Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 160247

Area Forecast Discussion
National Weather Service Buffalo NY
947 PM EST Sun Jan 15 2017

An area of high pressure will provide fair weather through Monday
evening. Low pressure will then move through the central Great Lakes
on Tuesday with rain spreading across the region...which may begin
as a brief period of freezing rain in some spots. Mainly dry weather
will then return toward the end of the week as high pressure builds
into the Great Lakes. Temperatures will run well above normal most
days through next weekend and into the following week.


Overnight high pressure draped across New York State will drift
eastward to the Atlantic coastline. Increasing southwesterly flow
on the backside of the departing high will continue pushing a
lingering band of stratus across the far eastern Finger Lakes and
portions of the North Country northeastward...which will result in
clearing skies across the eastern Finger Lakes and increasingly
cloudy conditions across the North Country. Based on regional obs
and satellite trends...have again sped up the northeastward
progression of the stratus a bit from continuity. Temperature-
wise nighttime lows will be very close to mid winter normals...
ranging from the lower 20s along the lakeshores to the mid and
upper teens inland.

On Monday any remaining stratus across the North Country will move
away and dissipate early in the morning. This will leave some
morning sunshine in most areas. Through the day mid/upper level warm
advection will increase in advance of the next system approaching
the Ohio Valley. This will allow mid/high clouds to thicken and
lower from southwest to northeast through the day, with the western
Southern Tier becoming mostly cloudy by mid afternoon. Ongoing weak
warm advection will bring temperatures to a little above normal,
with mid to upper 30s in most areas.


An ejecting wave from near Baja California will track toward the
Great Lakes Monday night and Tuesday, while a surface high moves
through central Quebec. The result across our forecast area will be
initially cold surface temperatures with warm advection aloft
supporting some freezing rain at the onset of precipitation before
switching over to all rain on Tuesday.

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, where
freezing rain chances will be lowest. 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 (a few hundredths to a tenth of an inch)
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
(mainly the lake plains). Greatest ice accumulation will interior
valleys of the western Southern Tier. Uncertainty in timing and
location is too great for any headlines to be issued at this time.

The bulk of precipitation will fall as plain rain Tuesday and
Tuesday night, with a transition to more scattered showers by
later Tuesday night and into Wednesday. 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. Showers will taper off on Thursday, with high
temperatures still running above normal (highs U30s to L40s, lows


There is very high confidence that temperatures will average well
above normal across our forecast area during this period...and for
that matter...into the final days of the month. An unusually strong
190kt H25 Pacific East Asian jet will continue to help flood the
Lower 48 with Pacific modified air. This powerful jet will be a
product of a highly anomalous tropical ridge centered near the
Hawaiian Islands and a closed low that has been persistent over
Alaska. For what its worth...a collection of ensembles even suggests
that the strength of the Hawaiian ridge has a once in a generation
return interval for this time of year.

This overlying pattern will keep a split flow in place over North
America...where a dominate sub tropical jet will be part of
amplifying ridge over the eastern third of the country. While
this impressive ridge will support very mild and relatively benign
weather for our region through this time frame...there will come a
time when the proverbial pendulum is going to swing the other way.
That will come as we come out of the weekend when the much
discussed ridge will move to our east. A gaping...wide open Gulf
ahead of a dynamic negatively tilted trough will then set the stage
for what could be a very rainy event for our region later Monday
into Tuesday...but that is getting a little ahead of ourselves.

As for the details of this Friday to Sunday period...
Ridging over the Great Lakes Thursday night and Friday will promote
fair dry weather with temperatures Friday afternoon climbing well
into the 40s.

A weakening mid level trough is forecast to push north across our
region Friday night into Saturday. While this feature will be
accompanied by a fair amount of cloudiness...there does not appear
to be enough forcing to warrant anything more than slght chc pops.
The mercury will climb a few degrees higher for Saturday
afternoon...with highs approaching 50 F over the western counties.
These temps will be more than 15 deg F above normal.

An amplifying ridge will pass across our region Saturday night and
Sunday. Once this feature passes...the door will be wide open for
GOMEX moisture to stream northwards to the Lower Great Lakes. While
dry weather be featured to end the weekend...some showers late
Sunday or Sunday night cannot be ruled out...especially over the
far western counties.


Overnight high pressure draped across New York State will drift
eastward to the Atlantic coastline. Increasing southwesterly flow
on the backside of the departing high will continue pushing a
lingering band of mainly low VFR stratus across the far eastern
Finger Lakes and portions of the North Country northeastward...
which will result in clearing skies across the eastern Finger Lakes
and increasingly cloudy conditions across the North Country. Most
areas will be predominantly VFR through the night...with just some
spotty MVFR ceilings possible within the lingering band of stratus.

The leftover stratus will clear from the North Country early Monday
morning...with mid and high clouds out ahead of the next system then
thickening/lowering from southwest to northeast through the balance
of the day. Conditions will again be predominantly VFR...with just
some spotty MVFR cigs possible across the North Country early in
the day.

Monday night and Tuesday...Deterioration to MVFR/IFR with rain
developing...and possibly beginning as a brief period of freezing rain.
Wednesday...MVFR/IFR with scattered rain and snow showers...which
will be more numerous east of Lake Ontario.
Thursday...Mainly VFR with a chance of rain and snow showers
east of the lakes.
Friday...Mainly VFR.


High pressure draped across New York State will move off the east
coast Monday and allow southwest winds to increase to around 15 knots
on Lake Ontario...though conditions will remain below Small Craft
Advisory levels. Meanwhile...lighter winds will continue to prevail
on Lake Erie.


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 27-29. 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.





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