-- Discussion containing changed information from previous version are highlighted. --
203
FXUS61 KBUF 051801
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
201 PM EDT Sun May 5 2024

.SYNOPSIS...
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A cold front will push across the region this evening,
producing showers and a few thunderstorms through tonight. Rain
will then end from west to east later tonight, with high
pressure bringing a return to dry weather Monday. The dry
weather will last through most of Tuesday before a warm front
brings a chance of showers and thunderstorms late Tuesday
through Wednesday.
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&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
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Early this afternoon radar shows an area of steady rain showers
across the Eastern Lake Ontario region. This area is along an
area of DPVA and will continue to move eastward with the
shortwave. Elsewhere there`s only sparse showers as of 2 p.m.
However, daytime heating will result in very limited surface
based instability which could result in some showers and
possibly a thunderstorm late afternoon into early evening. Then
a cold front approaching from the west will trigger some showers
as it moves through tonight. There could be a few thunderstorms
along this line this evening due to the lingering instability,
but by late tonight expect only scattered showers with this
boundary.

Low level flow will become quite weak along and behind the cold
front tonight, and drier air will lag behind by several hours.
Abundant low level moisture and weak flow will likely allow areas of
fog to develop from late evening through the overnight, with some of
this fog possibly lasting through early Monday morning.

Weak surface high pressure will then build across the region on
Monday and Monday night. There will be a north to south clearing
trend during the day Monday. Fair weather Monday night, with
mostly clear skies outside of some lingering clouds near the
Pennsylvania state line which will be close to the stalled
frontal boundary.

Despite the cold frontal passage, afternoon sunshine will allow
temperatures to rise into the upper 60s to lower 70s on Monday.
Good radiational cooling Monday night with lows mainly in the
40s. Forecast hedges towards a wider diurnal spread (warmer
highs and cooler lows) due to the clear skies and light winds.
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&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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On Tuesday the surface ridge axis will slowly drift east to New
England weakening in the process...while the leading edge of a
sprawling mid level trough and associated surface low over the
north- central states slowly works its way into the Upper
Mississippi Valley. As this does so...a warm frontal boundary
snaking southeastward from this system will slowly push
northeast across the Ohio Valley. While this latter feature
could draw close enough to support the potential for a couple
widely scattered showers across the Southern Tier later on in
the afternoon...the day should otherwise feature continued dry
weather with just a modest increase in cloud cover across far
western New York. With our airmass starting to warm again highs
should generally range through the 70s...though it will again be
a bit cooler along the lakeshores due to onshore flow.

Tuesday night the various guidance packages suggest that the warm
frontal boundary will lift further northeastward and into our region
while also becoming increasingly wavy as a supporting mid-level
shortwave ripples eastward across the central/eastern Great Lakes.
This will bring a general southwest-northeast increase in cloud
cover and eventually the likelihood of some showers as the evening
progresses...with a few thunderstorms also becoming possible due to
the arrival of some weak elevated instability. Otherwise it will be
a notably milder night with lows ranging from around 50 across the
North Country to the mid and upper 50s south of the NYS Thruway.
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&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The long term period continues to look wet with at least a chance of
showers for the entire forecast area each day. A mid/upper level low
over the northern Rockies will slowly track east, opening to a large
scale trough through the second half of the week.

Earlier in the week with the trough/mid-level low to the west,
periods of weak ridging over the region will give way to developing
sfc lows and shortwave troughs that will bring an influx of GOMEX
moisture north into the region. Moisture and large scale synoptic
lift will provide for periods of showers with some breaks in the
precip.

The larger trough will setup over the region by Friday, and persist
through at least the weekend. This will provide for several rounds
of showers, especially as different shortwave troughs track
through/around the larger trough. Cyclonic flow and the trough in
general over the region will also result in cooler temperatures.

Embedded thunderstorms will be possible at times, especially during
the middle of the week when instability will be a bit better than
later in the week.

Temperatures will start out above normal with highs in the mid 60s
to upper 70s from the higher terrain east of Lake Ontario to the
lower elevations of WNY respectively. Day-to-day cooling is then
expected through the rest of the period as the trough moves into the
region. Below normal high temperatures are expected for Saturday
with temperatures only reaching the low 50s to near 60 for the
afternoon.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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Low level moisture will remain in place for most of the 18Z TAF
cycle. This afternoon mainly MVFR cigs with IFR across higher
terrain. Area of showers across eastern Lake Ontario region will
exit to the east by late afternoon. Otherwise, scattered
instability showers and isolated thunderstorms are possible
across Western NY. Then steadier showers and possibly an
isolated thunderstorm with the passage of a weak cold front this
evening.

More low moisture behind this front, with IFR cigs likely along
with areas of fog. Expecting vsby to drop to around one mile,
but it will vary with lower vsbys possible at times.

Improving conditions late tonight and Monday morning as drier
air builds in from the northwest. Expect mainly VFR flight
conditions by Monday afternoon.

Outlook...

Monday night and Tuesday...VFR.

Tuesday night and Wednesday...VFR/MVFR. A chance of showers and thunderstorms.

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

Friday...MVFR. Showers likely.
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&&

.MARINE...
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Negligible winds and waves through Tuesday. There may be some
marine layer fog over Lake Erie and Lake Ontario this afternoon
through tonight as a warm/moist airmass overlays the cold lake
waters.
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&&

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

&&

$$

SYNOPSIS...Apffel/Hitchcock
NEAR TERM...Apffel/Hitchcock
SHORT TERM...JJR/SW
LONG TERM...SW
AVIATION...Apffel
MARINE...Apffel/Hitchcock