679
FXUS61 KBUF 031902
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
302 PM EDT Wed Jul 3 2024

.SYNOPSIS...
Our stretch of rain free weather will come to an end later this
afternoon and evening when a weak cold front will generate some
showers and drenching thunderstorms. While most areas will then be
rainfree for the Fourth of July, there will only be minimal relief
from the heat and humidity. The next round of widespread showers
and a few thunderstorms will then arrive Friday night.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
A broad longwave trough and attendant surface low over northern
Ontario Province this afternoon will shift northeast into Quebec
across Hudson Bay later tonight. Additional shortwave energy well to
the south of this low is moving across southern Ontario in tandem,
with its associated cold front currently across Michigan and the
central Great Lakes. Deep SSW flow and moisture advection within the
warm sector of this system is causing a rather sultry afternoon to
unfold with much more heat and humidity compared to the last couple
of days. Temperatures have climbed well into the 80s in most spots
with corresponding Tds in the upper 60s to near 70.

While so far it has remained dry today, a prefrontal trough will
slowly work its way through the eastern Great Lakes from west to
east later this afternoon and through this evening. A 40kt LLJ
moving into the region along this feature will allow convection to
blossom across the region, with showers and a few thunderstorms
first expected to first develop across the Southern Tier where
instability is greatest. More widespread convection will spread into
areas north and northeast as the prefrontal wave/LLJ move eastward,
though these showers/storms may lose some steam as the jet weakens
in strength. On the flip side, there is some uncertainty in how
quickly the deeper moisture pulls away behind the trough, which
could allow additional showers/thunderstorms to develop late tonight
as additional weak forcing arrives ahead of the primary cold front.
In any case, PWATs nearing 2" within the soupy airmass ahead of
these boundaries will support a few torrential downpours in the
heavier showers/storms. Despite bulk shear values increasing to near
40kts with the arrival of the LLJ, the somewhat unfavorable timing
of the prefrontal trough and poor mid level lapse rates should
inhibit the severe potential. Otherwise...It will be a rather muggy
night with lows in the upper 60s to low 70s and plenty of residual
humidity.

Shower coverage will taper off late tonight into early Thursday
morning as the frontal boundary moves south and stalls across
Pennsylvania. Mainly dry weather will then persist through
Independence Day as the better moisture and forcing for precipitation
remains well to our south, but an isolated shower or thunderstorm
can`t be ruled out across the Southern Tier and southern Finer Lakes
region. With very little of an airmass change on the `cooler` side
of the boundary, expect another warm and humid day, though not
quite as oppressive. Highs will range in the low to mid 80s with
dewpoints still well into the 60s.

Mainly dry weather for Thursday night as weak surface high pressure
remains over the region. Light winds at the surface and aloft will
make any firework smoke slow to clear. Lows will again be warm,
ranging in the mid to upper 60s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
Potent southeasterly flow will encompass the area on Friday. This
flow will strengthen through the afternoon and evening hours,
eventually turning more southerly. Off the deck, consensus 850 hPa
temperatures surge toward +18 to +19C and momentum mixes through the
boundary layer below that level. This combined with southeasterly
flow, which relegates the lake influence to almost nil across the
majority of the area, should all for temperatures to skyrocket on
Friday. Highs should jump toward 90F, especially along the Lake Erie
shoreline, Buffalo area, and the Genesee Valley.

Friday`s warmth will be short-lived as the brisk southerly flow
comes in advance of a southwesterly low-level jet nose that nudges
into the area by Friday evening. This combined with a right entrance
of an upper jet streak and solid DPVA should work on the remaining
instability from the hot day on Friday to trigger widespread showers
and thunderstorms Friday evening in WNY that spread eastward
overnight.

Organized ascent slowly translates across the area into Saturday,
when the North Country should be the shower focus for the early half
of the day at least. The remainder of the area looks to largely move
into the mid-level dry slot of the system that will be occluding by
that juncture over the northern Lake Huron region. Thus, deep layer
dry advection and modest cold advection should at least temporarily
cut off rain chances from west to east as the afternoon ensues on
Saturday. Likewise, temperatures will be falling back in cold air
advection to a bit below normal across at least the western half of
the area.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Surface ridging and drier air moving in behind the cold frontal
passage gives fairly high confidence that the area will see dry
weather through Monday. Showers and thunderstorms return to the
forecast for the Tuesday through Wednesday period as a mid level
trough enters the region and a wave of low pressure tracks to our
north bringing a cold front through the region.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
VFR fair weather early this afternoon will begin to deteriorate
early this evening ahead of a pair of frontal boundaries approaching
from the northwest. Showers and thunderstorms will likely develop
and move into the region from west to east ahead of these
boundaries, mainly after 21z.

Cigs will begin to lower across the region tonight as showers begin
to taper off in coverage with the passage of the second frontal
boundary, mainly after 06z. While cigs are expected remain VFR at
KBUF/KIAG/KROC, for areas south and east a mix of MVFR to IFR cigs
are expected. Across the hilltops of the Southern Tier, localized
LIFR cigs are possible (including at KJHW)

A return to areawide VFR conditions expected after daybreak Thursday
as the lower cloud cover begins to lift. No showers or thunderstorms
expected at any of the TAF sites through the day, but an isolated
shower/storm can`t be ruled out in the Southern Tier or Finger Lakes
region.

Outlook...

Friday...Mainly VFR with increasing chances for showers and
thunderstorms.
Friday night...MVFR with showers and thunderstorms likely.
Saturday...Mainly VFR with decreasing chances for showers.
Sunday and Monday...VFR.

&&

.MARINE...
A cold front will approach the region this evening with an
increasing risk for thunderstorms. A stiff southwest breeze will
persist ahead of this front, with a moderate chop on the eastern
nearshore waters through early tonight.

In the wake of the cold front...fair weather will return to the region
later tonight with subsiding southwest breezes.

Looking ahead to the Fourth of July...gentle to moderate winds will be
in place throughout the region. These winds will be from the
southwest on Lake Erie and primarily from the west on Lake Ontario.
Winds will then shift out of the east Friday, becoming southwesterly
again by Saturday when the another round of SCAs appears likely.

&&

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

&&

$$

SYNOPSIS...PP/RSH
NEAR TERM...PP
SHORT TERM...Fries
LONG TERM...TMA
AVIATION...PP
MARINE...PP/RSH