Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 182015

Area Forecast Discussion
National Weather Service Buffalo NY
315 PM EST Thu Jan 18 2018

Lake snows east of the lakes this afternoon will finally wind down
tonight and Friday...with the snow lingering longest east of Lake
Ontario. Otherwise Friday will mark the beginning of a pronounced
warming trend that will last through Monday as high pressure settles
off the Carolina coastline and pumps progressively milder air into
our region. Our next chance for widespread precipitation will then
arrive later Monday and Monday night...when low pressure is expected
to track across the Great Lakes and bring a round of rain showers to
the region.


As of early afternoon...the Lake Erie lake snows have weakened
notably over the last 3 hours or so...however the combination of
these and winds of 15-25 mph (with gusts to 30-35 mph) is still
producing significantly reduced visibilities along with areas of
blowing/drifting snow...leading to slick spots on area roadways.
While this activity will continue to gradually diminish and
eventually disintegrate into some leftover scattered snow showers
by late this afternoon/early this evening as low level warming
erodes away at the supporting snow growth region...have left the
Winter Weather Advisory intact for now based on the aforementioned
lingering impacts.

Meanwhile off our other lake...the Lake Ontario lake snows remain
better organized thanks to the relatively long fetch across the
much more open waters of that lake...with a broad area of light to
moderate snow continuing to focus on areas from the Tug Hill
northward to Watertown and Fort Drum. These will likely produce
additional accumulations of 2-3 inches through the rest of the

Outside of the main lake effect areas...the rest of the day will
just feature mostly cloudy skies and much more scattered snow
showers/flurries...along with cold afternoon highs ranging from
the upper teens to mid 20s.

As we move on into tonight...a rather well-defined shortwave will
weaken while quickly rippling eastward across our region. The brief
boost in moisture and lift provided by this passing feature will
bring some short-lived scattered snow showers to areas from roughly
about the New York State Thruway northward. As for the lake snows...
the Lake Erie activity may get a very brief boost from this feature
as it passes through this evening...before continued low level warm
advection finally shuts these down for good overnight. Meanwhile the
Lake Ontario lake snows will tend to weaken some from their current
state as the supporting snow growth region shrinks up...though these
will still probably manage to hang on through the night thanks to
the boosts provided by the passing shortwave and the much more open
waters of Lake Ontario. Expect an additional 1 to 3 inches out of
these...which will be enough to maintain the existing Winter Weather
Advisories for the eastern Lake Ontario Region through tonight.

On Friday heights will rebound across our region in the wake of the
shortwave...and this in concert with continued steady low level warm
air advection will help to steadily wear down the Lake Ontario lake
snows...with these producing another inch or so of accumulation
before finally disintegrating into some leftover scattered snow
showers. Otherwise the day will be largely dry with morning clouds
giving way to some partial sunshine south of Lake Ontario...with the
aforementioned warm air advection also helping to boost temperatures
back into the lower to mid 30s in most places...and possibly even to
the upper 30s across interior portions of the Genesee Valley.


Friday evening there may still be a few light lake effect snow
showers east of Lake Ontario. These will quickly end during the
evening as inversion heights drop below 4K feet and low level
moisture is stripped away as a warm front moves northeast across
the area. Otherwise it will be dry Friday night, with more in
the way of clouds near the Canadian border in closer proximity
to the retreating warm front, and more clearing near the PA
state line. It will become quite windy again with a tight
pressure gradient and a 50+ knot low level jet crossing the
area. An inversion and poor low level lapse rates will not allow
for full mixing, but nonetheless expect gusts in the 35-40 mph
range overnight. Expect lows of around 30 on the lake plains of
Western NY, and mid to upper 20s elsewhere. These lows will
occur during the evening, with mixing and warm advection forcing
slowly rising temperatures overnight.

On Saturday the warm frontal boundary will sag back to the south
across Lake Ontario and the eastern Lake Ontario region as a weak
backdoor cold front. Convergence and frontogenesis will be very
weak, but there may be just enough when combined with lake moisture
and upslope flow to produce some very light precip east of Lake
Ontario. The cloud bearing layer may be too warm to support ice
nuclei, so if precip materializes it may be in the form of drizzle
or freezing drizzle. For the rest of the region, expect dry
conditions with low clouds increasing as low level moisture
increases. It will remain quite windy, with gusts of 35-40 mph in
the morning slowly coming down through the day as the low level jet
core moves off to the east. Expect highs within a few degrees of 40
in most areas, with mid to upper 30s for the North Country.

