Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 221742
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
142 PM EDT Mon May 22 2017

.SYNOPSIS...
Showers east of Lake Ontario will taper off this afternoon with
clouds slowly clearing from west to east during the late afternoon
and evening. A weak ridge of high pressure will bring dry weather
Tuesday through most of Wednesday. Low pressure will then bring more
rain to the region Wednesday night and Thursday.

&&

.NEAR TERM /THROUGH TUESDAY/...
An area of showers along a pre-frontal trough will exit the eastern
Lake Ontario region through mid afternoon. The actual surface cold
front is lagging the pre-frontal trough by about 50 miles and may
produce a few more scattered showers through late afternoon east of
Lake Ontario. Otherwise the rest of the area will remain dry, with
clouds giving way to increasing amounts of sunshine across Western
NY through late afternoon with post-frontal drying and a developing
stable lake shadow off Lake Erie combining to dissipate cloud cover.

A weak ridge of high pressure surface and aloft will build over the
Lower Great Lakes tonight. Subsidence and drying associated with
this high will continue to support clearing this evening, with the
eastern Lake Ontario region the last area to clear overnight. The
clearing skies and a fairly cool airmass will allow for some
radiational cooling overnight. Expect lows in the upper 40s to around
50 on the lake plains, with low to mid 40s in the cooler sections of
the interior Southern Tier and Lewis County.

On Tuesday the weak surface ridge will remain in place from the
upper Ohio Valley to New England. Meanwhile warm advection and a
weak mid level shortwave will move northeast across southern
Ontario. This feature will have little direct impact on our area,
with any scattered showers remaining north of the Canadian border.
It will bring some increase in moisture and cloud cover, with both
mid level clouds and diurnal cumulus developing across the region.
Stable lake shadows will allow more sunshine northeast of Lakes Erie
and Ontario. Temperatures will rebound, with highs in the lower to
mid 70s away from lake influences. Weak synoptic scale flow and
strong differential heating will allow local lake breezes to develop
with winds becoming onshore along all the shorelines in the
afternoon, keeping temperatures cooler within a few miles of the
lakes.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...

High pressure is forecast to drift/expand into New England
through the next 24-36 hours. This should bring dry weather into
Wednesday morning while being supported with low amplitude
ridging building over the Northeast states so have backed
off/delayed arrival of POPs for Wednesday afternoon. Skies will
be partly cloudy while the surface high keeps any precipitation
shielded to our northwest and southeast. Temps warm above normal
into the low to mid 70s Wednesday benefiting from warm air
advection under southerly flow. Overnight temps Tuesday night
will remain mild also due to southerly flow and warm advection
aloft with lows only slipping into the 50s.

Chance POPs are in place for Wednesday afternoon increasing to likely
Wednesday night into Thursday as a surface/700mb low is shown by
models slowly lifting across the Ohio Valley or southwest Ontario
depending on your model of choice. The combination of mid-upper
forcing from a deep trough, mid-low level moisture transport and a
low level jet and occluded front should result in fairly widespread
rain showers shifting across western and central NY ahead of the
low. There is also a possibility of a few elevated thunderstorms
Thursday as the core of the mid-level low pivots near western NY.
The low looks to transfer its center from near the eastern Great
Lakes to off the southern New England coast Thursday night as the
trough becomes negatively tilted. Chance POPs are in place behind
this low with some lingering wrap around moisture Thursday night.
Temperature-wise, readings should remain just above average
Wednesday with highs in the upper 60s/lower 70s slipping back into
the low to mid 50s Wednesday night. Cooler temps are expected
Thursday just shy of climo due to the extensive cloud cover and
associated precipitation.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
The newly positioned coastal low will shift north into the Gulf of
Maine on Friday. Wrap around moisture and west to northwest upslope
flow off the lakes will keep chance POPs in play across western and
central New York. Slight to low chance POPs are forecast for Friday
night and Saturday as 00z models generally show our forecast area
between storm systems albeit with some timing differences with the
arrival of the next system. 00z EC and GEM models then show the next
system could bring in rain Saturday night or Sunday morning. The
system is forecast to then spread some rain showers north and east
across western and central NY through Sunday where mid-range chance
POPs have been included.

In regards to temperatures...the mercury will average close to
normal for Friday under weak cool advection and chances of showers
with max temps mainly in the mid 60s. Warmer air is then expected to
arrive for the weekend when highs will be upper 60s to lower 70s
with mid 70s possible is spots on Sunday. Low temps will remain
mild, only dipping into the low to mid 50s each night as dewpoints
do not slip below 50.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
An area of showers will exit the eastern Lake Ontario region this
afternoon as a cold front sweeps east across the area. Abundant low
stratus along and behind the cold front will continue to bring a mix
of VFR and MVFR CIGS to the region this afternoon, with skies slowly
clearing and returning to VFR from west to east from late afternoon
through the evening.

A weak ridge of high pressure will then build over the Lower Great
Lakes region tonight and Tuesday with VFR prevailing. Weak warm
advection and diurnal cumulus will bring some increase in cloud
cover on Tuesday, with CIGS remaining VFR.

Outlook...

Tuesday Night and Wednesday...Mainly VFR.
Wednesday night...VFR/MVFR with a chance of showers.
Thursday...VFR/MVFR with showers likely.
Friday...VFR/MVFR with a chance of showers.
Saturday...Mainly VFR.

&&

.MARINE...
Southwest flow in the wake of a departing cold front will continue
to bring Small Craft Advisory conditions to Lake Erie through early
this evening with waves building to 3-5 feet. Winds will be lower on
Lake Ontario and also shorter duration, which will prevent any
notable wave action. Weak high pressure will then build over the
Lower Great Lakes tonight through Wednesday, providing a period of
light winds and flat wave action through the middle of the week.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Beach Hazards Statement until 8 PM EDT this evening for NYZ010-
     019-085.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ020-
         040-041.

&&

$$

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



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