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320
FXUS61 KBUF 260027
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
827 PM EDT Tue Jun 25 2024

.SYNOPSIS...
Warm and humid conditions tonight will last into Wednesday, along
with increasing chances of showers and some thunderstorms,
especially by Wednesday afternoon. Cooler and less humid conditions
expected Thursday and Friday. Active weather returns Saturday as a
cold front crosses the region.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
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Remnant moisture and weak ascent associated with a decaying MCS
over southern Ontario Province and will move east of our region
this evening. Regional radar and sfc obs showing an area of
showers tied to this system moving east of Lake Ontario in
tandem. Meanwhile, additional shower development is being
observed back over Lake Erie and in the western Southern Tier out
ahead of an elevated warm front to the west. Elevated
instability on the order of 500J/kg MUCAPE along this feature
could support a few rumbles of thunder in the area this evening.
Otherwise, despite winds increasing aloft, the patchy cloud
cover and setting sun have inhibited BL mixing to allow the
breezy winds across far western NY to begin subsiding.

A cold front will slide southeast into the region tonight behind
the warm front with additional chances for showers or an
isolated thunderstorm. The best chances should again be across
the North Country closer to the support from the upper-level
jet, though will need to monitor trends as latest hi-res
guidance also shows more showers and a few thunderstorms
developing back across WNY after midnight as a reinforcing wave
of low pressure rides along the frontal boundary. Otherwise,
overnight low temperatures will be warm, only falling back into
the mid and upper 60s.

Wednesday should start off relatively quiet as the frontal boundary
working south overnight stalls out over the region. This boundary
will waver back northward during the day as a frontal wave moves
north along it from the Ohio Valley. The Southern Tier will have the
best chance to emerge into the warm sector, with some potential that
the warm sector lifts as far north as the I-90 corridor by
afternoon. The coverage of thunderstorms and the potential for
severe weather will depend greatly on the position of the frontal
boundary with the degree of instability highly dependent upon where
the warm sector is located. Latest HREF/NBM guidance only indicates
300-400J/kg CAPE building by the afternoon, possibly a result of
patchy cloud cover expected to be over the area. While CAPE values
remain in question, sufficient shear looks to be present especially
along the Southern Tier, which lines up with the Marginal Risk for
severe storms maintained by the latest SPC Day 2 Convective Outlook.
PWATs surging to near 1.5 inches bringing at least some threat for
heavy rainfall. The greatest risk of this will be across the western
Southern Tier which will lie closer to the track of the passing
frontal wave. Outside of the shower and thunderstorm chances, expect
another day of temps in the upper 70s to low 80s.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
Steadier showers and storms will continue into Wednesday evening
from the western Southern Tier into the Finger Lakes region as a
wave of low pressure moves northeastward along the slow-moving wavy
frontal boundary draped across this region. Scattered lighter
showers will also be possible for areas north of the boundary before
the frontal wave responsible for all of this activity exits east of
the area by the early overnight hours, allowing this initial wavy
cold front to finally press southward out of our area. Another
shortwave trough will then dive southeastward out of the upper Great
Lakes, crossing the eastern Great Lakes region late Wednesday night
and Thursday. This feature will also help force a secondary cold
front southeastward through western and northcentral NY late
Wednesday night through the midday/early afternoon hours on
Thursday. With deeper moisture associated with the initial wave
having departed to our east, not expecting more than some scattered
lighter showers/isolated rumble of thunder as the boundary passes
through the area, mainly from the Genesee Valley eastward. Depending
on the speed of the front, a few showers may linger across eastern
areas through late morning/early afternoon Thursday, with areas
toward the North Country/SL Valley continuing with at least the
slight chance for a few diurnally driven light showers through late
in the day as the southern periphery of the passing shortwave aloft
grazes northern NY. Otherwise, a much more refreshing airmass will
advect in across the region in the wake of the frontal passage as a
dome of high pressure builds in from the west bringing dry weather
through Friday with comfortable temperatures and humidity levels. In
fact, below normal temperatures are expected Thursday with highs
ranging from the upper 60s to low 70s. Similar to the first part of
the work week, high pressure then slides east of the area Friday
with a warming southerly return flow boosting temperatures back near
normal with highs mainly in the mid 70s to low 80s.

