Area Forecast Discussion
Issued by NWS Buffalo, NY

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773
FXUS61 KBUF 230820
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
420 AM EDT SAT JUL 23 2016

.SYNOPSIS...
Hot and humid conditions will last through the weekend as high
pressure moves across the Lower Great Lakes. Outside of some showers
and thunderstorms across the North Country and Saint Lawrence
Valley today...conditions will be largely rain free. A cool front
will then bring at least a chance of showers and thunderstorms
Monday as it crosses our region...then dry weather and above-
average temperatures return to the area for much of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A weak frontal boundary will drop across the region today and while
temperatures will not be much cooler, it will bring much drier air.
Dew points ahead of the front are in the upper 60s to lower 70s, but
as this front moves southward across the region dew points will drop
into the upper 50s to lower 60s. High temperatures today will still
be well above normal with most areas topping out in the mid to upper
80s with some lower 90s across low-lying areas in the Genesee Valley
and Finger Lakes regions. Even so, it will feel a bit more
comfortable than yesterday due to the lower humidity.

The frontal passage will largely be a dry one, with maybe a few
clouds with otherwise mostly sunny conditions. The one notable
exception is the St. Lawrence Valley and North Country which will
be closest an upper level trough axis which extends into New
England. A strong consensus of model guidance drops a vort max
across this region this afternoon which is likely to spark some
showers and thunderstorms. Storms will be more widespread to the
north and east, but there is a good chance storms will clip Lewis
and far northern Jefferson counties. Suspect that the lake breeze
will keep Watertown dry despite some model QPF guidance to the
contrary. The vort max should provide dynamic lift and mid-level
wind shear, and this along with favorable diurnal timing may
result in a few strong to severe thunderstorms. SPC has this area
in a marginal risk.

Tonight high pressure will expand across the entire cwa with fair
weather and mainly clear skies. The drier air mass combined with
favorable radiational cooling should allow temperatures to cool
quite nicely, probably a bit cooler than consensus guidance. Lows
should range from the mid and upper 50s across the interior valleys
to the mid 60s across the lake plains.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Summer`s heat and humidity will remain with us through Monday as
upper level ridge of high pressure remains over the Eastern U.S. A
zonal flow will dominate the U.S. Sunday and Monday, with a fast
moving shortwave advancing eastward along the US and Canadian
border. This shortwave, currently near Montana and southern Alberta
Province Canada will reach WNY later Sunday night, and may trigger a
few showers and thunderstorms late Sunday night and Monday.

First, for Sunday 850 hPa temperatures ranging from +18 to +22c
across the CWA will yield another hot afternoon with air
temperatures peaking in the mid 80s to lower 90s. Though dewpoints
may actually start the day at a comfortable level (in the 50s) we
will see an increase in moisture within the boundary layer through
the day which will increase these dewpoints to 60, and the lower 60s
by Sunday evening.

This increase in moisture will peak Monday ahead of a cold front
that will near us from the Upper Great Lakes. A few showers and
thunderstorms will be possible Sunday night within a layer of
elevated instability. Greatest chances for storms will be near the
lake plains and the Southern Tier. Later Monday after the initial
round of showers and thunderstorms, we will see an increase in
convection, this tied to the surface as daytime heating increases
SBCAPE values to 1000 to 1500 J/KG. This activity, while possible
across the CWA will have the highest chances inland along lake
breeze boundaries across the interior Southern Tier, Genesee Valley
and Finger Lakes region. A stiff southwest wind off Lake Erie Monday
will likely bring another dry late morning and afternoon period with
sunshine. Later Monday the cold front will cross the region,
bringing chances for additional showers and thunderstorms before
drier and slightly cooler weather reaches us Monday night and into
Tuesday.

Highs Monday will again top out in the mid 80s to lower 90s, before
cooler air reaches us Tuesday with daytime highs in the low to mid
80s. Tuesday should be dry with high pressure expanding eastward
across the Eastern Great Lakes region.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Surface high pressure will build slowly east across the Great Lakes
region Tuesday night and Wednesday with another period of dry, sunny
weather. Despite the weak cold frontal passage on Monday, there will
be little change in airmass with just slightly less humidity, but
still above normal temperatures. Expect highs on Wednesday to reach
into the mid to upper 80s in most areas, with a few 90 degree
readings possible in the normally warmer spots of the Genesee
Valley.

Thursday and Thursday night a trough will move east across Ontario
and Quebec. The stronger forcing will remain well north of the
Canadian border, with a trailing weak surface cold front moving east
across the Great Lakes. The frontal passage will provide at least
some chance for scattered showers and thunderstorms, with spotty
coverage.

The latest 00Z ECMWF and GFS guidance clears the front east of the
area later Thursday night, with weak high pressure allowing dry
weather on a light northerly flow to return by next Friday.
Temperatures will be knocked back a notch to a little closer to
average behind the front by Friday.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
High pressure building southeastward from the Upper Great Lakes
will largely provide our region with fair/dry VFR weather through
the TAF period, though there will be a couple of exceptions.

There is a small chance fog will develop tonight, with some
guidance hinting at this. Since winds should not go calm overnight and
the lack of rainfall will only carry a tempo for JHW with VFR
conditions elsewhere.

Showers and thunderstorms will develop this afternoon and may pass
near ART, but probably will stay just east of the terminal
location.

For tonight, high pressure will expand across the area with VFR
conditions outside of a small chance for Southern Tier valley
fog.


Outlook...
Sunday...VFR.
Sunday night and Monday... Mainly VFR with a chance of showers
and thunderstorms and associated brief MVFR/IFR.
Tuesday and Wednesday...VFR.

&&

.MARINE...
While lake breezes should once again bring a light to moderate chop
to nearshore waters this afternoon, high pressure moving overhead
should keep associated winds lighter negating the need for any SCAs
or beach hazard statements.

Some scattered showers and thunderstorms will be possible across the
Saint Lawrence Valley this afternoon.  Some storms may be strong,
with gusty winds and small hail.

Generally quiet conditions should persist across Lakes Erie and
Ontario Saturday night and Sunday... before a weak cold front
crosses the region on Monday and brings the next chance for showers
and thunderstorms.

&&

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

&&

$$

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



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