Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 232352
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
752 PM EDT FRI SEP 23 2016

.SYNOPSIS...
A much cooler airmass will be in place this weekend behind a cold
front. Incoming high pressure will bring a return to sunshine
Saturday and Sunday. Another cold front will cross the region late
Monday through Tuesday and bring the next chance of rain.

&&

.NEAR TERM /THROUGH SATURDAY/...
A few scattered light showers/patches of drizzle and low clouds will
linger across much of western and central New York along and south
of the NY Thruway through this evening. High pressure building south
behind an earlier cold front passage will bring drier air and help
slowly clear skies north to south. The combination of a short
northerly fetch, extensive mid level dry air, and a stout inversion
near 5K feet will prevent any lake effect rain showers. The lakes
will be able to generate/sustain some cloud cover however, with
north to northeast low level flow favoring areas from the western
Finger Lakes westward across western NY for some lingering cloud
cover overnight, aided by upslope flow. The North Country and
Central NY will see at least partial clearing with no off-lake
component.

Steady cold advection will bring much cooler temperatures overnight.
Expect lows in the upper 40s across most of the area, with lower 40s
east of Lake Ontario with no lake modification to the airmass. North
to northeast flow will keep areas within a few miles of the
lakeshores in the lower to mid 50s.

On Saturday surface high pressure over northwest Ontario province
will begin to nose into the Lower Great Lakes. Subsidence and drying
associated with the surface high will help to scour out any
remaining lake effect clouds south of the lakes by midday. A few
scattered diurnal cumulus will develop across the higher terrain of
the Southern Tier and Finger Lakes, with any clouds mixing out as
drier air continues to move in. The coolest airmass of the season
will settle into the area on Saturday. Expect highs in the mid 60s
in most locations, with lower 60s on the hills. The North Country
will be deeper into the cool air, with lower 60s at lower
elevations and mid 50s across the higher terrain.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH TUESDAY/...
High pressure will settle upon the region Saturday night, bringing
clear skies and light winds. A pool of cold air will be centered
near northern New England Saturday night, where sub-zero 850 hPa
temperatures will reside. We will still be on the western edge of
this pool of cold air through the night, with the cooler air aloft
over our eastern zones.

The combination of clear skies, light winds and cool air overhead
will bring favorable radiational cooling conditions, with many areas
dipping down into the 40s, and interior regions dropping down into
the mid to upper 30s. This will likely allow for frost formation,
across the interior So Tier, and North Country, with greater
confidence across the North Country which will lie closer to the
colder air aloft. Frost in these regions is near the norm, with the
average first frost here around the third week in September. Closer
to the rivers in the valleys frost will not be likely, but some
patches of fog will be possible.

A crisp, but sunny start to Sunday. As the surface high pressure
scoots eastward, and upper level ridge of high pressure bears upon
us, we should see afternoon temperatures warm nicely into the 60s
which is near normal. It will remain dry Sunday night though mid and
high level clouds will likely keep overnight lows a few degrees
warmer than the preceding night. There may still be additional frost
across North Country Sunday night, but not as great in coverage
area.

Our next system will be forming across the plains Sunday, as a deep
upper level shortwave trough of low pressure drops from the Northern
Rockies towards the Northern Plains. This system will be advancing a
Pacific based cold front across the lower 48-states. Meanwhile, a
steady flow of moisture from the Gulf of Mexico will be circulating
around a southeastern area of high pressure, with this plume of
moisture advecting northward up the lower Mississippi Valley and
eventually along and ahead of the cold front.

This system will bring a chance for rain Monday afternoon across the
western counties of NYS, with rain possibly reaching as far east as
the North Country. The likely period for rain showers will be Monday
night as a cold front crosses the region. Reasons for increasing the
Pops for Monday night will be upper level height falls, and
convergence along a low level jet, with the jet nose within a nearly
saturated layer from the surface up through 10K feet. The nocturnal
passage of the cold front and limited instability will reduce
chances for thunder, and for now will not include it in the
forecast.

There is still some timing differences on the passage of the surface
cold front, and will continue with chance pops Tuesday morning
across our eastern zones where shower along the cold front may still
reside, while allowing for a dry period Tuesday morning across WNY
where a dry slot behind the cold front will likely be found.

Scattered showers will again increase across the region Tuesday
afternoon as daytime heating combined with the passage of the upper
level trough axis and return of ambient moisture may bring a few
showers.

Highs on Monday will reach into the upper 60s to mid 70s. Warmest
areas will likely be along the Lake Erie shore, and the western lake
plain where southeast winds will downslope. Cooler Tuesday with
widespread 60s found.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Model consensus (GFS/GGEM/ECMWF) slowly brings an upper level trough
axis across the region on Tuesday night. Temperatures aloft will be
modestly cooler, dropping down to around +3C at 850mb. This will be
cold enough for some modest lake enhancement.  Lake enhancement
along with moisture from the trough and weak surface low will result
in some showers Tuesday night into Wednesday which will be most
prevalent downwind of the lakes. Considerable clouds and cooler air
aloft should keep high temperatures in the 60s on Wednesday.

The upper level trough will gradually exit east into New England on
Wednesday with a large ridge of high pressure forecast to build into
the area Thursday and Friday. This will bring pleasant fall weather
at the end of the week with quite a bit of sunshine, and gradually
warming temperatures. Because of the dry pattern, expect a slightly
wider diurnal range of temperatures with highs on Friday likely to
warm well into the 70s.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Radar shows some trailing widely scattered light showers/drizzle
shifting north to south this evening. A widespread area of IFR and
MVFR CIGS in low stratus accompanies these showers behind the front.
Expect these low cigs to only slowly improve overnight supported by
northeast upslope flow and some contribution from lake effect
moisture. Expect IFR to last longer across the higher terrain of the
western Southern Tier and western Finger Lakes. Overnight some lake
effect clouds may persist south of Lake Ontario with areas of MVFR,
with partial clearing and VFR elsewhere.

On Saturday any remaining lake effect clouds with local MVFR CIGS
will scatter out by mid to late morning. This will leave some
diurnal cumulus across higher terrain inland from the lakes
during the afternoon with mainly VFR for the afternoon.

Outlook...

Sunday through Monday...VFR...except for some patchy overnight/
early morning valley fog with local IFR across the Southern Tier.
Monday Night and Tuesday...Areas of MVFR with a chance of showers.
Wednesday...VFR/MVFR with a chance of showers.

&&

.MARINE...
Moderate northeasterlies will continue on Lake Ontario and Lake Erie
through the rest of tonight. This will continue to support Small
Craft Advisory conditions along the south shore of both lakes.

High pressure begins to nose into the Lower Great Lakes Saturday
with winds diminishing below advisory level through the morning
hours. Winds and waves will subside further Saturday night and
Sunday as the surface high builds into western Quebec and the Lower
Great Lakes.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 11 AM EDT Saturday for LEZ040.
         Small Craft Advisory until 11 AM EDT Saturday for
         LOZ042>044.

&&

$$

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


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