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000
FXUS61 KBUF 232336
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
736 PM EDT Tue Apr 23 2024

.SYNOPSIS...
A wave of low pressure will move over the eastern Great Lakes
tonight, followed by a strong cold front Wednesday morning,
generating periods of rain across the region. The rain will end from
north to south Wednesday afternoon, and may even mix in with a few
wet snowflakes before ending across higher terrain. An expansive
area of Canadian high pressure will then assure us of fair dry
weather Thursday and Friday, before a few showers return this
weekend. Temperatures remain chilly on Thursday, followed by day-to-
day warming with readings soaring to well above normal levels by the
second half of the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
A sharp mid level trough will advance east across the Great Lakes
overnight, providing a period of large scale ascent as DPVA and
height falls overspread the region. A weak wave of low pressure will
move northeast over the eastern Great Lakes overnight, with
associated low level flow adjustments aiding in low/mid level
convergence and deformation across the area, supporting several
hours of widespread rainfall.

Radar imagery showing rain rapidly expanding across the region early
this evening in response to the arrival of stronger forcing from an
approaching wave of low pressure. The incipient airmass ahead of the
rain was very dry, so there will be plenty of sub-cloud evaporation
through the first hour or two of rainfall, keeping the rain reaching
the surface on the light side. Rainfall rates will increase once the
low levels saturate by mid evening, with a few pockets of moderate
rain expected. The most widespread rain will fall across Western NY
through the first half of the night, followed by a brief break in
organized rain late tonight. East of Lake Ontario, the most
widespread rain will fall from late evening through the overnight.

Wavy cold front moves into northern portions of the area early
Wednesday morning, then will push southeast across the remainder of
the area through the morning hours. The cold front will bring
another round of showers to the region Wednesday morning, aided by
weak lake induced instability and increasing northerly upslope flow.

Decent CAA in the wake of the front will cause temperatures to fall
from the 40s into the 30s for most areas. Enough moisture will
linger briefly in the colder air that precipitation may end as a few
wet snowflakes across higher terrain (especially east of Lake
Ontario) before rapidly tapering off from north to south from late
morning through mid afternoon. May be able to squeeze out a slushy
coating across the Tug Hill Plateau and western foothills of the
Adirondacks around late morning just before the precipitation ends.

Skies should then rapidly clear from north to south through the
afternoon as much drier air builds in, with sunshine likely
returning, especially across northern portions of the area. It will
be a very chilly day with many area remaining in the 30s to low 40s
after peaking in the low to mid 40s to start the day.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
Broad troughing spread across the East Coast earlier in the week,
will begin to pull east into the Atlantic Ocean Thursday and Friday.
Meanwhile, mid-level ridging spread across the upper Midwest fill in
across the lower Great Lakes in the wake of the trough. A shortwave
trough within the next longwave trough spread across the western
half of the CONUS will traverse the Central Plains Friday and Friday
night.

Looking further into the details, surface high pressure centered
over the eastern Ontario and western Quebec will continue to dive
south into the Great Lakes and Ohio Valley Wednesday night and
Thursday. This high will then continue to sag south into the
Atlantic by Friday night. Overall this will support dry weather
Wednesday night through Friday.

The aforementioned shortwave trough will support a surface low over
the Central Plains Friday evening. As the night progresses, a
surface warm front will advance northeastward towards the lower
Great Lakes late Friday night/early Saturday morning.

Despite the dry weather, conditions will continue to remain on the
cool side due to the exiting troughing pattern overhead. Highs
Thursday will range in the upper 40s to low 50s. A slight warm up
Friday with highs peaking in the low 60s to a few mid 60s across the
I-90 corridor along the Lake Erie shoreline of Western New York.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The main story for the weekend and early next week will be the
strong warmup, as well as on and off chances for showers and
thunderstorms.

