Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 190542

Area Forecast Discussion
National Weather Service Buffalo NY
142 AM EDT Sat Aug 19 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. Elsewhere, a few
sprinkles will be found across Western NY as a weak mid level
shortwave crosses the region. 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.


A mid level trough will cross the region overnight into Saturday
morning with increased cloud cover and a few scattered showers,
especially east of the lakes with some modest lake enhancement. VSBY
will be mainly VFR, although any heavier lake enhanced showers east
of the lakes may contain brief/local MVFR. Low level moisture will
increase overnight into early Saturday, allowing MVFR CIGS to
develop across higher terrain.

On Saturday a mid level trough will cross the region and produce a
few widely scattered showers, especially across the western Southern
Tier. The MVFR CIGS across higher terrain will improve to VFR by
early afternoon.


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.


Moderate west to southwest winds will increase again on Saturday
with Small Craft Advisory conditions developing on both lakes.

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.


NY...Beach Hazards Statement from 6 AM EDT this morning through
     this evening for NYZ006-007-010-019-085.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ020-
         Small Craft Advisory from 8 AM this morning to 8 PM
         EDT this evening for LOZ042.
         Small Craft Advisory until 5 AM EDT Sunday for LOZ044-045.



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