Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 281853
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
253 PM EDT Wed Jun 28 2017

.SYNOPSIS...
High pressure will move off the mid-Atlantic coast tonight while a
low pressure system moves through the upper Great Lakes into
Ontario. A warm front will move across the region late tonight ahead
of the low, brining scattered light showers and even some rain for
the North Country. Scattered thunderstorms will develop late
Thursday, some could produce gusty to damaging winds. Unsettled,
warmer and humid weather will continue through the weekend before
high pressure builds in early next week bringing seasonable and
drier weather.

&&

.NEAR TERM /THROUGH THURSDAY/...
This afternoon, satellite imagery showing diurnal cumulus clouds
inland from the lake breezes off of the lower Great Lakes. Showers
will be suppressed under the ridging aloft as high pressure slides
off the mid-Atlantic coast through tonight. However, cannot rule out
an isolated shower in the Finger Lakes were a subtle wave can be
seen rippling through and agitating the cumulus field on visible
satellite imagery. Tonight, the cumulus field will subside with the
loss of daytime heating, however high, thin cirrus clouds will
spread across the region ahead of the next approaching low pressure
system. That low is currently located over Minnesota, and will track
through the upper Great Lakes and into Ontario overnight. A warm
front extending eastward ahead of the low will sneak northward
across the region overnight into early Thursday morning. Light
showers will develop along the frontal boundary, as dry air from the
exiting high pressure undercuts the showers.

By Thursday morning the frontal boundary will be in place across the
North Country, with locations south of Lake Ontario established into
the warm sector. A shortwave will ride along this boundary, helping
to force a more widespread area of rain for the North Country. This
will also organize an area of scattered showers with perhaps a few
rumbles of thunder that will move across locations south of Lake
Ontario during the morning hours. In the wake of this shortwave, we
should see perhaps some sunshine breaking through to help
destabilize the warmer, humid airmass advecting into the region.
Depending on how unstable this airmass can get, we should see some
thunderstorms develop off the combination lake breeze / pre-frontal
trough by late Thursday afternoon. The wind field will be fairly
fast and unidirectionally increasing with height in the warm sector.
This will support a marginal threat for severe weather, mainly in
the form of isolated damaging wind gusts.

However, this will be a scenario where Buffalo/Niagara Falls and
Watertown likely remain mostly dry if not sunny at times through
Thursday afternoon. This will be due to the robust, synoptically
aided southwesterly flow lake breeze that will develop. A core of
40+ knot winds will develop near 2kft, which will funnel up Lake
Erie. The warm advective pattern, with poor low-level lapse rates
across the Niagara Frontier will help keep all of that wind from
mixing down. However, can easily see gusts topping out around 35
knots, or 40 mph. Would not rule out a couple gusts around 45 mph,
especially at Niagara Falls, with the mainly 220 wind direction that
can tend to have an isentropic downslope effect off of the cooler
Lake Erie.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Thursday night will mark the beginning of a warm and humid period
with multiple opportunities for showers and thunderstorms lasting
through Saturday.  A warm front will already be north of the region
by Thursday night, while a weak cold front tries to move toward the
region. But while some weak troughs may move through Thursday night
or Friday, it`s looking less likely that the main boundary will make
much headway into WNY.  This appears to be due to the fact that the
slow moving upper level flow will spawn either a few surface lows
moving NE into the upper Great Lakes region or result in just one
low generally S of James Bay with a persistent trailing NE-SW trough
co-located with an upper level jet stuck over an area between about
Missouri to Quebec.  As a result, the region will end up in the warm
sector for the majority of the time until the cold front finally
wafts through late Saturday or Saturday eve.

The result will be low confidence on timing precipitation events
from Thursday Night through Saturday.   That said, it`s safe to say
that mesoscale boundaries will play some role in focusing
convection, with a high chance for ongoing convection inland of WNY
into the Eastern Lake Ontario region Thursday evening, with a lower
threat in lake shadowed regions along the lakeshores.  As lake
boundaries lose their influence, upstream convection may be able to
move across the lakes later Thursday night and Friday AM.  A repeat
idea is plausible on Friday, with lake breeze/convergent boundaries
driving higher convective chances toward Friday afternoon and
evening.

Finally on Saturday, the upstream frontal boundary should start
making some headway and either move through during the afternoon or
evening hours Saturday evening.  This will result another chance for
afternoon convection, particularly on lake breezes.

With warm and humid air in place for this period, expect
temperatures climb toward the low 80s in most spots but with
humidity levels being a little uncomfortable at times.  The sultry
night may be Friday Night through Saturday with dewpoints in the
upper 60s and/or near 70.

In terms of severe weather, there doesn`t appear to be too much of a
signal for widespread severe.  With the warm and moist airmass,
large hail is unlikely.  There might be a wind threat on Friday
inland along and east of lake breeze with higher shear, but this may
be isolated.  Possibly a slightly greater threat may be heavy rain,
particularly in the eve/overnight hours Friday night and/or Sat with
a stronger low level jet near about 30kts together with high PW
between about 1.75-2.00".

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
Saturday night and Sunday...this time period should mark the end of
an active pattern with high pressure slowly moving in with drying in
at least the mid levels. Humidity levels on Sunday will not be as
great as the last few days of June/beginning of July. The main
threat for additional showers will be on Sunday afternoon along lake
breeze convergent regions.

Sunday night and Monday...this period should be dry with weak high
pressure moving toward the region from the upper midwest. Dry
weather area-wide isn`t a guarantee this far out, but if the timing
of the current pattern holds, the natural progression should be
subsidence behind the Sunday system, with the exception of isolated
summer convection on lake breeze convergent regions by Monday
afternoon.

Monday night and Tuesday...High pressure generally over head should
negate any threat for convection.  The 12Z GFS is more optimistic
precipitation from the WV/VA Appalachians into PA while the EC is
dry with a slightly stronger ridge over Ontario extending S into NY.
Will lean on the dry side for now as the GFS has had some model
variability further upstream over the midwest when compared to a
more consistent pattern noted in successive EC runs.

Daily temperatures won`t stray too far off normals for this time of
year, with highs in the mid 70s to near 80 and lows mostly in the
60s, with a slight cooling trend into early next week.  Humidity
levels will vary, with some nights possibly warranting A/C while in
the warm sector, but at this time don`t see any extreme sultry days
or nights for weekend/early next week.  The warmest and most humid
period will be early/during Saturday while in the warm sector.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
Diurnal cumulus field around 5-7kft inland from the lake breeze this
afternoon will dissipate after sunset. Meanwhile mid and high level
clouds will increase from west to east overnight ahead of the next
approaching weather system. A warm front will move northward across
the region Thursday morning sparking some scattered rain showers
from a mid-level cloud deck, with more steady rain developing over
the North Country. VFR conditions will prevail trough tonight and
into Thursday morning.

Outlook... Thursday night through Sunday...VFR/MVFR with scattered
to occasionally more numerous showers and thunderstorms.
Monday... Mainly VFR.

&&

.MARINE...
High pressure building across the Lower Great Lakes will result in
winds and waves remaining below advisory levels through this evening.

As the next frontal system works its way into our region later on
tonight and Thursday...winds will then once again freshen out of the
south and southwest...potentially bringing advisory-worthy conditions
to both Lake Erie and the Upper Niagara River/Buffalo Harbor.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...CHURCH
NEAR TERM...CHURCH
SHORT TERM...ZAFF
LONG TERM...THOMAS/ZAFF
AVIATION...CHURCH
MARINE...CHURCH



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