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000
FXUS61 KBUF 122239
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
639 PM EDT Fri Apr 12 2024

.SYNOPSIS...
Deep low pressure will continue to progress northward into Quebec
tonight and Saturday. Periods of rain will continue to produce a
soaking rainfall this afternoon into tonight. Cold air arriving
tonight will change rain to wet snow, with some slushy accumulations
possible across the higher terrain tonight and Saturday morning.
Additionally, windy conditions will prevail into Saturday afternoon.
Expect some dry time Saturday night before the next clipper system
brings rain back into the region Sunday.

&&

.NEAR TERM /THROUGH SATURDAY/...
A very large and dynamic low pressure system centered north of
Lake Ontario will continue to gradually broaden into a deep
longwave trough over the eastern CONUS through Saturday. As it does
so, its 985mb surface low centered north of the forecast area will
slide northeast further into Quebec tonight. The aforementioned
trough will then translate east of the region tonight, with a cooler
airmass accompanying a secondary cold front to cross the region
tonight into Saturday.

The next area of rainfall associated with a secondary cold front is
already moving across the Southern Tier. As the night progresses,
and an area of colder air will advect across the region, and this
will allow the rain to change over to wet snow. Snowfall
accumulations will be terrain dependent with accumulation of 4 to 8
inches possible across the interior areas away from Lake Erie of the
Southern Tier of Southern Erie, Wyoming, Chautauqua, Cattaraugus,
and Allegany counties. This being said, a Winter Weather Advisory is
in effect from 11PM tonight through 2 PM Saturday.

A switch over to snow will also occur across the higher terrain
east of Lake Ontario with some accumulating snow tonight through
Saturday, however due to the later arrival of the cold air to the
eastern half of the area giving a shorter window for cold air to
remain across the area, don`t expect accumulations to become
impactful.

Snow will then change back over to rain Saturday shortly after
sunrises and continue to pull east out of the area throughout
Saturday afternoon. This will support the start of a short dry
period Saturday evening.

Additionally under the cold air advection regime, breezy southwest
winds will continue into this evening creating gusts between 45 to
50 mph northeast of Lake Erie impacting Niagara, Orleans, Erie,
Genesee and Chautauqua counties. In the wake of the secondary cold
front, winds will shift westerly tonight and continue to ramp up
across WNY and the Genesee Valley. Winds again will gust up into the
45 to 50 mph range tonight through Saturday morning. This all being
said, a Wind Advisory remains in effect across far WNY (Niagara,
Orleans, Erie, Genesee, and Chautauqua counties) through 2 PM
Saturday, a Wind Advisory is also in effect from 11 PM tonight
through 2 PM Saturday for Monroe, Wayne, Wyoming, Livingston,
Ontario, Cattaraugus, and Allegany counties.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
The mid-level trough finally exits east of the region Saturday night
and then is briefly replaced by ridging aloft. This should wrap up any
remaining precipitation lingering across the forecast area as we
head into Sunday but the break will be short-lived.

A shortwave trough and compact area of low pressure is advertised to
drop across western and northcentral NY on Sunday. This will bring
another shot of rain to the region to finish out the weekend. We
even could see a few rumbles of thunder within the warm sector and
also with the cold frontal passage. This would mainly be focused
across western New York (Finger Lakes region and points west) and
closer to the NY/PA line. This is where models continue to advertise
roughly 300-600 J/kg of CAPE. In terms of rainfall amounts...basin
averages will range between 0.25"-0.50" with very localized higher
amounts given any thunderstorm. There will also be quite the
dichotomy in high temperatures found across the region. Highs east
of Lake Ontario will `likely` struggle to make it out of the 40s,
with a much warmer airmass found across the Finger Lakes region and
western New York with 50s to low 60s.

Drier weather returns Sunday night as high pressure builds into the
region behind this lastest system. Dry weather will continue
Monday and we should see a gradual day to day warming trend with
highs climbing into the 60s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The medium range guidance packages have been trending slower with
the large cutter-type low forecast to track northeastward from the
central Plains in the Tuesday-Wednesday period...with the latest
consensus suggesting that this system will reach the Upper Great
Lakes by later Wednesday afternoon and evening. Owing to this slower
progression...the bulk of Tuesday now looks to be dry...with just an
outside chance of a couple showers reaching far southwestern New
York later in the day. Better chances for some showers should then
overspread the area from west to east Tuesday night and especially
Wednesday as this system pushes one or more warm frontal segments
across our region...with some limited instability potentially also
allowing for a few thunderstorms across portions of the area south
of Lake Ontario Wednesday afternoon. Have generally upped PoPs into
the likely range as we push through the day Wednesday...though have
undercut NBM probabilities somewhat given the above mentioned
slowing trend in the guidance...which if continued would result in
the precip arriving even more slowly than currently forecast.

