Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241417
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1017 AM EDT SUN JUL 24 2016

.SYNOPSIS...
An upper level trough will slowly cross the region tonight into
Monday which will produce a few scattered showers and thunderstorms.
A trailing cold front will pass through our region Monday
evening...followed by slightly cooler and less humid weather Tuesday
before temperatures and humidity trend upward again Wednesday and
Thursday. A weak area of low pressure will cross the region Friday
and Saturday bringing the next chance of showers and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
An upper level ridge axis will drift east across the area through
midday and then flatten this afternoon with the approach of an
upstream shortwave. Despite the upper level ridging, an expansive
area of dense mid level clouds from upstream convection will
overspread the area from west to east today. This will produce
cloudy skies from late morning on across western NY, and by early
afternoon for the Genesee Valley and western Finger Lakes, with
clouds reaching central NY and the North Country later this
afternoon.

The thickening cloud cover will keep temperatures down somewhat in
an otherwise very warm airmass. Expect highs in the mid 80s across
western NY, with a better chance of upper 80s to near 90 in central
NY where sunshine will last longer. Light synoptic scale flow will
allow local lake breeze circulations to develop, with cooler
temperatures along the lakeshores.

By this evening, the forecast gets considerably more tricky. 00Z
guidance did a poor job initializing ongoing convection across the
Central Great Lakes with thunderstorms extending further south than
model consensus. Radar imagery late this morning shows the upstream
MCS taking a decided turn to the right, following the mid level
thickness lines and instability gradient, which will take most of
the convection into western Ohio this afternoon. To the north of the
main area of convection, an area of stratiform rain across southeast
lower Michigan is moving east in our general direction.

Following recent radar trends and forecast trends in the 06Z NAM/GFS
and HRRR guidance it appears most of this more northern activity
should weaken, probably passing to our south early evening. However
some guidance, the 00Z ECMWF in particular, develop more convection
along this boundary supporting chance POPS across the western
Southern Tier this evening as this first weak mid-level wave moves
through. Later tonight, it is hard to rule out a shower or
thunderstorm as this wave moves east into the Saint Lawrence Valley,
and as another trough approaches from the west. This is a low
confidence forecast, trending to rather broadbrush chance POPS late
tonight.

Tonight will be another warm night, especially across the lake
plains where an increasing downslope SSW flow should keep
temperatures from falling below the mid 70s along with steadily
rising dewpoints.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
Monday our region will lie within a warm sector of a storm system,
with a warm front draped across CNY, and a cold front nearing from
the west. Aloft a shortwave over the central Great Lakes region will
be tracking eastward across northern U.S. and southern Canada.

There may be a few showers and rumbles of thunder early Monday
morning, this as a warm front completes its passage across the CWA.
Behind the front daytime heating will send instability values
upwards. As the upper level shortwave nears us from the west there
will be mid level height falls, and increasing mid level lapse
rates. There will also be a good amount of moisture as drier air
will not arrive till later in the day Monday and Monday night. This
will allow for PWATs to climb north of 1.5 inches.

There will be a concern for some of these thunderstorms to become
severe through the day Monday. Bulk shear values will be greater to
the northern portions of the CWA, which will be closer to the upper
level shortwave, with shear magnitudes of 35 to 40 knots. This
should be enough to support a few clusters of thunderstorms Monday,
with damaging wind gusts the greatest threat. WBZ in the 9 to 11k
foot range will be favorable for hail, and while not the greatest
threat there will be potential for some hail development within
stronger thunderstorms. Will go ahead and insert some enhanced
wording into the grids, for gusty winds and small hail...which will
line up well with SPC`s forecast of our region within a marginal
risk for severe thunderstorms.

Ahead of the cold front Monday a strong push of southwest winds over
Lake Erie will bring a stabilizing lake airmass across Metro
Buffalo. This will likely limit any shower and thunderstorm
development immediately downwind of Lake Erie by late morning, with
sunshine and a gusty SW wind instead likely through the afternoon.
Winds may gust upwards to 30 to 35 mph Monday afternoon across Metro
Buffalo.

It will be muggy Monday as dewpoint values will rise into the lower
70s ahead of the cold front. Air temperatures will be very warm as
well with afternoon readings in the mid 80s to lower 90s. This will
bring apparent temperatures into the mid 90s south of Lake Ontario,
and through the Genesee Valley and Finger Lakes region.

The cold front will sweep across the region Monday afternoon with
scattered thunderstorms. There may be a few lingering storms early
Monday evening towards eastern zones, otherwise we should be drying
out behind the cold front. Overnight lows Monday night will drop
back into the 60s. Tuesday behind the cold front shall be dry with
air temperatures still above normal for afternoon highs. High
temperatures will reach into the low to mid 80s.

Continued dry Tuesday night as surface high pressure from the
central Great Lakes region advances eastward. Northwest flow ahead
of this high pressure should hold humidity levels comfortable with
dewpoints remaining in the mid 50s to around 60.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
The pattern has the potential to become at least a little more
active from late week into the first half of next weekend. The
expansive mid/upper level ridge which has dominated the central and
eastern CONUS will be knocked back as the longwave pattern buckles
across North America, with a western ridge and eastern trough
pattern becoming established by next weekend. The developing
longwave trough in the Great Lakes and Northeast states will be
carved out by several mid level shortwaves, each of which will bring
a period of large scale ascent and increased deep layer moisture to
our region.

Looking at the details, the first relatively weak trough will
approach the Great Lakes Thursday afternoon and evening. This system
may touch off a few widely scattered showers and thunderstorms with
sparse coverage. Models begin to diverge on the timing details of
the finer scale features by Friday and Saturday, but most
operational and ensemble guidance show a more significant mid level
trough and associated surface wave moving through the Ohio Valley
and eastern Great Lakes either Friday or Saturday, with a better
chance of somewhat more widespread showers and thunderstorms.

Temperatures will continue to run hot through Thursday, with 850mb
temps of around +18C supporting highs around 90 at lower elevations
away from the lakeshores. More clouds and showers will bring
temperatures back closer to average by Friday and Saturday.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
High pressure will remain across the region through this morning,
and then slide east into New England. This high will provide VFR
conditions through the day with mid level clouds thickening from
west to east.

Convection across the Central Great Lakes region is roughly focused
along a mid-level wave which is forecast to gradually shift towards
Western New York this evening. Eventually this will bring a chance
for showers or possibly a thunderstorm tonight. These may produce
temporary MVFR/IFR conditions, with otherwise VFR conditions
expected for tonight.

Outlook...

Monday...Mainly VFR with scattered showers/thunderstorms and associated
brief MVFR/IFR.
Monday night...Mainly VFR with a chance of showers and thunderstorms
east of Lake Ontario in the evening.
Tuesday and Wednesday...VFR.
Thursday...Mainly VFR with a chance of showers and thunderstorms.

&&

.MARINE...
Generally quiet conditions should persist across Lakes Erie and
Ontario today. A weak trough/cold front will cross the region
tonight and Monday which will bring a chance of showers and
thunderstorms. Freshening southwesterlies out ahead of the front
will likely bring a period of advisory-worthy winds and waves to the
eastern end of Lake Erie Monday, before winds and waves diminish
Monday night. After that, we should see tranquil conditions return
to the lakes for much of the remaining week as a weak pressure
gradient will be in place across the region.

&&

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

&&

$$

SYNOPSIS...APFFEL/HITCHCOCK
NEAR TERM...APFFEL/HITCHCOCK
SHORT TERM...THOMAS
LONG TERM...HITCHCOCK
AVIATION...APFFEL/HITCHCOCK
MARINE...APFFEL/THOMAS



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