842
FXUS61 KBUF 260247
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1047 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 in the Southern Tier 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 /UNTIL 6 PM WEDNESDAY EVENING/...
Remnant moisture and weak ascent associated with a decaying MCS
continues to cross southern Ontario to Quebec late this evening.
Regional radar showing an area of showers tied to this system slowly
exiting the eastern Lake Ontario region 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. Some elevated instability present (200-500J/kg MUCAPE)
along this feature could support an isolated rumble of thunder this
evening before a weak cold front slide southeast into the region
overnight. This will support additional chances for showers or an
isolated thunderstorm, mainly through the first half of the night.
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 indicates more showers
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 in most locations.

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 will also bring 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.

&&

.SHORT TERM /6 PM WEDNESDAY EVENING 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 /03Z WEDNESDAY THROUGH SUNDAY/...
A weak low pressure system over southern Ontario Province will slide
east of the region this evening. While a broad area of light showers
will move through the North Country (KART/KGTB) until about 03z,
flight conditions in the region are expected to remain VFR.

A mix of VFR and MVFR conditions expected overnight as an elevated
warm lifts in from the west, before a weak cold front moves in and
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 and across WNY (KJHW/KBUF).
Periods of MVFR cigs will be possible in these areas, with a lower
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 in the
afternoon and impacts to flight conditions (MVFR to IFR) at
KJHW are likely, though confidence remains lower in shower and
thunderstorm coverage from KBUF northward. Outside of the areas
of precipitation, VFR will prevail through the day.

Outlook...

Wednesday night...MVFR to VFR with decreasing shower chances.
Thursday and Friday...Mainly VFR.
Saturday...Localized restrictions with shower likely and a
chance of thunderstorms.
Sunday...Mainly VFR.

&&

.MARINE...
Elevated south to southwest winds remain across Lake Erie and the
western end of Lake Ontario through tonight, producing moderate chop
on both lakes. Winds are expected to remain below SCA levels and the
greatest wave action will remain offshore, precluding additional
headlines on the waters.

Lighter winds and wave action is expected Wednesday but there will
be a better coverage of thunderstorms over Lake Erie in the
afternoon. A period of light, variable winds across the lakes will
precede increasing northwesterly winds behind a cold front Wednesday
night, though winds and waves are expected to remain below SCA
criteria.

&&

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

&&

$$

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