Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 291504

Area Forecast Discussion
National Weather Service Buffalo NY
1104 AM EDT MON AUG 29 2016

Surface high pressure will move across the Eastern Great Lakes
region with less humid conditions and cooler temperatures today and
Tuesday. A cold front approaches the Lower Great Lakes Wednesday
with a chance of showers and thunderstorms.


Current surface analysis depicts a surface trough dropping south
across Lake Ontario late this morning. Ahead of this feature,
visible satellite shows low level cloudiness along Lake Ontario and
the Genesee Valley slowly expanding westward across the Niagara
Frontier within a cool (850 hPa around +11-12c) and moist northerly
flow. Behind this surface trough, dewpoints are dropping into the
upper 50s upstream across Ontario Canada and it is this drier air
mass that will advect south into the lower lakes this afternoon.
However, this lagging of the drier air mass is allowing for lake
enhanced and upslope clouds to form over the region this morning.
For the rest of this morning, expect this low level cloudiness to
continue across the Niagara Frontier, Genesee Valley and northern
Finger Lakes region. Later on today, as drier air behind the surface
trough advects across the lower lakes this low level cloud deck
should erode through the afternoon hours such that much of the
region should become mostly sunny. Highs today will run several
degrees cooler with afternoon temperatures peaking in the upper 70s
to low 80s with comfortable humidity levels.

Tonight, surface high pressure will near the Eastern Great Lakes
region with clear skies and light winds. With a fresh cool airmass
overhead we should drop back into the 50s overnight, with a few
upper 40s over the traditionally colder spots of the Southern Tier
and east of Lake Ontario. A few areas on the lake plain and closer
to the warm lakes may remain near 60 overnight. We should also have
some valley fog form in the southern Tier and Genesee Valley.


This period will start out quiet as a low level ridge axis remains
anchored across the Great Lakes/Northeast. Mostly sunny conditions
expected on Tuesday as 850 mb temperatures increase to around +16C
supporting high temperatures into the lower to mid 80s, but with a
dry airmass in place these readings should be fairly comfortable.

The next feature of interest will be a southern Canadian trough
progressing through mean upper ridge across south central Canada.
This will eventually allow cold frontal boundary to drop across the
lower Great Lakes late Tuesday night into Wednesday. Blocking
anticyclone will contribute to some moisture availability question
with little opportunity for significant moisture transport into the
area in advance of the front. Frontogenetic flow should result in
some pooled moisture along and just in advance of this boundary that
should support scattered shower/storms during the day Wednesday.
Severe weather potential looks on the low side as shear profiles
should remain marginal and more robust shear profiles well to the
north across Upper Great Lakes/southern Ontario. A brief shot of
much cooler air appears to be in store behind this front with highs
Thursday only in the upper 60s to lower 70s.


While the start of this period will feature cool comfortable will be more noteworthy to point out the significant
day to day warming trend that will carry us into next week. The
ultimate factor leading to the return to above normal temperatures
will be the development of a strong jet across the Northern Pacific.
This jet will kick out persistent troughiness that will be in place
over British Columbia...a trough that we have not seen in a couple
months and at least partly responsible for the spell of cool
weather at the onset of this period.

In any case...the +120kt H25 jet will help to deamplify and broaden
the west coast trough...which in turn will lead to substantial
height rises downstream across the eastern half of the country.
Meanwhile...expansive high pressure will guarantee rain free weather
through the period. The details...

On Friday...a progressive upper-level trough with high-latitude
Canadian sourced air will pivot across New England. A dry...shallow
cool airmass will build across the region in its wake while a
sprawling surface high will move from the upper Great Lakes Friday
morning to over the forecast area Friday night into Saturday
morning. Despite 850 mb temperatures returning to around +10C Friday
afternoon...the shallow cool airmass will keep a low-level inversion
in place and thus high temperatures will remain in the upper 60s to
low 70s. We will see much more sunshine however on Friday as much
drier air builds in a lowering inversion heights will cancel out the
lake effect cloudiness from the prior day. Low temperatures will be
quite cool Friday morning and Saturday morning...however Saturday
morning looks the coolest as the surface high settles overhead and
allow for optimal radiational cooling. This will result in upper 40s
to lower 50s...with interior valleys and rural locations seeing some
low to mid 40s on Saturday morning.

Temperatures will then recover Saturday into Sunday as the sprawling
high pressure system slides off the New England coast and allows the
airmass to moderate with 850s back into the mid teens C. This will
bring temperatures back into the upper 70s Saturday and low 80s
Sunday and possibly mid 80s by Labor Day. With high pressure
remaining in control this should remain a dry period with fair

Looking  further down the road at the start of next week...strong
ridging over the eastern third of the country will encourage our H85
temps to return to at least the mid teens C. This will guarantee
that above normal temps will be in place across the Lower Great
Lakes. The only real uncertainty for this time period will be the
placement of any tropical systems along the East Coast.


Current surface analysis shows a surface trough dropping south
across Lake Ontario this morning. Ahead of this feature, low level
cloudiness along Lake Ontario and the Genesee Valley is slowly
expanding westward into KIAG/KBUF. This low level cloudiness will
impact these two locations for a brief period with a mixture of
VFR/MVFR CIGS between 14-16Z. After 16Z, with surface high pressure
and a drier air mass moving into the region expect this low level
cloudiness to diminish in coverage by early this afternoon.

Otherwise, with northerly upslope flow and some residual low level
moisture present expect cloud cover to be present across the high
terrain of the Southern Tier and Tug hill for this afternoon.
Despite the low level clouds, VFR conditions will largely dominate
this period for all TAF sites after 16Z as surface high pressure
continues to move into Western and North Central New York.

Tonight, under generally clear skies with excellent radiational
cooling, high confidence that valley fog will likely develop across
the Southern Tier.  This will produce lowering flight conditions
most likely at KJHW.

Tuesday night and Wednesday...Mainly VFR with a chance of showers
and thunderstorms.
Thursday and Friday...VFR.


Behind a cold front, an area of high pressure will drop across
the Eastern Great Lakes region today and tomorrow. This feature will
produce waves under 2 feet on the lakes and light winds.

A cold front will cross the lakes Wednesday and Wednesday night and
this will kick up the winds and waves a bit Wednesday night and into
Thursday on the lakes...though conditions may remain just below
small craft criteria.





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