After that time disagreement amongst the medium range packages
increases rather sharply for the Thursday-Friday period...resulting
in a correspondingly sharp increase in forecast uncertainty and
decrease in forecast confidence. In general the initial cutter low
should lift by to our north and weaken...though the guidance
disagrees on the path of the low and how quickly all this occurs...
as well as on the degree/location/timing of any secondary
cyclogenesis that takes place along its trailing cold front. As a
result the guidance envelope suggests a cold frontal timing for our
area that ranges anywhere from later Wednesday night/Thursday
morning on the fast end to Friday on the slow end...a difference of
24-36 hours. Given this degree of uncertainty...will need to keep
precip chances in place through both Thursday and Friday...while
also keeping these confined to the chance range.

With respect to temperatures...highs on Tuesday look to be a bit
cooler than previously forecast given the slower approach of the
cutter low...however these should still average out solidly above
normal. Warm advection associated with the low will then help to
pump readings up to unseasonably warm levels in the mid 60s to mid
70s on Wednesday. After that time a general downward trend in temps
is expected through the end of the work week...though the speed of
this will be heavily dependent upon the timing of the cold front/
secondary surface low. For now have just pulled temps back a bit for
Thursday given the amount of forecast uncertainty...before dropping
these back further into the 50s by Friday.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
A deepening low pressure system sliding just northwest of the region
across the central Great Lakes will send another round of rain
showers, and some wet snow through Saturday, resulting in highly
variable flight conditions.

Conditions will deteriorate to MVFR/IFR as rain showers re-enter the
forecast area from west to east. Additionally tonight, as
temperatures cool after sunset, expect rain to switchover to snow
across the higher terrain of the Southern Tier and eastern Lake
Ontario region.

Rain and wet snow showers will gradually end from west to east
Saturday, with all rain by Saturday afternoon. Expect flight
conditions to improve gradually to VFR from west to east as the
showers exit the region.

Outside of the precipitation, expect windy conditions to continue
this afternoon into Saturday afternoon. Initially southwest winds
gusting 40-50 knots across far WNY will shift westerly and spread
into the Genesee Valley.

Outlook...

Saturday Night...MVFR improving to VFR.
Sunday...VFR/MVFR with a chance of showers and possibly a
thunderstorm.
Monday...Mainly VFR.
Tuesday...Mainly VFR with a chance of showers late.
Wednesday...MVFR/VFR with showers likely.

&&

.MARINE...
A strengthening low pressure system cutting to our northwest will
send two cold fronts through the region. The second cold front will
arrive late this evening and cause winds to shift to the west.

These fronts are expected to cause gale force winds on both lakes,
first across Lake Erie into Saturday morning, then across Lake
Ontario tonight through Saturday night. Small Craft Advisories
precede the Gale Warnings across the western and eastern ends of
Lake Ontario.

A more substantiative calming of the winds and waves will arrive by
Sunday as surface high pressure crests over the region.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory until 2 PM EDT Saturday for NYZ001-002-010-011-
     019-085.
     Wind Advisory from 11 PM this evening to 2 PM EDT Saturday for
     NYZ003-004-012>014-020-021.
     Winter Weather Advisory from 11 PM this evening to 2 PM EDT
     Saturday for NYZ012-019>021-085.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LEZ020.
         Gale Warning until 11 AM EDT Saturday for LEZ040-041.
         Small Craft Advisory until 11 PM EDT Saturday for
         LOZ030.
         Small Craft Advisory until 11 PM EDT this evening for
         LOZ042-045.
         Gale Warning from 11 PM this evening to 2 PM EDT Saturday
         for LOZ042-062.
         Gale Warning from 11 PM this evening to 11 PM EDT Saturday
         for LOZ043>045-063>065.

&&

$$

SYNOPSIS...EAJ
NEAR TERM...EAJ
SHORT TERM...AR
LONG TERM...JJR
AVIATION...EAJ
MARINE...EAJ/PP