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489
FXUS61 KBUF 041809
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
209 PM EDT Sat May 4 2024

.SYNOPSIS...
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A weakening trough will produce a few spotty showers this
afternoon, but most of the time will be rain free. A wave of
low pressure will then move from the Ohio Valley this evening
across the eastern Great Lakes overnight through Sunday,
bringing a round of widespread rain to the region. The rain will
gradually taper off to scattered showers from west to east
Sunday, before ending entirely Sunday night. High pressure will
then build into the Great Lakes Monday with a return to dry
weather.
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&&

.NEAR TERM /THROUGH SUNDAY/...
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A weak trough will bring a small chance for showers this
afternoon, with the best chances along a convergence boundary
across the Niagara Frontier and Lower Genesee River Valley.
Later this afternoon, very limited instability could support a
few showers in the Western Southern Tier. However, the vast
majority of the day will be rain free, with afternoon highs
averaging about 10 degrees above normal.

A well defined mid level shortwave will then move from the Ohio
Valley this evening northeast across the eastern Great Lakes
overnight, generally following the path left by the remnants of the
trough that washes out over the area today. A 45+ knot
southerly low level jet ahead of the trough will bring a period
of enhanced convergence and low level moisture transport
overnight. This will combine with forcing from the shortwave to
produce a fairly widespread area of rain moving from southwest
to northeast across the region. Low stratus may intersect some
of the higher hills overnight through Sunday morning, resulting
in patchy fog across higher terrain.

Sunday, the mid level trough and associated forcing and deep
moisture will continue to move slowly northeast. Widespread rain
early in the day will gradually taper off to scattered showers from
west to east. The widespread rain should end in Western NY fairly
early in the day, while it will continue most, if not all day east
of Lake Ontario.

While the widespread rain will end across Western NY, an upstream
cold front will move into the far western end of the state by late
afternoon. This will combine with modest diurnal instability and
lake breeze convergence zones to support a few more scattered
showers in the afternoon and evening. Enough instability may develop
to support a few thunderstorms as well across Western NY.

Storm total rainfall amounts should average around a half inch,
but locally higher amounts of around an inch are possible east
of Lake Ontario where the rain will last longer.
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&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
The synoptic set up heading into Sunday night will feature a upper
level trough just north of the Great Lakes. The axis of this trough
will then pivot across the Canadian provinces of Ontario and Quebec
by Monday morning. A potent shortwave diving south into the trough`s
base Monday will cause the longwave trough to rotate east into the
Canadian Maritimes Monday night.

Down at the surface, low pressure centered over eastern Quebec will
continue to track northeast into the Canadian Maritimes, dragging
its associated surface cold front across the region Sunday night.
Meanwhile, surface high pressure across the central Great Lakes will
begin to advect east towards the eastern Great Lakes. Rain showers
ahead of the front will then finish crossing from west to east
Sunday night.

Surface high pressure will continue to advect east across the area
Monday and Monday night, resulting in a period of dry weather. Skies
will clear from northwest to southeast throughout the day, however a
disturbance passing east across the Ohio Valley towards the Mid-
Atlantic will support clouds to linger across the New
York/Pennsylvania state line.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A broad mid and upper level low over the northern Rockies and Upper
Plains Tuesday will gradually drift east across the northern half of
the contiguous United States throughout the remainder of the work
week. The track and progression of this low continues to have timing
and placement differences which also impacts the strength, timing
and placement of shortwave disturbances rotating through this
feature. This being said forecast confidence continues to remain
low.

Overall at the time of this update, expect this system to result in
unsettled weather with frequent opportunities for showers and some
thunderstorms throughout the Wednesday through Friday timeframe.
This being said the whole timeframe will not be a wash out, and a
few breaks in shower activity will be likely.

Now regarding temperatures for the end of the week, expect highs to
continue to average between 5 to 10 degrees above normal.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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VFR will prevail for the bulk of the area this afternoon,
although there will be some lingering MVFR cigs across the
Southern Tier. A wave of low pressure will move from the Ohio
Valley this evening across the eastern Great Lakes tonight. This
will bring a period of fairly widespread rain spreading from
southwest to northeast across the area from late evening through
the overnight. CIGS will deteriorate to widespread MVFR/IFR
shortly after the rain begins. Any pockets of moderate rain will
bring short term VSBY restrictions, and the low stratus may
intersect some of the higher hilltops overnight through Sunday
morning with some patchy fog/mountain obscuration across the
high terrain.

Steady rain will taper off from west to east, with cigs also
lifting some into the MVFR/VFR flight category during the
afternoon. Some instability will develop in the afternoon, with
widely scattered thunderstorms possible across Western NY.

Outlook...

Sunday night...VFR/MVFR. A chance of showers, mainly early.

Monday and Tuesday...VFR.

Wednesday...VFR/MVFR. Chance of showers with a chance of
thunderstorms.

Thursday...VFR/MVFR. Showers likely with a chance of
thunderstorms.
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&&

.MARINE...
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Moderate southeast winds through Sunday morning will produce
choppy conditions on the lakes, mainly in the offshore and
Canadian waters given the largely offshore wind component. Winds
will then become southwest and decrease from west to east
Sunday as a weak trough moves across the eastern Great Lakes.

Generally light winds are then expected Monday through Tuesday with
a weak pressure gradient in place across the eastern Great Lakes.
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&&

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

&&

$$

SYNOPSIS...Apffel/Hitchcock
NEAR TERM...Apffel/Hitchcock
SHORT TERM...EAJ
LONG TERM...EAJ
AVIATION...Apffel
MARINE...Apffel/Hitchcock