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991
FXUS61 KBUF 231828
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
Issued by National Weather Service Pittsburgh PA
228 PM EDT Mon Sep 23 2024

.SYNOPSIS...
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As a mid-level disturbance departs the region, a few isolated rain
showers will linger into the nighttime hours. An approaching and
crossing warm front will bring a more widespread round of rain
showers Tuesday afternoon and night. A crossing cold front may
then linger rain into Wednesday, especially east of Buffalo.
Temperatures Tuesday and Wednesday will creep back above normal
for much of Western and Central New York.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Showers have become more isolated across the region early this
afternoon as a mid-level wave departs to the east. Some apparent
convergence near the eastern end of Lake Erie is keeping a few
light showers/sprinkles going there, with much of the steadier
rain now to the east of Oswego. Southeast downslope flow has
allowed temperatures to rise to near or above 70 at DKK and BUF,
with most other areas in the 60s.

Weak surface low pressure over Lake Erie will degrade into an
inverted surface trough tonight, while an associated surface
boundary remains situated near or just west of BUF/IAG. Cloud
cover will linger through the night, with only isolated
showers/sprinkles expected at most with overall weak forcing.
Low temperatures tonight will range from the lower 50s on the
Tug Hill, to mid 50s upper Genesee Valley to around 60 closer to
the Lakes.
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&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
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A deep longwave trough will advance from the Mississippi Valley
Tuesday towards the Great Lakes and Ohio Valley by Wednesday. Models
are in decent agreement that the large-scale trough will evolve
separate northern and southern stream components, with a closed
cutoff low developing near the Ohio-Mississippi River confluence,
and a negative tilt trough and/or closed low develop across eastern
Ontario into Quebec by Thursday morning.

Tuesday morning will be mainly dry, with a few isolated showers at
most across the region.  However, during the afternoon, a shortwave
embedded in the developing northern portion of the large scale
trough will cross the Great Lakes and surface low pressure will lift
into lower Michigan by Tuesday night. With lift supported by the
shortwave and a surface warm front, and strengthening southwest flow
bringing precipitable water values in the 1.5 to 1.6 inch range by
Tuesday evening, widespread showers appear to be a good bet later
Tuesday and Tuesday night.

On Wednesday, as the Michigan surface low lifts into Quebec, the
system cold front will be dragged across the eastern Lakes and
reside in the eastern portions of the forecast area by afternoon. A
weak wave along the boundary may keep higher PoPs going here, while
drier air tries to build in behind the boundary in western New York,
leading to a drier forecast. This drier air becomes more widespread
across the region by Thursday as the northern shortwave trough axis
shifts more towards New England, although a few showers may continue
in the eastern Lake Ontario region, closest to sufficient moisture
and forcing.
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&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
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Dry weather appears likely through at least the Thursday night
through Saturday period.  A ridge appears likely to set up in the
western New York area between upper level low pressure across the
Canadian Maritimes, and another upper low centered somewhere in or
near the Lower Mississippi Valley.  The only fly in the ointment
could be related to this week`s potential Gulf tropical activity, as
a small bit of moisture from what would be remnants at that
point could sneak into areas south and west of Buffalo on
Saturday, producing some showers.

Uncertainty regarding the Mississippi Valley upper low increases
thereafter according to model cluster analysis, with the slight
majority of scenarios keeping the low center more or less in place,
while others try to open the system and eject it to the northeast.
This latter scenario would lead to a wetter forecast for western New
York by the end of the forecast period. Given this uncertainty, the
NBM idea of some low PoPs across areas generally near and west of I-
390 during the Sunday/Monday period is a good one. Temperatures will
continue run a little above normal overall.
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&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 15Z, a cold front is currently situated west of BUF/IAG
and a warm front is lingering just south of KART and producing
light to moderate rain.

There is a ton of variability in the TAFs when it comes to
restrictions depending on the plume of low-level moisture and
if areas have received rain or not. Northern NY is still
experiencing VFR (with lower dew points) while KJHW has been
battling low cigs and prevailing LIFR.

Hi-Res guidance suggests elevated probabilities (above 50%)
LIFR to IFR conditions around KJHW through 17Z to 18Z.

Elsewhere, the probability of MVFR conditions across the region
are elevated (above 60%) through late this evening and into
early Tuesday morning. As well as restrictions, isolated rain
showers/drizzle can`t be ruled out in the vicinity of terminals.

Outlook...

Tuesday...IFR to MVFR cigs over the western counties in scattered
showers and thunderstorms, but mainly VFR and dry east of Lake
Ontario.
Wednesday...IFR to lower end MVFR region-wide with the
likelihood of more showers and thunderstorms.
Thursday...MVFR with scattered showers...mainly east of Lake
Ontario.
Friday...VFR.

&&

.MARINE...
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Southeast wind will continue through tonight, approaching 20
knots over the offshore waters of eastern Lake Ontario. Waves of
3 to 5 feet can be expected here along the Canadian border
waters.

South to southeast wind will continue into Wednesday as a
stalled cold front over central Lake Erie. Once this front
passes on Wednesday, wind will veer through southwest and to a
westerly direction during the Wednesday night/Thursday period.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Thomas/Hefferan
MARINE...CL