Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 160952

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

Lake effect snows will continue across portions of the forecast area
today before high pressure brings an end to the snowfall by this
evening. This high will cross the region tonight and Sunday, with
dry weather for the second half of the weekend. Temperatures will
warm above freezing Monday as a warm front lifts across the region,
bringing a chance for rain and snow showers into Tuesday before a
cold front sweeps across the lower Great Lakes Tuesday night,
bringing a return to more wintry conditions by Wednesday.


A look at regional radar continues to show two well-defined lake
plumes ongoing off of Lakes Ontario and Erie respectively, as the
region remains under cold cyclonic flow around an upper level trough
centered across Quebec. In fact, the Lake Erie bands have become
better organized over the last couple of hours, likely due to an
increase in synoptic moisture and lift associated with a warm
frontal boundary lifting towards the region. Headlines remain in
place as these bands will continue to bring several more inches of
snowfall to the North Country and western Southern Tier, with
heaviest amounts focusing on the Tug Hill plateau and Chautauqua
Ridge, respectively.

Lake snows will persist at least into the early afternoon hours. As
we move into the afternoon however, the Lake Ontario band is
expected to be shoved south of the lake as a potent shortwave drops
across the lake, finally shoving the upper level trough axis out of
our region. This will likely bring a brief shot of snow to areas
south of the lake, including the Rochester metro, this afternoon,
though amounts should be modest as flow will be increasingly sheared
and moisture diminishing. Snowfall will be slowest to diminish
across the western Southern Tier, owing to the presence of the
nearby warm frontal boundary that will introduce a synoptic
component to the snows there, hence the higher forecast totals
across the Chautauqua Ridge. Nonetheless, by the end of the day, we
should see snow wind down even there, as flow veers to the northeast
and high pressure begins to build into the region. The passage of
the shortwave and the approach of the warm frontal boundary mean
that the coldest air will be past our region today, and temperatures
should rise into the mid to upper 20s across most areas.

The aforementioned area of high pressure will moves across the lower
Great Lakes tonight, allowing for clearing skies, at least across
the northern zones. The nearby warm front will likely keep clouds in
place from the Thruway corridor south overnight. This will produce a
sharp temperature gradient across the forecast area, with lows
ranging from around 20 near the PA border to the single digits below
zero in the North Country.


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

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.


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.


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.


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.
Thursday...Mainly VFR.


Small craft advisories remain in effect this morning for most zones,
as a cold westerly wind continues to stir the waters of the lakes.
In fact, the SCA for Buffalo Harbor has been extended by a few more
hours, as winds have been a little slow to diminish. Nonetheless, we
should see winds veer to the north, and eventually the northeast as
an upper level disturbance cross the region. This will be followed
rapidly by high pressure, which will bring winds down tonight, and
allow for calmer conditions on the lakes for the second half of the

Southwest winds will begin to freshen on Monday, as a warm front
lifts across the lower Great Lakes and a trough of low pressure
associated with a deep low pressure system over James Bay
approaches the region. This will likely necessitate a round of small
craft advisories for Lake Erie by Monday night, and eastern Lake
Ontario by Tuesday morning.


NY...Lake Effect Snow Warning until 10 AM EST this morning for
     Lake Effect Snow Warning until 1 PM EST this afternoon for
     Lake Effect Snow Warning until 4 PM EST this afternoon for
     Winter Weather Advisory until 1 PM EST this afternoon for
     Winter Weather Advisory until 4 PM EST this afternoon for
MARINE...Small Craft Advisory until 1 PM EST this afternoon for LEZ040-
         Small Craft Advisory until 8 AM EST this morning for
         Small Craft Advisory until 7 PM EST this evening for



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