Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 270223

Area Forecast Discussion
National Weather Service Buffalo NY
1023 PM EDT TUE JUL 26 2016

High pressure will track across the Eastern Great Lakes tonight. Dry
weather will persist until a weak cold front drops southward from
Canada on Wednesday night bringing a few stray showers and
thunderstorms to the North Country Wednesday night and Thursday.


High pressure across the eastern Great Lakes will result in fair
weather and clear skies overnight. This will allow temperatures
to mid 50s to lower 60s across the Southern Tier and eastern Lake
Ontario regions, and to the lower 60s elsewhere. There may be some
river valley fog forming across the Southern Tier.

Skies will start nearly clear on Wednesday 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 across the Saint Lawrence
valley along the leading edge of the front, mainly late Wednesday
afternoon. High temperatures will be 3-5 degrees warmer than
today with highs 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 generally persist through this TAF period as
high pressure remains in control through tonight and Wednesday.
There may be valley fog across the Southern Tier. This may result
in a few hours of variable visibility at JHW, but confidence is
low so its TAF will only carry a few hours of MVFR conditions.
Otherwise there will be an increase in cloud cover on Wednesday as
a weak cold frontal boundary drift south over the Lake Ontario
basin and St. Lawrence River valley, then dissipates Wednesday


Wednesday night...Mainly VFR.
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
Wednesday, followed by another high 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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