Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 270608

Area Forecast Discussion
National Weather Service Buffalo NY
208 AM EDT WED JUL 27 2016

High pressure will track across the Eastern Great Lakes this
morning. Dry weather will persist until a weak cold front drops
southward from Canada tonight bringing a few stray showers and
thunderstorms to the North Country tonight and Thursday. Chances of
showers and thunderstorms will continue into the weekend as a broad
trough temporarily digs into the Great Lakes and Northeast States.


High pressure is ridged across the eastern Great Lakes and Northeast
States early this morning. This will continue to provide fair
weather with infrared satellite imagery showing clear skies. The
clear skies and light winds will allow temperatures to fall into the
mid 50s to lower 60s across the Southern Tier and eastern Lake
Ontario regions, and to the lower 60s elsewhere. There is likely
some river valley fog forming across the Southern Tier as KJHW
briefly reported 1 1/4SM visibility at 06z.

Skies will start nearly clear after sunrise but a weakening cold
front moving southward across Ontario will bring increasing high and
some mid clouds to the region during the afternoon. There will be a
low chance to slight chance of convection north of Lake Ontario and
east across the Saint Lawrence valley along the leading edge of the
slow moving cold front, mainly late afternoon. High temperatures
will be in the mid to upper 80s in most areas, with around 90
degrees across the interior valleys.


The weather will become increasingly unsettled across the region
during this a low amplitude trough over the Great Lakes
will eventually support the development of at least one sfc wave
over the Ohio Valley and Mid Atlantic states. While this scenario
will lead to some showers and thunderstorms...especially over the
Southern Tier...significant rains are not expected. The details...

A weak cool front will sag south across our forecast area late
Wednesday night and Thursday. Since there will be little if any
synoptic forcing from this feature...any showers or thunderstorms
will have to be generated from diurnally induced instability during
the day Thursday. For the overwhelming majority of the forecast area
though...this 24 hour period should be rain free.

Mid level energy currently over the Mississippi Delta will drift
north and eventually get picked up by the westerlies Thursday which time it will develop a wave along a stalled frontal
boundary over the Ohio Valley. This will be part of the same front
that limped through our region earlier in the period. In any
case...the wave is expected to push east along the boundary...moving
well south of our forecast area. While the bulk of the associated
showers from this wave will be found over Pennsylvania...forcing
from the sfc wave could produce a few showers over the Southern Tier
and Finger Lakes regions.

On Friday...the wave over Pennsylvania will gradually push off the
New Jersey coast. While this will keep the bulk of the associated
showers and thunderstorms south of the border...there will be the
opportunity for scattered showers and thunderstorms over our region.
Any such pcpn will remain focused on the Southern Tier and southern
portions of the Finger Lakes.

The synoptic forcing will exit our region Friday there
will be a diminishing chance for any pcpn over our forecast area
with the bulk of the night being damp but rainfree.


The medium range guidance packages remain somewhat out of sync
during this period...only coming together in their solutions as we
come out of the weekend. This will result in relatively low
confidence in the forecast for the weekend...which could be rather
unsettled for parts of the area.

The disagreement between the medium range ensembles comes down to
the position of a wavy frontal boundary over the Mid Atlantic Region.
Initially...this will continue to serve as a pathway for individual
waves to cross from the Ohio Valley. The northern fringes of these
features will enhance the opportunity for showers and thunderstorms
over the Southern Tier...while areas further north will be more
influenced from high pressure centered over eastern Canada.

As we exit the weekend...the Canadian sfc high will become more
dominant..moving further to the south over the Lower Great Lakes.
This will encourage fair weather to return to all of the forecast
area while temperatures will average just a few degrees above normal
late July normals.


VFR conditions will persist through today as high pressure remains
in control. There is likely some river valley fog forming across the
Southern Tier as KJHW briefly reported IFR VIS at 06z. This may
result in a few hours of variable visibility at JHW. Otherwise there
will be an increasing high cloud cover later today as a weak cold
frontal boundary drifts south over the Lake Ontario basin and St.
Lawrence River valley.


Thursday...Mainly VFR with a chance of showers and thunderstorms.
Friday through Sunday...VFR/MVFR with a chance of showers and


High pressure will remain across the Eastern Great Lakes through
today with a weak cold front pressing south across Lake Ontario
tonight. This will then be followed by another high pressure area
late in the week. Winds and waves are expected to remain below small
craft criteria into the beginning of the weekend.





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