Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 181900

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

A few showers or isolated thunderstorms will be possible this
afternoon and early this evening well inland of the lakes ahead of a
cool front that will slide across the region tonight. This will
usher in slightly cooler and drier conditions for Saturday, 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.


The lake shadow is in full force downwind of the lakes this
afternoon, with fair skies across the Niagara Frontier and Jefferson
County. Cu fields are more well-defined well inland from the lakes,
and it is still possible that we may see a few pop-up showers late
in the day, provided the cap in place can be broken. Otherwise,
things will remain relatively quiet as we move into the evening
hours, with the gusty winds diminishing around sunset, as the low
levels decouple.

It should be a quiet night across the area as a cold front slides
across the region. In the wake of the front, weak ridging will keep
things dry, though plenty of shallow moisture will be lingering, as
evidenced by the widespread cloud cover upstream across Michigan,
and this means there will be clouds hanging around for a good
portion of the night. With dewpoints behind the front only falling
into the low 60s, look for lows in the low to mid 60s.

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.


Expansive high pressure over the Upper Mississippi Valley Wednesday
afternoon will gradually settle to the southeast across the Lower
Great Lakes and Ohio Valley by Thursday. This will allow for
significant improvement in our weather with fair weather
returning...along with a pronounced turn to cooler and more
comfortable (lower dew points) conditions. Temperatures by Thursday
will average at least 5 deg f below normal.


VFR conditions prevail this afternoon, with breezy SW winds gusting
25-30 kts downwind of the lakes, preserving clear skies across the
Niagara Frontier and at KART. VFR conditions will prevail this
evening, with diminishing chances for showers late in the day across
the western Finger Lakes. Otherwise, look for gradually lowering
cigs overnight as a cold front slides across the region and low-
level moisture to the west moves into the forecast area, with MVFR
cigs developing across some areas, with potential IFR cigs in the
Southern Tier.

An upper level disturbance crossing the region on Saturday will
bring a renewed chance for showers and thunderstorms, mainly inland
of the lakes. Otherwise, like today, cigs will improve through the
morning hours, with decks scattering out downwind of the lakes,
thanks to lake shadowing. Southwest winds should gust to around 15-
20kt in the afternoon, though not much higher as upper level flow
will be weaker than today.


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.


Brisk southwesterly flow will maintain small craft advisory
conditions on the east end of Lake Erie thorugh this evening, though
winds should relax overnight as a cold front crosses the area.
Southwest winds will freshen once again Saturday afternoon, however
they should fall shy of advisory levels, as supporting upper level
winds will not be as strong.

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 until 11 PM EDT this evening for
MARINE...Small Craft Advisory until 2 AM EDT Saturday for LEZ040-041.
         Small Craft Advisory until 11 PM EDT this evening for



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