could supply an increase in synoptic moisture while further lowering
850H temps, potentially fueling another round of more substantial
lake effect snow.

Temperatures through the week will continue to run well below
normal, with high temperatures only in the teens to mid 20s and lows
in the teens to single digits.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
VFR weather will be found across much of the region through
Friday...but IFR to MVFR conditions in lake effect snow will be
found east of both lakes...including at KJHW and possibly KELZ.

Otherwise...it will be rather windy during this TAF period with sfc
gusts as high as 30 knots.

Outlook...

Friday night through Sunday...IFR/LIFR in bands of lake effect snow
southeast of the lakes, otherwise MVFR/VFR with scattered light snow
showers.
Monday...Mainly VFR, but MVFR in scattered snow showers across the
Srn Tier.
Tuesday...VFR, but MVFR in lake snow showers southeast of both lakes.

&&

.MARINE...
Strong low pressure over the Canadian Maritimes will move slowly
northwest across Quebec, reaching James Bay later Saturday while
starting to weaken. Gales will continue on eastern Lake Ontario
through most of tonight...while high end small craft advisory
conditions will be found most elsewhere.

Moderately strong WNW winds will continue Saturday through Saturday
night on Lake Ontario and Lake Erie before gradually diminishing
Sunday. This period will very likely include at LEAST gale force
wind gusts on Lake Ontario and could include another round of
sustained gale force winds.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Lake Effect Snow Warning until 6 PM EST Sunday for NYZ004>008-
     012-019-020-085.
     Winter Weather Advisory until 6 PM EST Sunday for NYZ021.
MARINE...Small Craft Advisory until 7 PM EST Friday for LEZ020.
         Small Craft Advisory until 4 PM EST Sunday for LEZ040-041.
         Small Craft Advisory until 4 PM EST Sunday for LOZ042.
         Gale Warning until 4 AM EST Friday for LOZ043>045-063>065.

&&

$$

SYNOPSIS...RSH/TMA
NEAR TERM...Hitchcock/RSH/TMA
SHORT TERM...Apffel
LONG TERM...PP
AVIATION...RSH/TMA
MARINE...RSH/TMA