080
FXUS61 KBUF 062344
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
744 PM EDT Sat Jul 6 2024

.SYNOPSIS...
High pressure centered over the Ohio valley tonight will drift
northeast across our forecast area Sunday through Monday. This will
assure us of fair dry through the start of the new work week...but
then a slow moving cold front will likely generate some rainfall in
the form of showers and thunderstorms Tuesday into Wednesday.
Meanwhile...temperatures that will be close to normal to end the
weekend will once again well above normal ahead of the cold front.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
Regional radar shows most shower and thunderstorm activity
outside the forecast area this evening. An isolated shower
remains possible across Allegany county and near the Lake
Ontario shoreline of Niagara and Orleans county this evening.

Tonight...high pressure centered over the Ohio valley will slowly
drift east and expand across the Lower Great Lakes. After a few
early evening showers/storms across the Srn Tier...the sfc high will
help to promote fair dry weather. While mild...the mins tonight will
be a few degrees lower than those from early this morning as they
will range from the upper 50s across much of the Srn Tier to the
lower 60s most elsewhere. Valley fog is possible across the
western Southern Tier and Black River valley south of Lowville
overnight.

High pressure over the region Sunday and Sunday night will then
guarantee nice weather to end the weekend. The mercury will
generally top out in the lower 80s on Sunday with mins in the upper
50s (Srn Tier/Lewis co) to lower 60s Sunday night.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Weak surface high pressure under a broad mid-level ridge will
gradually pull east of the region Monday. While this will maintain
the mostly dry pattern into Monday night, a mid level warm front
will lift into central NY from the south between Monday evening and
Tuesday morning. An uptick in synoptic moisture advecting northward
with the front combined with diurnal instability could touch off an
isolated shower or thunderstorm, mainly in the vicinity of the
Finger Lakes region. Otherwise, Monday will be quite warm though not
overly humid, with highs in the mid to upper 80s, a few readings in
the low 90s in the typical warm spots in the Genesee Valley.
Lows Monday night will range in the mid to upper 60s in most
areas.

Much more unsettled weather expected Tuesday as broad longwave
troughing to the west over the Great Lakes slowly encroaches on the
forecast area. An attendant area of surface low pressure crossing
from the upper Great Lakes to Quebec across southern Ontario will
send a cold front towards the region from the northwest, causing
downstream convection through the course of the day. Chances will be
greatest in the afternoon during peak diurnal heating, though
overall shower/storm coverage is more uncertain here...As there will
be a notable lack of low-level jet support or height falls aloft to
focus or increase general coverage of storms through the day. There
will also likely be other factors that will come into play Tuesday,
such as the tightening mid-level thermal gradient leftover from the
earlier warm front, in addition to any lake-induced boundaries that
develop. In any case, PWATs climbing between 1.5 and 2 inches could
still support a few locally heavy downpours Tuesday into Tuesday
night.

Any convection should begin to wind down after midnight Tuesday
night, especially over the western counties as drier air begins to
work in along the upstream cold front. A lower end chance for
showers/thunderstorms will linger overnight as the main longwave
trough remains upstream over the Great Lakes. Model guidance begins
to diverge more significantly here though, especially the latest 12z
GFS which now indicates the trough ingesting some moisture from the
remnants of TS Beryl and advecting it into the region. At this
juncture will label this an outlier solution as it is in sharp
contrast to the latest CMCNH/ECMWF, but something to keep an eye on
with future updates. Temperatures will be a couple of degrees cooler
Tuesday night compared to Monday night, with a larger range of 60s
for overnight lows.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As this period opens on Wednesday...there has been at least some
increase in spread on how quickly the initial trailing cold front
from Tuesday`s system exits our region...with the 12z GFS notably
slower and wetter compared to both its previous continuity and the
other medium range packages...and now offering a fairly rainy day
for at least areas south of Lake Ontario. In contrast...the GEM/old
00z ECMWF already have this boundary through our region by the start
of Wednesday morning...and still attempt to pivot a much weaker
secondary cold front across our area through the course of the
day...with pcpn ranging from lighter/spottier to largely
nonexistent. Given the outlier nature of the 12z GFS and its rather
abrupt break from its own continuity...will not quite buy into it
just yet and instead will continue to lean more towards the latter
packages and our own continuity for now...with the secondary cold
front and broad troughing aloft supporting the potential for some
additional scattered showers/isolated storms during Wednesday.
Generally drier weather should then follow for Wednesday night as
surface-based ridging and drier air noses across our region.
Otherwise cooler and more comfortable air will filter back across
our region following the passage of the above cold fronts...with
highs Wednesday pulling back to the upper 70s/lower 80s...and lows
Wednesday night in the lower to mid 60s.

After that forecast uncertainty increases as we work through the
rest of this period...as the various guidance packages are
struggling with their handling of the remnants of Tropical Cyclone
Beryl and their interaction with the next mid level trough pushing
east from the Plains States. The above in turn greatly influence
where the departed main frontal zone stalls out to our south...and
then exactly how far northward this boundary returns and when it
does so as one or more weak waves of low pressure ripple along it
later on in the week.

Given the above and the resultant decrease in forecast confidence...
have leaned more heavily toward blended guidance later on the
week...albeit with slightly higher chance PoPs Friday into
Saturday where there is at least some semblance of agreement on
a surface wave passing near or over our region. With PWATs
potentially rising to around 2 inches around that time owing to
the injection of some tropical moisture...there could be at
least some potential for locally heavy rainfall late in the
week. Otherwise...temperatures should average out a bit above
normal Thursday through Saturday...with daily highs mainly in
the 80s and nightly lows largely in the 60s.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
VFR conditions will continue across the eastern Great Lakes
region this evening. Surface high pressure will move into the
region tonight through Sunday. Only hiccup might be fog
development across valley locations across the western Southern
Tier and Black River valley south of Lowville.

Dry weather with some VFR diurnal cumulus expected through
Sunday.

Outlook...

Monday...VFR.
Tuesday...Restrictions possible with showers and thunderstorms
likely.
Wednesday...Restrictions possible with a chance of showers and
thunderstorms.
Thursday...Mainly VFR with a low chance of showers and thunderstorms.

&&

.MARINE...
High pressure will build over the lower Great Lakes tonight into
the start of next week. This will bring a period quiet
conditions through mid week with a weak pressure gradient
favoring light winds and limited waves. The light flow will
allow for some local lake breezes to form each day.

&&

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

&&

$$

SYNOPSIS...RSH
NEAR TERM...HSK/RSH
SHORT TERM...PP
LONG TERM...JJR
AVIATION...HSK
MARINE...Apffel/HSK/TMA