Area Forecast Discussion
Issued by NWS Buffalo, NY

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450
FXUS61 KBUF 241816
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
216 PM EDT TUE MAY 24 2016

.SYNOPSIS...
Summertime weather is on its way with highs climbing through the 70s
and into the 80s by this weekend.  Along with the warmer
temperatures, an increase in humidity will also bring back chances
of showers and thunderstorms each day leading up to and into the
Memorial Day weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
A narrow ridge of high pressure, at the surface and aloft is located
just to our west this afternoon and is expected will build east
across our region through tonight. A closed upper-level low over New
England will shift off the coast as the ridge approaches. The dry
airmass as supported by a very dry 12z KBUF RAOB along with
subsidence from the approaching ridge is supporting the abundant
sunshine across the region. Highs will top out mainly in the upper
70s to about 80 degrees this afternoon except northeast of Lakes
Erie and Ontario where lake breezes will hold temperatures near the
shores about 10 degrees cooler.

Tonight we will continue to see fair weather as the mid-level ridge
tracks east across the forecast area. Clear skies early will then be
replaced by increasing clouds from northwest to southeast as models
forecast an increase in moisture ahead of a weak shortwave and
surface front tracking into the central Great Lakes. Models show a
few showers developing along this surface boundary overnight but
should remain largely to our west and north over Ontario Canada. The
increase in cloud cover and a steady westerly breeze will help keep
overnight lows in the 50s to near 60.

On Wednesday the mid-level ridge will be temporarily flatted as the
subtle shortwave trough moves across the eastern Great Lakes. This
will be mirrored by a surface trough/windshift which would be the
focus for a chance of thunderstorm development Wednesday mainly
toward the afternoon hours. The 12z NAM builds 500-1500 j/kg of
surface CAPE ahead of this trough mainly across the southern shore
of Lake Ontario and inland of a southwest Lake Erie lake shadow
where surface dewpoints should climb into the 50s to about 60
degrees. Have added chance POPs for some thunderstorms during the
afternoon hours for these areas. 0-6 km Shear is forecasted to be
only 20-30 kts which should keep any thunderstorms that do develop
sub-severe. Temperature-wise expect again to climb into the
U70s/L80s with a gusty west to southwest flow boosting highs
potentially into the mid-80s in the warmer valley locations. A Lake
Erie lake breeze will keep locations along the shoreline including
downtown Buffalo about 10-15 degrees cooler.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
Any lingering showers east of Lake Ontario will end Wednesday
evening. This will leave a mainly dry night as a ridge of high
pressure builds from New England to the Mid Atlantic.
Temperatures will remain quite mild with lows in the lower 60s on
the lake plains of western NY, and mid to upper 50s in the cooler
Southern Tier valleys and North Country.

Thursday will bring the best chance for more widespread showers and
thunderstorms as more coherent forcing crosses the region. Model
consensus continues to track a mid level trough across the region
but some 12Z runs are a bit weaker than previous runs. Even though
this may limit areal coverage somewhat, increasing boundary layer
moisture will result in surface based instability to support some
showers and thunderstorms.  These may produce locally heavy
downpours, but otherwise a lack of deep layer shear will limit
thunderstorm intensity.

Showers and scattered thunderstorms will slowly diminish in coverage
Thursday night with the loss of diurnal instability and as better
forcing and warm advection exit to the east. However the environment
will be very moist with ample elevated instability that it would
only take a weak upper level disturbance to spark a thunderstorm.

On Friday there is little indication from model guidance that there
will be any significant upper level waves, however surface based
instability is likely to result in some showers and thunderstorms.
These are most likely form along or just inland of lake breeze
boundaries. More organized activity should taper off Friday night,
but similar to Thursday night it is difficult to rule out a stray
shower or thunderstorm.

Temperatures will be above normal throughout the period with highs
mainly in the lower to mid 80s on Thursday, and the mid to upper 80s
on Friday. It will be a bit cooler along the immediate lakeshores
due to the lake breeze. Also, dew points will rise to near 70 on
Friday, resulting in quite muggy conditions considering for May.
Overnight lows will also be on the warm side, with lows in the 60s
on Thursday and Friday nights.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A very summery pattern will be firmly in control through early
next week across the region as a classic Bermuda high sets up over
the western Atlantic, pumping heat and humidity into the Ohio
Valley and Northeast. The warmth and humidity will bring a chance
of a few scattered showers and thunderstorms each day, but there
will be plenty of rain free time as well.

Looking at the details, on Saturday the heart of the mid/upper
level ridge will build directly overhead. Temperatures are likely
to peak on Saturday, with highs in the mid to upper 80s inland
from the lakes. Expect scattered thunderstorms to develop with a
peak in coverage during the afternoon and evening with diurnal
heating. The better chances of convection will be found along and
inland of the lake breeze boundaries, with the lowest chances over
and northeast of the lakes.

By Sunday and Monday more Atlantic moisture may be drawn into the
area as easterly flow increases up the east coast ahead of a weak
quasi-tropical low drifting northward through the southeast states.
This may bring a little better coverage of showers and scattered
thunderstorms, and also decrease the reliance on diurnal instability
and lake breezes for convection to develop. Temperatures will remain
well above average for late May.

Looking farther ahead, it looks like the summer heat and humidity
will continue through the first week of June as the Bermuda high
sits in place and zonal flow remains confined to north of the
Canadian border.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
A ridge of high pressure will build across the region tonight
continuing VFR conditions. Clear skies will be replaced by some
increasing high clouds from the west overnight.

On Wednesday a weak trough, surface and aloft is forecast to cross
the eastern Great Lakes. This may trigger a few showers and
thunderstorms near Lake Ontario and inland from Lake Erie but
confidence is any activity at any of the TAF sites is not high
enough for inclusion in the TAFs at this time. Have stepped Cigs down
to BKN035 for now by 18z.

Outlook...
Wednesday night...VFR with a slight chance of showers.
Thursday through Saturday...Mainly VFR with a chance of showers and
thunderstorms.

&&

.MARINE...
A ridge of high pressure will build across the lakes tonight
continuing fair weather with breezy westerly winds. Winds and waves
will remain fairly negligible through the next few days. The
tranquil pattern will continue through the end of the week, although
a few thunderstorms may produce locally higher winds and waves at
times each day from Wednesday through next weekend.

&&

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

&&

$$

SYNOPSIS...SMITH
NEAR TERM...SMITH
SHORT TERM...APFFEL
LONG TERM...HITCHCOCK
AVIATION...SMITH
MARINE...SMITH



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