Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 151844

Area Forecast Discussion
National Weather Service Buffalo NY
244 PM EDT Tue Aug 15 2017

High pressure over the Upper Great Lakes this evening will gradually
build across our forecast area during the upcoming 36 hours. This
will guarantee a scintillating day across our region on Wednesday
before more unsettled weather arrives late Thursday into Friday.


Scattered showers and thunderstorms will be found across parts of
our region late this afternoon into the early evening a
robust shortwave passing by to our north will push a weak cool front
through the region. Some of the convection could be rather strong...
as 40 to 45 knots of shear will be found within a very unstable
(1000-1500 j/kg MLCAPE) environment. The greatest threat from the
convection will be localized torrential downpours...wind gusts to 40
mph and pea sized hail.

This activity will diminish during the early evening hours...with
all of the showers and storms forecast to end by the time it gets
dark. The overnight hours will then feature gradually clearing
skies...although some fog will be likely in the Southern Tier
valleys and in areas that picked up significant rains from the
afternoon convection. Since most of the forecast area (exception
North Country) will not experience an airmass change in the wake of
the front...temperatures tonight are expected to drop to within a
few degrees of 60.

On Wednesday...a large area of high pressure will supply us with an
absolutely beautiful late summer day. We can look forward to
bountiful sunshine and light winds with temperatures generally
climbing into the mid and upper 70s.


Surface high pressure will be overhead Wednesday night with clear or
mostly clear conditions, at least through the evening.  Toward
Thursday morning, some cirrus should be moving in with slowly
increasing clouds as the next system starts to move into the
Northern Great Lakes.

Thursday and Thursday night...the next feature of interest is
readily visible via satellite, with a clearly defined upper level
trough over the Western US.  As this feature moves off the
intermountain region and into the Central Plains, it will draw
moisture northward from the Gulf of Mexico...primed to move into
Western NY either late Thursday or Thursday night.  Will forecast a
categorical rain showers/chance of thunderstorms for Thursday night
for all but the Eastern Lake Ontario region.  Model QPF seems a
little on the low side considering high moisture content
(precipitable water near 2.0"), so will lean toward the higher side
with basin averages probably near/above 0.5" with of course higher
amounts in heavier showers.

A cold front sweeps across western New York Friday. This will
maintain chances for scattered showers and possible thunderstorms,
especially east of Lake Ontario.

While a mid level cyclonic flow will be in place across the Great
Lakes, weak surface ridging in the wake of the front will combine
with a dry slot to provide a mainly dry Friday night.


This should generally be a dry forecast period...especially from
the second half of the weekend into the start of the new work week.

On Saturday...the medium range guidance packages are in disagreement
with the placement of the next longwave trough. Will lean more
towards the ECMWF...which suggests that the base of a trough passes
across the Lower Great Lakes while pushing a frontal boundary over
the region. Will carry low chc pops for this low confidence forecast
while holding afternoon temperatures in the mid 70s for most areas.

Much better agreement is then found between the various packages for
Sunday and Monday. A large sfc high is forecast to build across the
Lower Great Lakes. This would provide us with fair weather...and
nearly ideal sky conditions for viewing of the solar eclipse here in
western New York. Stay tuned.


While VFR conditions will be in place across the region this
afternoon...there will be an increasing amount of showers and
thunderstorms. Any of the thunderstorms could briefly limit cigs and
vsbys to MVFR levels.

In the wake of a passing cold front and its associated convection
this evening...widespread VFR conditions will be in place across the
region. The exception will be across parts of the Southern Tier
where IFR conditions in fog and stratus will be likely after 08z.

High pressure moving over the area on Wednesday will produce
tranquil VFR conditions.

Thursday...VFR deteriorating to MVFR as showers and thunderstorms
increase later in the day and at night.
Friday...Mainly VFR with a chance of showers and thunderstorms.
Saturday night and Sunday...VFR with a chance of showers.


While generally light winds and negligible waves will be found
across the Lower Great Lakes this evening...winds will freshen late
tonight and early Wednesday in advance of a large surface high.
Winds will also veer to the choppy conditions can be
expected in the nearshore waters west of Irondequoit Bay Wednesday
morning. During the afternoon as the large surface high builds over
the lake...winds and waves will subside.

Conditions will deteriorate over the Lower Great Lakes late Thursday
and Thursday night as a series of frontal boundaries will cross the
region. While winds and waves will remain below small craft advisory
levels during this period...there will be a heightened risk for
special marine warnings from an increasing coverage of





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