Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 150847

Area Forecast Discussion
National Weather Service Buffalo NY
347 AM EST Sun Jan 15 2017

An area of high pressure will provide for fair weather across the
Eastern Great Lakes region today through Monday. Air temperatures
will be seasonably cool, with a bit more sunshine Monday. An area of
low pressure will then advance through the Great Lakes region
Tuesday and Wednesday, spreading rain through New York...that may
begin as a little freezing rain across Western and North Central
New York at the onset Tuesday.


A back door cold front is dropping southward across southern Canada
this morning, impending into a broad area of high pressure that is
centered over the northern Corn Belt States. As this feature drops
across Lake Ontario this morning, just enough convergence ahead of
the front, combined with weak lake effect snow parameters may bring
scattered light snow showers along the southern shoreline of Lake
Ontario this morning. These light lake effect snow showers will fade
to flurries through the morning as convergence diminishes and drier
air entrains into the weak bands. Total snow accumulation today will
be minor, generally a dusting to half inch of snow.

There is a fair amount of low level moisture associated with this
front, and we will have a fairly extensive deck of stratus this
morning across the region before drier air associated with the broad
area of high pressure erodes the clouds.

Skies will begin to clear this afternoon, and further clear tonight.
Temperatures today will reach to around 30 south of Lake Ontario,
while behind the cold front east of Lake Ontario, highs will
generally be around the mid 20s. Tonight with the clearing skies, we
will drop back into the teens to lower 20s with a light southerly
flow preventing a large drop in temperatures tonight.


A weak ridge of high pressure will result in an uneventful day
Monday, with dry weather and quite a bit of sunshine. Temperatures
will be above normal, with highs in the upper 30s to lower 40s.

After this, a weak area of surface low pressure will slowly track
over top of a mid-level ridge located across the Southeastern
states. This diffuse surface low will slowly track from near
Illinois Monday night to Southern Ontario Tuesday night. A consensus
of 00Z guidance is slightly slower than previous runs with this
system, but is still in good agreement supporting high confidence in
measurable precipitation even though amounts will be modest.

The main forecast concern is the potential for some freezing rain at
the onset. With the exception of the Eastern Lake Ontario region,
temperatures aloft are generally warm enough to make precipitation
type a question of rain or freezing rain with the surface
temperature the determining factor. Initially the warm layer will be
around +2C across the Eastern Lake Ontario region where a brief
period of sleet is possible.

Precipitation will gradually spread from southwest to northeast late
Monday night through Tuesday. Expect surface temperatures to be near
freezing when precipitation starts in most areas. Temperatures
should rise quickly in downslope regions across the lake plains
adjacent to the Chautauqua Ridge during the day Tuesday. The wave is
relatively weak with guidance only showing 850mb winds increasing to
about 40 kts. As a result temperatures will probably be very slow to
rise on Tuesday, with highs on Tuesday cooler than most guidance,
especially MOS based guidance. Even with the slow rise, expect any
ice accumulations to be light with temperatures starting off very
close to freezing at the onset of precipitation and then slowly
rising as rain persists.  Some areas may be just above freezing with
all precipitation falling as rain.  Uncertainty in timing and
location is too great for any headlines to be issued at this time.

The bulk of precipitation will fall Tuesday and Tuesday night, with
a gradual transition to all rain during this time. By Tuesday
evening precipitation should be all rain with the possibly exception
of the North Country. Precipitation amounts should average between a
quarter and a half inch.

A second shortwave originating from the northern branch of the jet
stream is forecast to cross the region late Tuesday night into
Wednesday. This will maintain a chance of showers on Wednesday.
Thermal profiles mainly support all rain, but some wet snow is
possible across higher terrain if some of the cooler model guidance
verifies. Highs on Wednesday will be above normal, generally within
a few degrees of 40.


The main story during this period will be continued above normal an initially quasi-zonal flow in the wake of the
midweek system will give way to building large-scale ridging across
our region by the end of the week. Expect daytime highs mostly in
the lower to mid 40s Thursday to steadily warm to the 45-50 range
by the end of the period...while nighttime lows will fail to drop
below the 30s.

