Area Forecast Discussion
Issued by NWS Buffalo, NY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS61 KBUF 210248

Area Forecast Discussion
National Weather Service Buffalo NY
948 PM EST Mon Nov 20 2017

High pressure will move off the mid Atlantic Coast overnight.
Warmer air will move into the region Tuesday before the next
cold front plows across the area Tuesday night bringing rain
showers. Colder air moving in behind the front could bring some
light mixed precipitation later Tuesday night with some minor
lake effect snow showers Wednesday and Thursday.


Lake effect snow showers have ended due to warming temperatures
aloft which are limiting dendritic snow growth. Lake effect
clouds will linger east of Lake Ontario through the evening
hours followed by mainly clear skies overnight. Despite the
clearing, temperatures will remain steady or slowly rise
overnight due to the increasing SSW flow which will prevent
radiational cooling and warm air advection.

On Tuesday, high pressure off the mid Atlantic coast and an
approaching cold front will result in brisk southwest winds
during the day. The strongest winds will be across the Niagara
Frontier where winds will gust to 45 mph. Mixing of a 50 knot
LLJ will be limited due increasing high clouds in advance of the
cold front.

Precipitation associated with the front will likely hold off
until early evening leaving nearly the entire daylight hours
rainfree with a decent amount of sunshine. Trajectories bring
our air in from the Ohio/Tennessee Valleys which would support
guidance high temperatures in the upper 40s to lower 50s.


Tuesday night a cold front will cross the region forced by a
shortwave moving through the lower Great Lakes. Rain showers will
spread across the region along and ahead of the cold front,
eventually switch to and ending as snow late Tuesday night. Any snow
accumulations will be limited to the higher elevation of the
Southern Tier and east of Lake Ontario, and will likely be on the
order of a half inch with a few isolated spots up to a inch.
Precipitation will shut down fairly quickly in the cold air
advection behind the cold front, however some minor lake response
will linger east of Lake Erie and Lake Ontario in Wednesday morning.

High pressure will build across the region Wednesday, which will
help suppress any lingering lake effect Wednesday morning, causing
it to diminish through the day. This will produce a mainly dry day
on Wednesday for Thanksgiving travel, along with near normal

Expect seasonable conditions for Thanksgiving as surface high
pressure to our south shifts eastward. Another shortwave passing
well to our north will drag a weak cold front near the North County
by Thanksgiving evening, and may help elicit a weak lake effect
enhancement off Lake Ontario Thanksgiving night. This will likely
produce some scattered snow showers and light accumulations there.
Otherwise, expect a mainly dry Thanksgiving day across the region.

On Friday...mainly dry and uneventful weather will return as another
narrow ridge of high pressure quickly traverses the region in the
wake of Thursday night`s cold front. As the axis of this ridge
departs to our east...developing warm air advection will help
afternoon highs to largely climb back into the lower 40s south of
Lake Ontario...and into the mid to upper 30s across the North


12Z global models are in agreement with tracking a deep storm system
north of the Great Lakes Friday night and into Central Quebec
Saturday. Southerly flow ahead of this system should result in a non-
diurnal temperature trend Friday night with surface temps rising
ahead of an approaching cold front. Expect that temperature profiles
by the time the cold front arrives will support mainly plain rain on
Saturday with some gusty winds. A strong low level jet and cold
front will combine with a deepening mid-level trough to force this
period of rain showers Saturday as the system passes to our north.
Synoptic moisture is not expected to be anomalously high which
does not support a significant amount of rainfall while the jet
trailing the front would likely keep wind gust sub-advisory level.
Surface highs on Saturday will be pre-frontal with a model consensus
pointing toward mid to upper 40s.

A trailing blast of arctic air behind the cold front should support
a good chance of some upslope and lake effect snow showers Sunday
into Monday. 850mb temps are forecast at this time to dip close to
-15C on Sunday which would support some extreme lake induced
instability and lake induced equilibrium levels rising above 10kft.
Northwest flow would steer lake effect snow bands and lighter
upslope snow showers to the southeast of the lakes with what appears
to be enough synoptic moisture to support a decent lake effect
event. With this still being 6-7 days away have limited POPs to
chance range but this will be something to watch closely especially
for those traveling back home after Thanksgiving. Surface
temperatures will run well below normal with the forecasted blast of
arctic air. Highs Sunday and Monday will likely remain below or just
at freezing.


Expect widespread VFR conditions overnight and Tuesday. The
main concern will be LLWS with the 00Z Buffalo sounding already
showing winds approaching 45 knots just above the surface, with
these forecast to increase overnight resulting in wind shear.
LLWS will subside when winds mix to the surface more readily
during the day Tuesday, resulting in gusty surface winds in some


Tuesday night...VFR/MVFR. Showers likely.
Wednesday...Rain and snow showers with a chance of MVFR/IFR.
Thursday...VFR, but MVFR in lake effect -SHSN E of the lakes.
Friday and Saturday...Mainly VFR.


Fresh to strong southwesterlies will continue across the lower Great
Lakes through Tuesday, before a cold front moves through Tuesday
night, turning the winds out of the northwest. Moderate to fresh
northwesterlies then will continue through the mid week period.
While the small craft advisories will continue through Tuesday on
the Niagara River and Buffalo harbor, the headiness will be extended
through Wednesday for the Lake Erie and Lake Ontario nearshores.
Conditions may briefly improves Thursday as the graident relaxes,
but winds and waves will again increase toward the weekend ahead of
the next approaching low from central Canada.


MARINE...Small Craft Advisory until 6 PM EST Tuesday for LEZ020.
         Small Craft Advisory until 1 PM EST Wednesday for LEZ040-
         Small Craft Advisory until 6 PM EST Tuesday for
         Small Craft Advisory until 7 PM EST Wednesday for



MARINE...APFFEL/TMA is the U.S. government's official web portal to all federal, state and local government web resources and services.