Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
652 am EST Tuesday Feb 9 2016
while a stalled storm system over the lower Great Lakes will keep
the region shrouded under clouds today...only light nuisance
precipitation is expected. As the system starts to move away
tonight...colder air will deepen in its wake with accumulating lake
snows developing east of both lakes. These lake snows will persist
into the weekend...at which time our first true Arctic airmass of
the season will invade the area. Frigid temperatures during the day
Saturday will hover within a few degrees of zero with dangerously
low wind chill values.
Near term /through tonight/...
despite an impressive synoptic pattern over the country...we can
generally expect a 'whole lot of nothing' to happen across our
region until later tonight when some lake snows will begin to be
A highly amplified +pna jet stream pattern will be in place across
the continent today. This will feature a stacked closed low over the
lower Great Lakes region...but with little to no real dynamics
remaining within this mature system...we will only experience a
wealth of clouds with spotty precipitation. While there will be a
deep enough dendritic snow growth area within our cloud cover...the
lower boundary layer will warm to well above freezing by midday...so
the precipitation will become mixed with or will change to a little light
rain for some areas. The only real organized snow will be found
across the north country early this morning where some weak lift is
found in the vicinity of a stalled frontal boundary. Snow accums today
will range form a trace/coating in most areas to as much as an inch
north of the tug.
Tonight...the broad storm system will slowly 'open up' and drift
east to the Adirondacks. While general synoptic lift will remain
weak under the departing system...deepening cold air its wake will
establish enough lake driven instability to generate some lake
effect snow. This mesoscale lake response may take much of the night
to get going though...as Lake Delta t's should not reach critical
values until after midnight. The most likely area for lake snows by
daybreak will be across the southern tier where a couple inches of
accumulation will be possible along the Chautauqua ridge. Outside of
this lake effect...there will only be some scattered light snow
Short term /Wednesday through Thursday/...
the persistent surface low which has been meandering to our west
will finally move across the lower lakes early Wednesday morning
before rippling down the inverted trough into New England by
Wednesday afternoon. Moist cyclonic flow will increase as the low
moves east of our latitude...with several middle level shortwaves
providing additional large scale ascent. The synoptic scale moisture
and ascent combined with low level convergence will produce
widespread light snow Wednesday and Wednesday evening across the
region. Expect accumulations of an inch or two Wednesday and another
inch or two Wednesday night outside of lake effect areas. By
Thursday the general synoptic snow will be coming to and end outside
of lake effect areas.
As colder air filters into the region Wednesday lake enhancement
will become a concern...transitioning into more pure lake effect
Wednesday night and Thursday southeast of the Lakes. Lake induced
equilibrium levels steadily rise on Wednesday to around 10k feet by
afternoon...and remain there through Thursday as 850mb temperatures plummet
to around -22c.
Off Lake Erie...
Initially Wednesday this will be more of a lake enhancement and
upslope scenario with deep synoptic scale moisture and ascent still
in place. Westerly flow off Lake Erie will provide additional
moisture and some instability...with a strong upslope signature
noted in mesoscale model guidance along the Chautauqua ridge and the
Wednesday night the deeper synoptic scale moisture and ascent pull
away...leaving more of a pure lake effect scenario to unfold.
Westerly boundary layer flow initially during the evening will veer
northwest overnight. This will transition the lake enhancement into
multiple bands of lake effect snow primarily over Chautauqua and
Cattaraugus counties and possibly still clipping far southern Erie
County. Upslope will still play an important role...with the higher
snowfall rates likely focusing on the higher terrain just inland
from the lake.
The same pattern remains in place Thursday with northwest flow
producing multiple bands of lake effect snow across the western
southern tier...with greater amounts focusing across the higher
terrain just inland from the lake. Late Wednesday night and Thursday
the newest mesoscale model guidance suggests the potential for an
upstream connection to Lake Huron. These upstream connections are
often the key to achieving a more significant lake effect snow event
with northwest flow off Lake Erie...with notable contributions of
moisture and convergence coming from the upstream lake.
Given the above evolution...expect the heaviest snow to fall
Wednesday with the lake enhancement and upslope...and then again
later Wednesday night and Thursday morning if the upstream
connection to Lake Huron develops. With this in mind...we will go
with a lake effect snow watch for Chautauqua...Cattaraugus...and
southern Erie counties. The greatest amounts will likely fall in a
fairly narrow corridor just inland from the lake along the
Chautauqua ridge where totals from late tonight through Thursday
afternoon may reach 12-16 inches. Totals across the Boston Hills may
also reach 8-12 inches. Amounts will be considerably lower along
the Lake Erie shore...and also farther inland across the western
Off Lake Ontario...
