873
FXUS61 KBUF 061039
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
639 AM EDT Sun Jul 6 2025

.SYNOPSIS...
Ahead of a slow-moving cold front, hot and humid air
will flow into the region with many areas reaching Heat
Advisory criteria this afternoon. The front will bring showers
and thunderstorms to the region Monday with locally heavy
rainfall possible. Mostly dry and more comfortable weather for
Tuesday through Wednesday before becoming unsettled again in the
latter half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
The eastern Great Lakes will remain situated between expansive sfc
high pressure out in the western Atlantic and a couple of phasing
shortwaves with an associated cold front across Ontario and Quebec
through tonight. Deep southwesterly flow will continue to pump a hot
and humid airmass into the region, with 850H temps climbing to near
+20C by this afternoon. This will translate to sfc high temps in the
low 90s for many areas across the Lake Plains, with mid 90s possible
in the Genesee Valley. With Tds in the mid 60s to low 70s adding a
few degrees to the corresponding heat indices, Heat Advisories
remain in effect for these areas. Lake breeze influences will likely
keep areas right near the shorelines a few degrees cooler. Muggy
weather will continue into tonight with lows only in the low/mid 70s
across the lower terrain areas.

Otherwise, the influence of high pressure will keep the region
mostly dry through tonight with a couple of potential exceptions. A
few isolated showers or storms will be possible near a weak LLJ
across the North Country and St. Lawrence River through the day (15-
25% chance). Then, as the aforementioned cold front begins to near
the region from the central Great Lakes tonight, a few showers or
storms could creep in from the northwest (15-20% WNY, 20-25% N.
Country).

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Monday and Monday night broad upper troughing over eastern Canada
will gradually amplify as additional shortwave energy ripples
through it...which will in turn encourage the wavy frontal boundary
to our north to slowly push southeast through our area as a cold
front...with an increasing percentage of model guidance also
suggesting the development and passage of a weak pre-frontal trough
Monday afternoon. At this juncture...the exact timing of the cold
front itself remains at least a bit in question as the various
guidance packages exhibit differences in just how much the remnants
of Tropical Storm Chantal impede the southeastward progress of the
boundary...with the frontal timing currently varying anywhere from
later Monday afternoon/early Monday evening (NAM/GFS) to Monday
night (GEM/ECMWF). For now have leaned more towards previous
continuity and blended guidance in this respect...however it`s
possible that this might need further refinement in subsequent
packages.

The above being said...it still appears that we`ll have a rather
wavy...slow-moving frontal boundary pushing through a very moist
antecedent airmass (PWATs of around 2 inches - which have come up
over the last 24 hours)...along with nearly unidirectional flow
profiles oriented roughly parallel to the frontal boundary. MBE
vectors look to be rather short...and with moderate instability and
tall/skinny CAPE profiles in place...the potential for training
cells and resultant localized heavy rainfall/flooding still
certainly appears to be in place. At this point...the area of
greatest risk for such appears to lie from the interior of the
Southern Tier northeastward across the Finger Lakes and into
portions of the North Country...where CAMs suggest convection could
focus along a composite of the aforementioned pre-frontal trough and
lake breeze boundaries. With all this in mind...have bumped up PoPs
a bit above NBM guidance...and have added a mention of locally heavy
rainfall to the forecast for Monday in collaboration with
surrounding WFOs. Otherwise...it should remain very warm on Monday
with highs in the mid to upper 80s in most places...while humidity
levels will also peak as surface dewpoints reach the upper 60s/lower
70s. While it`s possible that this combination of temperatures/
humidity levels could result in a few spots across the Finger Lakes
briefly tickling/reaching Heat Advisory criteria...this potential
appears to be rather brief/localized. Somewhat cooler and less humid
air will then gradually filter in behind the cold front as we push
through Monday night.

Tuesday and Tuesday night a modest bubble of surface high pressure
and drier air will gradually ridge southeastward into our region
from Ontario Province. Can`t rule out a few more isolated to widely
scattered diurnally-driven showers/storms along our southeastern
periphery during Tuesday with the frontal boundary still lingering
just a bit to our southeast...though aside from these dry weather
should prevail during this 24-hour period. Meanwhile temps and
humidity levels will continue to slowly drop off...with highs on
Tuesday mostly running in the mid 70s to lower 80s...and dewpoints
in the lower/mid 60s Tuesday falling into the upper 50s/lower 60s
Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
This period will be dominated by persistent broad upper-level
troughing across the Great Lakes and Northeast. Currently Wednesday
still appears to be on the drier side for the most part... with just
some limited afternoon convection possible across the Southern
Tier/interior Finger Lakes owing to the combination of diurnal
heating/a developing lake breeze boundary. Somewhat better and more
general chances for convection may then return later in the week in
tandem with a few shortwave passages...though the guidance
unsurprisingly continues to struggle with the details of these at
this distant vantage point. With that in mind...the chance PoPs
advertised by blended guidance still look fine for now. Otherwise...
temps during this period will average out near to slightly above
normal for this time of year...with dewpoints climbing back to
stickier (though not oppressive) levels after midweek.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Mainly VFR through the 12z TAF cycle as region remains situated
between offshore high pressure and a cold front over the central
Great Lakes. Skies will feature passing high clouds and diurnal
cumulus this afternoon. A few showers or thunderstorms will be
possible at times in the North Country with localized MVFR
conditions, though this activity is expected to remain away from
KART/KGTB.

Partial mixing of an overhead LLJ will lead to modest southwest wind
gusts (25-30kts) across the Niagara Frontier and St. Lawrence Valley
this afternoon (KIAG/KBUF/KART).

As the front draws nearer tonight, there will be a low chance (~20%)
of showers and thunderstorms at the TAF sites with localized MVFR.
The vast majority of this activity is expected to hold off until
after 12z.

Outlook...

Monday...Showers and thunderstorms likely with MVFR and localized
IFR restrictions possible.

Monday night...Mainly MVFR to IFR with decreasing chances for
showers and thunderstorms.

Tuesday and Wednesday...Mainly VFR.

Thursday...A chance of showers and thunderstorms with MVFR
restrictions possible.

&&

.MARINE...
The pressure gradient will tighten over the lakes today between high
pressure in the western Atlantic and a cold front to the northwest.
This will lead to breezy southwest winds in some areas approaching
SCA levels. Confidence is low to moderate as the setup looks very
marginal, though the two main areas of concern are the St. Lawrence
and Upper Niagara rivers, as the relatively cool lakes should
inhibit mixing of stronger winds across the open waters. Winds will
also be breezy over the southwestern end of Lake Ontario, though the
offshore direction should preclude the need for SCA headlines. While
strong winds aloft will remain overhead tonight, limited mixing
should allow sfc winds to diminish this evening.

Otherwise, a few thunderstorms will also be possible across the St.
Lawrence River through the day today. More widespread chances for
tstorms across the waters will arrive Monday, before the cold front
finally moves through the region later Monday evening. Post-frontal
winds will become northwesterly into early Tuesday, though sub-SCA
conditions are expected through the rest of the week.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for NYZ001>006-011-013-014.
MARINE...Small Craft Advisory from 11 AM this morning to 8 PM EDT this
         evening for LEZ020.
         Small Craft Advisory from 11 AM this morning to 8 PM
         EDT this evening for SLZ022.

&&

$$

SYNOPSIS...PP
NEAR TERM...PP
SHORT TERM...JJR
LONG TERM...JJR
AVIATION...PP
MARINE...PP