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535
FXUS61 KBUF 280225
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1025 PM EDT Sat Apr 27 2024

.SYNOPSIS...
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A warm front will continue to produce a few scattered showers east
of Lake Ontario overnight, with mainly dry weather across Western
NY. Another warm front will cross the region Sunday, with several
rounds of showers and scattered thunderstorms, a few of which may
contain brief heavy downpours. A nearby frontal boundary will
continue to bring a chance of a few showers and thunderstorms Monday
through Tuesday, but much warmer temperatures will arrive Sunday and
last much of next week.
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&&

.NEAR TERM /UNTIL 6 PM SUNDAY EVENING/...
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Radar imagery late this evening showing dry weather prevailing for
the bulk of the area. The one exception is east of Lake Ontario,
where a few spotty showers remain in the warm advection regime
associated with an eastward moving warm front. A few of these
showers even have some brief heavy downpours associated with them.
Overall, expect coverage of showers to gradually diminish east of
Lake Ontario overnight, although they may not end completely. Across
Western NY, skies have cleared nicely this evening. The mainly clear
skies will last into the early overnight before clouds begin to
increase.

Late tonight another warm-frontal segment will begin to take shape
across the southern Great Lakes, supported by increased warm
advection from a strengthening southwesterly low level jet over the
Ohio Valley. The combination of moisture transport and isentropic
upglide across the warm frontal boundary, elevated instability, and
several convectively augmented vorticity maxima moving from west to
east atop the warm frontal zone will support an expanding area of
showers over Lake Erie and southern Ontario. This rain will
overspread Western NY Sunday morning, then develop/move ENE across
the rest of the area Sunday.

Expect several rounds of showers and a few thunderstorms to cross
the region Sunday. Given the elevated nature of forcing and
instability, the stability provided by the lakes will initially not
play a role. Later in the afternoon as the warm front drifts
northeast, a stable lake shadow will try to develop over and
east/northeast of Lake Erie, with lowering rain chances. Sunday will
not be a total washout, but increased POPS quite a bit from the
previous forecast given the handling of the warm front and
associated rain in the latest 18Z model guidance. A few of the
showers and storms may contain brief, heavy downpours as a
moderately humid airmass becomes established.

Sunday will be characterized by late spring-like humidity with temps
reaching into the lower 70s for the bulk of the region by mid to
late afternoon and dewpoints in the lower 60s.

The warm frontal boundary from Sunday will stall Sunday night, and
possibly start to drift back south as a cold front overnight. This
will maintain the chance of a few showers and isolated
thunderstorms, especially over and east of Lake Ontario.
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&&

.SHORT TERM /6 PM SUNDAY EVENING THROUGH TUESDAY/...
An upper level ridge will build into the eastern Great Lakes region
Monday. A ribbon of higher than normal PWATs will be on the western
side of the ridge, from the Lower Mississippi Valley to southern
Ontario. A cold front will likely be stalled and stretched from the
Niagara Frontier to the Finger Lakes region. A north-northeast flow
on the cool side of the boundary will inhibit mixing of warmer
temperatures aloft. High temperatures will reach the mid to upper
60s with locations south of Lake Ontario staying in the low 60s. The
stable airmass will keep mostly dry weather from north central NY to
Interstate 90. It will be a different story on the warm side of the
boundary where temperatures reach the upper 70s to low 80s, mainly
from the Buffalo Southtowns to the Finger Lakes and south across the
western Southern Tier. Surface based instability will increase
through the afternoon and with help from the close proximity to the
axis of higher moisture, showers and a few thunderstorms are
possible along and east of the lake breeze boundary.

The upper level ridge axis will move east and the axis of higher
PWATS will move into the region overnight. Based off BUF sounding
climatology, forecast PWATS will be near the maximum for late April.
The cold front across the region Monday will move north as a warm
front and as low-level winds increase from the south. There is
growing confidence that additional showers will develop on this warm
front. Upstream convection from earlier will approach the region
overnight. A convectively induced shortwave trough across southern
Ontario may drive showers and thunderstorms into north central
overnight. Mild conditions expected Monday night with lows in the
mid to upper 50s.

A cold front will be just to the west Tuesday morning. The plume of
higher moisture content will spread out and decrease as the upper
level ridge flattens across the Northeast Tuesday. Scattered showers
will be ongoing across portions of the region, especially around and
east of Lake Ontario Tuesday morning. The front will move into
western NY Tuesday morning and move east through the afternoon. The
current timing of the front looks like areas east of the Genesee
Valley will have the best chance for showers and thunderstorms
developing Tuesday afternoon. Confidence is low on the amount of
instability Tuesday due to the uncertainty in cloud cover and
showers from Tuesday morning. Shear will be in place east of the
boundary so if thunderstorms do develop there is a low chance they
could be strong. Warm Tuesday with highs from the upper 60s to the
low 70s, mid to upper 70s possible across valley locations in the
Finger Lakes. Showers and thunderstorms will end across western NY
by Tuesday evening and east of Lake Ontario by late Tuesday night.
Thunderstorms are capable of producing heavy rainfall but flash
flooding is not expected at this time.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
A weak shortwave ridge moves through the eastern Great Lakes
Wednesday through Wednesday night which will likely bring dry
weather to the region. After that...models shift or even flatten out
the ridge aloft by Thursday, and also depict moisture increasing
across region. Even with moisture increasing areawide shower and
storm potential will all depend on the various advertised subtle
features embedded within the flow aloft. For now...have kept chance
PoPs (30-50%) beginning Thursday afternoon through the Friday. Beyond
Friday, confidence further decreases with little consensus to
either a wet or dry forecast for the weekend. Eitherway...it does
appear like a mild week is on tap with temperatures remaining well
above normal with highs in the 60s Wednesday then climbing into the
70s for all locales.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
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A warm front will continue to produce a few spotty showers east of
Lake Ontario overnight, with dry weather prevailing elsewhere. There
will be a few areas of MVFR/IFR CIGS across the higher terrain east
of Lake Ontario and across the Southern Tier, otherwise mainly VFR
will prevail tonight including all the TAF sites.

Another warm frontal segment will develop over the southern Great
Lakes late tonight, then move ENE across the area Sunday. This will
bring several rounds of showers and widely scattered thunderstorms
to the region. A few pockets of heavier rainfall may produce
brief/local VSBY restrictions. Widespread MVFR CIGS will develop by
late morning and continue most of the day, with some IFR across the
North Country. Western NY should improve back to VFR late in the
day, especially southern areas of Western NY.

A low level jet will cross the area late this evening through Sunday
morning, producing low level wind shear especially across Western
NY.

Outlook...

Sunday night...MVFR/IFR with a chance of showers and a few isolated
thunderstorms.
Monday...VFR/MVFR with a chance of showers and thunderstorms.
Monday night and Tuesday...MVFR/VFR with showers becoming likely
along with a chance of thunderstorms.
Wednesday and Thursday...Mainly VFR.
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&&

.MARINE...
A warm front will move east of Lake Ontario this evening. Following
the passage of the warm front...a general southerly flow across the
Lower Great Lakes will weaken some while turning more southwesterly
tonight and Sunday. This will result in conditions remaining below
advisory criteria. This being said...a few thunderstorms will become
possible Sunday with locally higher winds and waves possible.

&&

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

&&

$$

SYNOPSIS...Hitchcock
NEAR TERM...Hitchcock/RSH
SHORT TERM...HSK
LONG TERM...AR
AVIATION...Hitchcock
MARINE...Hitchcock/JJR