000
FXUS61 KBUF 211529
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1129 AM EDT Sun Apr 21 2024

.SYNOPSIS...
High pressure will build into the area today, 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.

&&

.NEAR TERM /THROUGH MONDAY/...
A weak surface trough moving through western and northcentral
NY producing a few light rain and higher elevation snow showers,
possibly lingering into the early/mid afternoon across the
Genesee Valley and Finger Lakes. Otherwise, mainly dry weather
expected through this afternoon.

Otherwise, an upper level trough will remain across the forecast
area through Monday. Cyclonic flow will maintain cool and breezy
conditions, however unlike Saturday it will be drier. Expect lake
shadows to become established again by this afternoon with
stratocumulus forming along and inland of any lake breeze
boundaries. It will become breezy again today, however not as windy
as yesterday with gusts 20-30 mph this afternoon.

A cold front will move across north central NY tonight. The front
will encounter the dry airmass in place across the Northeast and
showers will diminish as they approach the region. Chilly tonight
with lows in the upper 20s to low 30s across the higher terrain to
the low 30s elsewhere. Warm air advection will begin Monday as the
core of the coldest air retreats to the northeast. Surface high
pressure will remain in place and dry conditions are expected across
the region. Warmer Monday with highs in the 50s and light winds.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
While this period will start innocent enough with fair dry weather
and moderating temperatures...a relatively flat upper level pattern
will experience significant amplification that will lead to very
active weather for the middle of the week. This will include a
general quarter inch dousing of rain to add to our already very
soggy start to Spring. The details...

A wedge of high pressure extending from Nova Scotia and coastal New
England to the Deep South will continue to provide fair dry weather
to the region Monday night through at least early Tuesday afternoon.
The return flow around the backside of this fair weather feature
will combine with a developing storm system over the Upper Great
Lakes to direct a deepening southerly flow of notably milder air
into our region. After several days of temperatures topping out in
the 40s to lower 50s...a well mixed (35-40 LLJ) environment of H85
temps arnd +2c will allow us to look forward to widespread readings
in the 60s Tuesday afternoon. This is where the `party` will end
though.

A vigorous Pacific based shortwave crossing the Upper Great Lakes
Tuesday afternoon will phase with an already established longwave
trough over eastern Canada during the course of Tuesday night. In
the process...a wavy sfc frontal boundary along the leading edge of
a sharp baroclinic zone will SLOWLY press through our forecast area
through midday Wednesday.

Initially...a large swath of widespread rain will advect into our
area from Ohio late Tuesday and especially Tuesday night. The
precipitation will be supported by low level convergence along and
ahead of a pre frontal sfc trough with significant reinforcing upper
level lift  in the vcnty of the left front exit region of a
cyclonically curved 120kt H25 jet. PWAT values will hover just below
1.0" in the environment...thus supporting some moderately heavy rain
at times. Will use 100% pops for the overnight period. While not
overly impressed with the potential for convection...there is just
enough elevated CAPE being advertised to maintain slgt chc wording
for thunderstorms...mainly for the western counties and more
directly for the Srn Tier. Basin average rainfall will be in the
vcnty of a quarter inch...with local amounts as high as a half inch.

As the last sfc wave exits our region along the slow moving frontal
boundary Wednesday morning...strong H925-70 frontogenetic forcing
will take over on the backside of the system. While the deepest
moisture will have been pushed across New England by this time...
there should still be enough moisture left behind during the morning
hours to support leftover showers and possibly some steadier pockets
of rain...mainly from the Finger Lakes eastward. The bulk of the
moisture will then be stripped away by midday Wednesday...while very
strong cold advection on gusty northwest winds will send H85 temps
plunging below zero. The leftover rain showers could end as a bit of
graupel or wet snow in the afternoon...especially across the
elevated terrain. The cold advection should also promote a
neutral...if not a non-diurnal temp trend for the afternoon with
temps slowly falling through the 40s during a time of partial
clearing.

A large Canadian sfc high centered over the Great Lakes Wednesday
night will be accompanied by an influx of very dry air...and this
will help to counteract a minimal lake response from a north-
northwest upslope flow over Lake Ontario. The result will be fair
dry weather...albeit it chilly with temperatures away from the lakes
falling below freezing.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
This period will largely feature fair dry weather with day to day
warming...as a ridge over the nations mid section on Thursday will
gradually push east to the Ohio valley and Lower Great Lakes by the
weekend. While this high confidence solution will guarantee that our
temperatures will climb to above normal levels...there is also
increasing confidence that clouds and showers will accompany the
warmer weather to start the weekend. More on that in the days to
come.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Mainly VFR conditions will continue across western and northcentral
NY through tonight.

Widespread stratus decks across the region producing CIGS mainly in
the 4-6 kft range currently, with some isolated MVFR CIGS found
across the higher terrain. A weak surface boundary will finish
crossing western NY/Finger Lakes region this afternoon producing a
few spotty light rain and higher elevation wet snow showers through
the afternoon. Very brief MVFR/IFR VSBYs may be experienced within
any isolated wet snow or graupel showers.

Otherwise, stable lake shadows will develop this afternoon with
stratocumulus remaining along and inland of any lake breezes, with
CIGS again in the 4-6 kft range for KBUF/KIAG over to KROC. Decks
should be mainly FEW-SCT across KJHW and KART. Southwest to west
wind gusts to 20-25 knots will become common across the terminals
this afternoon.

Winds diminish tonight. Aside from a stray rain or or wet snow
shower toward the Saint Lawrence Valley as a moisture starved cold
front pushes south across the area first half of tonight, dry
weather is expected through Monday as high pressure builds in behind
the boundary.


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 and Friday...Mainly VFR.

&&

.MARINE...
Westerly winds will again be on the increase this afternoon with
another period of Small Craft Advisory conditions expected on
Lake Erie and the Upper Niagara River, as well as the eastern
end of Lake Ontario through tonight. Weaker winds and waves will
reside across the waters Monday through Monday night. Southerly
winds will freshen on the waters Tuesday and will likely result
in Small Craft Advisory conditions into midweek.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until midnight EDT tonight for LEZ020-040-
         041.
         Small Craft Advisory until 6 AM EDT Monday for LOZ044-
         045.

&&

$$

SYNOPSIS...HSK
NEAR TERM...HSK/JM
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...JM
MARINE...HSK/JM