Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 260226

Area Forecast Discussion
National Weather Service Buffalo NY
1026 PM EDT MON JUL 25 2016

Skies will clear overnight following the passage of a weak cold
front. This front will usher in another period of fair and slightly
less humid weather that will persist through midweek. Another, much
weaker cold front will slide south out of Canada Wednesday night
into Thursday, bringing a slight chance of showers and
thunderstorms, but nothing that is expected to put a dent in the
current drought conditions.


The last of the isolated convection is moving into the Syracuse area
and away from our region, with the majority of the CWA seeing
clearing skies late this evening. The clear skies will continue for
most areas overnight, with some modest increase in cloud cover
possible again late tonight across the North Country as an area of
deeper moisture drops south out of Ontario.

Steady albeit weak cold advection behind the front will eventually
allow for somewhat cooler air to work into the area overnight, with
lows in the mid 60s on the lake plains and lower 60s in the Southern
Tier valleys and Lewis County. Radiational cooling combined with the
rain from earlier today may allow for some river valley fog across
the Southern Tier overnight and early Tuesday morning. For the rest
of the area, enough gradient wind should continue overnight to
prevent fog formation.

The upper level trough will complete its transition across the
forecast area overnight and will be replaced by low-amplitude upper
level ridging and surface high pressure across the Lower Great
Lakes. This should yield plenty of sunshine across most of the area
Tuesday with just some modest diurnal cumulus development along and
inland from the lake breeze boundaries. East of Lake Ontario cumulus
may become a little more widespread with model guidance suggesting a
more robust layer of moisture near 850mb. Highs will be in the low
to mid 80s, with 70s along the lakeshores from local onshore flow.
Slightly lower dewpoints in the upper 50s to lower 60s advecting in
behind the front will make it feel nominally more comfortable


There should not be much weather to contend with during this a low amplitude flow will be found along the length of
the Canadian border. While troughiness will characterize this
pattern over the Great Lakes region...a lack of baroclinicity and
low level forcing will mean that generally fair weather can be
anticipated. This despite the passage of a weak cold frontal
boundary. The day to day details...

High pressure centered over the Mid West will remain in control
across our forecast area Tuesday night. While light winds and clear
skies will encourage decent radiational cooling...we have not had a
fresh airmass change in a few the mercury is only forecast
to drop into the mid 60s across the lake plains while 50s will be
found across much of the Srn Tier.

A cold frontal boundary over the Upper Great Lakes will then slowly
push south across Southern Ontario during the day Wednesday...while
high pressure over the Mid West will gradually lose control of our
weather in the process. Nevertheless...fair weather will persist
across the region with H85 temps in the upper teens C supporting
afternoon readings in the upper 80s to near 90 for the lake plains
and in the valleys.

We can anticipate a weak frontal passage Wednesday night...but with
little forcing...will only raise pops to slgt chc while increasing
cloud cover. Temperatures overnight will be a few degrees higher
than the night before...but with dew points holding steady near should not be overly uncomfortable.

The frontal boundary will stall and wash out over Pennsylvania on
Thursday...while a ribbon of moisture in its wake will settle over
our forecast area. The bulk...if not all...of the day will be rain
free...but the passage of a shortwave in the northwest flow will be
enough to warrant low chc pops for the afternoon and evening. Since
a northeast low level flow will be in place in the wake of the
front with little instability...will only use a slgt chc for tstorms.

The various guidance packages remain out of step with each other as
we push into Thursday there is a `disagreement` as to
whether a wave will form along the west end of the aforementioned
frontal boundary. Will keep low chc pops in place for all but the
North Country. While there will be low confidence with these pops...
there is more certainty that clouds will remain in place...
especially over the western counties.


This period has the potential to be rather unsettled...or at least
more disorderly than what we have become accustomed to the past
couple months. The good news is that this would lead to some needed
rainfall for the region...but the bad news is that it would
adversely impact some peoples plans for the weekend.

Troughiness found over the Great Lakes region is forecast by some of
the ECMWF/GFS based ensembles to amplify somewhat...and this would
encourage waviness along a stalled frontal boundary over the Mid
West to evolve into an actual sfc low. Will use a compromise of the
HPC and ECMWF solutions...which favors such a sfc low development.
This feature is forecast to slowly track northeast across the Lower
Great Lakes during the course of the weekend while generating
scattered showers and possible thunderstorms in the process. Given
the low confidence of this forecast...will keep chc pops in place.


Overnight expect VFR in most areas, with some patchy valley fog in
the Southern Tier producing local IFR. It appears that enough wind
will remain just off the deck overnight to prevent fog from forming
at KJHW. Any valley fog will burn off early Tuesday morning. VFR
will then prevail across the entire region with some diurnal cumulus
developing by midday along and inland from the lake breeze
boundaries, especially east of Lake Ontario where somewhat deeper
moisture will be found.


Tuesday Night and Wednesday...Mainly VFR.
Thursday...Mainly VFR with a chance of showers and thunderstorms.
Friday and Saturday...VFR/MVFR with a chance of showers and


Winds will continue to diminish overnight on Lake Erie with waves
subsiding. Westerly flow to around 15 knots will persist on Lake
Ontario and generate moderate chop on the eastern half of the lake
later tonight and Tuesday, though conditions should remain just
below small craft advisory levels. After that, high pressure will
build across the Lower Great Lakes, with winds and waves remaining
generally tranquil through the remainder of the week.





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