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Area forecast discussion 
National Weather Service Buffalo New York
1026 am EST Tuesday Mar 3 2015

temperatures will rise into the 30s today and tonight as a warm
front pushes north across the lower Great Lakes. A wintry mix will
accompany the front bringing snow...sleet...freezing rain this
afternoon changing over to rain tonight. Colder temperatures will
return Wednesday as a cold front across there area with temperatures
running up to 20 degrees below normal Thursday into Friday helping
to drive lake effect showers east/southeast of Lake Ontario.
Temperatures will once again climb to within a few degrees of normal
by the coming weekend.


Near term /until 6 PM this evening/...

Only minor changes made to the morning update. Warm
advection/isentropic lift is under way across the region in
response to the rather large area of upper level divergence
extending from chi to near NYC on the south side of the 300 mb jet
core of around 130 knots. Regional radar mosaic shows a rather
extensive area of light snow extending from northern Indiana to near far
SW New York state. Mixed precipitation extends along and south of
I-90 through central Ohio and points west. Current forecast seems
reasonable with the expectation of 1 to 2 inches of snow before
transitioning to a mixture of sleet...freezing rain during the
afternoon. Enough warm air may move into the Lake Erie shoreline
plain to change all the precipitation to rain toward evening over
and southwest of buf. The change to all rain may extend east of
roc along the Ontario Lake Shore this evening while a few
locations in the higher southern interior may remain mixed near
elz. Made only slight changes to maximum temperatures and cloud cover.

Previous discussion... this morning regional satellite imagery
and surface analysis indicate that the much anticipated Colorado
low is taking shape over northern Colorado this morning while a broad
band of warm advection is showing up nicely in the form of a broad
swath of cloud cover extending from the High Plains across the
upper Midwest and southeast across Ohio/west PA. In fact the high
clouds forming the leading edge of this band are pushing across
western New York this morning. As clouds thicken through the
morning temperatures across far wny will rise a few degrees before

Cloud cover will continue to thicken and work its way east across
the forecast area. Precipitation will spread into far SW New York around
noontime as the leading edge of a zone of deep isentropic
uplift being supported by a 50 to 70kt 850mb jet arrives. Thermal
profiles will initially be cold enough to support all snow to start
with...however as we move through the afternoon hours and into the
early evening...substantial warming aloft above a stubborn
sub-freezing surface layer will create a widespread risk for
sleet/freezing rain across much of the forecast area. With precipitable waters
climbing in excess of 0... ranging from a couple of tenths to
a half inch will be possible across the region...distributed across
several precipitation types depending on elevation and timing. In general
most areas can expect around a half inch or so of wet snow this
afternoon before transitioning over to sleet/freezing rain.
Downsloping under brisk southerly winds will limit precipitation amounts
along Lake Erie...across the Niagara Frontier...north of The Finger
lakes to around a tenth or two of precipitation while amounts across
upslope areas of the western southern tier and The Finger lakes may
run as high as a third of an inch or more. Again...given that
surface temperatures are currently expected to hover near/just below
freezing...much of this precipitation is currently expected to fall as
sleet/freezing rain...resulting in what could shape up to be a very
hazardous evening commute this evening indeed. Needless to say...a
Winter Weather Advisory is currently in effect for all of western
and north-central New York for all of these hazards.

Colder antecedent air in place across the north country combined
with timing of precipitation and southerly upslope flow should allow for
greater snowfall totals to start with...generally 1-3 inches with 2-4
possible across the Tug Hill initially. However even this area is
expected to succumb to the warm advection aloft by this evening with
precipitation swapping over to sleet/freezing rain for a time. Eventually
much of western New York and The Finger lakes will warm above
freezing from west to east through the very late afternoon and into
the evening hours as the weak surface this point more of an
open wave...passes across Georgian Bay and the Ottawa Valley. This
will allow lingering precipitation to change over to all rain with precipitation
mixing back into snow or perhaps freezing rain/drizzle later tonight
as a cold front sweeps across the area. The one exception will be
across the Tug Hill where temperatures will struggle to break the
freezing mark and precipitation will likely revert back to snow as we move
through the night.


Short term /6 PM this evening through Friday night/...
cold air advection pattern will be well underway at the start of the
period behind the departing cold front. This will result in daytime
high temperatures Wednesday occurring in the morning and slowly fall
into the 20s during the afternoon. The incoming colder air mass will
change any precipitation which remains back over to snow.

