Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 130929

Area Forecast Discussion
National Weather Service Buffalo NY
429 AM EST Wed Dec 13 2017

A cold northwesterly flow will result in continued lake effect snow
and blowing snow across the region today. A short break is possible
this coming evening before another weak system moves into the region
tonight. Yet another system with both some lake effect and
widespread snow will move in by Friday and last through least part
of the weekend.


Northwest flow in the wake of a departing surface low over the Gulf
of Maine continues to drive multi-banded lake effect snow over the
southern lakeshores.

Off Lake Erie, a single stronger bands remains embedded within
weaker multibands. The strongest band across central Chautauqua
county has a Lake Huron connection supporting snowfall rates of up
to a half inch per hour across Portland and Stockton. The bands
should migrate back north in a weakening state after daybreak as the
a clipper approaches the Ohio Valley. Lake Effect Warnings will
remain in place through today with 4-7 inches expected in the most
persistent lake snows.

Off Lake Ontario, multibanded snow also continues across the
southern lakeshores in northwest flow. A connection to Georgian Bay
continues to provide additional support for an embedded stronger
band shifting across Northern Cayuga near 4am. Upslope flow over the
Tug continues some higher returns also with snow rates in both of
these two areas running a half inch per hour. Winter storm warnings
remain here due to some lingering synoptic snows east of Lake
Ontario with additional snowfall also 4-7 inches mainly from western
Wayne into southern Jefferson counties. Further west, Niagara,
Orleans and Genesee counties continue to see several weak bands which
may produce up to an additional 2 inches with reduced visibilities
through midday. Winter Weather Advisories remain in place there
while the Advisories for Allegany, Livingston and Ontario have been
cancelled will only an additional trace to an inch expected through
this morning. The arctic airmass will keep cold temps in place
today. Highs will only reach the mid teens to low 20s for WNY but
only mid teens east of Lake Ontario. Lingering northwest breeze will
hold wind chills within a few degrees either side of zero.

A clipper, shifting southeast across Minnesota this morning is
forecast to reach the Ohio Valley later today then shift south of NY
across PA tonight. Weak synoptic forcing in the presence of
plentiful 925-700 mb moisture on the north side of the clipper will
bring a widespread light snow across Western NY and Finger Lakes
tonight. Any lingering weak Lake Effect southeast of Lake Ontario
should be overtaken by forcing from the synoptic scale clipper snow
by midnight. The eastern Lake Ontario region is expected to miss out
on this system tracking to the south. The arctic airmass with
surface temps dipping into the low teens to single digits tight
should support SLR of 20:1 or better. Blended QPF ranging from 0.05-
0.15 should yield around an inch across the Finger Lakes with 2 to
perhaps as high as 4 inches for WNY. No headlines are expected for
these light amounts. The clipper will create light and variable
winds over our region overnight so wind chills will be negligible.


The clipper system will be moving off the Jersey coast Thursday
morning and associated moisture will be moving away from
Western/Central NY. High pressure will move across the Ohio Valley
Thursday and NW flow is expected across the eastern Great Lakes. Dry
conditions upstream and low inversion heights will limit lake effect
snow showers Thursday afternoon. As winds back and become more
westerly Thursday night into Friday, moisture will increase off the
long fetch of the lakes. Lake effect snow showers will increase
however accumulations will be minimal as dry mid-level air keep
bands weak until moisture returns Friday.

A closed low will drop south across Ontario Friday and an associated
surface low will move across the northern Great Lakes. Winds will
back further and warm air advection aloft will produce snow showers
across the region. As the closed low becomes an open wave Friday
night, strong lift and lake enhancement will likely produce heavy
lake effect snow downwind of the lakes. There is uncertainty as
to where the best placement of these lake bands will be at this
time but favorable conditions exist for possible
advisory/warning criteria downwind of the lakes.

Temperatures warm slightly Friday with temperatures in the mid 20s.
Cloud cover and snow showers will keep temperatures fairly steady
into Friday night.


A ridge builds in Saturday in the wake of a trough passage Friday
night. With cold air and moisture in place Saturday morning behind
the trough, lake effect snows will be ongoing downwind of the
eastern Great Lakes. However, the ridge and warm advection quickly
move in during the day Saturday, which will shut down any lingering
lake snows.

With downstream blocking finally relaxing a bit, the persistent cold
air that we`ve been experiencing is expected to lessen a bit. This
should allow for temperatures to begin moderating over the weekend
and into early next week. Some areas may even see temperatures a bit
above normal. The pattern however remains fairly active, shortwaves
will provide a few chances for snow showers, and possibly some mixed


Lake snows south of both lakes will continue to result in MVFR/IFR
visibilities and cigs thorugh about 18z. KART also is seeing IFR but
more due to wraparound moisture in the wake of the departing surface
low over the Gulf of Maine.

Lake snows will gradually diminish this afternoon with a brief
improvement to VFR by the end of the day. Tonight, another clipper
will shift south of NY but will bring back additional widespread
light snow and IFR especially toward the southern half of western NY
after 00z Thursday.


Thursday through Sunday...Several systems will move across the
region over the course the the week and weekend with both widespread
snow and localized lake effect with resulting IFR conditions.
There will be several periods of VFR between systems.


A deepening surface low continues to move northeast across the Gulf
of Maine this morning as an anomalously deep upper level trough
plows into the lower Great Lakes region. Behind the low, multi-
banded lake effect snow in northwest flow will continue into today.
Small craft advisory conditions continue on Lake Ontario and Lake
Erie through today.


NY...Winter Storm Warning until 7 PM EST this evening for
     Winter Weather Advisory until 1 PM EST this afternoon for
     Lake Effect Snow Warning until 7 PM EST this evening for
MARINE...Small Craft Advisory until 7 PM EST this evening for LEZ040-
         Small Craft Advisory until 1 AM EST Thursday for LEZ020.
         Small Craft Advisory until 4 AM EST Thursday for
         Small Craft Advisory until 7 PM EST Thursday for LOZ044-



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