Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241050

Area Forecast Discussion
National Weather Service Buffalo NY
650 AM EDT Sat Jun 24 2017

Sunny skies will prevail this morning, giving way to afternoon
cloudiness, with a few showers or thunderstorms possible across
portions of the forecast area. Temperatures will run cooler than
average this weekend, as upper level troughing moves across the
region. The cooler temperatures will be accompanied by showers at
times, particularly on Sunday and Monday, as a series of upper level
disturbances moving through the trough cross the area. The trough
will move east by Wednesday, with warmer temperatures expected by


Showers have largely ended across the forecast area this morning,
with the cold front now almost entirely through the area. Sunshine
will continue to spread east, as the last of the frontally-induced
cloudiness moves out of the area. Increasing sunshine this morning
will give way to increasing clouds this afternoon, as upper level
troughing moves into the area. Cooling temperatures aloft, along
with diurnal heating will allow for the development of widespread cu
during the afternoon, with a few showers and isolated thunderstorms
possible along the lake breeze boundary south of Lake Ontario as
well as the Boston Hills. With cooler air advecting into the region,
temperatures this afternoon will top out in the low to mid 70s
across most locales, with a few spots in the typically warmer
Genesee valley climbing into the upper 70s.

Any convective activity will come to an end during the evening
hours, with the loss of diurnal heating, leaving quiet and cool
night across the area. The cooler temperatures aloft, combined with
diminished cloud cover will translate to cooler readings than we have
seen at night of late, with lows dipping into the upper 50s along
the lake plains, with mid 50s across the higher elevations inland.


On Sunday, a broad mid-level longwave trough will extend from the
Northern Plains across the Great Lakes and into the Northeast
region. 00z GFS/EC models show a sharp mid level shortwave and
embedded vigorous vorticity max shifting through the base of the
longwave trough and crossing western and central NY during the day.
Synoptic scale lift from this shortwave and low-level forcing from a
surface trough and 30+ kt low level jet will contribute to scattered
to numerous showers and isolated thunderstorms. The most widespread
coverage will be during the afternoon corresponding to peak heating
and closer to the passage of the surface trough. Gusty southwest
winds 25-30kts downwind of the lakes should provide a lake shadow to
keep shower/storm coverage mainly inland. Temperatures will top out
a few degrees below normal due to the influence of the longwave
trough and associated pool of cool air aloft. Highs are forecast to
top out within a few degrees of 70. Dewpoints only around 50 will
yield very comfortable humidity levels.

In the wake of the surface trough Sunday night, 850mb temps become
cool enough to bring a potenial for some rare summertime lake
effect/enhancement east of the lakes. 850mb temps bottoming out
around +6C with lake temps +21C should support at least lake effect
clouds and even the risk for a chance of showers. Overnight lows
will again dip into the low-mid 50s and even upper 40s in the cooler
interior western Southern Tier and Tug Hill.

On Monday, another strong vort max and associated shortwave trough
is forecast to shift across the central toward the eastern Great
Lakes. Synoptic scale lift ahead of this looks to contribute to
another round of mainly diurnal influenced instability showers with
isolated thunderstorms. Taller shower/storm cells in this cool
environment may bring some small hail with a sub-10kft WBZ height.
Tough to say if lake shadows will again set up with weaker winds
aloft so have placed highest POPs into the likely range closer to
GFS moisture axis ahead of the shortwave mainly from the Finger
Lakes south and west. A lingering pool of cool air aloft will hold
temperatures below normal with highs forecast mainly in the mid to
upper 60s. Have left a chance for showers lingering through Monday
night as the vort max will shift overhead during the overnight
hours. Lower dewpoint air in place will help overnight temps to slip
back into the 50s with upper 40s possible in the interior western
Southern Tier and Tug Hill.


Latest runs of the medium range guidance indicate that the axis of
the longwave trough and associated vort max will be in the process
of shifting east of the forecast area on Tuesday. The cool air aloft
within the trough (again 850mb T around 6C) will support mainly a
diurnal threat for showers and possibly some thunderstorms. Similar
to Monday, taller shower/storm cells in this cool environment may
bring some small hail with a sub-10kft WBZ height. Again with
lingering cool air aloft, high temps will top out again in the 60s.

Surface high pressure centered over the southern Appalachians will
ridge north across the region Tuesday night and Wednesday allowing
for dry weather with mainly clear to partly cloudy skies. Temps will
still run a degree or two below normal.

Thursday and Friday, the high is forecast to shift off the Mid-
Atlantic coast with southerly winds bringing a return of increasing
moisture and warmth across western and central NY. Highs look to
push back above normal with readings in the upper 70s to low 80s. A
cool front looks to be the main focus for shower and thunderstorm
activity as both the GFS and EC models indicate it may become
stalled/stationary somewhere over the forecast area.


With the passage of a cold front overnight, the majority of the
forecast area has transitioned over to VFR conditions, with fine
flying weather expected across most areas this mornign, with the
exception of the North Country, where KART/KGTB remain under IFR
conditions. Regional satellite imagery indicates that these areas
should improve within the next hour or so, as the cold front is
nearly on the area`s doorstep.

VFR conditions will prevail throughout the day, though diurnal
showers and a few isolated thunderstorms may develop in the
afternoon, largely along lakebreeze boundaries along the KIAG/KROC
corridor, and SE of KBUF, over the Boston Hills. Convection should
rapidly diminish this evening, with the loss of diurnal heating,
giving way to more VFR conditions overnight.

Sunday through Tuesday...Mainly VFR with scattered to
numerous showers and thunderstorms...mainly in the afternoons.
Wednesday...Mainly VFR.
Thursday...VFR/MVFR with a chance of showers and thunderstorms.


Westerly flow developing in the wake of a cold front crossing the
area will generate a moderate chop across the eastern ends of the
lakes, with waves building to 3 feet by this afternoon. Waves will
rise higher on Sunday, particularly on the eastern half of Lake
Erie, as winds strengthen further as a strong upper level
disturbance moves through, and small craft advisories will likely be
needed on both lakes for Sunday afternoon into Sunday night. After a
brief respite Monday morning, another passing upper level
disturbance will likely bring another period of small craft advisory
conditions to Lake Erie Monday night.





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