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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBUF 202339
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
739 PM EDT Sat Apr 20 2024

.SYNOPSIS...
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High pressure builds across the area tonight, bringing mainly dry
weather that will last through the first part of the new work week.
Temperatures will be below average through Monday, before returning
to near normal levels by Tuesday.
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&&

.NEAR TERM /THROUGH SUNDAY/...
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This evening the convective showers are greatly diminishing with the
loss of daytime heating. We should see some clearing of the skies,
though a weak secondary surface trough will approach the region
later tonight with an uptick in mid level clouds. This weak surface
trough crossing the area tonight may possibly produce an isolated
rain or wet snow shower, otherwise mainly dry conditions expected
with a light westerly breeze. Lows tonight a bit below normal with
upper 20s across the higher terrain and low to mid 30s elsewhere.

Surface high pressure will be control for Sunday with mainly dry
conditions expected. However, with the main upper level trough
remaining in place aloft expect below normal temperatures and breezy
conditions to develop once again, but not as windy as today as a 35
knot LLJ will be absent. Highs will be mainly range through the 40s,
with some low 50s for the traditionally warmer spots. Another cold
front will approach late Sunday, however any precipitation
associated with the boundary will remain north of the area/nearing
the Saint Lawrence Valley through the end of the day.
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&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
A cold front albeit dry (moisture starved) is advertised to drop
south out of Canada Sunday night. We might see an isolated rain or
snow shower focused mainly across the St. Lawrence valley. Have low
end PoPs (20% or less) there, elsewhere it is `likely` to remain
dry. With its passage...a colder air mass will quickly sweep in
behind the front with 850H temps briefly down to -10C by Monday
morning. Modification of this chilly airmass then quickly occurs by
Monday afternoon. Given full late April sunshine we should see temps
push into the 40s east of Lake Ontario, with a range of 40s to low
50s found elsewhere.

Dry weather will persist Monday night with the ridge of high
pressure overhead slowly drifting to the eastern seaboard. Cold
night expected with lows in the 30s for most locales.

Tuesday...dry weather will slowly give way to increasing chances for
showers as a potentially strong cold front drops southeast across
the upper Great Lakes region. At this point...there still remains a
fair amount of uncertainty as guidance shows a wave (elongated) or
waves of low pressure developing along the front. There is also
varying degrees of QPF, and then how cold does it may get behind the
front. The GFS is `very` cold (potential outlier) behind the front
to the tune of -11C to -13C at 850H. Thinking the GFS is way too
cold but just can`t completely write it off just yet. That said...
we will need to see more run to run consistency. Even so...it is
looking fairly wet with widespread rain Tuesday night as the front
works into the region.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Heading into Wednesday morning, a robust albeit weakening mid-level
shortwave will be sliding east across the region. This feature will
be partially coupled with a deeper closed low just east of Hudson
Bay, with an elongated wave of surface low pressure ahead of the
system`s primary cold front extending from the Ohio Valley to
northeastern Quebec. A more distinct area of cyclonic flow at the
surface in the vicinity of the eastern Lake Ontario region will
quickly move in tandem with the southernmost shortwave, sliding east
into New England by the afternoon. There remains some uncertainty in
the strength of this surface wave over the eastern Great Lakes,
which will likely influence additional rainfall amounts and the
speed at which this initial cold front exits the region. The overall
trend will support the steadier more widespread rain beginning to
taper off across the western zones through the day, though the
latest CMCNH/ECMWF solutions indicate a bit more in the way of low-
level moisture and lighter wrap around showers sticking around into
Wednesday evening. Otherwise, it will be notably cooler Wednesday
with highs only in the 40s to low 50s.

Extra cloud cover and a few lingering showers could be weakly forced
by a secondary cold front that will sag southward into the region
late Wednesday into early Wednesday night, though a large expanse of
surface high pressure building across the Great Lakes and
southeastern Canada will lead to mainly dry weather across the
region overnight. A much cooler airmass will filter into the region
behind the secondary front which will support a rather chilly night,
as well as perhaps a brief mix with wet snow before the precip
completely tapers off. Though as mentioned previously in the short
term discussion...There is still an enormous discrepancy in how cold
this airmass gets between the deterministic ECMWF/CMCNH and GFS
solutions, as well as their respective ensembles. While the former
have consistently advertised 850H temps dipping to around -5C
overnight, the GFS continues to show temps closer to -13C. Will
continue to lean on the former and the NBM which support lows in the
low 30s to upper 20s across the hilltops, as opposed to widespread
20s advertised by the latter.

Other than a stray upslope shower across the Tug Hill/Western Dacks
Thursday morning, expect another cool albeit much drier day as high
pressure at all levels builds east over the region. Next chances for
rain will arrive Friday night and last through Saturday as the high
moves east of the region near the end of the week, supporting a
strong warm front that will move into the region from the southwest.
This will also initiate a warming trend, with temps averaging above
normal Friday and especially Saturday.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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For the 00Z TAFS VFR flight conditions are found, with a deck of
diminishing strato cumulus clouds from earlier in the day heating. A
weak secondary trough may return some mid level clouds later tonight
to Western New York, though flight conditions are expected to remain
VFR.

Gusty breeze this evening should end through the evening hours with
the loss of daytime heating. These gusts will return midday
tomorrow, with southwest gusts 20 to 25 knots through the afternoon
hours. These gusts will be a tad lower than today`s gusts which were
aided by a 35 knot LLJ that will be absent tomorrow.

Well defined lake breeze circulations tomorrow will form a line of
clouds between KIAG and KBUF...with these clouds (VFR) extending
eastward across KROC and the Finger Lakes region.

Outlook...

Monday...Mainly VFR.
Tuesday...Mainly VFR. A chance of showers later in the
afternoon.
Tuesday night and Wednesday...Areas of MVFR with showers.
Thursday...Mainly VFR.
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&&

.MARINE...
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Winds will temporarily diminish again tonight with small craft
advisories ending, then the winds increase again tomorrow with
another period of solid westerly flow Small Craft Advisory
conditions on Lake Erie and Lake Ontario. Overall, a poor weekend
for boating with chilly temperatures, strong winds, and high waves
much of the time.
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&&

.BUF WATCHES/WARNINGS/ADVISORIES...
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NY...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ040-
         041.
         Small Craft Advisory until 11 PM EDT this evening for
         LOZ042-043.
         Small Craft Advisory until 2 AM EDT Sunday for LOZ044-045.
-- End Changed Discussion --

&&

$$

SYNOPSIS...JM/Thomas
NEAR TERM...JM/Thomas
SHORT TERM...AR
LONG TERM...PP
AVIATION...Thomas
MARINE...Apffel/Hitchcock/HSK/Thomas