Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1140 PM EST Tuesday Jan 27 2015
high pressure will move overhead Wednesday...followed an area of low
pressure that will bring widespread snow to western New York on
Thursday. Another area of high pressure will move in later Friday
and cross the state for part of the weekend...before another low
brings a threat for more accumulating snow toward the end of the
weekend and into Monday. A blast of cold air will follow the low
with localized lake effect snow together with blustery conditions
Near term /through Wednesday/...
regional radars this evening display quiet conditions across wny and
ncny. Across our far eastern areas clouds associated with the East
Coast storm system will continue to fade through the overnight
hours. Clear skies will rule across wny.
With fresh snow-pack...particularly over the southern tier together
with clear skies and a decoupling wind field aloft as high pressure
approaches from the west...expect good radiational cooling for much
of the interior sections of western New York. Expect lows in the single
digits near the lakeshores and 0 to 10 below zero over the southern
tier/Eastern Lake Ontario region.
High pressure will move overhead or just south of New York state Wednesday for
clear skies across all of wny and ncny.
Short term /Wednesday night through Friday night/...
surface high pressure over the lower lakes Wednesday evening will
quickly drift to the East Coast by Thursday morning. The high will
briefly provide mainly clear skies and light winds during the
evening allowing for some early radiational cooling. This should
allow temperatures to drop into the single numbers in most areas with the
colder southern tier valleys and Tug Hill region possibly dropping
below zero. Overnight southerly flow will increase as the pressure
gradient increases between the departing high and low pressure
moving into the western lakes. The warm advection will bring
increasing high clouds...and also allow temperatures to begin to rise after
Thursday and Friday a progressive middle level trough will move through
the Great Lakes. Overall model quantitative precipitation forecast seems overdone given the low
track to our north...and the relatively weak nature of the system.
An embedded middle level vorticity maxima and associated surface low
will cross the region late Thursday afternoon and night...with the
surface low passing just north of lakes Erie and Ontario. Large
scale ascent in the form of DPVA and upper level divergence will
increase from west to east ahead of the trough on Thursday...with an
initial push of low/middle level warm advection also providing ascent.
This will bring an increasing chance of snow during the day from
west to east. A surge of milder air will move into the region with
the surface low tracking just north of the region...aided by south-southwest
downslope flow. This will push temperatures into the middle 30s for awhile
during the afternoon and evening on the lake plains of western New York
which will greatly limit snow accumulation initially at lower
Thursday night into Friday morning the surface low passes by...with
another middle level vorticity maxima embedded within the trough
providing large scale ascent and the surface cold front providing
another period of enhanced low level convergence. This will continue
to support periods of snow across the entire region...with upslope
flow developing overnight as boundary layer flow becomes more
westerly and then northwesterly by Friday morning. The combination
of added lift from upslope flow and somewhat cooler surface
temperatures across the higher terrain should allow the greater snow
amounts to focus across the higher terrain south of Buffalo and also
the Tug Hill region. This may bring totals into the 3-5 inch range
for Thursday through early Friday morning in these areas. Elsewhere
the marginal temperatures initially should keep amounts in the 1-3
inch range...with most of that coming Thursday night.
Much colder air will surge into the region on Friday behind the
surface low...with cold advection forcing temperatures to drop sharply from
late Thursday night through Friday. Temperatures may still be in the 20s
before daybreak Friday...but will then drop through the teens and
into the single numbers during the course of the day. Northwest flow
will support some lake response with moderate instability
developing...however a relatively dry airmass and lack of
connections to upstream lakes should keep this relatively light. The
northwest flow will favor multi-bands over a wide area south of Lake
Ontario...with the most persistent snow likely to be found from the
eastern suburbs of Rochester to Oswego County. Northwest upslope
flow and possibly some moisture from Lake Huron may also produce
some enhancement along the Chautauqua ridge. These areas may see an
additional 1-3 inches on Friday...but overall amounts will be light.
Limited northwest flow lake effect will continue Friday night
southeast of Lake Ontario with any additional amounts very light.
Temperatures will continue to drop to below zero in many areas
except the immediate lakeshores. The combination of wind and cold
temperatures may produce advisory criteria wind chills Friday afternoon and
Long term /Saturday through Tuesday/...
cold northwest flow may still support a Few Lake effect flurries or
light snow showers Saturday morning southeast of Lake Ontario...but
otherwise high pressure will build into the lower lakes and provide
a return to dry weather.
The operational model guidance has come into better agreement over
the past 24 hours with the handling of the system for Sunday and
Monday. Both the 12z GFS and European model (ecmwf) take a surface low from the lower
Ohio Valley Sunday to to the middle Atlantic or southern New England by
Monday as a southern and northern stream trough interact and phase.
This track and stream interaction would produce a solid shield of
accumulating snow to the north of the low track...including our
entire region. It should be noted that there is still a great deal
of spread amongst the 12z gefs ensembles with the timing and track
of this system...with some members keeping this system suppressed
and well south of our area...and some with timing almost 24 hours
different than the operational guidance. Given this ensemble
uncertainty and the time range...this system is still relatively low
confidence. Nonetheless with the GFS and European model (ecmwf) support have
increased probability of precipitation into the low likely range.
Behind this system another shot of Arctic air enters the region
Monday night and Tuesday. Both the GFS and European model (ecmwf) hint at the
potential for a west-northwest flow lake effect event...but obviously this is
subject to change being 7 days out.
Aviation /04z Wednesday through Sunday/...
at 06z VFR flight conditions were found...and is expected across all
wny for the remainder of the taf period as the high pressure moves
slowly east. Wednesday evening and night clouds will begin to
thicken aloft ahead of the next shortwave nearing US from the west.
Winds will remain light through the taf cycle...for the most part
less than 10 knots.
Thursday...IFR in snow by afternoon.
Friday...a chance of snow showers especially southeast of the lakes.
Saturday...no significant weather expected.
Sunday...increasing chance for IFR conditions in snow.
north winds generally 15 to 25 knots this evening will diminish as
high pressure moves toward the region from the west. Wind direction
will slowly back to the west Wednesday and eventually to the south
Marine...Small Craft Advisory until 4 am EST Wednesday for loz042>044.