Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 011431
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1031 AM EDT SAT OCT 1 2016

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
A vertically stacked low across the Ohio Valley will very slowly
lift to the north today. Stronger winds extend to the east of this
low from the upper levels down to 850mb and these are transporting a
stream of Atlantic moisture into Western New York.

Radar imagery showing most of the showers focusing on an arc from
the Genesee Valley to the Niagara Frontier at mid morning. This area
of rain should continue to move slowly northward through early
afternoon. Model guidance is doing a poor job of handling the
current situation, which offers below normal confidence with respect
to the placement of the steadier showers for the afternoon and
evening. Following radar trends as a guide, expect the more
persistent showers to be found across the interior Southern Tier,
Genesee Valley, and western Finger Lakes during the afternoon and
evening. Farther west, expect showers to be more scattered in nature
close to Lake Erie. The North Country will continue to miss out on
the showers through early evening, with dry but cloudy conditions
expected there.

Meanwhile, a diffluent flow aloft across the Lower Lakes and
Southern Ontario will result in a bit heavier rain where showers do
occur than we have seen in recent days. Some of the heavier
corridors of showers may drop a quarter to third of an inch of rain
in a few hours. Otherwise, expect cloudy skies today due to deep
moisture from the low. High temperatures will generally be in the
mid 60s.

Tonight the steadier showers will continue to lift north across Lake
Ontario and North Country, eventually exiting into Canada. Behind
this, it is difficult to find a source of large scale lift with
showers expected to taper off behind the departing wave across most
of Western New York late tonight. A developing SSE downslope flow
may even allow for a partial clearing across the lake plains. Clouds
and downsloping will keep temperatures from dropping much, with lows
in the lower 50s inland and upper 50s across the lake plains. Most
mesoscale guidance brings in the next area of steady showers across
Lake Erie toward daybreak Sunday as the core of the upper low
approaches.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
An upper level low will start this period south of Lake Huron Sunday
morning, and lift across New York state Sunday before settling out
to sea, south of New England Monday night.

There will be a good chance for showers to develop Sunday as this
upper level low crosses the region. In addition to enhanced
convergence around the upper level low, a fair amount of instability
will develop with MUCAPE values nearing 500 J/KG while lapse rates
steepen under the upper level low. Will continue to mention chance
for thunder Sunday. Sunday should not be a washout as there may even
be some brief breaks in the dark clouds, especially over eastern
half of the CWA.

As this upper level low carries eastward, chances for precipitation
will follow. By Monday morning chances for showers will mainly be
near Lake Ontario and then over our eastern zones, and activity
will be diminishing in coverage area. We should see an end to
showers from NW to SE through the day, though a developing
northwesterly flow behind the upper level low will likely maintain
a good deal of clouds over the region into Monday night.

High temperatures Sunday will range from the mid 60s to lower 70s.
Tuesday will have highs in the mid to upper 60s under the developing
northwest flow. Overnight lows both nights will remain in the low to
mid 50s for most areas under mostly cloudy skies. A few locations
in the inland So. Tier Valleys may drop into the upper 40s.

Tuesday the upper-level low will finally depart the region to our
east and heights will rise across the forecast area as a sharp upper-
level ridge builds eastward. Temperatures will moderate some on
Tuesday with decreasing cloud cover compared to Monday, with high
temperatures in the upper 60s to low 70s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
High pressure will remain anchored over eastern New England Tuesday
night through Thursday. This will bring several days of dry weather
with a good deal of sunshine for Wednesday and Thursday as
subsidence and dry air dominate from the eastern Great Lakes to New
England. Temperatures will run above normal, with highs in the lower
to mid 70s both days on the lake plains. The dry airmass will allow
for a wide diurnal range, with cool nights in the 50s on the lake
plains and 40s well inland.

Later Thursday night and Friday the next system approaches. A deep
mid level trough will advance into the western Great Lakes, with a
cold front pushing east into our region. Model guidance begins to
diverge to some extent on timing, with the ECMWF faster in bringing
rain into Western NY late Thursday night, while the GFS and most of
the GEFS ensemble members hold the rain off until Friday. For now
have kept Thursday night dry, with a chance of showers introduced
into the new day 7 next Friday.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
An upper level low across the Ohio valley will very slowly move
across the Lower Great Lakes region through early Sunday morning.
This will maintain quite a bit of low moisture, with fairly
widespread MVFR CIGS today, with IFR favored across the higher
terrain. Areas of showers will cross the region from time to time,
with the more widespread showers expected to focus on the interior
Southern Tier, Genesee Valley, and western Finger Lakes this
afternoon and evening. The heavier showers will contain brief
MVFR/IFR VSBY.

Surface winds will shift to the southeast behind the line of
showers this evening as the surface low refection tracks into
Eastern Michigan. Expect conditions to improve to VFR at BUF/IAG/ROC
with this wind shift to a downslope direction tonight, but lower to
IFR at JHW due to trapped low moisture.

Outlook...
Sunday and Monday...Areas of MVFR with scattered showers.
Tuesday and Wednesday...Mainly VFR.

&&

.MARINE...
An upper level low will very slowly lift northeast from the Ohio
Valley and into the Eastern Great Lakes through Sunday. This will
maintain a moderate easter flow which will be just enough to
require small craft headlines across western portions of Lake
Ontario through today. Winds will diminish as the upper low moves
closer to the region. When this system tracks across the area on
Sunday, there will be a chance for waterspouts on the lakes
through Sunday night.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LOZ042.

&&

$$

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


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