Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 260629

Area Forecast Discussion
National Weather Service Buffalo NY
229 AM EDT Wed Oct 26 2016

A cold northwesterly flow will continue into Wednesday morning with
any leftover lake effect precipitation southeast of Lake Ontario
ending by midday. Low pressure over the Midwest will then cross the
Lower Great Lakes Wednesday night and Thursday...while bringing a mix
of rain and wet snow that will change over to all rain during Thursday.
Another low pressure system will then bring another possible shot
of rainfall to the region this weekend.


For the rest of the nighttime hours and early Wednesday morning...
our region will remain under a somewhat sheared and weakening
north-northwesterly flow of cold Canadian air...between exiting
low pressure over the Canadian Maritimes and surface-based ridging
extending southeastward from central Ontario. This will maintain
a mix of partly to mostly cloudy skies across our region...with
the cloud cover generally also tending to slowly break up a bit
from southwest to northeast with time as drier air builds into the
area. Southeast of Lake Ontario...the airmass may remain moist enough
to support a few additional spotty sprinkles or light rain and/or
snow showers through early Wednesday morning...before crashing
inversion heights and the aforementioned drying trend help to
bring these to an end by late morning or midday.

Otherwise...Wednesday 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 lower to mid 40s. The upstream shortwave cresting
the upper level ridge will reach the Central Great Lakes region Wednesday
afternoon. This will spread clouds across Western New York later in
the afternoon, though any rainfall will likely wait until the early
evening hours.


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.


Through the rest of the night and Wednesday...VFR conditions will
prevail across the region with lingering 4-5 kft lake effect clouds
slowly breaking up and dissipating from southwest to northeast
through early afternoon...with mid and high clouds in advance of
the next system then spreading across far Western New York through
the balance of the day.

Wednesday night...low pressure over Illinois will track into the
Lower Great Lakes...while pushing a warm front into Western New
York. As this system will produce thickening/
lowering clouds across our region...while also spreading a mix
of rain and wet snow across areas south of Lake Ontario. Within
this latter region...flight conditions will lower to the MVFR/low
VFR ranges...with some spotty IFR possible. Meanwhile...VFR
conditions will continue to prevail across the Eastern Lake
Ontario region.

Thursday...A mix of rain/wet snow becoming widespread and changing
over to all rain...with widespread IFR/MVFR conditions developing.
Friday...MVFR with a chance of lake effect showers.
Saturday...MVFR/VFR with some showers becoming likely.
Sunday...Mainly VFR with a chance of showers.


Winds and waves will continue to drop off late tonight as high
pressure over Central Ontario extends southeastward across the
Lower Lakes Region.

Winds and waves will remain light Wednesday. Later Wednesday
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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