Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 190222

Area Forecast Discussion
National Weather Service Buffalo NY
1022 PM EDT Fri Aug 18 2017

Cooler air will flow across the region tonight, with a few showers
possible late tonight east of Lake Ontario. Saturday will
feature a mainly dry day though another passing upper level
disturbance will bring a chance for more showers and
thunderstorms, again mainly inland from the lakes. High pressure
will bring fair weather Sunday and Monday before another low
pressure system brings showers and thunderstorms on Tuesday.


For tonight and behind a cold front, cooler air is flowing
across the region, with 850 hPa temperatures dropping to around
10 to 12C over Lake Ontario. These temperatures combined with
weak surface troughing may generate a few lake enhanced rain
showers late tonight and into the early daylight hours of
Saturday. It does not get as cool over lake Erie, though a stray
sprinkle or shower cannot be ruled out here. Otherwise the
night should be fairly dry behind the cold front. Since the air
is still has a touch of a muggy feel, our overnight lows will
remain in the low to mid 60s...with some areas of fog possible
across the So. Tier.

Saturday will look similar to today, albeit with more cloud cover
hanging around, as a robust upper level trough crosses the lower
Great Lakes. While areas northeast of the lakes should once again
remain lake shadowed, the synoptic lift from the trough should
encourage the formation of scattered showers and thunderstorms
inland from lake breeze boundaries Saturday afternoon. Any
convection should move rapidly off to the east late in the day,
carried by the brisk westerly upper level flow. Temperatures will be
a little more mild, as nominally cooler/drier air will be in place
across the region, with highs generally in the mid to upper 70s.


On Saturday evening model consensus placed the axis of a 500 mb
trough across Western New York, with trough exiting into New England
Saturday night. Meanwhile, a cold front will drop southward across
the area. The combination of the shortwave and front will result in
a few showers, which may also be enhanced modestly by lake
moisture/instability and upsloping. Scattered showers south and east
of the lakes Saturday evening will shift to the Eastern Lake Ontario
region late Saturday night before ending by daybreak Sunday.
Otherwise, lows Saturday night will be in the mid 50s to around 60.
The coolest temperatures will be across the Southern Tier valleys
where patchy river valley fog can be expected.

A broad surface high will build in across the upper Ohio Valley
Sunday and then gradually move to the mid-Atlantic region through
Tuesday. This will bring an extended period of dry weather, with a
gradual warming trend through mid-week. Highs Sunday will be
seasonable, topping out in the upper 70s to lower 80s, then warming
well into the 80s in nearly all locations by Tuesday. High pressure
will also provide mainly clear skies Sunday into Monday, which
should provide favorable conditions for viewing the eclipse on

A strong shortwave is forecast to dive into the Great Lakes region
with low pressure forecast to strengthen as it tracks from Eastern
Michigan to Southern Quebec Tuesday. Model guidance is in fairly
good agreement, with a brisk southwesterly flow likely to result in
lake shadows which will keep much of the daytime hours dry. A strong
associated cold front will approach late Tuesday afternoon and move
across the region Tuesday night. A significant line of showers and
thunderstorms will develop ahead of this front and move across the
area Tuesday night. Although a ways off, there is a risk of strong
to severe thunderstorms with strong wind profiles supportive of
damaging wind gusts. Severe weather potential is still uncertain,
and may change based on the timing of the front.


Less humid conditions are expected work into the region in wake of
Tuesday nights cold front, as high pressure builds down from
southern central Canada into the Great Lakes region. Although
conditions will trend drier during the period it will be
noticeable cooler with temperatures averaging some 5 to 10
degrees cooler than normal, with high temperatures both Thursday
and Friday in the 60s to lower 70s.


MVFR/VFR flight conditions will be prevalent this TAF cycle, except
for across the So. Tier where some late night fog with IFR flight
conditions will be possible, and east of Lake Ontario where some
IFR/MVFR flight conditions will be possible in the early morning
hours of Saturday.

For the fog, the air will remain a bit moist still tonight as
dewpoints will remain moderately high...and as we cool tonight some
river valley fog and general area fog will be possible across the
So. Tier. This will include the KJHW terminal. Visibilities within
the fog will be IFR or lower.

East of Lake Ontario cooler air flowing over Lake Ontario on a
westerly wind may generate a few lake enhanced clouds...with a
passing shower also possible. Clouds are expected to have a deck in
the low MVFR range...including across the KART airfield. Some patchy
IFR flight conditions cannot be ruled out...especially over the
higher terrain of the Tug Hill.

Elsewhere it should remain quiet tonight with VFR and MVFR ceilings.
Tomorrow through the afternoon hours additional showers and
thunderstorms are likely to form, mainly inland and along lake
breezes. Greatest threat at this time appears to be the Southern
Tier where a TSRA mention will be in the TAFs.


Saturday Night...VFR
Sunday and Monday...VFR except for late night and early morning
valley fog with local IFR.
Tuesday...Mainly VFR, with a chance of showers and thunderstorms
late in the day.
Tuesday Night...MVFR/IFR, with showers likely and a chance of
Wednesday...Mainly VFR, with a chance of showers.


Have dropped the small craft advisory for the Niagara River as
winds have come down this late evening. Waves are still 5 foot
on the eastern end of Lake Erie, and the SCA here will
continue...though diminishing winds should bring lower wave
heights over the next few hours.

High pressure will move across the lakes Saturday night into
Sunday, resulting in more favorable boating conditions for the
second half of the weekend into Monday. Southwesterly winds will
freshen once more Tuesday night, ahead of another approaching
low pressure system.


MARINE...Small Craft Advisory until 2 AM EDT Saturday for LEZ040-041.



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