Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 240221

Area Forecast Discussion
National Weather Service Buffalo NY
921 PM EST Thu Nov 23 2017

A weak frontal boundary will help enhance some lake effect rain and
snow showers northeast of Lake Ontario this evening, and to a lesser
extend off of Lake Erie. High pressure will then bring a quiet but
mild day Friday ahead of a cold front Friday night into Saturday
morning with scattered rain showers. Some weak lake effect snow is
then possible again southeast of the lakes Saturday night into
Sunday with only spotty, very minor accumulation.


A mid level shortwave seen in WV imagery over the upper Great Lakes
will track across the lower Great Lakes this evening. The continued
height falls aloft and ascent ahead of the wave will help to
enhanced a minor lake response northeast of Lake Ontario. While most
the area will remain dry tonight, the lake response will bring a few
mixed showers northeast of the lakes. Off Lake Erie, nothing has
materialized so far, and conditions will only become less favorable
overnight for any lake response. With this in mind, expect nothing
more than lake enhanced clouds.

Off Lake Ontario, expect a little more response with a band of snow
showers developing over central/southern Jefferson and northern
Lewis counties mid to late evening, sinking south across the Tug
Hill through the early overnight. The snow may be mixed with some
rain near Lake Ontario, with mainly snow inland. Accumulations will
be limited to only a light coating in most locations, with up to an
inch or so across the higher terrain of the Tug Hill.

Otherwise, the weak ascent with the wave quickly departs to our east
overnight with drier air quickly building back in across the lakes.
Any lake response will diminish overnight, yielding a dry start to
the day Friday with just some lingering low-level lake clouds
overnight and early Friday especially along and north of the NYS
Thruway. These low clouds should scour out quickly Friday morning as
a stronger push of drier air and SSW downslope flow develops,
allowing for a good amount of sunshine from late morning on.

High pressure will slide to our east with the thermal ridge axis
arrive into western NY late in the day Friday. This will allow for
overnight low temperatures in the low to mid 30s on the lake plains
and upper 20s well inland to quickly climb to the upper 40s to low
50s on Friday. The warmest temperatures will be found in the typical
downslope regions across the lower Genesee Valley and Northern
Finger Lakes.


Mid level trough will dig east into the Great Lakes and Ohio Valley
Friday night into Saturday. Weak cold front associated with this
upper level feature will push east through the region Friday night
into Saturday morning. Moisture is limited, so for the most part,
light rainfall amounts are expected. A deep southerly flow ahead of
the front will keep temperatures from dropping off much Friday night.

Colder air will be slow to deepen behind the front, with the better
part of Saturday likely to be dry outside of lingering showers with
the front and associated shortwave.

A secondary cold front crosses the lower Great Lakes late in the day
Saturday which will allow for better lake responses. Temperatures
aloft will gradually fall behind the front, perhaps just cold enough
for some light lake effect rain or snow showers by Saturday evening.
Accumulating snows may not occur until later Saturday night into
Sunday when 850 mb temperatures drop to near -6C, but even at then
over-lake instability is not overly impressive. Snow amounts should
be on the light side given the marginal over-lake instability. The
best chances for minor accumulations will be in favored west-
northwest flow areas of the Chautauqua ridge, and areas southeast of
Lake Ontario from Rochester to Oswego. While accumulations are
expected to be on the lighter side, it still could make untreated
roadways more difficult to navigate. In addition, BUFKIT profiles
indicating plentiful low level moisture will be available through
the night even with lake induced equilibrium levels crashing below
5kft. This could be a set up for some freezing drizzle as surface
temperatures will be below freezing and lingering moisture will be
below the dendritic snow growth zone. This will need to be monitored
over the next few days.


Surface and mid-level ridging will build across western and central
New York Monday. Outside of a slight chance for a lingering shower
east of Lake Ontario, expect dry weather with low clouds breaking
for some sun. Temps with the ridging aloft will make a run into the
low 40s across WNY but likely linger in the 30s east of Lake Ontario.

The surface and mid-level ridge axis shift overhead Monday night
with a warm front also lifting north of Lake Ontario. The front
looks too far north to bring any risk of showers Monday night. This
will set the stage for some above normal temps forecast Tuesday.
Southerly flow should pick up ahead of what the 23/12z GFS/GEM show
as an approaching cold front with Tuesday also expected to be dry.
The models do show a strong 50 knot low level jet crossing our
region Tuesday which could lead to some gusty winds with diurnal
mixing. Surface temps may make a run toward the upper 40s to low 50s
with clouds increasing from the west. Both the GFS/GEM show the cold
front reaching into WNY Tuesday night with some widespread showers
while the ECMWF continues to be the more optimistic forecast with
the cold front or trough only glancing northern NY on Wednesday.
With these differences but persistence of the GFS/GEM solutions in
mind have bumped POPs to low chance Tuesday night into Wednesday.
Surface temps on Wednesday have some bust potential with the spread
in the timing and location of the cold front. Have leaned toward a
blend of guidance for now yielding mid to upper 40s for highs.

Generally expect Thursday to be dry with models forecasting a quick
moving surface high pressure behind the front/trough. Have included
slight chance POPs as the GFS shows enhanced moisture shifting north
form the Mid Atlantic north of a mid-level cut off low. Temps should
be close to seasonal averages with highs in the low to mid 40s
unless cloud cover/showers do work out as the GFS suggests.


Mainly very light lake effect precipitation will develop this
evening and continue through the early overnight east and northeast
of Lake Ontario. Expect areas of lake effect snow showers and local
IFR VSBY from late evening through the early overnight, mainly just
south and east of KART. All of this will end by Friday morning. CIGS
will be a mix of VFR and MVFR overnight, with MVFR favored east and
northeast of the lakes in plumes of lake effect clouds.

On Friday the lake effect clouds will quickly dissipate during the
morning as warmer air moves into the region. This will bring a
return to VFR with clearing skies.


Saturday...VFR/MVFR with rain showers likely.
Sunday...Mainly MVFR, localized IFR in -SHSN SE of the lakes.
Monday and Tuesday...VFR.


Small Craft Advisories are in place, as a moderate pressure gradient
remains in place between high pressure near the Mid Atlantic and low
pressure organizing over the Canadian Prairies. This low will cross
Ontario and Quebec through Saturday with a trailing cold front
crossing the Eastern Great Lakes region Saturday, and a secondary
cold front Saturday night that will bring a prolonged period of SCA
conditions to Lake Erie, and the far western and eastern sections of
Lake Ontario. A lighter southerly fetch of winds Friday will allow
for non-SCA conditions along the nearshore waters of central Lake


MARINE...Small Craft Advisory until 10 AM EST Sunday for LEZ040-041.
         Small Craft Advisory until 10 AM EST Saturday for LEZ020.
         Small Craft Advisory until 10 AM EST Friday for
         Small Craft Advisory until 4 AM EST Monday for LOZ042-045.



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