Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 271059
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
659 AM EDT WED JUL 27 2016

.SYNOPSIS...
High pressure will track across the Eastern Great Lakes this
morning. Dry weather will persist until a weak cold front drops
southward from Canada tonight bringing a few stray showers and
thunderstorms to the North Country tonight and Thursday. Chances of
showers and thunderstorms will continue into the weekend as a broad
trough temporarily digs into the Great Lakes and Northeast States.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure is stretched across the eastern Great Lakes and
Northeast States this morning. This will continue to provide fair
weather with visible satellite imagery showing clear skies across
upstate NY with some river valley fog in the Southern Tier.

A weakening cold front moving southward across Ontario will bring
increasing high and some mid clouds to the region during the
afternoon. There will be a low chance to slight chance of convection
north of Lake Ontario and perhaps far northern Niagara county as
well as east across the Saint Lawrence valley along the leading edge
of the slow moving cold front, mainly late afternoon. High
temperatures will be in the mid to upper 80s in most areas, with
around 90 degrees across the interior valleys.

Tonight the front will sag slowly southward ushered along by a
midlevel trough that is shifting over the Great Lakes. Meso-models
including the 4KM NAM and WRF indicate the front will stall over
Lake Ontario and just north of Lake Erie. Have included slight-
chance to chance POPs over the western end of Lake Ontario and
eastward to the Saint Lawrence River. Outside of the mention of
thunderstorms, for most of the forecast area expect a dry night.
There may again be some patchy river valley fog in the Southern TIer
as skies may remain mostly clear toward the NY/PA border. A
southwest flow will boost humidity levels again with very mild
overnight temps only dipping into the 60s for most.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Weak frontal boundary moving slowly south through the region will be
the focus  for scattered shower and isolated thunderstorm
development Thursday and Thursday night. Overall we`re looking at
fairly weak forcing with the parent upper low well north of the area
just east of James Bay, and any shortwave energy rounding the base
of the trough being meager at best. Associated convective activity
will be largely diurnally driven, with the best chances during the
afternoon and evening hours.

The Friday-Friday night forecast becoming a bit more clear as the
latest models coming more in line with the handling of the strength
and timing of a potential wave developing along the stalled front
south of the area. Latest ECMWF/NAM appears to have trended toward
the consistent GFS at suppressing the boundary and forcing a weak low
off the mid-Atlantic coast. This would suggest chances for any
shower activity would be confined to the southern portion of the
area.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The medium range guidance packages remain somewhat out of sync
during this period...only coming together in their solutions as we
come out of the weekend. This will result in relatively low
confidence in the forecast for the weekend...which could be rather
unsettled for parts of the area.

The disagreement between the medium range ensembles comes down to
the position of a wavy frontal boundary over the Mid Atlantic Region.
Initially...this will continue to serve as a pathway for individual
waves to cross from the Ohio Valley. The northern fringes of these
features will enhance the opportunity for showers and thunderstorms
over the Southern Tier...while areas further north will be more
influenced from high pressure centered over eastern Canada.

As we exit the weekend...the Canadian sfc high will become more
dominant..moving further to the south over the Lower Great Lakes.
This will encourage fair weather to return to all of the forecast
area while temperatures will average just a few degrees above normal
late July normals.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will persist through today for most site as high
pressure remains in control. KJHW is reporting IFR VIS in river
valley fog. The fog will erode by 13/14z then expect increasing high
cloud cover later today moving north to south as a weak cold frontal
boundary drifts south over the Lake Ontario basin and St.
Lawrence River valley. Tonight, the front will stall just to the
north of the TAF sites with VFR expected again for all but KJHW
where multiple guidance packages are pointing toward another round
of IFR river valley fog.

Outlook...

Thursday...Mainly VFR with a chance of showers and thunderstorms.
Friday through Sunday...VFR/MVFR with a chance of showers and
thunderstorms.

&&

.MARINE...
High pressure will remain across the Eastern Great Lakes through
today with a weak cold front pressing south across Lake Ontario
tonight. This will then be followed by another high pressure area
late in the week. Winds and waves are expected to remain below small
craft criteria into the beginning of the weekend.

&&

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

&&

$$

SYNOPSIS...SMITH
NEAR TERM...SMITH
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...SMITH
MARINE...SMITH



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