471
FXUS61 KBUF 090540
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
140 AM EDT Thu May 9 2024

.SYNOPSIS...
High pressure will build in from the northwest providing mainly dry
weather through at least the first half of Thursday, before shower
chances slowly increase toward the Pennsylvania state line Thursday
afternoon. This will be the start of an unsettled weather pattern
that will impact the region for the end of the work week into this
weekend as a series of low pressure systems cross the region.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
High pressure will nose southeast across the area in the wake
of a cold front. This will provide rain-free conditions across
all the area overnight, however plenty of lingering low level
moisture will ensure plenty of clouds hang around through the
remainder of the overnight. Lows will range through the 40s.

Latest trend in guidance continues with the overall slower and
further south solution with regards to a convectively augmented wave
of low pressure on Thursday. Meanwhile, weak surface high pressure
to the northwest remains nosed in across the region providing a
stabilizing, but cool northeasterly low level flow. With this in
mind, still appears it will remain rain-free through at least the
first half of Thursday with slowly increasing chances for showers
across areas south of the NYS Thruway, especially toward the NY/PA
state line later in the day. Conditions will once again become
increasingly unsettled with some showers likely to move across the
area Thursday night, bringing some additional mainly light rainfall
amounts. The stable/cool northeasterly flow will mean there will be
little to no risk for thunderstorms, but will also guarantee cooler
temperatures on Thursday that will actually be a bit below average
with highs ranging from the mid 50s to lower 60s. A few mid 60s will
be possible toward the Saint Lawrence Valley where more in the way
of sunshine is expected.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
High confidence for BELOW normal temperatures during this period...
particularly by day when the mercury is only forecast to reach into
the upper 50s to near 60. That will be a solid 5 to 8 degrees below
mid May normals. Meanwhile...it will generally be unsettled with
perturbations in the mean longwave trough supporting some showers
and thunderstorms. As for the details...

A shortwave will drive across the Lower Great Lakes on Friday...as a
wavy sfc frontal boundary will stretch across the Tennessee valley to
the Mid Atlantic region. The resulting DPVA and minimal height falls
will couple with a deep cyclonic flow and wealth of moisture to
warrant chc to likely pops over the far western counties and cat
pops over the Finger Lakes region and portions of the Srn Tier
where a change will be made in the wording from showers to rain.
There could be several hours of widespread/steady rain for that
area. Finally...H5 temps of -20c will enhance the instability
aloft...the mid levels will be stable enough to preclude the risk
for thunder.

A weak shortwave ridge will scoot across the forecast area Friday
night. While spotty showers may persist east of Lake Ontario...this
scenario will bring an end to the pcpn over the western counties.

Saturday...another robust shortwave will drop through the longwave
trough and pass just to the west and south of our forecast area...
along with a loosely organized sfc reflection. Unlike the previous
shortwave passage the day before (Friday)...this will focus the
associated forcing over the western counties. Will raise pops for
the Srn Tier to categorical...but being largely convective (H5 ~
-24c)...will maintain the wording of showers. The mid levels will be
more unstable as well...so will add slgt/chc wording for tstorms for
the western counties. Given the mean trough axis will cross the
region Saturday night...will maintain at least chc pops for showers.

A nominal 70kt H5 jetlet will dig into the base of the
aforementioned longwave trough over the region on Sunday and
encourage it to close off across New England. The slow exit of the
trough will keep at least scattered showers in place...particularly
over the Finger Lakes and Eastern Lake Ontario regions. Low single
digit H85 temps will keep the cool weather in place with the mercury
struggling to make it out of the 50s.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
A closed low and associated deep longwave trough centered in the
vcnty of Hudson Bay at the start of this period will rotate out
across Quebec during the course of the week. This will result in
height rises across the Lower Great Lakes that will lead to
temperatures finally returning to ABOVE normal levels.

While this general pattern will favor fair weather for the majority
of the period...another shortwave will push a cold front through the
region later Monday and Monday night. This will result in scattered
showers and a minimal risk for thunderstorms.

Dry weather should prevail with a passing shortwave ridge Tuesday
and Tuesday night...then energy in the southern stream will help to
support a storm system that should pass to our south on Wednesday.
Being on the northern fringe of this system...there will be the
potential for showers.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
MVFR/IFR CIGS expected overnight as a moist north/northeast upslope
flow develops in the wake of a cold front.

Weak high pressure will nose in from the northwest Thursday, thus
with low level drier air working in, expect areas from the Niagara
Frontier (KBUF/KIAG) east and northeast to KROC and KART to be in
the low VFR (3-5kft) CIG range by late tonight/early Thursday
morning, eventually scattering out through the morning hours leaving
behind mid level decks through the afternoon. Expect improvement to
low VFR at KJHW during the first part of Thursday morning.
Widespread VFR is then expected for Thursday afternoon, although
there will be the chance for a few scattered showers and MVFR CIGS
to return across the western Southern Tier (KJHW) late in the TAF
period.

Outlook...

Thursday night and Friday...Mainly MVFR. Showers likely and MVFR
stratus.

Saturday through Monday...VFR/MVFR. A chance of showers.

&&

.MARINE...
A light chop will remain on both Lakes overnight as winds shift to a
mainly light northeasterly flow overnight. This northeasterly flow
will strengthen some on Thursday and Thursday night. This will
result in choppy conditions along the south shores of both Lakes,
especially on Lake Erie where marginal Small Craft conditions will
develop on Thursday, with a better chance of seeing solid Small
Craft conditions later Thursday into Thursday night on Lake Erie as
winds freshen a bit more.

&&

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

&&

$$

SYNOPSIS...JM/TMA
NEAR TERM...JM/TMA
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...JM/TMA
MARINE...JM/TMA