Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 250147
AFDBUF

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

.SYNOPSIS...
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 summer...as 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.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
It will be another beautiful night across western and north
central New York...as 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 area...as 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.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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 west...an 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.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
A pair of frontal boundaries will quickly track across the forecast
area Monday into Tuesday with a chance of showers and thunderstorms.
The first frontal boundary will move through early Monday and will
provide the focus for shower and thunderstorm most likely south and
east of the both Lakes where the best instability (300-500 J/kg)
will be found across our CWA. Over the course of the day Monday, a
shortwave trough over central Quebec will quickly track east towards
New England into Monday night. As it does so, it will send another
frontal boundary south across the lower lakes, this frontal boundary
at this point looks weak and moisture starved with only a slight
chance of a shower or possibly a thunderstorm as it slips south
through the region. With its passage, any remainng storms will
quickly come to an end with surface high pressure building at the
surface and aloft over New York State. Wednesday, surface high
pressure slips off the Northeast Coast with return southerly flow
picking up and some sub tropical moisture creeping into our forecast
area with increasing chances for showers and thunderstorms late in
the week.

High temperatures will generally range from the U70`s to L80`s
inland away from the lakes for Memorial day (lake temperatures: Erie
51F and Ontario 50F). Tuesday through Thursday, look for highs in
the 70`s near 80F which will continue to be 5F-10F above normal for
late May(normal L70`s for Western and North Central NY).

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
High pressure over our region this evening 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.

Outlook...

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

&&

.MARINE...
High pressure in the vicinity of the Lower Great Lakes this evening
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
thunderstorms.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...HSK
LONG TERM...AR
AVIATION...RSH/TMA
MARINE...RSH/TMA


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