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Area forecast discussion 
National Weather Service Buffalo New York
645 PM EST Friday Dec 19 2014

high pressure will build from the central Great Lakes to New England
this weekend...while bringing drying conditions and near normal
temperatures to our region. This will be followed by a warming trend
early next week...with a storm system then developing over the Great
Lakes around the Christmas Holiday and potentially bringing our area
a round of gusty winds...along with rain eventually changing over to
some snow.


Near term /through Saturday/...
this will be a quiet period as high pressure draped across Ontario
province and the central Great Lakes builds eastward across New York
state. This will promote dry weather...though lower clouds will
linger in place across much of the area as low level moisture
remains trapped underneath a strong and slowly lowering subsidence
inversion. The main exception to this will be across the north
country...where stronger drying and the lack of an off-lake flow
should allow skies to at least partially clear tonight...then remain
partly sunny on Saturday. Elsewhere...some partial sunshine may also
develop across extreme far western New York during Saturday...while
mostly cloudy skies remain the general rule elsewhere.

Given the expected cloud cover and the lack of any real airmass
change...temperatures will largely continue to exhibit a small diurnal
range in the near term. Lows should mostly be in the lower to middle
20s tonight...with highs in the upper 20s to lower 30s then
following for Saturday. The one exception to this will again be
across the north country...where the aforementioned partial clearing
and drier overall airmass should allow temperatures to fall into the 10 to
15 degree range tonight...before recovering to the upper 20s on


Short term /Saturday night through Monday night/...
Saturday night and Sunday high pressure will remain ridged across
the northeast states. This will keep seasonable temperatures in
place with light winds and fair weather. Low clouds will linger
overnight trapped beneath the low level inversion but the inversion
will weaken on Sunday as the surface ridging relaxes. This may bring
a short opportunity to finally see some sunshine by the afternoon

Sunday night through Monday night a strong shortwave trough will
dive across the northern plains carving out a longwave trough across
the central states. This will form a surface low following a similar
path with southerly flow and moisture advection occurring across the
eastern Great Lakes. This will bring back increasing cloud cover
with warming surface temperatures and rising dewpoints. Some weak surface
ridging will linger across our region with weak isentropic upglide
mainly contributing to overcast middle and high clouds with just a
chance of light snow or rain later Monday into Monday night as
profiles moisten from the top down. If precipitation arrives a bit
faster than expected as often occurs in warm advection...a thin
layer of warm air overriding subfreezing surface temperatures may bring a
wintery mix mainly across the higher terrain before changing over to
all plain rain. Highs Monday will rise into the middle to upper 30s
across western New York with some Lake Shore areas reaching 40
degrees. The North County will remain a bit cooler only warming into
the middle 30s. Warm advection and southerly flow Monday night will
keep mild temperatures not falling much Monday night.


Long term /Tuesday through Friday/...
all eyes then focus on the potential for a travel disrupting winter
storm across the Great Lakes and northeast states leading up to
and following the Christmas Holiday. The overall theme will be a
complex area of low pressure spinning across the Great Lakes with
and associated cold/occluded front shifting northeast across the
Ohio Valley...mid-Atlantic and northeast states. On Christmas evening
warm moist air advecting north ahead of the front will bring rain
with mild temperatures to western and north-central New York. A
period of gusty winds is likely along and just behind this front
then cold air advection will bring a changeover to snow on
Christmas day as temperatures cool along with another period of strong
winds possible.

Finer details...on Tuesday into Tuesday night isentropic upglide and
warm air advection will bring chances for rain showers across our
forecast area. Guidance indicates surface temperatures will warm
into the 40s then remain nearly steady or rise Tuesday night
reaching near 50 degrees by Christmas evening. 90 percent of naefs
ensemble members indicate above climatology precipitable waters so there could be some
periods of moderate rainfall during Tuesday into Wednesday.

The cold/occluded front looks to cross western and central New York
on Christmas evening. A 50-60kt low level jet out in front may bring
some strong convectively driven winds but there is also a downslope
wind threat as winds forced over the higher terrain of the southern
tier and Tug Hill descend down to the Lake Shores. Following the
frontal passage cold air will begin to work across the lower Great
Lakes region. Without a steep ridge in the west the source region of
this cold air will be Pacific based and not Arctic based so this
lack of an Arctic airmass will bring a reduced threat of any
significant lake snows developing as 850mb temperatures should only drop to
around -8c to -10c. This will be cold enough however for an overall
change from rain to snow with a lake enhancement pending available
Post-frontal moisture.

Another period of strong winds is possible on Christmas day within
the colder airmass behind the front. Cold air advection will steepen
low level lapse rates helping to mix 850mb winds of 40-50kts down to
the surface. The 12z European model (ecmwf) is a bit stronger with this low level jet
showing 50-60kts. There is still lack of finer details in exact
timing and location of the weather impacts during the week of
Christmas. The forecast will continually be updated as we get closer
and those with travel plans will want to pay close attention to
these forecast updates throughout the weekend into next week.

Beyond Christmas...models show a brief period of fair weather
possible on Friday as shortwave ridging quickly shifts across the
lower Great Lakes. Further out we will be watching next weekend for
another possible Great Lakes cutter storm which could bring another
round of gusty winds.


Aviation /00z Saturday through Wednesday/...
mainly MVFR conditions will prevail overnight as a low stratus deck
remains locked in place...with some enhancement off the lakes. The
exception is at kart and the north country...where northerly flow
does not bringing added moisture from the lakes...resulting in VFR
conditions through much of the taf period. Kjhw in the higher
terrain across the southern tier could drop to IFR conditions

Saturday afternoon and night...gradual improvement to VFR area wide.
Sunday and Monday...VFR.
Monday night...mainly VFR with a chance of rain or snow.
Tuesday...VFR/MVFR with a chance of rain.
Wednesday...VFR/MVFR with rain...gusty winds are also possible.


high pressure building from central Ontario and the central Great
Lakes to New England will bring a period of relatively tranquil
conditions that will last through the upcoming weekend.

Looking further out into next week...relatively quiet conditions
should continue under a modest southeasterly flow regime Monday and
Tuesday...before a developing storm system potentially brings
stronger winds to the region Christmas evening and Christmas day.


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



near term...jjr
short term...Smith
long term...Smith

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