Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 160914
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
414 AM EST Sat Dec 16 2017

.SYNOPSIS...
Lake effect snow bands will drift southward overnight, with
periods of heavy lake effect snow falling across the Southern
Tier and Tug Hill region. High pressure will push towards our
region Saturday and Saturday night, ending lake effect snow
while maintaining the cold temperatures through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Lake effect snows continue to impact areas downwind of both Erie and
Ontario early this morning, as the region remains underneath cold
cyclonic flow aloft. Bands will continue to affect warned areas
through the night, and winter weather headlines remain unchanged.
Outside of lake bands, an area of dry air aloft is allowing from
breaks in the clouds, and expect partly cloudy skies overnight. In
spite of the fact that temperatures are considerably warmer than
last night, brisk westerly winds will keep wind chills in the teens
to single digits across the forecast area.

A secondary front will drop across Lake Ontario Saturday
morning, and this feature may briefly intensify lake effect
snow. This secondary front will also shove lake snows
southward, with light snow showers possible along the entire
southern Lake Ontario shoreline.

As high pressure drops southward later Saturday it will bring drier
air, along with lowering inversion levels...such that lake effect
snow will diminish through the day.

Temperatures will remain cold, with overnight lows in the teens.
West winds will bring wind chill values down into the single digits.
Saturday high temperatures will range across the mid to upper 20s.

During Saturday night high pressure centered over western Quebec
will briefly ridge southward across New York State. Subsidence and
drier air associated with the surface high will result in a largely
dry night...though at least some leftover clouds will persist across
areas south of Lake Ontario...which will like closer to a lingering
weak warm frontal boundary. Expect low temps to range from around zero
across the North Country where skies will be clearer...to the mid
and upper teens south of Lake Ontario.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
Expect a short warm up early next week after experiencing more than
10 days with below normal temperatures. High pressure passing from
NY into New England on Sunday will provide dry weather for most of
the day with increasing clouds ahead of an approaching warm front.
The warm front will be associated with a weak surface low tracking
across the Great Lakes. Temps should average below normal to close
out the weekend before the warm front arrives Sunday night. Highs
will range from the mid to low 30s in WNY and upper teens to mid 20s
for the North Country. Sunday night, we have continued chance POPs
for snow showers arriving ahead of the warm front which could mix
with some rain in the Niagara Frontier late. Forcing is not quite
strong enough to warrant anything higher than chance POPs at this
time.

We will then see above normal temps Monday and Tuesday behind the
warm front and within fairly zonal flow at 500mb. 850mb temps
rebounding back closer to 0C into Tuesday should translate into
surface highs in the mid 30s-40 Monday and upper 30s to mid 40s
Tuesday. A leading shallow shortwave trough passing over the Great
Lakes on Monday will then be followed by a broad but deepening
trough on Tuesday and Tuesday night. Each of these will be
accompanied by modified Pacific moisture resulting in continued
chance POPs for daytime rain showers and nighttime rain/snow
showers. The exception seems to be for the eastern Lake Ontario
region where models indicate better forcing and moisture will
combine for likely POPs. Later Tuesday into Tuesday night, a cold
front is forecast to cross our region supported by the mid level
trough. These features will drive higher POPs for rain showers
especially east of the lakes which will mix with or change to lake
enhanced and upslope driven snow showers overnight as cold air
deepens and overnight temps dip back into the 20s overnight. No
significant weather hazards are expected.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
High POPs for lake effect snows remain in place Wednesday as
northwest cold air advection drops 850mb temps to around -12C. This
flow would mainly impact locations southeast of the lakes. Outside
of the lake effect, chance POPs remain in between the lake effect
areas to cover for stray snow showers in weaker lake streamers south
of the lakes. Have lingered chance POPs for snow showers south of
the lakes into Wednesday night but expect some winding down as
surface-based ridging and drier air build into the region.
Temperatures will have returned to a little below average with highs
mainly in the upper 20s to lower 30s on Wednesday followed by lows
ranging from the teens to lower 20s Wednesday night.

Mainly dry weather expected Thursday with temps returning to near
normal before models show a stronger low pressure system crossing
the Great Lakes into New England Thursday night into Friday.
Southerly flow ahead this system should bring back above normal
temps for Friday along with increased precipitation probabilities.
Likely POPs have been forecast by Friday with an initial ptype of
snow gradually giving way to more in the way of rain over time as
temperatures warm.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
Lake effect snows will continue to affect areas downwind of
Lake Erie and Ontario overnight and through much of the day on
Saturday. Westerly flow will gradually veer more northwesterly
through the period, and this will keep bands south of
KBUF/KIAG/KART, however KJHW will continue to see MVFR/IFR
conditions through 18Z. The passage of a final upper level
disturbance will shove the Lake Ontario band south of the lake
around 18Z, bringing a brief period of -SHSN and potential
MVFR/IFR conditions to KROC. Otherwise, outside of lake bands,
expect VFR/MVFR conditions to persist through the TAF period.

Outlook...

Saturday night and Sunday...VFR.
Sunday night...MVFR with a chance of snow showers.
Monday...IFR/MVFR with a chance for rain and snow showers.
Tuesday...IFR/MVFR with rain likely.
Wednesday...IFR in lake effect snow likely SE of the Lakes,
MVFR/VFR in chance of snow elsewhere.

&&

.MARINE...
A cold front will cross the waters overnight, with winds veering
to west and then northwesterly. Waves will continue to increase
behind the cold front with small craft advisories in place for
the lakes and the Upper Niagara River.

High pressure will nose southward from Canada on Saturday, and bring
lighter winds and an end to the SCA. Light winds and waves will
continue Saturday and into Sunday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Lake Effect Snow Warning until 10 AM EST this morning for
     NYZ007.
     Lake Effect Snow Warning until 1 PM EST this afternoon for
     NYZ006-008.
     Lake Effect Snow Warning until 4 PM EST this afternoon for
     NYZ019-020.
     Winter Weather Advisory until 1 PM EST this afternoon for
     NYZ012-085.
     Winter Weather Advisory until 4 PM EST this afternoon for
     NYZ021.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for LEZ040-
         041.
         Small Craft Advisory until 8 AM EST this morning for
         LEZ020.
         Small Craft Advisory until 7 PM EST this evening for
         LOZ042>045.

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...APFFEL/THOMAS/WOOD
SHORT TERM...SMITH
LONG TERM...JJR/SMITH
AVIATION...WOOD
MARINE...APFFEL/THOMAS



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