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Area forecast discussion 
National Weather Service Buffalo New York
1247 am EST Sat Nov 29 2014

Synopsis...
some left over lake effect snow east of both lakes will slowly move
northward and weaken tonight. On Saturday...a warm front will slowly
move northeast across New York Saturday and Saturday night and bring
with it the likelihood of some light snow changing over to rain as
the airmass warms with time. Behind the warm front...expect a
relatively warm Sunday but with scattered showers followed by a cold
front Sunday night...with colder weather next week.

&&

Near term /through today/...
the large scale pattern will feature an increasingly flat/zonal flow
through Saturday. At the surface...high pressure will move over/east
of the Appalachians. Meanwhile warm air will be advected into New York as
a weak low over the northern plains states moves toward the northern
Great Lakes region by Saturday afternoon. But first the Current Lake
effect activity will continue to weaken overnight as lake induced
equilibrium levels continue to lower and the lake bands become
increasingly sheared by warm advection aloft. 00z NAM BUFKIT profiles
show lieq heights of around 6kft off Lake Erie falling below 5kft by
midnight and 6.5kft off Lake Ontario falling below 5kft by 12z.

East of Lake Ontario...
ktyx showing very weakly organized broad reflectivity returns along
the southeastern Lake Ontario shoreline. As steering flow backs this
evening the swath of lake snows will wiggle northward shifting out
of Oswego County after midnight and falling apart toward Watertown
overnight. The lake effect snow warning for Oswego County remains
with light accumulations ongoing.

East of Lake Erie...
kbuf radar showing the earlier very weak lake effect band has broken
up as of 03z with some weak high level echoes present as warm
advection is ongoing aloft. The previous lake band has become too
sheared with instability too weak for any continued lake effect
impact.

The remainder of the region should experience partly to mostly
cloudy skies with slowly rising temperatures after about midnight as
warm air advection begins.

On Saturday...the main focus will be continued isentropic lift ahead
of the approaching warm front. The airmass should be sufficiently
moist enough to spit out some light snow...with rain on the back
side as a 1-3 hour window of precipitation moves across the
region...perhaps becoming scattered or not quite reaching areas east
of Lake Ontario. Quantitative precipitation forecast should be minor...well under .1 for the
duration of the event...and with steadily temperatures any snowfall
should be insignificant or quickly melting. Otherwise Saturday
should be cloudy with temperatures slowly rising through the 30s for
all but the Eastern Lake Ontario region.

&&

Short term /tonight through Monday night/...
Saturday night and Sunday our region will be placed between an area
of high pressure along the eastern Seaboard...and low pressure
cutting across the western Great Lakes and towards James Bay. A
southerly moist flow between these two systems will maintain
abundant cloud cover...but also allow for temperatures to slowly
climb through the night...up from their Saturday afternoon maximum.
There will remain weak isentropic upglide forcing Saturday night
through Sunday for which slight chance to low chance probability of precipitation will remain.
P-type will be tricky as point soundings show a mix of snow/rain
overnight transitioning to just plain light rain by Sunday morning.
However with the bulk of the moisture below the dendritic snow
growth zone...drizzle or even some freezing drizzle is a possibility
Saturday night before above freezing temperatures ensue. Greatest
potential for this freezing drizzle would be the valleys of the
southern tier and north country where a shallow sub freezing layer
near the surface may linger. For now given the uncertainty...will
just continue with the snow/rain chances in the grids and evaluate
as we draw closer to Saturday evening.

Temperatures will continue to climb through the day Sunday...as
strong warm air advection brings highs into the upper 40s to middle 50s
across the region. Even though we will remain cloudy on Sunday...the low
sun angle this time of year becomes less of a factor to air
temperature...with the warming aloft...and downslope effects
becoming the main determining factor for air temperature. Thus the warmest
areas Sunday should be the lower elevations south of the hills.

Sunday night temperatures will remain mild...and precipitation
chances will increase ahead of a cold front. This cold front will be
attached to an area of low pressure that will be crossing from near
James Bay Sunday night to northeast Quebec by Monday morning. Rain
showers will become likely later Sunday afternoon and through the
night as the cold front works its way across our state. A southwest
flow up Lake Erie should allow for additional moisture to pool ahead
of the cold front and as such will raise probability of precipitation to categorical for
much of western New York. As cold air races in behind the cold front
a few light snow showers late Sunday night are possible before
precipitation ends.

