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000
FXUS61 KBUF 131449
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1049 AM EDT Sat Apr 13 2024

.SYNOPSIS...
Deep low pressure will continue withdrawing northward across Quebec
this afternoon...with rain and higher elevation wet snow tapering
off and winds slowly diminishing from from west to east. High
pressure will then cross the area tonight bringing a brief period of
dry weather and lighter winds. Warmer temperatures will return ahead
of a compact Clipper system that crosses the area on Sunday bringing
another round of showers and a few thunderstorms, before high
pressure returns brings a mainly dry start to the new work week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
With the late morning update...have sped up the diminishing trend to
the precipitation a little bit based on radar trends across far
western New York...which show the back edge of the precip
progressing eastward a little faster than previously forecast. Have
also dropped the westernmost Wind Advisory...as METAR and mesonet
obs both show that wind gusts have fallen to below advisory levels
across the far western counties.

Otherwise, large storm system that has produced all of the active
weather the past few days will continue to pull north through Quebec
this afternoon. This will allow rain and wet snow shower activity to
continue to slowly taper off from west to east through the day. An
additional light slushy accumulation will be possible across the
highest terrain east of Lake Ontario, mainly through midday before
strong mid April diurnal effects force a changeover to rain or just
make it nearly impossible for snow to accumulate. The other main
story will continue to be the winds with gusts to near 50 mph
lasting into the afternoon hours from the Finger Lakes east to
Oswego County. A Wind Advisory remains in place until 2 PM for
portions of the Genesee Valley and the Finger Lakes Region...and
until 5 PM for N. Cayuga and Oswego counties. These conditions will
make for a cold and raw day with highs ranging from the upper 30s on
the hilltops to the mid an upper 40s elsewhere.

Transient high pressure will cross the region tonight bringing a
brief period of mainly dry weather, while also finally allowing
winds to relax some. Lows will mainly range through the 30s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
On Sunday, a weakening 40kt LLJ will nose into the eastern Great
Lakes across the Ohio Valley, as a stronger 100kt upper-level jet
drives a northern stream shortwave trough southeast across the upper
Great Lakes. The confluence of these two features will cause Q-
vector convergence out ahead of this shortwave trough, resulting in
broad surface cyclogenesis and a low that will quickly drop through
the region. The low`s attendant warm front will lift into the region
through the day, before being quickly shunted southward as a cold
front later Sunday evening. Another round of widespread rain showers
and a few thunderstorms will accompany this clipper system Sunday.
Rain showers should first spread inland from Lake Ontario Sunday
morning, then push southward as the low crosses the region through
Sunday afternoon. While some weak elevated instability could bring
an isolated rumble of thunder to WNY Sunday morning, daytime heating
in the warm sector Sunday afternoon will cause MLCAPE values to
increase to around 300-600J/kg across the Southern Tier, with the
higher end values being found near (and especially south of) the
NY/PA line. Thus, this is when and where the highest chances for
thunderstorms are expected Sunday. 0-6km bulk shear values between
40-50kts could support a few stronger/better organized storms in
this area as well, though as alluded to earlier, the greatest
instability is expected to remain south of our area across PA.
Rainfall amounts have trended a bit higher with this latest guidance
but are still expected to average between 0.25"-0.5" in most areas.
Thunderstorms and locally heavy downpours will result in isolated
higher totals.

The presence of the frontal boundary over the region Sunday will
result in a fairly large north to south spread in high temperatures.
Highs up in the North Country will be mainly in the 40s, possibly
the low 50s across the lower terrain areas, while highs in the upper
60s are expected to the south near the NY/PA border. Temperatures
will average in the 50s in between.

As the system exits the region early Sunday night, it will become
increasingly sheared apart and wash out to the southeast.
Shower/thunderstorm chances will quickly taper off from north to
south across the region with areawide dry weather expected for the
second half of the night. Clouds will likely linger for much of the
region, especially over the higher terrain of the North Country and
Southern Tier. Temps will bottom out in the low 40s south of Lake
Ontario overnight, with upper 30s east of the lake.

Mostly dry weather will continue through Monday night as weak
surface high pressure builds into the forecast area from the upper
Great Lakes. There could be a few showers across northern
Jefferson/Lewis counties Monday as weak shortwave energy embedded
within a large scale trough over Quebec approaches the area.
Otherwise, highs Monday should average in the 50s, with lows Monday
night in the low 40s to upper 30s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The medium range guidance packages continue to favor a slower track
with the large cutter-type low forecast to shift 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, Tuesday is expected to remain dry. 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
continued to undercut NBM PoPs a bit here as there remains a good
deal of uncertainty in the timing of expected breaks in the precip
between the warm frontal segments and the system`s primary cold
front.

After that time disagreement amongst the medium range packages
increases rather sharply for the Thursday-Friday period...resulting
in a correspondingly sharp increase in overall 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 Thursday afternoon through Friday...while
also keeping these confined to the chance range.

With respect to temperatures, highs on Tuesday should average on the
warm side in the low to mid 60s as surface high pressure slides to
our east and causes a general southeasterly flow to develop. Warm
advection associated with the low will then help to pump readings up
to unseasonably warm levels in the mid 60s to low 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. At this juncture, high temperatures are expected to
fall back into the 50s and upper 40s by Friday.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
Large low pressure system that has been responsible for the wet and
windy conditions over the past couple of days will finally pull away
from the area this afternoon. Rain and higher terrain wet snow
showers will taper off from west to east across western NY through
early afternoon, then from the Finger Lakes east through the mid and
late afternoon. Expect MVFR/isolated IFR CIGS to linger through much
of today, before gradual improvement to VFR begins from west to east
starting mid to late afternoon in the west, with KART last to come
up to VFR sometime during the evening hours. Windy conditions will
continue through much of the day with 30-40 knot gusts south of Lake
Ontario and 20-30 knots toward the North Country.

It will dry out this evening along with winds coming down through
the evening hours as high pressure builds in briefly tonight. KART
may keep MVFR CIGS through the evening hours, otherwise expect mainly
VFR at all sites tonight.

Outlook...

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...
With winds having fallen below gale force on Lake Erie...have
converted the Gale Warning there to a Small Craft Advisory.
Meanwhile gale force winds and Gale Warnings continue on Lake
Ontario...with Small Craft Advisories continuing for the Upper
and Lower Niagara River.

The Gale Warnings on western Lake Ontario remain set to expire this
afternoon...and on eastern Lake Ontario late this evening. These
will be replaced by Small Craft Advisories that will last until
winds come down from west to east through this evening and tonight.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory until 2 PM EDT this afternoon for NYZ003-004-
     012>014-020-021.
     Wind Advisory until 5 PM EDT this afternoon for NYZ005-006.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LEZ020.
         Small Craft Advisory until 11 PM EDT this evening for
         LEZ040-041.
         Small Craft Advisory until 11 PM EDT this evening for
         LOZ030.
         Gale Warning until 2 PM EDT this afternoon for LOZ042-062.
         Gale Warning until 11 PM EDT this evening for LOZ043>045-
         063>065.

&&

$$

SYNOPSIS...JM/JJR
NEAR TERM...JM/JJR
SHORT TERM...PP
LONG TERM...JJR/PP
AVIATION...JM/JJR
MARINE...JM/JJR