Area Forecast Discussion
Issued by NWS Buffalo, NY

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257
FXUS61 KBUF 282321
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
721 PM EDT THU JUL 28 2016

.SYNOPSIS...
A weak cold front will slide southward across New York State
tonight with warm and humid conditions, then a wave of low
pressure will move south of the region Friday, bringing chances
for scattered showers and thunderstorms to the Southern Tier. Weak
high pressure on Saturday should limit shower activity to near the
Pennsylvania state line. The chances for scattered showers and
thunderstorms increase again Saturday night through Sunday night.

&&

.NEAR TERM /THROUGH FRIDAY/...
A weak cold front will continue to move southward across New York
State tonight, which may support just a few evening showers or a
thunderstorm. Most convection will be limited to the Southern
Tier, but there may also be a slightly lesser chance across the
Saint Lawrence Valley and North Country, closer to the 100kt+
250mb jet aloft. There will be little airmass change overnight as
mild and humid conditions will persist, overnight low temperatures
in the lower to mid 60s inland and over higher terrain and to the
upper 60s or low 70s near the Great Lakes and within urbanized
areas.

Northerly winds set up on Friday which should bring slight cooler
and less humid air to the region. A wave of low pressure passing
eastward across Pennsylvania, on its way to becoming a coastal low
off the Mid-Atlantic states. It will bring an enhanced chance of
showers and thunderstorms to the Southern Tier on Friday, but the
rest of the forecast area should remain free of any precipitation.
High temperatures will be in the upper 70s to lower 80s, which
should feel more comfortable than it has been for the past many
days.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
A broad midlevel trough and embedded vorticity maxima is forecast to
cross from the Midwest and Great Lakes to the Mid-Atlantic and New
England regions through the weekend. This trough will trigger a
surface low somewhere from the Ohio/Tennessee River Valleys shifting
east to the Mid-Atlantic region. Sufficient synoptic moisture will
be in place ahead of the trough and low to drive some showers and
possible thunderstorms mainly south of our forecast area on Saturday
then shifting north and east across our region on Sunday.

Large differences remain between the relatively dry 12z GFS and more
moist 12z ECMWF which leave a lower than normal confidence in a
forecast at this short range. While most of Friday night should be
dry, have introduced chance POPs across the Southern Tier later
Friday night. POPs have been increased some on Saturday while edging
them a little further north to hedge at least partially toward the
wetter EC model but still preserving a majority of continuity.

Higher confidence is found on Sunday where a sharper embedded
shortwave trough and higher level of instability looks to drive a
more widespread area of showers and thunderstorms. The highest POPs
over the weekend timeframe will be in place on Sunday. By Sunday
night the trough axis will shift east of the forecast area with POPs
tapering off as high pressure and mid-level ridging arrive from the
west. Temperatures over the weekend will be cooler than recent days
but still averaging a touch above mid-summer normals. Easterly winds
should prevent cooler temperatures from occuring on the eastern
shores of Lake Erie due to some downsloping.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
During this period...surface-based ridging initially draped across
the Central Great Lakes will gradually push eastward and crest
across our region Tuesday and Tuesday night...before drifting off
the Atlantic coastline Wednesday and Thursday. Meanwhile aloft...
initial low-amplitude troughing will give way to a building upper
level ridge by the end of the period.

After a lingering chance of showers across southern and eastern
sections during the first half of Monday...the above evolutions in
the large-scale pattern will support a return to dry weather for
the remainder of the period...along with a steady day to day warming
trend thanks to a developing warm air advection regime and increasing
large-scale subsidence. While the exact degree of warming we can
expect still remains a bit unclear given continued differences in the
medium range guidance...a general consensus approach would suggest
daytime highs climbing from the lower half of the 80s on Monday to
the mid 80s to lower 90s by Thursday...with nighttime lows also
warming back into the mid 60s to lower 70s by the end of the period.
Accompanying the building heat will also be a return of more humid
conditions...with dewpoints climbing from around 60 on Monday to
the mid 60s by Thursday.

&&

.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
Expect mainly VFR conditions tonight and Friday. A front will
gradually drop south across the area, and this may result in
scattered showers and possibly a thunderstorm this evening.
Coverage will be very spotty, and largely avoiding TAF sites.

The front will be south of the region on Friday and as a wave of
low pressure passes the area to the south, there may be scattered
showers and thunderstorms across the Southern Tier but it should
be far enough to the east to avoid KJHW.

Outlook...

Friday night through Sunday...VFR/MVFR with a chance of showers and
thunderstorms.
Monday and Tuesday...VFR.

&&

.MARINE...
A wave of low pressure will track from central Pennsylania to east
central New York State tonight supporting a freshening northeasterly
wind, especially on eastern Lake Ontario where wind speeds may
approach small craft criteria toward Friday morning. This will bear
watching in later forecasts.

High pressure will build in across the lower Great Lakes later
Friday and into Saturday resulting in diminishing winds and waves.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...TMA/WCH
NEAR TERM...TMA/WCH
SHORT TERM...SMITH
LONG TERM...JJR
AVIATION...TMA/WCH
MARINE...CHURCH/TMA/WCH



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