Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 300558
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1258 AM EST Wed Nov 30 2016

.SYNOPSIS...
After a cloudy and mild night a wave of low pressure will spread
rain across the region on Wednesday. Behind this wave of low
pressure a colder airmass will sweep across the region Wednesday
night with some lake effect rain showers Wednesday night and
Thursday that will mix with some snow Thursday night.

&&

.NEAR TERM /THROUGH TODAY/...
Through the rest of the night...mid and high clouds out ahead of
the next wave of low pressure will quickly overspread the region
from southwest to northeast...resulting in the current clear to
partly cloudy skies turning increasingly cloudy once again. With
the arrival of these clouds...any fog that developed across the
Southern Tier Tuesday evening should quickly dissipate...with
fog/low clouds persisting longer east of Lake Ontario. Overnight
lows will range through the 40s...or some 15 to 20 degrees above
normal.

The final day of November will end on a wet note. A broad longwave
trough will spawn a wave of low pressure overnight across the
southern Mississippi Valley. This low will pick up additional Gulf
of Mexico moisture while racing northward through the night.
Isentropic lift of this moisture will likely bring an area of rain
to SW NYS just before sunrise tomorrow. This low will cross the
Ohio Valley tomorrow, reaching near WNY by late tomorrow
afternoon. In addition to rain spreading across the region, there
may be some patches of fog forming, this time mainly across the
higher terrain of WNY, and then later in the day near the center
of the low as it clips NW NYS.

Overall rainfall will range from a quarter to half an inch with
this system, and should be handled by local streams and creeks.

Highs tomorrow will remain mild again ahead of the cold front
trailing this wave of low pressure. We should see air temperatures
again climb into the 50s across the region.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
Broad, vertically stacked closed low will move east from Southern
Ontario into Quebec Wednesday night, pushing a cold front east
across the Lower Great Lakes. The steadiest rains will move east of
the area with the passage of the cold front. Only marginally cold
air behind the front initially with 850 mb temperatures only falling
to around -2 to -3c by Thursday morning. This cooler flow combined
with incoming wrap around moisture may generate some lake
enhanced/upslope rain showers east of Lake Erie before Thursday
morning. The cold air advection regime will allow for a better mixed
environment with gusty winds developing behind the front. Momentum
transfer scheme of Bufkit profiles suggesting gusts to 40 to 45 mph,
especially downwind of the lakes. Overnight temperatures only slip
back into the lower 40s at lower elevations and upper 30s higher
terrain by Thursday morning, still a good deal above normal.

Thursday, elongated area of surface low pressure will have moved off
to the north with associated broad upper closed low move into
Southern Quebec. This will maintain a deep mixed layer with the
gusty winds continuing. Moisture continuing to wrap into the region
and steady weak cold air advection will maintain lake
enhanced/upslope rain showers east of the lakes. Thermal profiles
through the day too warm to support snow until Thursday night and
Friday as boundary layer temperatures cool sufficiently to trend
rain showers over to a mix and change over to wet snow, especially
across the higher elevations. Thermal profiles continuing to be too
warm to support any meaningful snow accumulation, with only minor
accumulations expected across the higher elevations.

Friday night and Saturday, the pattern into the weekend will be for
troughing to remain over eastern Canada with high pressure off to
the south and west. This will result in a continuation of a
west/northwest flow with lake enhanced/effect rain/snow showers
continuing, more persistent southeast of the lakes. The lack of
really cold air will limit any snow accumulation to minor amounts
across the higher elevations.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Saturday night through Sunday, cool WNW flow will remain in place,
supporting a few scattered rain and wet snow showers, and some
limited lake effect southeast of the Lakes. Temperatures will be
seasonable, with highs in the lower 40s at lower elevations and mid
to upper 30s across higher terrain both days this weekend.

Model guidance diverges significantly by early next week, with
plenty of run to run and inter-model differences in the handling of
a Pacific trough advancing east across the nation. This system will
be born from a split flow regime, with a southern and northern
stream system possibly phasing as they move east across the nation.
The ECMWF is a solid 24 hours faster with this system than the GFS,
bringing rain and warmer temperatures into the region by Monday,
while the GFS would delay this trend until Tuesday. Given the model
uncertainty, have maintained chance POPS going into Monday with the
arrival of milder air holding the precip as rain.

Model discrepancies and differences aside, it does appear that there
will be a non-diurnal temperature trend Monday night, with a warming
low level jet and steady or rising temps through the night into
Tuesday morning. A peek into the coming week also shows little in
the way of a profound cool down as the truly cold air remains far to
our west and northwest, across the Inter-Mountain region to the
Canadian West. Winter may have to wait until its official date on
the calendar.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Overnight...mid and high clouds out ahead of the next wave of low
pressure will quickly overspread the region from southwest to
northeast...resulting in the current clear to partly cloudy skies
turning increasingly cloudy once again. With the arrival of these
clouds...any fog/attendant restrictions that developed across the
Southern Tier Tuesday evening should quickly dissipate...though
areas of fog/low clouds will likely persist longer east of Lake
Ontario.

An area of low pressure rippling northeastward from the Ohio and
Tennessee Valleys will then bring a period of rain to the region
during the day on Wednesday...with the majority of this focusing
across areas along and south of a KBUF-KROC-KART line. Expect
mainly VFR conditions to lower to MVFR and/or IFR during
the afternoon as the wave of low pressure moves by.

Wednesday evening...expect MVFR/IFR with another round of
showers.

Outlook...
Thursday and Friday...MVFR/IFR with lake effect rain/snow showers
likely.
Saturday and Sunday...Mainly VFR w/areas of MVFR east of the
lakes with rain/snow showers.

&&

.MARINE...
A light southerly flow tonight will begin to back to easterly by
tomorrow morning, this as a wave of low pressure nears the Ohio
Valley.

Tomorrow an easterly flow will strengthen on the Lakes, likely
reaching just over 20 knots on the western end of Lake Ontario, thus
the need for a Small Craft Advisory starting Wednesday afternoon.

This area of low pressure will cross the eastern Great Lakes region
Wednesday night, with a strong cold air advection following on a
westerly wind. This will bring SCA conditons to both the lakes and
rivers Wednesday night and into Thursday night. There is a small
possibility that near gale force winds will occur within the strong
cold air advection behind the cold front Wednesday night on the
Lakes.

On the Eastern Great Lakes, continual bursts of cold air will
maintain winds and waves near or above SCA thresholds into the
weekend. There is a possibility that the SCA will need to be
extended for the Lakes beyond the current end time of Friday and
Friday night.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory from 6 PM this evening to 10 PM EST
         Friday for LEZ040-041.
         Small Craft Advisory from 7 PM this evening to 4 AM EST
         Friday for LEZ020.
         Small Craft Advisory from 7 PM this evening to 1 AM
         EST Friday for LOZ030.
         Small Craft Advisory from noon today to 10 PM EST Friday
         for LOZ043.
         Small Craft Advisory from noon today to 1 PM EST Friday
         for LOZ042.
         Small Craft Advisory from 10 PM this evening to 10 PM EST
         Friday for LOZ044-045.
         Small Craft Advisory from 10 PM this evening to 1 AM
         EST Friday for SLZ022-024.

&&

$$

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



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