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681
FXUS61 KBUF 231042
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
642 AM EDT Mon Sep 23 2024

.SYNOPSIS...
A mid level disturbance will cross the Lower Great Lakes today,
bringing widespread showers to Western New York, with activity more
scattered east of Lake Ontario. Cloudy skies today will promote
temperatures much closer to early autumn normal. As a warm front
pushes across our region Tuesday night and Wednesday more widespread
rainfall will occur across the entire region.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Water Vapor Imagery this early morning displays a shortwave trough
now over eastern end of Lake Erie. At the surface an area of
low pressure can be found over central waters of Lake Erie.

For today this mid level shortwave will race out ahead of the
surface low...with the surface low weakening once the mid level
shortwave passes by. Lift ahead of the shortwave trough will
continue the light rain showers through WNY today, becoming
scattered farther to the east across the North Country. Will carry
categorical PoPs this morning, but just chance PoPs east of Lake
Ontario which will lie farther from the weakening surface low and
greater ascent aloft.

There is minor instability of several hundred J/KG of MUCAPE across
WNY today, enough that thunder chances are not zero, but not great
enough to place thunder into the grids, especially since we should
remain cloudy through much of the day today.

Rain showers will lighten and taper off through the late morning and
afternoon hours from west to east. The surface low will reside to
our west through tonight, within an inverted surface trough. There
may be a lingering shower or two with convergence and remaining low
level moisture within this inverted surface trough tonight, but
activity should be light considering a mid level ridge aloft will be
passing overhead.

Winds will remain from the southeast today and tonight. This
downslope flow will favor warmest areas near Lake Erie, across the
Lake Plain and also near the Saint Lawrence Valley. Here highs
around 70, and lower 70s for Buffalo and down the NYS Thruway
corridor along Lake Erie. Inland temperatures across the higher
terrain will remain in the lower 60s. Lows tonight will range from
the lower 50s on the Tug Hill, to mid 50s upper Genesee Valley to
around 60 closer to the Lakes.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
A deep longwave trough will advance from the Mississippi Valley
Tuesday towards the Great Lakes and Ohio Valley by Wednesday. The
trough will undergo an interesting evolution, with the sharp
northern stream portion moving east across Ontario Wednesday and
into Quebec by early Thursday. This feature, along with several
shortwaves will continue to produce active weather across our region
Tuesday through Wednesday. Meanwhile, a strong shortwave digging
into the western portion of the trough Tuesday will be left behind
and evolve into a cutoff closed low over the south central US, where
it will meander within a building mid/upper level ridge through the
end of the week. Model and ensemble guidance is coming into better
agreement that this closed low will be too far away to influence our
weather later in the week.

Looking at the details, Tuesday morning the remnants of the first
shortwave may still be producing a few scattered showers across
Western and Central NY, but coverage of any rain will initially be
sparse in the morning. Later Tuesday afternoon through Tuesday night
a shortwave ejecting northeast out of the mean longwave trough will
cross the Great Lakes, with a surface low tracking northeast across
lower Michigan late Tuesday to near Georgian Bay by early Wednesday.
Large scale forcing will increase ahead of this feature, supported
by diffluent mid/upper level flow and upper level jet support. A 35+
knot southerly low level jet will aid in transporting deep moisture
into the region. The combination of forcing and moisture will
support an area of widespread showers moving into Western NY later
Tuesday afternoon, then spreading across the entire area Tuesday
night. Limited instability may support some isolated embedded
thunder.

Wednesday, the mid level shortwave and low level features will
continue to move northeast and weaken with time. A baroclinic zone
will remain draped from the Appalachians to eastern NY, and model
guidance suggests another wave of low pressure may move along this
boundary later Wednesday through Wednesday night, maintaining a
higher chance of rain across eastern portions of the area.
Meanwhile, drier air will attempt to move into Western NY,
supporting decreasing rain chances by Wednesday afternoon and
Wednesday night.

Thursday, the northern stream trough will dig from Quebec into New
England. Associated forcing and deeper moisture may clip the eastern
Lake Ontario region, where the best chance of showers will be found.
Meanwhile, surface high pressure and associated drier air and
subsidence will build into the Great Lakes, allowing mainly dry
weather to return to Western NY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A much drier pattern is shaping up for Friday through next weekend
in the past few runs of operational and ensemble guidance. An
expansive mid level low will continue to spin through the south
central CONUS, with another mid level closed low moving from the
Canadian Maritimes into the North Atlantic over the weekend. A
strong mid/upper level ridge will build over the Great Lakes between
these two systems, with associated dry air and subsidence supporting
dry weather Friday through Sunday. The dry airmass will support cool
nights and warm afternoons, with high temperatures running a little
above average.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
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For the 12Z TAFS light rain showers are pushing their way into
far WNY, with ceiling heights now lowering to IFR over the
Southern Tier (KJHW) and MVFR over WNY. There is a lower
probability of these showers reaching KART.

Southeast flow ahead of a cold front this forecast period...with
this cold front remaining just to our west.

Ceiling heights will largely remain in the MVFR range today.
There will be some morning IFR in the Southern Tier.
Additionally, some pockets of low end VFR ceiling heights are
possible, especially if this southeast flow becomes a little
stronger, developing downslope flow that will lift these
ceilings for KBUF/KIAG and KROC.

VFR, or high end MVFR may linger east of Lake Ontario where moisture
will not be as deep.

Tonight will be mainly dry, though a few isolated rain showers
cannot be ruled out. Ceiling heights lingering in the MVFR
range, may lower to IFR for the Southern Tier and possibly
portions of the northern Niagara Frontier where low level
moisture from earlier rain showers remains ample.

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 regionwide with the likelihood of
more showers and thunderstorms.
Thursday...MVFR with scattered showers...mainly east of Lake
Ontario.
Friday...VFR.
-- End Changed Discussion --

&&

.MARINE...
Winds will be from the southeast today and tonight. These southeast
winds will approach 20 knots over the offshore waters of eastern
Lake Ontario...with waves around four to five feet rolling into the
Canadian waters today.

This cold front will stall just to the west of the Lower Great
Lakes, with a south to southeast flow maintained over the Lake
waters through Wednesday. Eventually this cold front will push
eastward, with winds veering to a westerly flow Wednesday night and
Thursday.

&&

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

&&

$$

SYNOPSIS...Thomas
NEAR TERM...Thomas
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...Thomas
MARINE...Thomas