Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 260257

Area Forecast Discussion
National Weather Service Buffalo NY
1057 PM EDT Tue Oct 25 2016

A cold northwesterly flow will continue tonight and into tomorrow
morning with isolated lake effect precipitation southeast of the
lakes. A low pressure system tracking out of the Midwest is then
expected to cross the lower Great Lakes tomorrow night and Thursday,
bringing widespread rainfall, and hilltop snowfall. Another round of
rainfall will be possible later this weekend, as another low
pressure system drops across the region.


Low pressure will gradually exit into the Canadian maritimes as
high pressure builds across the Great Lakes. This will result in a
weakening northwest flow which will shift to the north late

Temperatures will cool to about -8C at 850mb, resulting in some
lake effect clouds and possibly in some light lake effect
precipitation. Radar shows some light showers this evening, but as
the lake induced equilibrium level lowers later tonight cloud
tops may not be cold enough to support precipitation. For most,
this will produce a few sprinkles with a chance of showers
southeast of Lake Ontario where synoptic moisture is a bit deeper
and air aloft a bit colder. This also may mix with snow. A
consensus of high resolution QPF guidance initially captures
these areas well, but is overdone late tonight as the equilibrium
level lowers.

It will remain chilly through the overnight period, even though
there will be slight warm air advection through the night. Lake
effect clouds should be fairly widespread, but clear skies
outside of these will allow for overnight lows to drop below
freezing in these locations. Consensus guidance appears too cold
with cloud cover expected to be more widespread than most guidance
depicts. There will not be any mention of frost, nor headlines as
that program has ended for the year.

Tomorrow will remain mostly dry under a mix of clouds and sunshine.
With a pool of cold air remaining overhead daytime highs will be
limited to the low to mid 40s. The upstream shortwave cresting the
upper level ridge will reach the Central Great Lakes region tomorrow
afternoon. This will spread clouds across Western New York later in
the afternoon, though any rainfall will likely wait until the early
evening hours to fall.


Upper level energy will be working through the Midwest into the
Great lakes Wednesday night, as a weak surface low rides across the
southern Great Lakes. Plenty of moisture advection within a 45 to 50
knot low level jet focused on the Ohio valley and lower Great Lakes
to support developing rain Wednesday night. Potential precipitation
type issues develop, especially for areas east of the Genesee
Valley. Temperatures should slowly fall off of their afternoon highs
as cloud cover increases with the northeast progression of the warm
front. Most of Western New York will remain warm enough for the
precipitation arriving during the evening to remain as all rain.
However, higher elevations of the Southern Tier and Finger Lakes
will likely see snow mixing in with the rain, as temperatures fall
toward freezing. Farther to the east, as the precipitation reaches
there later at night into Thursday morning, we could see at least a
few of hours of snowfall, with accumulations of around an inch, with
perhaps the the highest portions of the Tug Hill, seeing a 2 to 4
inch accumulation in some locations, as temperatures there will
experience the longest period of time near or just below freezing.

The southeasterly flow ahead of the low will be well placed to
generate reasonably strong downsloping winds off the Chautauqua
Ridge along the Lake Erie shoreline Wednesday night into early
Thursday morning, perhaps gusting as high as 45 mph.

Precipitation will change over to rain everywhere on Thursday as the
compact area of low pressure system tracks directly across the lower
Great Lakes, with strong warm air advection and diurnal component
coming into play. The strong warm air advection pattern will
generate a widespread swath of isentropically driven rain, with many
locations seeing upwards of an inch of rainfall.

This rain will give way to rain showers Thursday night, as the low
shifts east of Lake Ontario and a secondary low develops along the
Mid-Atlantic coast. Developing cold air advection on the backside of
the system on a fairly uniform west-northwest flow will likely
support lake effect rain showers downwind of the lakes, with perhaps
a few snowflakes mixing in across the hills of the Southern Tier and
Tug Hill towards Friday morning, when temperatures fall into the mid
30s. Lows in the upper 30s elsewhere should preclude any snowfall

Lake effect showers should taper off on Friday as surface ridging
and warm advection take hold across the region. This ridging will be
embedded within a highly progressive, low-amplitude, flow aloft. In
fact, there will little in the way of clearing associated with the
ridge as it rapidly crosses the area and the next warm front sets up
across the lower Great Lakes Friday night into Saturday.

Models differ with regards to the exact track and speed of the low
pressure system that will be aiding in the development of the warm
front across the area, but all guidance currently indicates that
Saturday should be another wet day across Western and North-Central
New York.


GFS and ECMWF are close in agreement as to the timing and track of
the surface low on Sunday. GFS is a bit faster but both models move
the low eastward across the Lake Ontario basin and northern NY. Rain
should diminish following cold front passage, likely during the
afternoon given a compromise between models, then colder air on
northwest wind brings some lake effect response Sunday night. 850mb
temps fall to around -2C overnight, then this bubble of colder air
will be quickly offset by burgeoning warm advection on Monday.
Ridging aloft should suppress any precip for Monday and Tuesday.
850mb temps will climb to +10C by midday on Tuesday.

High temperatures on Sunday will reach the mid to upper 50s across
Western and Central NY with lower 50s for the North Country, then
temperatures will fall Sunday night following the cold front with
lows in the upper 30s to lower 40s. There should be a quick rebound
on Monday with highs once again in the lower to mid 50s, then lower
40s Monday night. The warmer air moving in on Tuesday will boost
temperatures to the upper 50s and low 60s over northern NY and the
lower to mid 60s for Central and Western NY.


VFR conditions were in place at 00Z even though lake effect
clouds were widespread across the region at around 4-5k feet. High
pressure centered just to the north of Lake Ontario will nose
southward across the TAF sites tonight, providing a partial
clearing, while maintaining VFR flight conditions with light

Northwest winds will begin to back to northerly tomorrow noontime,
with continued VFR flight conditions through Wednesday evening.
Lingering lake effect clouds will dissipate and be replaced by
high clouds approaching in advance of the next system late in the

Wednesday night and Thursday...MVFR/IFR with rain showers likely.
Friday...MVFR with a chance of lake effect showers.
Saturday and Sunday...MVFR/IFR with rain becoming likely.


Northwest winds have dropped off a bit allowing the small craft
headlines to be dropped. Winds will continue to drop off late
tonight as the high pressure ridge builds.

Winds and waves will remain light tomorrow. Later tomorrow night
and into Thursday an easterly flow will begin to build wave
heights on the western portion of the Eastern Great Lakes bodies
of water.





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