Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241833

Area Forecast Discussion
National Weather Service Buffalo NY
233 PM EDT Thu May 24 2018

High pressure moving off the Mid Atlantic coast tonight will
circulate warmer and increasingly more humid air into our region for
the upcoming holiday weekend. This will certainly make it feel like
the first official weekend of apparent temperatures will
climb to levels more typical of July. The summery airmass will
support some scattered thunderstorm activity...which should become
more common as we push deeper into the long weekend.


It will be another beautiful night across western and north
central New a wealth of dry and continued subsidence
from an exiting area of high pressure will offer up clear skies
and comfortable temperatures. The exception to the clear skies
will be some cirrus that will graze the North Country as a weak
wave will cross eastern Ontario into Quebec. Mins tonight will
range form the upper 40s in the coolest Srn Tier valleys and in
a few spots across Lewis county to the mid 50s most elsewhere.

Friday promises to be another salubrious day across our
forecast a deamplifying mid level ridge will settle
over the Lower Great Lakes. This will support another day of
full sunshine... although some debris cloudiness will be found
over the Thousand Islands region as a result of some convection
near and upstream from the Ottawa Valley. Mother Nature will
tack a couple degrees onto the H85 temps (16c)...and as this
airmass becomes fully mixed...we can anticipate that our
afternoon highs will range from within a few degrees of 80 across
the North Country to the mid and upper 80s in the Genesee Valley
and in the warmer Southern Tier valleys.

As we head into the holiday weekend Friday night...a shortwave
digging across the Upper Great Lakes will combine with the offshore
surface high to deepen the south to southwest flow across our
region. This will promote an even milder night with temperatures
forecast to hold above 60 degrees. There may also be a shower or two
across the North Country as a cold frontal boundary will sag south
across the Ottawa Valley.


The sub-tropical ridge will become surpressed off the southeast
coast this weekend and return flow will advect moisture and warmth
into the eastern Great Lakes through Memorial Day. This will lead to
the chance of showers and thunderstorms, mainly in the afternoon and
early evening.

High pressure located well off the east coast will continue to move
eastward Saturday. A cold front will be stretched from west to east
from Lake Superior to northern New England Saturday. A weak pressure
gradient will exist across Western and Central NY as that boundary
stays well to the north. A southwest flow will persist, mainly
across Western NY with lighter winds east of Rochester including the
North Country. Forecast soundings continue to show weak lapse rates
as dewpoints in the upper 50s/low 60s are expected and subtle
subsidence is still present with high pressure off the coast.
Temperatures will rise into the 80s inland and in the upper 70s
along the lake shores. Some interior valleys may see the upper 80s.
As moisture increases through the day, a cu field will likely
develop especially along any lake breeze boundaries. Showers and an
isolated thunderstorm are also possible mainly across the Southern
Tier and interior Western NY/Western Finger Lakes region and along
lake breezes as well as far upstate NY where a boundary persists.

Further upper level trough will approach Ontario Province
Saturday and showers and thunderstorms are expected to develop
across the pennisula Saturday afternoon. The loss of daytime heating
will surpress most of the activity across the Great Lakes Saturday
evening however any stronger showers or storms will likely move
eastward Saturday evening, making their way across Lake Ontario.
Activity is expected to diminish as they move into an unfavorable
environment however can`t rule out an isolated shower mainly near
the Lake Ontario shoreline Saturday night.

Better conditions exist Sunday for showers and thunderstorms across
the eastern Great Lakes as the upper level trough moves further east
across southern Ontario Province. The frontal boundary to our north
will sag southwestward moving across the North Country and into
Western NY by late Sunday afternoon. A weak gradient flow will also
result in a favorable environment for lake breeze development and a
southwest flow will cause dewpoints to reach the mid 60s by
afternoon. Instability will increase with SBCAPE around 400-800 J/KG
expected by afternoon. The upper level wind field will be weak so
the probability for strong to severe thunderstorms is low. Best
chance for showers and thunderstorms will be Sunday afternoon east
of Lake Erie and then across the region into Sunday evening as
activity that forms across the Ontario Pennisula moves eastward.
Temperatures will reach the 80s Sunday however with showers and a
possible thunderstorm around, temperatures will likely be a few
degrees cooler than Saturday.

The upper level trough will move into northern New England Sunday
night and showers and any thunderstorms will wane into the evening
hours. Upstream activity will also diminish as it moves eastward but
may produce additional showers across the forecase area with the
North Country seeing the longest period of showers into Sunday night.


A frontal boundary will sag southward across the region Monday and
Monday night, keeping some scattered shower or thunderstorm chances
in place across forecast area. Then an area of high pressure builds
into the region Tuesday. The center of the high pressure will be
just north of Lake Ontario by Tuesday night, and will slide
southeast towards the New England coast on Wednesday. Tuesday
through Wednesday will be dry as this area of high pressure provides
tranquil weather for the region. PW values will slowly increase as
the area of high pressure shifts to the east allowing for the next
influx of moisture and eventually shower chances later in the week.

High temperatures will generally be in the upper 70s to the low 80s.
Low temperatures will range from the upper 50s to lower 60s Sunday
night through Wednesday night. Both high and low temperatures will
be around 10 degrees above normal compared to late May averages.


High pressure over our region late this afternoon will make its way
off the Mid Atlantic coast later tonight. This will keep fair VFR
conditions with light winds in place across our region...although
some late night fog could produce a few hours of MVFR vsbys for
sites like KJHW and KELZ.

Mid level ridging supporting the aforementioned surface high will
then support continued VFR conditions through at least Friday
evening...although a stray shower cannot be ruled out from KART to
the Thousand Islands region.


Friday night...VFR.
Saturday...Mainly VFR. A chance of showers or an isolated
Sunday and Monday...Mainly VFR with some showers and thunderstorms


High pressure in the vicinity of the Lower Great Lakes late this
afternoon will slowly push off the Mid Atlantic coast tonight...
then will become anchored well offshore through much of the upcoming
holiday weekend. This will result in light to occasionally moderate
breezes through Friday night with insignificant waves.

As we make our way through Saturday...a weak cool frontal boundary
will sag south across Lake Ontario. This will encourage southwest
winds on Lake Ontario to shift to an easterly component while very
light winds will be found on Lake Erie.

While generally light winds will persist through the remainder of
the holiday weekend...there will be an increasing risk for





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