Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 200535

Area Forecast Discussion
National Weather Service Buffalo NY
1235 AM EST Fri Jan 20 2017

Low clouds will persist across the region tonight. A weak trough
will cross the area Friday with a period of rain showers during
the afternoon and evening across Western and Central NY. Mainly
dry weather will then return for the start of the weekend with
temperatures remaining well above average.


Very patchy drizzle will persist overnight hours before ending by
daybreak Friday. Low stratus will persist through the night before
the low clouds scour out quickly Friday morning as low level flow
becomes southeast and increases ahead of the next system. Overnight
temperatures should remain nearly steady in the lower to mid 30s.

A mid level trough will move across the region Friday with an
increasing chance for rain later in the day Friday and early evening
on Friday. The rain will arrive by late morning in Chautauqua
County, then overspread the rest of Western NY during the afternoon.

High temperatures on Friday will climb to the mid to upper 40s
across Western New York to the Finger Lakes region, with the influx
of warm air associated with the trough and southerly winds.
Highs across the North Country will be in the lower 40s as the
trough will slower to arrive, but the temperatures will hold nearly
steady or rise during the evening and overnight Friday night.


Broad troughing will gradually expand across the western two-thirds
of the country through the coming weekend, forcing upstream riding
downstream across the lower Great Lakes. This will produce a
generally benign forecast across our forecast area through the
period. Showers associated with a warm front pushing north across
the region will fall apart Friday evening as they cross the forecast
area as upper level vorticity is sheared out.

While it will certainly be an unseasonably mild weekend across
Western and North-Central New York in the wake of the warm front,
with highs in the 40s, with portions of Western New York even
creeping into the low 50s will be a rather dismal
weekend overall, as low-level moisture currently in place across the
area combined with additional shallow GOMEX moisture being supplied
from the Ohio valley is expected to remain trapped underneath the
ridging overhead. This will keep low clouds trapped across much of
the forecast area, with patchy fog and drizzle likely hanging around
through much of the weekend. The lingering cloud cover will limit
diurnal temperature swings, with lows on Friday night and Saturday
night ranging from the mid 30s in the North Country to the lower 40s
in Western New York. Increasingly northeasterly flow Sunday into
Sunday night will cool things into the 30s across the forecast area.


While concerns remain over the impending coastal storm expected to
impact the northeastern U.S. Monday into Tuesday...there is far less
certainty with regards to the impact on Western and North-Central
New York at this time. The 12Z GFS run has shifted the deformation
zone on the western periphery of the coastal low sharply to the
east, and now keeps the bulk of the forecast area largely dry, with
the exception the eastern edges of the area. The 12Z ECMWF/GEM
models still attempt to bring a trowal across the heart of the
forecast area late Monday into Monday night, but shunt this feature
northwards into Canada by Tuesday morning. Model profiles do
continue to suggest a changeover to snow, so if the ECMWF/GEM
solutions verify, we could see a widespread accumulation of several
inches of snow from the Genesee valley east, however confidence in
this remains low at this time - particularly given that the
precipitation associated with these strong coastal lows tends to be
focused more to the east of our forecast area.

Upper level ridging is progged to cross the area Tuesday night
before the next system, a classic Colorado low, kicks out of the
plains and across the Great Lakes. This can be expected to bring
another round of precipitation, likely in the form of snow changing
over to rain, to the forecast area on Wednesday, with precipitation
changing over to snow behind the low as colder air finally moves
back into the region Thursday. Current guidance continues to
indicate a pattern change, with longwave upper level troughing
shifting to the east, signaling a return to winter by the end of
next week going into next weekend.


Low stratus will continue through the rest of the night with
widespread IFR CIGS across western NY and MVFR from the Genesee
Valley eastward to the eastern Lake Ontario region. Patchy light
drizzle and fog will also continue east of both lakes overnight with
areas of IFR VSBY.

The fog and low stratus will quickly erode Friday morning as
southeast flow just off the deck increases, with downslope winds
helping to scour out the low level moisture. Rain will arrive in the
afternoon across Western NY, with initial VFR conditions
deteriorating back to MVFR and IFR Friday evening as the low levels
saturate. IFR will likely become widespread again Friday night with
low stratus, patchy fog and drizzle.


Saturday and Sunday...Areas of IFR/MVFR in low stratus.
Monday and Tuesday...Areas of MVFR/IFR with rain or wet snow.


Winds and waves will remain light overnight as the pressure gradient
relaxes across the Lower Great Lakes. Relatively light winds will
then persist through the end of the weekend as a weak pressure
gradient remains in place.





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