Lakeshore Flood Warning 16, NWS Buffalo, NY

Area Forecast Discussion
National Weather Service Buffalo NY
919 AM EDT Tue Oct 10 2017

.SYNOPSIS...
High pressure will build across the region today. A weak area of
low pressure passing to our south will bring rain to the area
Wednesday and Wednesday night. High pressure will then bring
mainly dry weather and above normal temperatures for the end of
the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Areas of low stratus will persist through late morning before
breaking apart into diurnal cumulus inland from the lakes by early
afternoon. Following the varying amounts of cloud cover this
morning, expect a mix of sun and clouds for the afternoon with the
greatest sky cover over higher terrain and least along the
lakeshores. Expect more above normal temperatures with highs in the
upper 60s to lower 70s.

A very weak front will slide south out of Ontario and into our
region late in the day and tonight with a modest increase in cloud
cover. An upper wave is expected to interact with the frontal
boundary late tonight with the leading edge of a rain shield
developing across the Ohio valley possibly reaching western New York
by Wednesday morning.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
A remnant mid level shortwave trough and surface low which was
responsible for some snow Monday over the central Rockies is forecast
to shift into the Ohio Valley by Wednesday and across Pennsylvania
Wednesday night. 00z models are all in agreement of the track of
this weak storm system. Warm southerly flow will transport Gulf of
Mexico sourced moisture over an 850mb thermal gradient. Forcing from
the temperature advection and synoptic support from the mid-level
trough will bring another soaking rain to western and south-central
NY Wednesday into Wednesday night with fairly steady rain in place
for some 6 to 12 hours. For the North Country, drier air associated
with Canadian high pressure trying to build south from Ontario should
act to shield the region from much if any rain where only chance
POPs have been preserved. While rainfall will not be as significant
as what fell from the tropical remnants of Nate, QPF from this mid-
week system will approach half to three-quarters of an inch across
western NY per 00z models.

On Thursday, the heart of the large Canadian surface high will shift
east over Maine. Mid-level ridging is then forecast to build across
western and central NY trapping lingering low level moisture with
mostly cloudy skies remaining in place through the day. Continued
weak warm air advection will bring a slight/low chance for some
drizzle. Temperatures on Thursday will run a few degrees warmer than
those of Wednesday with only low clouds to keep insolation very
limited. Highs should climb into the low to mid 60s.

On Friday, Mid-level ridging will remain over the East Coast with
the only change to the weather pattern being the center of High
Pressure shifting from Maine eastward to the south of the Canadian
Maritimes. Low level moisture will remain trapped over western and
central NY per model 925-700mb RH fields leading to keeping low
clouds in the forecast through the day. Support from an 850mb low
level jet may help with triggering a few isolated/scatted showers or
perhaps drizzle. Weak warm advection will allow temps to climb into
mid-upper 60s for most of the region south of Lake Ontario. The
stalled pattern may finally break later on Friday night as
strengthening southwest flow ahead of a Midwest cold front advects in
some drier air. Lingering cloud cover will allow overnight temps
Wed/Thur night to only slip back into the low-mid 50s for much of
western NY and mid-upper 40s east of Lake Ontario.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
Consensus of 00z models shows the Mid West cold front referenced in
the Short Term discussion will slow over the central Great Lakes on
Saturday. This boundary looks to then become a warm front running
from Lake Ontario east into the SLV on Sunday in response to a
deepening Great Lakes cutter low. There is still a decent spread in
the location and speed of the cutter low Sunday and Monday as it
tracks across the Great Lakes then on into either Quebec or off the
East Coast. This spread will keep low-mid range chance POPs in play
Sunday and Monday for WNY/CNY while the SLV features likely POPs
being closer to the center of the low Sunday. A trailing strong cold
front may cross western and central NY with a threat for gusty
possibly near Advisory-level winds. Once timing and location of this
front are fine-tuned in later model runs, POPs may be increased in
future forecasts.

Temperature-wise, the broad sub tropical ridge centered over the
southeast part of the country will keep our temperatures above
normal through the weekend before a return to near normal
temperatures is forecast to occur on Monday behind the Great Lakes
cutter storm. Highs in the low-mid 70s Saturday are forecast to slip
to only warming to around 70 on Sunday then possibly only as high
as 60 on Monday. Of course if the front is slower then Monday may
also be an above normal temperature day.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
Weak high pressure will build across the region today. Low stratus
will persist through midday with areas of MVFR and IFR CIGS. The low
clouds will break apart into diurnal cumulus this afternoon with
cloud bases rising to mainly VFR. The diurnal cumulus will dissipate
this evening, and give way to thickening and lowering VFR mid level
clouds overnight ahead of the next system.

Approaching low pressure will spread rain in WNY toward sunrise
Wednesday morning, but restrictions are not expected until after 12z.

Outlook...

Wednesday...Areas of MVFR/IFR with rain likely.
Thursday through Saturday...Mainly VFR.

&&

.MARINE...
High pressure will bring light winds through tonight. Low pressure
will then pass by to our south on Wednesday. This may bring a period
of stronger northeast winds to Lake Ontario with winds and waves
approaching Small Craft Advisory levels.

&&

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

&&

SYNOPSIS...TMA
NEAR TERM...HITCHCOCK/TMA
SHORT TERM...SMITH
LONG TERM...SMITH
AVIATION...HITCHCOCK/THOMAS/TMA
MARINE...TMA

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