Saturday night will be dry with a weak surface ridge in place across
the eastern Great Lakes. Expect a good deal of cloud cover with NAM
and GFS BUFKIT soundings showing a rather extensive layer of low
level moisture in place, which is a common occurrence during a mid
winter warm-up with warm air crossing cold, snow covered ground. The
majority of the day Sunday will be dry and cloudy with a few
exceptions. A warm frontal segment will sharpen across the Saint
Lawrence Valley, and this may bring some light snow or rain to the
North Country where colder temperatures hang on. Another warm
frontal segment may bring rain showers to Western NY by late in the
day. Highs will again be within a few degrees of 40 in most areas,
with mid 30s for the North Country.

Monday and Monday night a more significant trough will advance into
the central Great Lakes. Warm advection and moisture transport will
increase across our region Monday, which may support a few showers
from time to time. A cold front will then cross the region late
Monday or Monday night, with the ECMWF a little slower on timing
than GFS based guidance. A plume of deep moisture ahead of the front
combined with increasing ascent will produce periods of rain. Monday
will likely be the warmest day of the stretch, with at least mid to
upper 40s likely in Western NY.

The combination of rain, and increased snowmelt from higher
temperatures and dewpoints may bring some flood concern by later
Monday and Monday night. This warm-up is not as dramatic as last
weekend, and rain amounts are also likely to be lower given the fast
passage of the cold front. Nonetheless, there may be some potential
for ice jam flooding by late Monday and Monday night.


Tuesday into Wednesday, colder air will rush back into the region
with a blustery southwest to west wind behind the cold front. This
will bring a return to more typical mid-winter temperatures for mid-
week along with lake effect snow within wraparound moisture and
lowering 850mb temps. Will have to keep an eye on how the ice cover
on Lake Erie evolves over the early week warmup, as it will have an
impact on the magnitude of whatever lake effect snows develops in
Western NY.


Through the rest of today...IFR conditions in lake effect snow will
persist at KBUF/KART...with a mix of MVFR/VFR cigs and much more
scattered snow showers found elsewhere.

Tonight and upper level disturbance will quickly cross the region
from west to east. This will bring some brief scattered snow showers
to areas from roughly KBUF-KROC-KSYR northward...while also helping
to maintain some weakening lake snows east of Lake Ontario. Expect
flight conditions to range from IFR in the lake snows east of Lake
Ontario (including around KART) to predominantly MVFR elsewhere.

On Friday...lingering lake snows east of Lake Ontario will
disintegrate into some scattered light snow showers...with MVFR
conditions otherwise prevailing there. Meanwhile south of Lake
Ontario...fairly widespread MVFR cigs in the morning will gradually
give way to VFR conditions from south to north as drier air begins
spreading into the region.


Friday night...Mainly VFR.
Saturday through Sunday...Widespread MVFR ceilings redeveloping on
Saturday...then persisting through Saturday night and Sunday.
Monday and Monday night...VFR/MVFR with rain showers developing.
Tuesday...MVFR/IFR with rain showers changing to snow showers before
ending...then areas of lake effect snow also developing east of the
lakes Tuesday night.
Wednesday...VFR/MVFR with a chance of snow showers.


A persistent pressure gradient will maintain brisk west-
southwesterly flow across the lakes into the upcoming weekend, and
small craft advisories remain in place into Saturday. High pressure
nosing across the region will relax the winds Sunday before winds
freshen once again on Monday ahead of a strong low pressure system
tracking out of the central Plains.


NY...Winter Weather Advisory until 7 AM EST Friday for NYZ006>008.
     Winter Weather Advisory until 7 PM EST this evening for NYZ010-
MARINE...Small Craft Advisory until 10 PM EST Saturday for LEZ040-041.
         Small Craft Advisory until 4 AM EST Sunday for



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