Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241419

Area Forecast Discussion
National Weather Service Buffalo NY
1019 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


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

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.


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. 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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