Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 301856

Area Forecast Discussion
National Weather Service Buffalo NY
256 PM EDT FRI SEP 30 2016

A slow moving upper level low over the Ohio Valley will move towards
the region. This will result in periodic rain showers through the
weekend. Along with plenty of clouds, temperatures will be a little
cooler than recent days. Improvement is expected by the early to
middle part of next week once the slow moving storm system moves
away from the region.


Water vapor imagery currently shows the center of the upper low
over the Indiana and Kentucky border. Nearly all high resolution
models advertise little or no rain into the evening for the bulk of
the area, with the exception of far eastern portions of the area.
This seems reasonable based on current radar trends showing little
if any activity across the western two thirds of the area and one
light rain band lifting across the North County.

Through tonight, the center of the low is forecast to only inch up
to the Indiana/Ohio border. The complex upper level pattern is
keeping most of the models from being able to pin down on any one
corridor for the rain band or bands to set up making it very
difficult to adjust the placement of the greatest chances for
precipitation overnight.

The current water vapor images shows this complex structure with
several trowel walls to possibly zero in on. One across the Mid
Atlantic region and one across Ohio/West Virginia. Current
thinking is that as the southeasterly 850 mb jet peaks tonight it
will draw up a round of showers, probably focused on Western New
York which will be closer to the exit region of the cyclonic upper
level jet max east of the low.

For Saturday, if current thinking is right, expect the rain band
focused across Western New York to shift eastward across the
region during the morning hours. Models then suggesting a dry slot
will rotate into the region leaving the better part of Saturday
dry or least a giving a diminishing trend to any shower activity.


By Saturday night an upper low will remain stalled across Eastern
Michigan, with the best forcing having lifted north of the forecast
area. Model guidance shows no significant waves embedded in the
cyclonic flow, and thus expect mainly a drying trend overnight from
south to north with most areas seeing plenty of dry time outside of
an isolated shower.

On Sunday this upper low will slowly track eastward, reaching the
Lower Great Lake and/or Western New York on Sunday night. 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 under the upper low may
support some thunderstorms Sunday afternoon and evening. Also worth
noting is the increasing chances for waterspouts on the lower Great
Lakes Sunday into Sunday night given the steeper lapse rates under
the upper level low and warm lake surface temperatures in the upper

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

For Monday into Tuesday the upper-level low will finally depart the
region to our east and heights will rise across the forecast area
into Tuesday as a sharp upper-level ridge builds eastward. Monday
will be mainly dry outside of a few isolated/scattered showers in the
eastern Lake Ontario region. Low level moisture in the northerly
flow behind the departing low will however keep Monday mostly cloudy
across the area with high temperatures remaining in the mid to upper
60s. Temperatures will moderate some on Tuesday with decreasing
cloud cover compared to Monday, with high temperatures in the upper
60s to low 70s.


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.


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 east
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.

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


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

The upper-level low will track across the lower Great Lakes on
Sunday, and will bring increasing chances for waterspouts across the
lakes through Sunday night.


MARINE...Small Craft Advisory until 2 AM EDT Saturday for LOZ043.
         Small Craft Advisory until 6 AM EDT Saturday for LOZ042.



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