Lake effect will be much slower to evolve as the boundary layer flow
will be disrupted Wednesday by the close proximity of the surface
low. Expect some lake enhanced snow to develop late Wednesday
afternoon and evening east of the lake across the Tug Hill as colder
westerly flow becomes established. Later Wednesday night through
Thursday boundary layer flow becomes west-northwest...allowing more pure lake
effect snow to develop southeast of the lake.
Mesoscale model guidance suggests the lake effect snow will spread
out with multiple bands along much of the South Shore from Niagara
County east to Oswego County. The 290 flow would suggest a relative
maximum in snowfall coverage and intensity across Wayne and northern
Cayuga counties extending into the Syracuse area. Farther west snow
showers will also impact the Rochester area. The current mesoscale
model guidance suggests the upstream connection with Georgian Bay
will end up across the Niagara Frontier late Wednesday night and
Thursday. Since the upstream connection is not forecast to link up
with the Better Lake Ontario banding across Wayne/northern Cayuga
counties...it appears watch/warning criteria is less likely off Lake
Expect snowfall amounts from Wednesday morning through Thursday
afternoon of 2-4 inches in general along the South Shore of Lake
Ontario. The somewhat better banding across Wayne and northern
Cayuga counties may produce 4-7 inches. The wildcard is the Georgian
Bay band...which may produce a few locally higher amounts to the
west of Rochester.
Temperatures will continue their downward slide with early day highs
on Wednesday in the lower 30s across lower elevations and middle to
upper 20s on the hills. Temperatures will drop during the afternoon
as cold advection increases in the wake of the departing low. By
Thursday highs will only be in the middle teens across lower elevations
and lower teens on the hills.
Long term /Thursday night through Monday/...
Lake effect snow will weaken initially Thursday evening as a narrow
surface ridge briefly crosses the lower lakes and brings increased
shear and dry air. Later Thursday night into Friday morning boundary
layer flow will back more westerly...with lake effect snow possibly
becoming better organized again east of the lakes.
Friday afternoon the Arctic cold front will approach...the cross the
region Friday evening. The Arctic front itself will produce a few
snow showers and possibly a snow squall. Expect lake effect snow to
intensify east of the lakes just ahead of the Arctic front possibly
producing decent accumulations...then move south overnight and break
apart into multiple bands south of the lakes as boundary layer flow
becomes northerly. Lake effect snow will then continue south of the
lakes Saturday through Sunday as true Arctic air pours across the
lower lakes. The instability will be extreme with such a cold
airmass...but all airmasses this cold are also very dry. The dry
air...short northerly fetch...and poor cloud microphysics in the
bitterly cold air will likely keep accumulations relatively minor
for Saturday through Sunday.
The big story this weekend will be the extreme cold. Medium range
guidance remains consistent in bringing the coldest airmass of the
winter by far into the lower lakes and New England. Both the GFS and
European model (ecmwf) take 850mb temperatures down to around -32c on Saturday. To put this
in prospective...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 frigid airmass will keep
highs in the lower single numbers on Saturday...and if the timing
works out with the core of the cold crossing during the day highs
may not get above zero. Lows Saturday night will be below zero
everywhere...and 20 below or better across the north country with no
lake influence. The combination of bitter cold and wind will produce
dangerously cold wind chills.
The core of the cold begins to move off by Sunday afternoon with a
rapid warm-up to near average by Monday. The next system will
approach by Monday with a chance of another general light snow.
Aviation /12z Tuesday through Saturday/...
a large storm system centered over the lower Great Lakes will
spread MVFR ceilings across the bulk of the region this morning...with
pockets of IFR ceilings. The most concentrated areas of IFR conditions
this morning will be across the higher terrain of the southern tier
(cigs) and also north of the Tug Hill (vsbys).
The MVFR/IFR conditions will marginally improve during the midday
and afternoon...then conditions will once again deteriorate during
the course of tonight. This will especially be the case over the far
western counties...where snow will reduce conditions to IFR during
the wee hours of the morning.
Wednesday through Thursday...MVFR/IFR in periods of snow.
Friday...MVFR. A chance of snow showers.
Saturday...VFR/MVFR...chance of snow showers.
a broad...stationary storm system will be centered over the lower
Great Lakes today. This will result in light to moderate breezes
this morning...then as we progress through the midday and
afternoon...southwest winds will freshen on Lake Erie. Winds and
waves will likely reach Small Craft Advisory levels on Lake Erie by late afternoon...
and will certainly be in place tonight. Meanwhile winds will remain
relatively light on Lake Ontario.
On Wednesday...the large storm system will push east across New
England and the Canadian Maritimes. This will promote fresh to
strong westerlies on both lakes Erie and Ontario...which will become
more northwesterly Wednesday night. A Small Craft Advisory will be needed to be
issued for Lake Ontario in a later forecast package.
New York...Lake effect snow watch from late tonight through Thursday
afternoon for nyz019-020-085.
Marine...Small Craft Advisory from 4 PM this afternoon to 2 PM EST
Thursday for lez040-041.