Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 240258

Area Forecast Discussion
National Weather Service Buffalo NY
1058 PM EDT Wed Aug 23 2017

An large upper level trough over the Great Lakes will make for cool
and mainly dry weather across the region through the rest of the
week. A few spotty light showers will remain possible at times
through Friday morning...before high pressure then brings dry
weather from Friday afternoon right on through the upcoming weekend.


As expected, showers have dissipated with the loss of diurnal
heating and the passage of an upper level vorticity lobe across the
region. Surface high pressure is building into the region, and skies
have cleared out in the wake of the departing showers. With the
clearing skies, radiational cooling will cause temperatures tonight
will drop to the upper 40s in the higher terrain to near 60 closer
to the lakeshores.

While the night should start out clear, cloud cover will begin to
increase starting in the late overnight/early morning period as the
next spoke of vorticity and shortwave behind the upper level low
over Quebec approaches the area. The increasing vorticity advection
will be in conjunction with increased lake instability, as 850 temps
falling to +6C support equilibrium levels in excess of 10kft. With
this increased vorticity advection and enhanced lake instability, we
will see a chance for showers by the morning commute. Cloud cover
and the best chance for showers will increase primarily over the
south shore of Lake Ontario during the late overnight/early morning
time period.

Thursday, the shortwave approaching from the Central Great Lakes
along with vorticity will generate some forcing for the area and
therefore going with chance pops for most of the BUF CWA.
Additionally some increased moisture as suggested by 18Z GFS and NAM
support at least chance pops. Best forcing from the shortwave and
vorticity should remain south and east of the BUF CWA as it
continues to move south into PA and the Mid-Atlantic. Current
upstream temperatures in the Central Great Lakes range from the low
to mid 60s and that slightly cooler air will advect into the area
on Thursday when highs for the region will mostly range from the mid
to upper 60s...which is more reminiscent of temps for mid-late


Thursday night lake effect rainshowers will develop southeast
of Lakes Erie and Ontario in the cold northwest flow. Overnight
lows will range from the upper 40s across the interior southern
tier and the north country to the mid 50s along the lake shores.

By Friday morning the lake effect rain showers will be waning as
drier air builds across the region. This should occur before sunrise
off Lake Erie and during the early morning off Lake Ontario...
followed by increasing amounts of sunshine during the afternoon.
Highs will continue to be about five to ten degrees cooler than
normal, struggling to get within a few degrees of 70.

Expect mainly clear skies Friday night as surface high pressure
builds into the eastern Great Lakes. Lows dropping into the low to
mid 40s across the interior sections and north country to the low
50s near the lakes.


High pressure will be anchored over the Northeast this weekend, with
a cool NW flow aloft providing for comfortable levels of humidity
and just fair weather afternoon cumulus. The upper level trough will
exit Monday...and we`ll be within a quasi-zonal flow aloft through
the remainder of the period with a upper level cut off low over the
midwest. We should hold onto our dry pattern through at least
Tuesday, if not Wednesday depending upon how quickly eastward this
upper level low advances.

The end of the month will finish with comfortable late summer
temperatures...near the average of mid 70s...and dewpoints will be
comfortable, generally in the upper 40s to lower 50s. Nights may
become cool, with mid 40s possible early in the period across
interior valleys.


With the last of the showers diminishing, VFR conditions should
prevail through much of the night, with clearing skies and light
winds allowing for the development of valley fog in the Southern
Tier, potentially affecting KJHW.

With a seasonably cool airmass moving overhead, and light NNW flow
off of Lake Ontario, it is possible that we will see some lake-
enhanced showers develop along the Lake Ontario shoreline late
tonight, with isolated to scattered showers developing farther
inland during the day on Thursday, as another shortwave drops south
across the Great Lakes. Outside of any showers, expect fairly
widespread SCT-BKN cigs to develop by 18Z, again courtesy of
lingering moisture and cool air aloft, however cigs should remain
VFR outside of any showers.

Outlook... Thursday Night...VFR. Area of IFR in valley fog in the
Southern Tier late.
Friday...A chance of morning showers southeast of the lakes...otherwise VFR.
Saturday through Monday...VFR.


High pressure building in from the Midwest has caused winds and
waves to diminish below advisory levels this evening, and the last
of the advisories have been dropped at this time. With high pressure
remaining in place through the weekend, expect tranquil conditions
on the lakes to persist for the next several days.





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