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Area forecast discussion 
National Weather Service Buffalo New York
1101 am EST Thursday Feb 11 2016

Synopsis...
cold west-northwesterly flow will remain in place across the lower
Great Lakes with areas of lake effect snow today. Tonight and
Friday...ahead of the Arctic front southwesterly flow will develop
shifting lake effect snows back northward across Buffalo and
Watertown areas. Behind the Arctic front expect dangerously cold
temperatures and wind chills through Saturday night.

&&

Near term /through tonight/...
a west-northwesterly flow of cold air will continue lake effect
snows east-southeast of the lakes today in a multibanded
orientation due to shorter fetch across the lakes. High pressure
over the Ohio Valley will expand north and east through this
afternoon and should weaken the lake snows some from what we saw
last night as the capping inversion lowers to around 8kft.

Kbuf radar shows a narrow band of snow with a Georgian Bay
connection extending from Niagara County southeast to northern
Erie...Genesee and Livingston counties. This should continue to
settle south through this morning which would bring it across metropolitan
Buffalo and into Wyoming counties. This band could bring a brief
period of intense snows with reduced visibility and a quick fresh
coating of maybe an inch of snow as it shifts south.

Across the Southern Lake Ontario shoreline multiple narrow bands of
lake effect snow will continue to impact the southern shoreline
counties where warnings will remain up. An additional inch or two of
snow is possible from Niagara east to Monroe counties from these
lake snows.

Further South...Lake snows have largely settled south toward Erie PA
with just some scattered snow showers across the southern tier. The
latest hrrr model indicates the narrow band of snow near Erie will
shift back north across Chautauqua and Cattaraugus counties this
afternoon with a potential for 2-3 additional inches of snow which
is why the lake effect snow warnings will remain in effect despite
this the current lull in activity.

Ktyx radar continues to show several narrow bands of lake effect
snow impacting northeast Wayne...northern Cayuga and Oswego County
which may bring an additional 1-3 inches through today. There are
also some light snow showers further north drifting across Jefferson
and Lewis counties which should only bring up to an additional inch
through today.

Outside of the Main Lake effect snow areas...the remainder of the
region will just experience much lighter and much more scattered
transient lake and orographically-driven light snow showers...with
only minor additional accumulations expected. Otherwise it will
be cold and on the brisk side again...with daytime highs only
ranging from around 10 above across the highest terrain to the middle
teens elsewhere.

Tonight...a continued west-northwesterly flow will continue to
maintain weaker lake snows southeast of the lakes for a good
portion of this evening...with this activity being held more
in check by the aforementioned lowering capping inversion...
which will run between 3 and 5 kft off Lake Erie...and will drop
to between 4 and 5 kft off Lake Ontario. After that time...gradual
backing of the low level flow to westerly and then west-southwesterly
in advance of an approaching Arctic front will result in the lake
bands slowly migrating northward through the balance of the night...
with the Lake Erie activity reaching the Buffalo southtowns...and
the Lake Ontario lake snows reaching the Tug Hill region by
daybreak. While a continued lower cap and increasing amounts
of directional shear below it should keep the migrating lake
snows from becoming terribly organized...the gradually increasing
fetch across both lakes should allow for at least some increase
in strength late...enough for the bands to produce an additional
inch or two of accumulation during their northward migration.
At this point it appears that the more significant accumulations
from these will hold off until during the day on Friday...when
deepening moisture and a rising cap out in advance of the
approaching Arctic boundary should allow for a noteworthy uptick
in band organization...more on which is discussed in the short
term section below.

Outside of the lake snows...expect a quiet and largely dry night
tonight...with lows ranging from around zero across the north
country to the 5 to 10 above range elsewhere. Given a developing
warm air advection regime...these will likely occur around
midnight...before giving way to slowly rising temperatures
overnight.

&&

Short term /Friday through Friday Night/...
Lake snows will reorganize and intensify Friday as the flow backs
to southwest in response to a weak low dropping south from Canada
and ahead of the advancing Arctic boundary.

Off Lake Erie...forecast soundings continue to show a fairly well
aligned southwest flow low level flow developing early Friday.
Initially moisture will be limited...but with the approach of the
low and long fetch down the lake...expect a fairly consolidated and
intense lake effect band to develop. Consensus high resolution
guidance continues to reflect these trends. The rgem along with the
NAM/GFS all suggest a strong convergence should continue to lift
northward into Buffalo metropolitan area during the day Friday. Favorable
lake parameters will exist with plenty of over-lake instability as
inversion heights approach 10k feet within a well aligned southwest
flow...with the band possibly extending inland across Wyoming and
Genesee counties...and even perhaps as far north as Niagara and
Orleans counties if the flow can back enough. For now will maintain
the lake effect snow due to uncertainties in the exact placement of
the heaviest band.

Off Lake Ontario...a well aligned southwesterly flow is forecast to
develop Friday similar to Lake Erie. This will not only tap into
moisture from an approaching shortwave...but also moisture from
whatever forms off Lake Erie. This will bring the potential for
significant snows on Friday into Friday night for Watertown and
vicinity...with the band possibly extending inland across northern
Lewis County. 850 mb temperatures around -16c and inversion heights
forecast to rise to nearly 15k feet and a favorably dendritic snow
growth zone should provide favorable parameters for significant
snows. Will maintain the lake effect snow watch for Jefferson County
and add Lewis County with the potential for significant lake snows
reaching the northern part of the County.