Light lake effect snow showers expected within a fairly
unidirectional west northwest flow regime Wednesday night and
Thursday. Model soundings showing inversion heights rising to 6-8kft
for a period as a shortwave moves through...supporting at least a
period of minor accumulating snows for areas east and southeast of
Lake Ontario downwind of the open water.

Thursday will be a cold day as highs will struggle to reach 20 with
a deep pool of Arctic air over western and northern central New
York. Wind chill values likely as cold as 5 below at times...
especially away from any lake influences.

Lows Thursday night will be very cold...with low single digits on
the lake plains and single numbers below zero across the colder
interior locations. At least some limited lake effect snow will
linger southeast of Lake Ontario...but lowering inversion heights
and drying low levels should keep this limited.


Long term /Saturday through Monday/...
temperatures will remain below average through the long term period
as the longwave trough remains in place across eastern North
America...although not as extreme as what we have seen. A few weak
systems will move through the northwest flow aloft and bring a
chance of some light snow and reinforcing shots of colder air.

Looking at the details...on Friday high pressure will build from the
Ohio Valley into the middle Atlantic with a ridge extending northward
towards the lower lakes. This should keep the bulk of the area
dry...although westerly flow off Lake Ontario may still produce a
few snow showers east of the lake.

On Saturday both the GFS and European model (ecmwf) bring a weak middle level and
surface trough through the region with a chance of a few snow
showers. This is followed by high pressure on Sunday before another
trough and clipper low moves through the Great Lakes Monday with a
chance of light snow.

Looking a little farther ahead...medium range guidance and ensemble
members continue to suggest the potential for a pattern change
around the middle of the month. Both the GFS and European model (ecmwf) bring a
trough into the West Coast...forcing strong downstream height rises
and warm advection spreading into the central Continental U.S. By around March
11th or 12th. This should progress east towards the middle of the
month. Beyond that...gefs ensemble members suggest more of a typical
March pattern developing with swings up and down in temperature as
more progressive systems move east across the nation.


Aviation /15z Tuesday through Saturday/...
at 12z VFR flight conditions were found across the region. A warm
front will lift across the region today...bringing first a burst of
snow with IFR flight conditions. Expect the snow to arrive across
kjhw/kbuf/kiag between 16z and 19z...kroc/kart between 18z and 21z.

A southerly low level jet around 50 knots at 2k feet will cross the
region this evening. This feature will not only bring milder air
northward...but also bring possible low level wind shear. Within the warm air
advection regime mixing of the strongest winds aloft to the surface
will not be likely...but the tight pressure gradient at the surface
should be enough to maintain winds gusting 15 to 25 knots that would
minimize the low level wind shear potential.

After a several hour period of snow warmer air advancing northward
will transition this snow over to sleet/freezing rain and later this
evening plain rain. There may be a minor improvement in visibilities
as this transition occurs.

Colder air will then sweep across the region after midnight...and
change the rain back to snow. Additionally clouds will lower across
the MVFR near the lakes and IFR across the higher
terrain of the southern tier and east of Lake Ontario.

Light southeast winds this morning will increase in speed through
the day while veering around to southwesterly through the taf cycle.

Wednesday...breezy. MVFR with a chance of snow Showers. Lake effect
snow likely east and southeast of Lake Ontario. Thursday...MVFR with
a chance of snow Showers. Lake effect snow likely southeast of Lake
Friday and Saturday...mainly VFR.


south-southeasterly winds will strengthen Tuesday evening as an
area of low pressure skirts north of the lake...necessitating
small craft advisories from Hamlin beach to Mexico Bay. Fresh
westerlies will develop later Tuesday night into Wednesday in the
wake of a cold frontal passage with Small Craft Advisory
conditions developing across the rest of the open waters of Lake
Ontario and lasting through Wednesday night. High pressure crosses the
area once again Thursday...providing a brief respite before
southwesterlies freshen again Friday as low pressure once again
passes to the north of the lakes.


Buf watches/warnings/advisories...
New York...Winter Weather Advisory from 3 PM this afternoon to 4 am EST
Wednesday for nyz006>008.
Winter Weather Advisory from 2 PM this afternoon to 1 am EST
Wednesday for nyz003>005-013-014.
Winter Weather Advisory until 1 am EST Wednesday for nyz001-
Marine...Small Craft Advisory from 7 PM this evening to 8 am EST
Wednesday for loz043-044.
Small Craft Advisory from 11 PM this evening to 7 PM EST
Wednesday for loz042.



near term...
short term...
long term...

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