Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 251507
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1107 AM EDT MON JUL 25 2016

.SYNOPSIS...
An upper level trough will slowly cross the region today producing
scattered showers and thunderstorms. A trailing cold front will
pass through our region this evening...followed by slightly
cooler and less humid weather Tuesday before temperatures and
eventually humidity levels trend upward again Wednesday and
Thursday. A weak area of low pressure will then cross the region
Friday and Saturday bringing the next chance of showers and
thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
Showers and thunderstorms continue to work their way across Western
and north-Central new York this morning. The initial round that
moved through Western NY in time for the morning commute has
largely departed the eastern edge of the forecast area into
central NY, with an area of trailing stratiform making its way
into the Eastern Lake Ontario region. This initial round of
convection is tied to a warm front making its way across the
region that is tied ultimately to a surface low centered near
James Bay. Another broken line of convection is approaching
Western NY at this time.

Expect several rounds of showers and thunderstorms to traverse the
forecast area through the rest of the morning and into the afternoon
hours as the area will remain within a moist and unstable warm
sector airmass ahead of a trailing cold front currently moving into
the western edge of southern Ontario. Increasing shear and
instability within this warm sector ahead of the approaching front
should allow for some of these thunderstorms to become strong to
marginally severe as they track in Western NY this afternoon, with
the main threat being strong and possible damaging winds with any
stronger storms, as well as small hail. The widespread cloud
cover should tamp down temperatures and as a result have backed
off forecast highs for this afternoon, going with low to mid 80s,
with some of the higher elevations of the Southern Tier and North
Country perhaps not even getting out of the 70s.

The cold front will cross the forecast area this early this evening.
Convection ahead of the front will push off to the east and out of
the forecast area. Upstream satellite imagery indicates we should
see rapid clearing behind this front with WV imagery indicating
strong subsidence along/behind the upper level trough axis driving
the front. While temperatures will cool slightly behind the front,
upstream dewpoints will remain in the lower 60s, and with clearing
skies and winds becoming light, we will see the potential for patchy
fog across lower lying areas, particularly those areas that see
substantial rainfall today. Temperatures will fall into the 60s
overnight.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Generally uneventful weather will unfold through this period as flat
zonal flow aloft, combined with surface high pressure expanding
across the Eastern Great Lakes region bring very warm afternoons and
mild nights. Tuesday 850 hPa temperatures in the 14 to 17c range
will bring low to mid 80s for highs, while on Wednesday 850 hPa
temperatures of 16 to 19c will bring mid to upper 80s for highs, and
possibly a few 90F readings in the Genesee Valley.

A fast moving shortwave will ripple by to our north on Wednesday,
though limited moisture should bring nothing more than a few more
cumulus clouds during the afternoon hours.

A weak cold front will sag southward later Wednesday night,
bringing a slight chance for a shower or thunderstorm to SLV late.

The better radiational cooling conditions this period will be
Tuesday night, with clearer skies and lighter winds which will allow
for temperatures to lower to the mid 50s to mid 60s. Wednesday night
will likely be a few degrees warmer.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
While drought busting rains are not anticipated during this
period...there is relatively high confidence that the pattern will
be more active...so many areas should pick up at least a little
rainfall. This will be due to a subtle shift in the dominant ridge
that has been in firm control of the country.

Unlike the past couple weeks when an expansive sub-tropical ridge
either flexed its muscles with anomalously high heights over the
nations mid section...or stretched from ocean to ocean across the
southern half of the Conus...this time frame will feature low
amplitude troughing over the Great Lakes region. Meanwhile...the
heart of the aforementioned ridge will have retrograded to the
Desert Southwest. This upper level transition will encourage a
little more baroclinicity across the Great Lakes region...which
should support a more active storm track.

At the surface...the period will open with a wavy frontal boundary
that will be stalled in the vcnty of the Mason Dixon Line. It is
interesting in that all of the real baroclinicity...lift and moisture
will be found a few hundred miles north of the sfc front. This
should initially keep the bulk of any showers and thunderstorms
north of the international border...but as push into Friday...a
fairly well organized wave will develop over the Mid West and slowly
track east along the front. The ensembles are all over the place
with the location...speed and track of this wave...but all are in
general agreement that the system will move close enough to our
region to help generate more widespread rainfall. The best
opportunity for some rain would be Friday and Friday evening with
basin average rainfall averaging under a quarter inch...but locally
up to three quarters of an inch.

Confidence drops off for the weekend as a second wave could bring
another round of beneficial showers and thunderstorms to the
forecast area. This will largely depend on the strength of the first
system though...so will only use relatively low pops to express this
potential.

In terms of temperatures...while mercury levels will generally be
lower than those of the past few weeks...there is high confidence
that they will remain close to...if not still a few degrees above
normal.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Showers and thunderstorms will continue to move across the forecast
area in several waves through this afternoon as the area remains in
a warm and unstable airmass ahead of an approaching cold front.
Conditions will generally be VFR with periods of VFR/MVFR conditions
in showers and thunderstorms.

The cold front will cross the forecast area around 00Z, with any
showers and thunderstorms pushing off to the east and out of the
forecast area as the front moves through. Gusty SW winds this
afternoon will give way to light winds behind the front tonight, and
with skies clearing, we will likely see the development of patchy
fog across low lying areas, particularly in the Southern Tier, that
will potentially generate IFR/LIFR conditions after 06Z. Fog may
also affect KIAG late tonight/early Tuesday morning. Fog should
clear out after 12Z, giving way to widespread VFR conditions on
Tuesday.

Outlook...
Tuesday and Wednesday...Mainly VFR.
Thursday...Mainly VFR with a chance of showers and thunderstorms.
Friday...VFR/MVFR with a chance of showers and thunderstorms.

&&

.MARINE...
A cold front will move east across the lower Great Lakes today. A
fresh southwesterly breeze will develop ahead of this, supporting
low-end small craft advisories on Lake Erie and the Upper Niagara
River. Winds should be strongest near the shoreline where the lake
breeze will help enhance the flow.

Winds will diminish tonight following the passage of the weak front,
with winds and waves then expected to remain below Small Craft
Advisory levels through midweek.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Beach Hazards Statement until 8 PM EDT this evening for NYZ010-
     085.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ020-
         040-041.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...WOOD
SHORT TERM...THOMAS
LONG TERM...RSH/THOMAS
AVIATION...WOOD
MARINE...APFFEL/THOMAS



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