This cold front will cross the region late Sunday night...with air
temperatures continuing to fall through the day on Monday. A few
showers of snow or rain will linger Monday ahead of the shortwave
trough that will still be crossing our region. Synoptic showers of
rain and snow should end through the midday hours...but
precipitation will linger a little longer to the southeast of the
lakes where lake effect snow flurries and light snow showers may
fly. Behind this cold front high pressure/drier air will expand
eastward from the upper Great Lakes through the day. Too much drying
in the lower levels...and a low capping inversion/bit of wind shear
will likely keep the lake effect snow to a minimal through the day
Monday.

An area of high pressure will cross southern Canada through the
night Monday night. Drier air associated with this high pressure
will likely clear the clouds by evening time such that a clear sky
with little wind remains for the night. The only exception will be
southeast of the lakes where lake clouds may lingering into the
better part of the night before thinning. Expect a cold
night...especially across the north country where a bubble of -20c
850 hpa air will be skirting by. Lows temperatures for the north
country could plummet into the low single digits here. Otherwise
lows will generally be in the teens overnight with a light and
variable wind.

&&

Long term /Tuesday through Friday/...
Tuesday broad surface high pressure will be centered over SW Quebec
with an axis extending southward towards the Ohio Valley and Middle
Atlantic States. A shortwave ridge passing overhead should give
enough subsidence to support a mostly sunny day as winds veer around
to easterly. Though abundant sunshine the morning hours will still
be quite cold considering the single digit and teen temperatures
that we will be starting off with.

Tuesday night and Wednesday our flow will veer around toward
southerly...a direction that will bring warming aloft. There will be
modest isentropic upglide and a moistening airmass will eventually
support some light precipitation (snow/rain or possibly freezing
rain) later Tuesday night and through the day Wednesday. Greatest
chances for precipitation will be later Wednesday and Wednesday
night when the tail end of a Canadian cold front passes across the
eastern Great Lakes region. Additional lift from this feature may
bring light rain showers later Wednesday...possibly tapering off as
some light snow Wednesday night behind the cold front. Limited lake
parameters may allow for a lake effect snow response as cold air
deepens over the eastern Great Lakes...but for now the set-up for
snowbands looks poor with lake induced equilibrium levels below 5k
feet and a fair amount of wind shear and not the greatest amounts of
moisture.

Thursday and Friday the 12z operational model runs of the GFS/European model (ecmwf)
begin to diverge. The GFS slides an area of high pressure across the
western Great Lakes region on Thursday while the European model (ecmwf) drops this
high pressure towards the Ohio Valley...and subsequently pushes the
cold front much farther southward across the southeast.

Both models give evidence that after this cold front passes through
our region Wednesday/Wednesday night it will eventually return
northward as a warm front with a surface wave along the boundary.
The GFS is much quicker with the return flow...where as the European model (ecmwf)
which is a little more amplified in the pattern is slower...which
makes sense with the position of the surface high. For now will
leave chances for precipitation in both days...Thursday and Friday
due to the uncertainty of how the end of next week unfolds.

A clear start to the day Tuesday will start this time period off
cold...behind a recently departed cold front. Daytime temperatures
will average 10 to 15 degrees below normal. However the remainder of
the week looks to average around normal with the absence of any cold
Canadian airmass.

&&

Aviation /06z Saturday through Wednesday/...
VFR conditions are found across the region with the only exception
being kbuf/kiag with MVFR lake clouds/flurries. Only lingering lake
activity will continue to weaken overnight as the lower lakes become
under the influence of increasing shear and high pressure aloft.

On Saturday...a warm front will approach the region and bring the
likelihood of a 1-3 hour window of snow...changing over to rain on
the backside as the shield of precipitation quickly moves east
across the state. This area of precipitation should tend to fall
apart as it moves into the central portion of the state. Thus
expect some MVFR...but mainly VFR conditions.

Some low level winds shear is possible Saturday night as a 50kt low
level jet shifts across The Lower Lake region. Confidence remains
too low to include in the taf at this time.

Outlook...
Sunday...mainly VFR. Chance -ra. Sunday night...MVFR with -shra/shsn
with cold front. Monday and Tuesday...VFR.
Wednesday...mainly VFR with a chance of -ra.

&&

Marine...
high pressure centered over the Appalachians and off the East Coast
Saturday. A warm front will move into the region late Saturday and
Saturday night which may increase winds/waves back to advisory level
but the southerly flow would keep the highest waves toward the
Canadian water. A cold front will move across the region Sunday
night.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

Synopsis...Smith/zaff
near term...Smith/zaff
short term...Thomas
long term...Thomas
aviation...rsh/Smith/zaff
marine...Smith/zaff

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