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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBUF 130945
AFDBUF

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

.SYNOPSIS...
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Windy and raw conditions will continue today as deep low
pressure continues to progress northward through Quebec. Rain
and wet snow shower activity will slowly taper off from west to
east through the day, with some additional slushy accumulations
possible across the highest terrain. High pressure crosses the
area tonight bringing a brief period of dry weather and lighter
winds. Warmer temperatures then 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 bringing a mainly dry start to the new work week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Rain and higher elevation wet snow ongoing with upper level low just
to our northeast and secondary surface cold front crossing the
region. Colder air continues to work in and we have seen some wet
snow across the higher terrain of the interior Southern Tier, and
recently across the Tug Hill, however it`s having a difficult time
sticking. With that said, still have 1 to 4 inches possible across
the highest hilltops of the interior Southern Tier, with a couple
inches possible on the top of the Tug Hill. Will hold on to Winter
Weather Advisory for now.

Otherwise, large storm system that has produced all of the active
weather the past few days will finally pull north through Quebec
today. This will allow rain and wet snow shower activity to slowly
taper off from west to east through the day. An additional light
slushy accumulation will be possible across the highest terrain,
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 through midday or so across western NY, but
lasting into the afternoon hours from the Finger Lakes east to
Oswego County. A Wind Advisory remains in place until 2 PM for the
Finger Lakes west 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.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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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.
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&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
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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.
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&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
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Rain showers occuring at most terminals with the higher terrain of
the Southern Tier now seeing some wet snow, including KJHW as next
next mid level shortwave and secondary cold front crosses the
region. Mainly MVFR CIGS across the lower terrain with IFR CIGS
higher terrain, although a period of IFR CIGS is possible across the
lower terrain sites into the first part of this morning. VSBYS will
also be reduced to MVFR/IFR at times in snow showers. It will remain
windy with westerly gusts 30-40 knots south of Lake Ontario, 20-30
knots expected across the North Country.

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 today. 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/IFR CIGS to linger through much of today,
before gradual improvement to VFR begins from west to east starting
mid to late afternoon, 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 will coming down
through the evening hours with mainly VFR expected at all sites by
late in the 06Z TAF period.

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.
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&&

.MARINE...
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The second of two cold fronts will currently crossing the region
with a wind shift to the west behind the boundary.

Gale force winds continue on Lake Erie and are currently ramping up
from west to east on Lake Ontario. Gale Warnings are in effect for
all of Lakes Erie and Ontario with high end Small Craft Advisories
for the Upper and Lower Niagara River. Gale Warning on Lake Erie
expires late this morning, while Gale Warnings on western Lake
Ontario expire this afternoon and late this evening for eastern Lake
Ontario. These will be replaced by Small Craft Advisories that will
last until winds come from west to east through this evening and
tonight.
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&&

.BUF WATCHES/WARNINGS/ADVISORIES...
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NY...Wind Advisory until 2 PM EDT this afternoon for NYZ001>004-
     010>014-019>021-085.
     Wind Advisory until 5 PM EDT this afternoon for NYZ005-006.
     Winter Weather Advisory until 2 PM EDT this afternoon for
     NYZ012-019>021-085.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LEZ020.
         Gale Warning until 11 AM EDT this morning 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.
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&&

$$

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