Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 211122

Area Forecast Discussion
National Weather Service Buffalo NY
622 AM EST Sat Jan 21 2017

Abundant low level moisture will result in plenty of low clouds,
patchy fog, and drizzle through much of the weekend with
temperatures well above average. A complex area of low pressure will
then move northward along the east coast early next week. This
system will spread rain into the area Monday, which may change to
wet snow late Monday into Tuesday as colder air filters into the
region. A return to more typical mid winter cold and snow is
expected to arrive late next week.



A weakening mid level trough and surface warm front will continue to
move northeast across northern NY this morning. Behind this
weakening trough, abundant low level moisture has been left behind
with widespread low stratus, areas of fog, and areas of drizzle.
Through this morning, the most widespread drizzle will be found
east of both lakes where a combination of convergent southwest
flow off the lakes and upslope flow are enhancing the drizzle
production. The most widespread and dense fog will be found across
the higher terrain where the low stratus is intersecting the
hills, and also along the Lake Erie shore including the Buffalo
Metro area as higher dewpoints advect over the cold lake.

The drizzle and fog should diminish in most locations by midday or
early afternoon as low level flow becomes more south to southeast,
allowing some weak downsloping on the lake plains. The one exception
will be across the higher terrain of the interior Southern Tier and
east of Lake Ontario where the drizzle and higher elevation fog may
persist through the day.

Tonight a weak ridge will build over the region, and force the low
level inversion to strengthen overnight. The strengthening inversion
and remaining low level moisture will continue to support low
stratus, which will likely expand again overnight. Expect fog and
drizzle to return as well, with the most widespread fog and drizzle
likely to be found across higher terrain and near the lakes.

Temperatures will remain way above average for late January. Expect
highs today in the low to mid 50s in many areas, with low to mid 40s
across the North Country. Record highs for today are 69 at BUF, 71
at ROC, and 57 at ART and are all well out of reach. Lows tonight
will only pull back into the lower to mid 40s in most locations,
with upper 30s across the North Country.


Ridging aloft will persist into Sunday, which, on the plus side,
will maintain the very mild temperatures across the region, but will
unfortunately also maintain the subsidence inversion keeping the
dreary low stratus and areas of drizzle in place. This will make
Sunday nearly a carbon copy of Saturday, with high temperatures
again topping out in the low 50s in western NY to the mid 40s in the
North Country.

The focus then becomes the developing storm system that is currently
coming onshore in southern California. This low pressure system will
track across the southern CONUS this weekend where it will
eventually turn north along the Appalachian Mountains Sunday night
into Monday. This anomalously deep low pressure system will be in
place near the Mid-Atlantic states on Monday with increasingly
anomalous easterly winds and Atlantic moisture advection across New
York state. This strong and efficient moisture advection into the
region combined with the impressive diffluent flow aloft ahead of the
closed 500mb low will generate widespread rainfall across the
forecast area on Monday.

The really tricky part of this forecast comes into play later Monday
afternoon and overnight Monday night, as the chance of precipitation
changing over to snow increases. There are several details that will
be critical to whether or not precipitation changes over to snow,
and where the heaviest precipitation will fall. First, global models
have struggled with the exact track of this low pressure system for
the last few days, but have settled back on a more westerly track
(conducive to more widespread precipitation across the region). As
this wave comes onshore today and moves into the SW CONUS, the RAOB
network will finally get a much better sampling, and thus today`s
model runs with this additional data should start to help clarify
whether this more westerly trend will hold. Second, models also are
having a very difficult time with the thermodynamic profiles, which
will be critical since the airmass with this storm is overall
lacking much in the way of true cold air. The difference between
rain and snow or significant accumulating snow will come down to
dynamical cooling processes, precipiation intensity and even
elevation. The GFS continues to be most modest with temperatures,
but still generates some snowfall across the North County where it
tracks the heaviest precipiation. The EC and Canadian are overall
colder and support more widespread snowfall, but any significant
accumulations could still be limited to where rates are highest to
force surface temperatures to near freezing. Unfortunately at this
point there are still a lot more questions than answers, but the
potential for significant accumulating snow is still on the table.
Given the latest model guidance, the best potential for significant
accumulating likely remains from near the Finger Lakes into the
North Country. Will continue to mention this in the HWO. By Tuesday
precipitation will taper off from west to east and high temperatures
will be held to the low to mid 30s.


Tuesday night into Wednesday the low pressure system will exit to
our east, but a shortwave trough on the leading edge of a broad
trough carving out across the CONUS will move through the Great
Lakes. This clipper will move from near Iowa Tuesday night to over
Lake Ontario by Wednesday evening while weakening. With marginal
temperatures already in place and warm advection ahead of the wave,
expect rain and snow showers to overspread the region Wednesday,
turning to mainly rain showers during the day Wednesday. Showers
will change over to mainly snow in the cold advection behind the
wave by Thursday with some increasing lake/orographic enhancement on
the cold advective westerly flow. Temperatures will slowly fall
through this period as large scale trough becomes established over
the Great Lakes, and will likely return to more normal or below
normal readings by the weekend. Along with this colder air will come
increasing chances for Lake Effect snows by next weekend.



Abundant low level moisture in the wake of a weakening trough will
continue to support widespread IFR in low stratus, fog, and drizzle
across most of the region through this morning. CIGS and VSBY may
occasionally drop to near airfield minimums through mid morning
across higher terrain and east of the lakes, including KBUF. The low
level flow will become more south to southeast during the midday and
afternoon, which should allow for improvement to MVFR or even VFR on
the lake plains including most of the TAF sites during the course of
the afternoon.

The abundant low level moisture will remain in place however, and a
steepening low level inversion and nocturnal cooling will likely
allow stratus to expand again tonight. Expect a return to more
widespread IFR after 03Z Sun, with areas of fog and drizzle also
forming again and bringing IFR VSBY overnight. Conditions again
appear favorable for CIGS and possibly VSBY to drop to near airfield
minimums at times overnight, especially across higher terrain and
near the lakes.


Sunday...Areas of IFR/MVFR in low stratus, fog, and drizzle.
Monday and Monday night...Areas of MVFR/IFR with rain changing to
wet snow.
Tuesday...Areas of MVFR/IFR with wet snow mixed with rain.
Wednesday...VFR/MVFR with a chance of rain and snow.


A weak pressure gradient will maintain light winds at less than 15
knots today through Sunday morning. Low pressure will then develop
and move slowly north along the east coast early next week, while
high pressure remains parked over Quebec. The increasing gradient
between the two will bring stronger northeast winds to the Lower
Great Lakes late Sunday through Tuesday, with winds peaking Monday
and Monday night. This will likely bring higher end Small Craft
Advisory conditions to the lakes early next week.





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