With respect to precipitation chances...leftover scattered rain
and snow showers across our region at the start of the period will
gradually wind down Wednesday night and Thursday morning as the
supporting area of wraparound moisture gets stripped away and modest
surface-based ridging builds in from the Ohio Valley. After that...
mainly dry weather is expected for the balance of the period with
our region largely under the influence of building ridging both at
the surface and aloft.


For the 06Z TAFS VFR flight conditions will be common...with the
exception being a backdoor cold front that will drop across the
northern TAF locations, bringing a brief period of MVFR CIGS. This
front will also bring just enough cold air to allow for scattered
lake effect snow showers...these falling along the southern
shoreline of Lake Ontario this morning, possibly clipping the KROC
airfield. A VCSH will be in play for this airfield this morning.
Otherwise dry air will clear the clouds through the day with TAF
sites remaining VFR through Sunday night with light winds.


Monday...Mainly VFR.
Tuesday...MVFR/IFR with rain likely. Rain may begin as a brief
period of freezing rain.
Wednesday...VFR/MVFR with a chance of rain and snow showers.
Thursday...Mainly VFR.


A weak cold front will drop southward, across Lake Ontario this
early morning and will providing for some cooler air to flow across
Lake Ontario. Winds will reach upward to 20 knots on the southern
and eastern shoreline of Lake Ontario today for which Small Craft
Advisories will remain in place. Winds will quickly diminish this
afternoon as high pressure reestablishes itself over the Great
Lakes region.

Winds will increase a bit Monday afternoon on a southwest flow.
Stronger winds will be across Lake Ontario, and they may produce
additional SCA conditions on the eastern end of the Lake later
Monday and into Monday night.


Flooding remains along the Allegheny River this morning. Olean
remains just above flood stage after cresting late Friday. Olean
will continue to slowly fall this morning, dropping below flood
stage by late this morning.


The main story for next week and beyond will be the extended
period of above normal temperatures not only in our region, but
for much of the eastern 2/3 of the nation. Over the next two
weeks, a strong closed low will remain parked over the Bering
Straits, forcing a strong Pacific East Asian jet to extend farther
east than normal. This will continue to bring a parade of Pacific
systems into the western United States, while also supporting
zonal flow and a flat ridge downstream across the central and
eastern part of the country. The westerly flow across the
continent will support strong Chinook warming off the Rockies,
with warmth spreading to the east coast and even well north into
southern and central Canada.

The warmth will last for another 12 days or so, but there is a
significant pattern change brewing beyond that. A Sudden
Stratospheric Warming event has just occurred in the northern
hemisphere. These events occur when planetary waves propagate
vertically into the stratosphere, with wave breaking and dampening
processes acting to rapidly warm the stratosphere over the high
latitudes and greatly distort the Stratospheric Polar Vortex.

This warming and disruption in the stratosphere has been shown in
numerous studies to slowly feed back into the troposphere, with a
strong tendency for high latitude blocking to increase about 2
weeks after the warming takes place. High latitude blocking
increases the ability of polar air to spread southward into the
mid latitudes, and increases the chances of cold and wintry
weather locking in for a longer period of time.

It appears the long range guidance is beginning to capture this
idea, with the GEFS and NAEFS ensembles suggesting a more highly
amplified flow starting late this month, with a ridge developing
over Alaska and the West Coast while a deep longwave trough
begins to establish across central and eastern North America. The
developing ridge in Alaska may also promote a period of cross
polar flow, draining frigid Siberian air into northern Canada.
GEFS ensembles also support a more negative NAO and AO pattern
towards the end of the month. Putting all this together, it
appears the pattern should become much colder and more wintry
around January 25-27. Past stratospheric warming events suggest
this cold pattern may last for quite some time, and may support
the potential for periods of well below normal temperatures by the
end of the month and first half of February. Stay tuned.


MARINE...Small Craft Advisory until 1 PM EST this afternoon for



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