Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 130551
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
151 AM EDT Fri Oct 13 2017

.SYNOPSIS...
While high pressure over the Canadian maritimes will provide us with
mainly dry weather today...it will also continue to circulate
Atlantic moisture over the region which will result in a fair amount
of cloud cover. We can then anticipate a return to indian summer for
at least the first half of the weekend...as temperatures both days
will climb well into the 70s. A sharp cold front will bring an end
to the late summer warmth late Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure anchored over the Canadian maritimes will provide us
with fair dry weather today (Fri)...but it will also be largely
responsible for a fair amount of cloud cover. The clockwise
circulation around the large fair weather system has been
directing abundant Atlantic moisture back across our region for
the past couple of days...and now as the H925-70 flow veers to
the southwest...the corresponding low level cloud cover that is
trapped beneath a staunch subsidence inversion (arnd 9k ft) will
be advected from the western counties across the entire
forecast area (incl Eastern Lake Ontario region).

While temperatures today will average above normal...the wealth of
cloud cover will keep a lid on things. H85 temps in the vcnty of 10c
(8c east of lk Ont) would normally support afternoon mercury
readings in the 70s...but given the cloud cover...we can anticipate
highs to range from the low-mid 60s across the Southern Tier and
Eastern Lake Ontario region to the upper 60s across the lake plains
west of the Finger Lakes.

Tonight (Fri Night)...the large surface high will ease a little
further offshore. This will encourage a stronger southwest flow
aloft that will aid in pushing the aforementioned Atlantic
moisture into eastern New York while advecting a little drier
air in the low levels across our far western counties. This
should lead to a little clearing overnight for the far western
counties...but the stronger flow will also briefly establish a
weak baroclinic zone from the ensuing warm advection. The later
could be enough to touch off a shower or two for the eastern
lake Ontario region. It will thus be a milder night...with mins
forecast to range from the mid 50s across the Southern Tier and
Lewis County to near 60 along the immediate lake shores. These
readings will be at least 15 degrees f above normal mid October
values.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Saturday the weak cold front will continue to move southeast
across Ontario and stall near or just north of Lake Ontario. The
bulk of the deeper moisture and frontogenesis will remain on
the Canadian side of the border, but a few widely scattered
showers may sneak into the Niagara Frontier and North Country.
Areas near the Canadian border will see more in the way of cloud
cover, with a little more sun from the Southern Tier to the
western Finger Lakes. Ongoing warm advection will push
temperatures to well above normal, with highs in the lower 70s
in most areas.

Saturday night the frontal boundary will remain stalled during the
evening across southern Ontario, then begin to move back north
overnight as a warm front in response to flow adjustments downstream
of a strong trough moving into the Upper Midwest. There may be a few
widely scattered showers in the evening along and north of the
Thruway as warm advection increases. These showers will end from
south to north overnight. Temperatures will be very mild, with lows
in the mid 60s on the lake plains and upper 50s in the coolest
Southern Tier valleys and Lewis County.Winds have
diminished, allowing the small craft headlines to be dropped.
After this, a

Sunday and Sunday evening a strong surface low will move from the
central Great Lakes to western New England, deepening further with
time. A trailing strong cold front will cross our region from west
to east during the afternoon and evening. The morning will be mainly
dry in the warm sector. After that, expect a fairly solid band of
showers and possibly a few scattered thunderstorms to advance from
west to east across the area in the afternoon, forced by strong mid
level DPVA and low level convergence along the advancing cold front
and mid level trough. The rain will not last too long, tapering off
from west to east during the late afternoon and evening.

A strong wind field just off the deck will move across the area
Sunday, with the strongest winds in the warm sector and right along
the cold front. Instability will be marginal, but it may end up
being a low CAPE/high shear environment with a narrow band of
showers and possible thunderstorms producing at least gusty winds,
with some marginal potential for damaging winds. In addition to
convective wind potential, it will become windy in general on
Sunday. Low level lapse rates may be sufficiently steep to support
gusty winds even ahead of the cold front, with the strongest winds
expected within a few hours of the cold frontal passage. BUFKIT
profiles from both the NAM and GFS suggest the potential for
advisory winds gusting to 50 mph along and northeast of Lake Erie,
and also northeast of Lake Ontario.

Sunday night strong cold advection will drop temperatures into the
40s overnight. It will initially be dry behind the cold front, but
late Sunday night wrap around moisture and increasing lake induced
instability will support some lake effect rain showers southeast of
the lakes.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
It will be back to fall for the early part of this period as a
several shortwave troughs of low pressure pass across the
region. Temperatures may warm back to around 70F for the close
of the period.

Monday will open the week chilly, with an upper level trough
overhead and temperatures at 850 hPa dropping below zero. A
northwest flow over increased lake instability will likely bring
lake effect rain showers SE of the lakes. Will have highest pops for
now across Chautauqua County where there are some hints of an
upstream connection to Lake Huron. Highs Monday may be the coolest
since early May across the region with many areas only rising into
the upper 40s to lower 50s. It will feel cooler than that with a
brisk NW wind and cloudy skies, especially with lake influences.

The core of the cold air will be brief, passing us Monday afternoon.
By Monday night WAA aloft and the influx of drier air will end lake
effect rain showers...though low clouds off the lakes will linger
through the night. Clearing skies inland, and light winds may allow
for some frost formation well inland from the lakes.

Tuesday another shortwave trough will bear down upon the region.
There is still some uncertainty with the amplitude of this trough.
Will for now continue with slight chance pops east of Lake Ontario,
through a less amplified trough would bring less threat for rain,
and increased amounts of sunshine. There could also be some gusty
southwest winds Tuesday ahead of the trough, with the strongest
winds in the typical areas northeast of the lakes and across the lake
plains. Again a less amplified trough would likely diminish the wind
threat some.

Wednesday and Thursday high pressure will settle upon the region
with clear skies...and temperatures again rising back above normal.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
While high pressure over the Canadian maritimes will continue to
support fair dry weather across western and north central New York
today...it will also be responsible for pumping low level Atlantic
moisture into the region. The corresponding cloud cover through
daybreak will range from MVFR to VFR for KBUF, KIAG and KROC
to IFR for many of the Southern Tier sites (KJHW, KELZ) experiencing
IFR cigs.

By late morning-midday...the MVFR to IFR cigs over the western
counties should grudgingly lift to VFR levels. Meanwhile VFR
conditions will persist east of Lake Ontario.

For Friday night...MVFR to VFR cigs will once again be found across
the region.

Outlook...

Saturday...VFR.
Sunday...VFR/MVFR, chance -TSRA, windy with strong cold front.
Monday...Mainly VFR. A chance -SHRA SE of the lakes.
Tuesday...VFR

&&

.MARINE...
High pressure over northern New England and the Canadian Maritimes
will extend SE though eastern NYS through Friday. A south to
southwest flow will develop Friday with winds expected to remain
below small craft criteria thorugh Saturday. The only area which
will be close is eastern Lake Ontario near the St Lawrence where
waves will build to 4 ft.

A strong cold front will move through the region on Sunday, with
thunderstorms and possibly gale force winds behind the front.  SCAs
will likely on a NW flow into Monday with lake effect showers.

&&

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

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...HITCHCOCK
LONG TERM...THOMAS
AVIATION...RSH
MARINE...RSH/ZAFF



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