Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 152136
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
436 PM EST Fri Dec 15 2017

.SYNOPSIS...
A cold front will advance across the region this evening,
strengthening lake effect snow bands east of the Great Lakes. These
lake effect snow bands will drift southward tonight behind the cold
front, with periods of heavy lake effect snow falling across the
Southern Tier and Tug Hill region. High pressure will push towards
our region tomorrow and tomorrow night, ending lake effect snow
while maintaining the cold temperatures through the weekend.

&&

.NEAR TERM /THROUGH SATURDAY/...
A surface low is near Georgian Bay late this afternoon, with a
cold front slicing across eastern Michigan, and the western
Ohio Valley. At 4 p.m. latest radar imagery shows a band of
heavy snow developing north of Lake Erie, centered just west of
the Niagara River. Radar trends show this band is moving
southeastward which lends confidence that the band will drop
across the Buffalo metro area early this evening. Heavy lake
effect snow will move from near Niagara Falls at 5 p.m. to the
Buffalo southtowns around 7 p.m. This will bring a quick 2-4
inches of snow to the Buffalo metro area during this two hour
window. After this, the band will continue to shift southward
into Ski country and the Western Southern Tier.

A similar story will play out a few hours later off Lake
Ontario. Heavy snow will move through Watertown between 10 p.m.
and 1 a.m. Expect a slightly slower motion and more moisture to
result in a quick 3 to 6 inches for the metro area, even though
its arrival will be well after the evening commute in the
Watertown area.

The upper level shortwave, and surface cold
front will cross our region between 00Z and 06Z, with surface
winds veering behind the cold front. This will act to push the
snows southward, first off Lake Erie, and then off Lake Ontario.

Lake Induced Equilibrium levels will increase to around 12K
feet off both lakes, and with near saturation within the snow
dentritic growth zone, and added lifting along the front there
may be some rumbles of thunder near the lakes.

By late this evening a westerly flow will settle lake snows
southward across Ski Country and the Southern Tier off Lake Erie,
and across the Tug Hill east of Lake Ontario. Snowfall rates will be
most impressive along and for several hours behind the front. A
secondary front will drop across Lake Ontario Saturday morning, and
this feature may briefly intensify the Lake Ontario band across the
Tug Hill and Oswego County region. 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.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH TUESDAY NIGHT/...
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.

On Sunday the surface ridge will slide eastward into eastern Quebec
and New England. Increasing warm air advection on its backside will
result in clouds increasing across our region from southwest to
northeast through the day...with the chance of a few rain showers
arriving across the Southern Tier late as moisture and shortwave
energy pool along the slowly re-energizing warm front draped along
the NY/PA border. Otherwise daytime highs will finally begin to
rebound given the ongoing warm air advection regime...with afternoon
highs ranging from the mid 20s across the North Country to the 30s
across most areas south of Lake Ontario.

Sunday night and Monday broad warm air advection will continue across
our region...with the aforementioned warm front slowly lifting north
across the area. This will result in plenty of cloud cover and
general chances for some snow showers Sunday night...with these then
transitioning over to mainly rain showers on Monday as the atmospheric
column continues to steadily warm. With respect to temperatures...
lows will range from around 20 across the North Country to the
upper 20s and lower 30s across most areas south of Lake Ontario
Sunday night...with highs on Monday then reaching into the mid to
upper 30s east of Lake Ontario and to around 40 elsewhere.

Monday night our region will again be under the influence of broad
warm air advection out ahead of a modest mid level trough/attendant
surface low pushing into the Upper Great Lakes. This will result
in continued plentiful cloud cover and scattered shower potential...
with the column likely remaining warm enough to support mostly rain.
At the surface...nighttime lows will range from the lower to mid 30s
east of Lake Ontario to the mid and upper 30s elsewhere.

Finally...during Tuesday the aforementioned trough/surface low will
make their way further eastward and slowly push their attendant
cold front across our region...along with some scattered to numerous
rain showers. The antecedent mild airmass in place out ahead of
the front will result in one more day of milder temperatures with
area highs reaching into the lower to mid 40s areawide...before
steady cold air advection in its wake pushes readings back down
into the mid and upper 20s Tuesday night. Coupled with an eventual
increase in moisture...the ongoing cold advection regime will also
result in the redevelopment of some lake snows east and southeast of
the lakes Tuesday night...for which some likely PoPs remain in play
from continuity.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
On Wednesday lake effect snows should continue southeast of both
lakes (especially Lake Ontario) before winding down Wednesday night
as surface-based ridging and drier air build into the region. Meanwhile
temperatures will run a little below average...with highs mainly in
the lower 30s on Wednesday followed by lows ranging from the teens to
lower 20s Wednesday night.

After that...the medium range guidance packages remain in general
agreement on another low pressure system developing northeastward
across the Great Lakes and Northeastern states late in the week...
though considerable discrepancies remain as to the exact strength...
timing...and track of the low. In a general sense...this system
should bring a warming trend for the latter portions of the work week
along with renewed precipitation chances...with an initial ptype of
snow gradually giving way to more in the way of rain over time as
temperatures warm.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
Expect a 1-2 hours period of heavy snow at BUF/IAG between
22Z-00Z. This will lower visibility to a quarter mile in heavy
snow, significantly (but temporarily) impacting flight
operations. High confidence in occurrence and moderate
confidence in timing with forecast likely to be withing 30 min
of bands arrival. The heavy snow will reach JHW later this
evening. ROC will not be impacted as much, with much less
intense snow since its further from Lake Erie. Expect heavy snow
off Lake Ontario which will impact ART between 03Z and 06Z.

These bands of snow will drop southward behind the cold front with
veering winds...where they will then persist through the night with
LIFR or lower conditions for several hours across KJHW.

Winds will be gusty for a brief time with the frontal passage, with
gusts 20 to 25 knots.

Tomorrow morning band of lake effect snow off each lake will weaken
with flight conditions returning to mostly VFR by the close of the
TAF cycle.

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...
Southwest winds will increase later this afternoon, ahead of a cold
front. These winds will bring small craft conditions to both lakes,
and the Upper Niagara River.

The cold front will cross the water bodies between 7pm and 1 am
tonight, with winds veering to west and then northwesterly.
Waves will continue to increase behind the cold front.

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 from 10 PM this evening to 10 AM EST
     Saturday for NYZ007.
     Lake Effect Snow Warning from 10 PM this evening to 1 PM EST
     Saturday for NYZ006-008.
     Winter Weather Advisory until 1 AM EST Saturday for NYZ010.
     Winter Weather Advisory until 10 PM EST this evening for
     NYZ001.
     Lake Effect Snow Warning until 4 PM EST Saturday for NYZ019-
     020.
     Winter Weather Advisory until 1 PM EST Saturday for NYZ012-085.
MARINE...Small Craft Advisory until 1 PM EST Saturday for LEZ040-041.
         Small Craft Advisory until 4 AM EST Saturday for LEZ020.
         Small Craft Advisory until 7 PM EST Saturday for
         LOZ042>045.

&&

$$

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



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