A weak mid level ripple and associated low level warm frontal
segment will cross the area Friday night, with increasing chances
for showers and a few thunderstorms from west to east as the night
wears on. Of note will be the very humid airmass that advects into
the area behind the frontal passage. Dew points mainly in the
comfortable low to mid 50s range late Friday will surge into the mid
60s to near 70 Saturday morning. This will keep lows Friday night on
the warm side, especially across areas south of Lake Ontario with
low temperatures only falling back into the mid and upper 60s, a tad
cooler across the North Country.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A well defined shortwave trough will cross the Great Lakes Saturday,
deepening an area of surface low pressure that will advance from the
northern Great Lakes through southern Quebec Saturday. A deep
southerly flow ahead of this trough will advance moisture northward,
increasing PWATs to nearly 2 inches across the eastern Great Lakes
region. Showers and thunderstorms are expected to form Saturday and
continue through the evening hours of Saturday before a cold front
crosses the region from west to east late. The timing of the cold
front, cloud cover holding instability back to around 750 J/KG or
less and poor mid level lapse rates under 6 C/KM are not favorable
for strong to severe storms. However, 0-6 km bulk wind shear values
35 to 45 kts could aid in strength to the storm if any taller storms
can develop.

Behind the cold front a much drier airmass will settle upon the
eastern Great Lakes. We`ll still have to contend with a few showers
Sunday with the passage of the upper level trough, but drier air and
eventually cooler airmass (mid single digit Celsius 850 hPa
temperatures) will bring a cool night Sunday night with lows in the
mid 40s to mid 50s. Fair weather Monday, with comfortable dewpoints
in the 40s and 50s with high pressure nearby. Tuesday a return
southerly flow along with the approach of a shortwave from the west
may trigger a few showers or thunderstorms.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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A weak low pressure system over southern Ontario Province will slide
east of the region this evening. While a broad area of showers will
move through the North Country (KART/KGTB) until about 02-03z,
flight conditions in the region are expected to remain mainly VFR.

A mix of VFR and MVFR conditions expected overnight as an elevated
warm lifts in from the west, before a weak cold front stalls over
the region. This will maintain a chance for showers and an isolated
thunderstorm at the terminals, though chances look to be greatest
across the North Country (KART) and across WNY (KJHW/KBUF). Periods
of MVFR cigs will be possible in these areas, as well as a low
chance of IFR between 08z-12z at KJHW. Elsewhere, VFR is expected to
prevail

Wednesday, a wave of low pressure will ride along the stalled
boundary and cause showers and thunderstorms to develop across the
region. Chances will be greatest in the Southern Tier and impacts to
flight conditions (MVFR to IFR) at KJHW are likely, though
confidence remains lower in shower/thunderstorm coverage from KBUF
northward. Outside of showers and thunderstorms, VFR is expected to
prevail through the day.

Outlook...

Thursday and Friday...Mainly VFR.
Saturday...Localized restrictions with shower likely and a
chance of thunderstorms.
Sunday...Mainly VFR.
-- End Changed Discussion --

&&

.MARINE...
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Elevated south to southwest winds remain across Lake Erie and the
western end of Lake Ontario through tonight, producing a light to
moderate chop on both lakes. Greatest wave action will be mainly
offshore, but a period of Small Craft conditions will persist into
the evening. SCAs remain in effect for Lake Erie though 03Z this
evening.

Lighter winds and wave action is expected Wednesday but there will
be a better coverage of thunderstorms over Lake Erie.
-- End Changed Discussion --

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
NY...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ040-
         041.
-- End Changed Discussion --

&&

$$

SYNOPSIS...AR/PP/TMA
NEAR TERM...PP/TMA
SHORT TERM...JM
LONG TERM...Thomas
AVIATION...PP
MARINE...AR/PP/TMA