-- Discussion containing changed information from previous version are highlighted. --
980
FXUS61 KBUF 051843
AFDBUF

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

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
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.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
-- Changed Discussion --
On Tuesday the axis of surface-based ridging will slowly drift from
New York State to New England...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...with this feature drawing close enough to support the
potential for a few widely scattered showers/an isolated
thunderstorm across the Southern Tier later on in the afternoon.
Otherwise...the day should feature continued dry weather with just a
modest increase in cloud cover across far western New York. As for
temps...the general warm air advection pattern across our region
will allow highs to range through the 70s in many areas...though an
onshore flow will keep the south and southeastern shores of both
lakes notably cooler.

Tuesday night the warm frontal boundary will make its way across
western New York while also becoming increasingly wavy over time as
a supporting mid-level shortwave ripples eastward across the
central/eastern Great Lakes. This will bring a continued southwest-
northeast increase in cloud cover and eventually the likelihood of
some showers as the night 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.

On Wednesday the aforementioned shortwave will slide further east to
New England...with one or more surface waves along the now-stalling
frontal boundary eventually consolidating into a single broad
surface low over southeastern NY and southern New England. As this
occurs...any synoptically-driven showers and any embedded storms
should tend to taper off from west to east through the day. Latest
guidance suggests that this diminishing trend may even be quick
enough to support largely dry conditions across far western New York
for much of the day...though even there cannot completely rule out a
few additional widely scattered afternoon showers/storms as a
developing lake breeze convergence zone interacts with diurnally-
driven instability. High temps are a bit of a tricky call at this
juncture as the various guidance packages all show differing degrees
of cooling aloft behind this system...though a rough model consensus
suggests that readings may end up ranging from the mid-upper 60s
across the North Country to the mid-upper 70s across interior
portions of the Finger Lakes and Southern Tier.

Wednesday night a weak bubble of high pressure will slide across New
York State...before giving way to a sharp mid-level trough/surface
low making their way east from the Upper Midwest/Lower Ohio Valley
later on in the night. As a result we can expect partly cloudy skies
and largely dry/quiet weather Wednesday evening to eventually give
way to increasing clouds and renewed chance of showers across
Western New York by later on in the night. Otherwise...lows will
generally be in the upper 40s to lower 50s.

On Thursday the mid-level trough will make its way across the
central Great Lakes...with its attendant surface low gradually
becoming better organized as it slides east across the Upper Ohio
Valley and into far southwestern New York. Increasing moisture and
DCVA/isentropic upglide out ahead of this system will bring an
increasing likelihood of showers across our area from southwest to
northeast...with some weak instability also possibly supporting a
few embedded thunderstorms across the Southern Tier. With the
increased cloud and pcpn coverage expected...highs on Thursday will
be cooler than those of the preceding few days...with maxes ranging
from the lower 60s across the higher terrain to the mid and upper
60s elsewhere.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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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.

Day-to-day cooling is 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.
-- End Changed Discussion --

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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.

&&

.MARINE...
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.

&&

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

&&

$$

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