On Saturday, a sfc-700mb ridge of high pressure will be well east of
the region over New England, while the upper level ridge lags behind
to the west. This will allow a warm front associated with a low over
the upper Midwest to move out of the Ohio Valley and across the
forecast area through the day. Isentropic lift on this wing of warm
advection will bring a swath of rain showers to the region west to
east. Shower coverage will be highest across WNY in the morning,
before this batch of precip then slowly falls apart as it traverses
eastward, becoming further detached from its parent low and running
up against the strong ridge over New England. Temps should be
similar to those seen on Friday, generally ranging from the upper
50s to the low/mid 60s.

The more pronounced warming trend will come starting Saturday night
as the broad low to the west weakens and slides across the upper
Great Lakes to Canada. This will cause the overhead upper level
ridge to flatten and perhaps allow a few additional showers/tstorms
to cross into the region overnight. Thereafter, the synoptic pattern
will eventually evolve into something resembling an Omega block,
with a stubborn ridge of high pressure across the eastern CONUS
flanked by waves of low pressure on the lee side of the Rocky
Mountains and a closed low across the northwestern Atlantic. Strong
anticyclonic flow around the sfc high off the East Coast will begin
to circulate much warmer air across much of the eastern CONUS
including the Great Lakes through the remainder of the weekend and
into early next week. At this range...it appears low temps Saturday
night should range in the 50s, closer to normal daytime highs for
late April. Thereafter Sunday and especially Monday will be the
warmest days we have seen in quite a while with temps climbing well
into the 70s in many areas, possibly even low 80s across the typical
warmer spots across the interior Genesee Valley. A cold front should
then bring temps back down a few degrees Tuesday, though still
remaining warm the 60s and low 70s.

While this synoptic pattern lends high confidence in temperatures
averaging well above climatological norms, confidence in chances for
additional showers and thunderstorms after Saturday remains low. The
main uncertainty stems from how the closed low over the Atlantic
evolves, as well as the strength/timing of the additional waves of
low pressure to the west cresting over the ridge. In general expect
shower and thunderstorm chances to roughly follow the diurnal
heating trend, being greatest in the afternoon and early evening
hours each day, with plenty of dry time mixed in. More widespread
showers should arrive with the front on Tuesday though PoPs are
mainly in Chc range as uncertainty in the timing of the front
remains low.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
A wave of low pressure will move across the eastern great Lakes
tonight, producing periods of rain. Dry low levels ahead of the rain
will keep CIGS/VSBY VFR for the first few hours of rain, but as the
low levels saturate expect areas of MVFR CIGS to expand mid to late
evening. A few pockets of moderate rain may also reduce VSBY at
times. The first area of rain associated with the wave of low
pressure will taper off temporarily late tonight.

A cold front will then move south across the area Wednesday morning
with another round of showers. Increasing northerly upslope flow
just behind the front will bring a few hours of widespread IFR CIGS
Wednesday morning. CIGS will then improve and scatter out from north
to south in the afternoon, with VFR prevailing by late in the day.

Outlook...

Wednesday night through Friday...VFR.
Saturday...VFR/MVFR. A chance of showers.
Sunday...Mainly VFR. A chance of showers.

&&

.MARINE...
Fresh southwesterlies continue through early to mid evening. This
would typically favor Small Craft Advisory conditions, but the early
season cold dome effect is likely coming into play as model guidance
is holding waves down for most areas, however there will still be
some decent chop on the waters. The exception remains for the
western third of Lake Ontario (W of Hamlin Beach), where a SCA for
that area remains in effect.

A wavy cold front will slowly pass through the region tonight. While
winds and waves will briefly subside in the process (especially on
Lake Ontario), a notable but short-lived increase in northerly winds
can be expected on Wednesday. While the fetch will not be overly
favorable for significant wave increases, a brief period of moderate
northerlies will still generate Small Craft Advisory conditions on
Lake Ontario, and very choppy conditions on Lake Erie.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LOZ042.
         Small Craft Advisory from 7 AM to 5 PM EDT Wednesday for
         LOZ042-045.
         Small Craft Advisory from 7 AM to 8 PM EDT Wednesday for
         LOZ043-044.

&&

$$

SYNOPSIS...Hitchcock/JM
NEAR TERM...Hitchcock/JM
SHORT TERM...EAJ
LONG TERM...PP
AVIATION...Hitchcock
MARINE...Hitchcock/JM/RSH