Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 301518
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1118 AM EDT FRI SEP 30 2016

.SYNOPSIS...
An upper level low, cut off from the main jet stream, will meander
over the Midwest through the weekend while periodically sending rain
showers across the region.

&&

.NEAR TERM /THROUGH TONIGHT/...
An upper level closed low over southern Indiana will slowly lift
northward towards Ohio through tonight. To the east of the
feature a southeast flow of Atlantic moisture continues over the
mid-Atlantic region, with this flow supplying moisture for
several rounds of rain showers over the next 24 hours.

Upper level divergence will not be as strong as this upper level low
lifts northward, and with a weaker LLJ will hold chances for rain
today in the chance range, except for the Finger Lakes area where
low likely pops will be in place over the higher terrain. Regional
radars displaying shower activity increasing across the eastern
Finger Lakes, while only scattered activity seen elsewhere.

Tonight another wave of moisture and increase LLJ should bring rain
showers up across a portion of WNY from OH late tonight. Along with
this deeper moisture may come lowering ceiling heights across the
So. Tier such that there may be some hill top fog by the end of
Friday night.

It will remain cloudy through the period which will lower the
diurnal temperature cycle, with highs today in the 60s (warmer
northward, cooler across higher terrain of the south) and lows in
the low to mid 50s. Some areas across the North Country where
moisture will not be as deep may drop back into the upper 40s
overnight.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
An upper level low across Indiana will slowly drift north on
Saturday. Model consensus lifts a modest low-level jet of around 30
kts at 850mb northward into Western New York on Saturday. A band of
showers is likely to develop along this axis of stronger winds and
enhanced moisture with this area of showers expected to lift
northward into Western New York Saturday morning, then pivot west
into Southern Ontario late in the day. Would also not rule out some
rumbles of thunder with this Saturday afternoon and evening with
cooling temperatures aloft increasing mid-level lapse rates.
Although showers will mainly be focused on the low level jet, it is
difficult to completely rule out a shower elsewhere due to the close
proximity of the upper low. However showers should be quite sparse
in the wake of this, with mainly dry conditions developing late in
the day across the Lower Genesee Valley.

By Saturday night the upper low should remain stalled across Eastern
Michigan. Most model guidance shows no significant waves embedded in
the cyclonic flow, and although a few showers cannot be ruled out.

On Sunday this upper low will slowly track eastward, reaching the
Lower Great Lake and/or Western New York on Sunday night. Model
guidance differs a bit on the timing and track with the 00Z
consensus is slower than previous model guidance. The steadiest
showers are likely to be just to the north of the surface low and
underneath the upper low which may be slightly offset from the
surface reflection. Showers are likely across the western two-thirds
of the cwa by Sunday afternoon. Showers should then gradually lift
across Lake Ontario and into the Eastern Lake Ontario region late
Sunday night. Steeper lapse rates may support an isolated
thunderstorm Sunday afternoon.

Total precipitation amounts through this period won`t be very high,
likely ranging between a quarter and three quarters of an inch. The
greatest amounts are likely to be across the Niagara Frontier and
Lower Genesee Vally where this rainfall should be beneficial.
Temperatures should remain above normal for the weekend, especially
on Sunday when temperatures should rise into the upper 60s to lower
70s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The cut-off upper level low will slowly shift eastward into New
England by Monday night. Some showers with this departing feature
will linger across the region on Monday with an isolated
thunderstorm possible.

Dry weather will return for the middle portion of the week with
skies gradually clearing as the upper low exits and temperatures
aloft warm. A 500 mb ridge will build behind the departing system
with surface high pressure resulting in mostly clear skies and
above normal temperatures for Wednesday and Thursday. This ridging is
in response to a deep trough pushing across the western states then
becoming negatively tilted while lifting across the Plains states.
Daytime temperatures through the entire long term period will
exhibit day to day warming M/U 60s Monday warming to U60s/L70s by
midweek. Overnight temps will drop into the M/U 40s across the
interior locations with L/M 50s near the lake shores each night.

Looking further out toward the end of next week we will be keeping a
close eye on model trends with Hurricane Matthew. 00Z runs of the
GFS/ECWMF has trended east which would keep tropical moisture out of
our region. This said, there considerable uncertainty this far out
with future shifts in model guidance possible.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Mainly VFR flight conditions across the region through this
afternoon with a widespread mid cloud deck in place. Patchy MVFR
flight conditions will be found across the Western Southern Tier,
and these conditions should largely prevail through the afternoon.

Periodic passing of rain showers will be possible, especially south
of Lake Ontario this afternoon. Activity should remain scattered and
confidence and timing does not warrant anything more than a VCSH at
this time.

There will be an increase to the moisture fields later tonight,
especially after 06Z when deepening moisture may bring MVFR/IFR
flight conditions south of Lake Ontario.

Winds will remain from an easterly direction through the TAF cycle.

Outlook...
Saturday through Monday...Areas of MVFR with scattered showers.
Tuesday...Mainly VFR.

&&

.MARINE...
An upper level low will only shift slightly northward from the Ohio
Valley this afternoon. This will maintain the easterly wind fetch
over the Eastern Great Lakes through the afternoon. On the western
half of Lake Ontario the easterly winds will remain strong enough
to maintain small craft advisory conditions into tonight, and
possibly extending further into Saturday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 2 AM EDT Saturday for LOZ042-043.

&&

$$

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


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