Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 261045

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

A cold northwesterly flow will continue into this 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 tonight and Thursday...while bringing a
initial 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


Through this morning...our region will remain under the influence
of 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 tending to
gradually break up a bit from southwest to northeast over time as
drier air slowly 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
this morning...before crashing inversion heights and the above
mentioned drying trend help to bring these to an end by late
morning or midday.

This afternoon...dry weather is expected with the remnants of the
lake effect clouds fading out southeast of Lake Ontario...while mid
and high clouds out ahead of the next system begin spreading into
far Western New York. Otherwise...chilly conditions will continue
with the lingering cold Canadian airmass helping to keep daytime
highs confined to the lower to mid 40s in most places...with our
highest terrain likely not making it out of the upper 30s.

Tonight...low pressure over Illinois will track into the Lower
Great Lakes...while pushing a warm front into Western New York.
Deepening moisture and strengthening warm air advection as this
system approaches will result in clouds thickening/lowering across
the region from southwest to northeast...with a swath of stratiform
precip then following suit as large scale lift increases along and
ahead of the warm front/the nose of a 40-50 knot southwesterly
low level jet pushing toward our area from the Ohio Valley. While
the arrival of the precip may ultimately turn out to be a little
slower than previously thought based on a consensus of the 00z
guidance suite...a mix of likely to high-end categorical PoPs still
looks reasonable for areas from the Finger Lakes westward by late

With respect to precipitation type(s)...model plan views/soundings
in conjunction with expected surface temperatures suggest that the
precip will initially begin as a mix of rain and wet snow across far
Western New York this evening...before transitioning to predominantly
rain by late tonight as progressively warmer air invades the atmospheric
column. Meanwhile from the Genesee Valley eastward...the atmosphere
should remain cold enough to support a rain/wet snow mix or even just
some plain wet snow through the overnight hours. While any snow will
likely struggle to accumulate much given its wet nature and the still-
warm antecedent ground conditions of mid-autumn...some minor accums of
a half inch to an inch or so will certainly be possible from the higher
terrain of Wyoming and Allegany counties eastward across the Finger
Lakes Region...with the greatest overall potential for these found
across the Bristol Hills in Livingston and Ontario counties.


Precipitation will be ongoing across Western New York as we move
into the daylight hours on Thursday and will continue to advance
northeastward into the North Country through the day as a surface
low attended by a prominent upper level trough tracks directly
across Western New York. While precipitation should have already
changed over completely to rain across Western New York by the
morning commute, areas from Wayne/Ontario counties north and east
will likely see a mixture of rain and snow to start the day, as
surface temperatures will be hovering near freezing, before
precipitation rapidly changes over to all rain by lunchtime as
temperatures rise into the 40s. The one exception will be across the
Tug, where near freezing temperatures may hang around for most of
the day, and wet snowfall may accumulate on the order of 1-2 inches.
Given the strong isentropic forcing and strong upper level support
that this system will have, widespread rainfall on the order of
around a half inch will be possible elsewhere on Thursday.

The surface low will continue to track across Lake Ontario and into
the northern Adirondacks Thursday night, while a secondary low
develops near Long Island Sound as the upper level trough becomes
negatively tilted. The impacts of this transition will largely be
felt across Southern New England, while closer to home we will see
the rain taper off as the low pulls away from the area and colder,
drier air wraps in behind the low. While the cold air will increase
lake instability, rapid drying aloft and encroaching ridging
upstream will severely limit any lake effect precipitation
opportunities. Most likely, we will see widespread lake-induced
cloudiness in the wake of the low Thursday night into Friday
morning, but little if any in the way precipitation. Cold advection
behind the departing low will drop temperatures back into the 30s.

The encroaching ridging eluded to above will quickly scoot across
the region Friday into Friday evening, providing a brief break from
the cloudiness before clouds increase once more behind the ridge
axis ahead of yet another approaching low pressure system. This
system, embedded within a faster lower amplitude flow regime, will
rapidly pass by to our north on Saturday, with the main impacts
consisting of a period of showers as a cold front associated with
the low crosses the region. After a fairly dramatic warm-up ahead of
this front, with temperatures potentially reaching the lower 60s
ahead of the front, readings will fall back into the 40s Saturday
night behind the front.


While we will see a cool-down behind the front, with highs in the
lower 50s Sunday, temperatures will once again climb above average
as we move into the new week. In fact, by Tuesday we could see
readings climb into the upper 60s as an upper level ridge crests
across the region and strong warm advection develops across the
lower Great Lakes in advance of yet another northern stream low
pressure system, very similar to Saturday`s system.

Precipitation-wise, the period will feature generally dry
conditions, with perhaps a few lingering showers behind the
departing cold front on Sunday before upper level ridging dry things
out Monday. A slightly more SW-NE orientation of the upper level
flow may steer Tuesday`s system far enough north of the area to
limit shower chances, and will stick with just a slight chance for
the time being.


Through the course of today...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.

Tonight...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 areas of
IFR developing across the higher terrain. 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.
Thursday night...Lingering widespread IFR/MVFR cigs with rain
diminishing from west to east.
Friday...Improvement to MVFR/VFR.
Saturday...VFR/MVFR with scattered to numerous showers developing.
Sunday...Mainly VFR with a chance of showers.


High pressure over central Ontario Province will extend southeastward
across the Lower Great Lakes today...while bringing a period of lighter
northerly to northeasterly winds and correspondingly much lower waves
than what has been experienced the past few days.

Tonight and Thursday...low pressure over the Midwest will track
northeastward across the Lower Lakes region. While the strengthening
easterly to southeasterly flow regime out ahead of this system will
bring increasing waves to eastern Lake Erie and Western Lake Ontario
tonight...the greatest wave action will remain offshore. On Thursday...
winds on Lake Erie will temporarily lighten as the center of the low
passes either near or directly over that lake...while brisk south-
easterlies will continue across much of Lake Ontario...with the
greatest wave action again remaining offshore.





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