On Friday evening...a powerful Arctic front will surge south across
the region. This Arctic front will likely capture and merge with the
lake effect snow band off Lake Ontario...with a very heavy snow
squall passing south across the Eastern Lake Ontario region. This
will likely produce an inch or two of snow in many areas...with
locally higher amounts southeast of the lakes where the lake
contribution maximizes. Behind the Arctic front...multiple streamers
of lake effect snow showers will develop south of the lakes late
Friday night as flow becomes northwest and eventually north
northwest. The front will also usher in bitterly cold temperatures
which will be below zero in most areas by daybreak Saturday.

&&

Long term /Saturday through Wednesday/...
a frigid Arctic airmass will take hold of the eastern Great Lakes
and New England this weekend. A consensus of 12z guidance drops
850mb temperatures to around -30c at Buffalo during the day at
Buffalo...with -33c across the Eastern Lake Ontario region. The
coldest temperature ever recorded at 850mb on a kbuf sounding in the
month of February is -28c...and the coldest ever recorded for any
month is -32c.

This will result in bitterly cold temperatures during the day
Saturday with daytime temperatures struggling to rise above zero.
Daytime highs will almost certainly be below zero in the Eastern
Lake Ontario region. Persistent winds of 10 to 15 miles per hour on Saturday
night will limit radiational cooling...but even so it will be very
cold with below zero lows region-wide. Lows of -20f or colder are
possible across the north country with no moderating lake influence.
The combination of moderate winds and frigid temperatures will
produce dangerously cold wind chills late Friday night through early
Sunday morning. Issuing a wind chill watch for the entire
County Warning Area...areas near the lakeshores may only reach advisory criteria
however need to highlight this dangerously cold weather.

The frigid north flow over the lakes will produce widespread lake
effect snow showers across western and central New York. Despite the
extreme instability...airmasses this cold are also very dry and
temperatures become too cold for dendrites. This will force
snowflakes to be very small and limit accumulations...although
several inches are likely south of both lakes. The lake effect snow
will diminish in coverage and intensity Sunday. 12z guidance is a
bit faster moving the surface ridge across the region...with lake
effect snow likely to taper off by Sunday night.

After this there is general model agreement that temperatures will
warm back to near normal early next week. However...the 12z European model (ecmwf)
is significantly different from the GFS/ggem. The European model (ecmwf) has
consistently developed a strong wave of low pressure with
significant quantitative precipitation forecast across our region which would fall as rain or
snow. The ggem/GFS have this system but keep it well to our
east...and instead are a bit colder with a chance for light snow
showers. The forecast will reflect a consensus between this
guidance...with near normal temperatures and chance probability of precipitation.

&&

Aviation /16z Thursday through Monday/...
Lake effect snows and attendant IFR/LIFR will be found east-
southeast of the lakes today and into this evening...with MVFR/VFR
conditions and much more scattered snow showers prevailing
elsewhere. Expect the most significant lake snows of the day to
come this morning...with the activity then gradually weakening
from west to east this afternoon and evening in conjunction with
diminishing upstream connections...the intrusion of drier air
aloft...and a lowering capping inversion.

From the late evening hours on through the remainder of
tonight... gradual backing of the low level flow to westerly and
then west- southwesterly in advance of an approaching Arctic front
will result in weaker lake snows slowly migrating northward...with
the Lake Erie activity reaching the Buffalo southtowns...and the
Lake Ontario lake snows reaching the Tug Hill region by 12z
Friday. Expect IFR/MVFR to prevail within the migrating lake
snows...with general VFR conditions the rule elsewhere.

Outlook...
Friday...IFR/MVFR with snow showers likely...and areas of
heavier lake effect snow east/northeast of the lakes.
Saturday...IFR/MVFR in lake effect snow showers south of the lakes...
with MVFR/VFR across the north country.
Sunday...a chance of IFR/MVFR in weakening lake effect snow showers
south of the lakes...otherwise MVFR/VFR.
Monday...mainly VFR with a chance of snow showers.

&&

Marine...
a brisk flow of progressively colder Arctic air will continue to
overspread the region through the weekend...resulting in a prolonged
period of advisory-worthy winds and waves across the lower lakes.

In addition to the above...the passage of an Arctic cold front later
Friday afternoon and Friday evening will also usher in a truly frigid
airmass for later Friday night and the upcoming weekend...which in
conjunction with the aforementioned winds will result in a greatly
heightened potential for heavy freezing spray.

&&

Buf watches/warnings/advisories...
New York...Lake effect snow watch from late tonight through late Friday
night for nyz007-008.
Wind chill watch from late Friday night through Sunday morning
for nyz001>008-010>014-019>021-085.
Lake effect snow warning until 4 am EST Friday for nyz004>006.
Lake effect snow warning until 4 PM EST this afternoon for
nyz001>003-019-020.
Lake effect snow watch from late tonight through Friday
evening for nyz012-019-020-085.
Lake effect snow watch from late tonight through Friday
evening for nyz010-011.
Marine...Small Craft Advisory until 7 PM EST this evening for lez020.
Small Craft Advisory until 7 PM EST Saturday for lez040-
041.
Small Craft Advisory until 7 PM EST this evening for
loz030.
Small Craft Advisory until 7 PM EST Saturday for
loz042>045.

&&

$$

Synopsis...AR/jjr
near term...jjr/Smith
short term...Levan/tma
long term...apffel/Levan
aviation...jjr/Smith
marine...jjr/Smith

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