928
FXUS61 KBUF 062024
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
424 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/...
Partly to mostly sunny skies will be found throughout much of the
region for the rest of the afternoon...although widely separated
showers and thunderstorms will still be possible along two main
focusing boundaries.

While less active than from this morning... a low level convergence
zone will stretch from about IAG to ROC with a more active lake
breeze boundary that will extend from near JHW northeastward across
the Finger Lakes to Oswego county. There will be plenty of
instability for the convection to work with in this area with 35-
40kts of bulk shear...so its not out of the question that any given
storm could get strong to severe. Otherwise...these are more likely
to just be heavy rainers with localized wind gusts to 40 mph.

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.

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 warmspots 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 /21Z SATURDAY THROUGH THURSDAY/...
Mainly VFR conditions through the 18z TAF cycle as surface high
pressure slowly builds into the region from the Ohio Valley.

Lake breeze boundaries will allow a few widely scattered showers and
thunderstorms to persist until early this evening. As of about
1730z, a broken line of showers and thunderstorms extending from
roughly KIUA to KSDC will continue to translate eastward. This
activity is not expected to impact any of the TAF sites, though a
few weaker showers west of this boundary may occasionally move
across KIAG, KROC, and KJHW through 21z.

Shower chances and cloud cover diminish quickly after sunset
tonight. Valley fog is expected to develop in the Southern Tier late
which will likely cause vsby reductions at KJHW to IFR or lower.

Any fog will dissipate following sunrise Sunday morning. Dry weather
with some VFR diurnal cumulus expected through the day.

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...
Winds will pick up today, following the passage of a cold front.
Conditions will approach small craft criteria on Lake Erie today,
with southwesterly winds increasing to 15 to 20 knots at times this
afternoon. Elsewhere winds pick up but will remain below sca
criteria.

High pressure will build over the lower Great Lakes Sunday and 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...RSH
SHORT TERM...PP
LONG TERM...JJR
AVIATION...PP
MARINE...Apffel/TMA