Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
426 am EST sun Dec 8 2013
a cold flow off the Great Lakes will keep skies mostly cloudy across
western and north-central New York through this evening...along with
lingering snow showers east and southeast of the Great Lakes. High
pressure building over the region will bring some clearing overnight
before clouds increase ahead of an approaching warm front on Sunday.
The front will bring a mixed bag of precipitation Sunday night
before a cold front crosses the region Monday with seasonably cold
temperatures along with the potential for lake effect snows through
much of the coming week.
Near term /until 6 PM this evening/...
regional radars this late evening display a lake effect snow
band...broad and less intense this evening across the northeast tip
of Wayne County...Cayuga and into Oswego County and then points
inland. Over western New York light snow showers and flurries fly
generally south of Route 20 off Lake Erie...and also along the
southern shoreline of Lake Ontario. Infrared satellite imagery displays
drier air now to the north and west of Lake Ontario...with the
Georgian Bay moisture connection now greatly diminished.
Off Lake Ontario...surface analysis this late evening continues to
display a northwest wind across the northern shoreline of Lake
Ontario and across the north country...including west-northwest at
Watertown New York. South of the Lake A west to southwest flow is
found. This wind flow will likely maintain a lake effect snow band
through the night...though with drier air from upstream beginning to
entrain into the band...the snow band will likely remain light
through the remainder of the overnight. Moisture profiles continue
to display plentiful moisture from the surface upward through about
-18c...and with the low level lift from surface convergence...will
maintain the lake effect Snow Advisory for several additional inches
of snow on top of what has already fallen today and this evening.
The band of snow should lift back to the north later overnight as
high pressure from the Ohio Valley begins to push into the region
and winds back slightly.
Off Lake Erie...synoptic moisture is not as great and weak lift is
providing for light snow showers and flurries. Will continue with
low chance probability of precipitation through the night...with a possible additional half
to one inch of fresh snow across spots in ski County and the western
southern tier north of I-86.
Sunday...Lake effect snow east of Lake Ontario will continue to
weaken and become more cellular through the morning hours. Later
Sunday there may be a short lived break in the action as surface
high pressure moves across the region. Middle and upper level moisture
will then be on the increase by afternoon as the flow turns
southeast and warm advection increases. There could be some flurries
which breaks out across the southern tier very late in the day...but
model suggestion is to hold the main activity off until Sunday night
from the system approaching from the southwest. Bias corrected
numbers suggesting high temperatures Sunday in the middle to upper 20s.
Short term /Monday through Tuesday night/...
a complex surface weather pattern will be lifting north across New
York through Monday with double-barreled low pressure centers
lifting to our west and east. The western low is the deeper parent
low which will be centered near Lake Superior. A surface trough
and warm front will stretch from this low across the lower Great
Lakes region to a secondary low center just off the New Jersey
coast. Across New York in between the the two lows models show
warmer but drier air working north overrunning colder sub-freezing
Both NAM and GFS BUFKIT plan views show the impact of the warmer air
will be to raise the height of the prime dendritic snow growth zone
up to around 15kft while the drier air will strip strip away middle
level moisture leveling a saturated profile below 10kft. The
disconnect of the snow growth region and best moisture usually leads
to a drizzle or freezing drizzle environment. With surface temperatures
still below freezing early Monday have worded the forecast grids
with freezing drizzle instead of snow then as surface temperatures warm
into the upper 30s to around 40 through the day eventually see a
change over to drizzle across western and north central New York
through the day. The lingering low level moisture will keep overcast
low clouds through the day.
Colder air will work back across New York Monday night as winds veer
to westerly behind the departing storm system lifting across eastern
Canada. 850mb temperatures will drop to between -12c and -15c
through the night but the westerly flow across the lakes will have
limited synoptic moisture to work with. Will continue with focusing
lower chances of snow downwind of the lakes with the limited
moisture with maybe some snow flurries across the remainder of the
forecast area. Low temperatures will reach into the low 20s.
Through Tuesday a continued generally westerly flow will continue
across New York with synoptic moisture increasing ahead of a shortwave
that is forecast to shift across the Great Lakes. Further cooling of
850mb temperatures later Tuesday will lower the snow growth zone down to
around 5kft and raise lake inversion heights up above 10kft. This
combination will help lake effect snow bands to become better
organized over the lakes through the day with chances of lake effect
snows increasing east of the lakes right through the overnight
Still a little too far out to determine how much snow can be
expected and for more exact locations of the bands which will likely
pivot north some as the short wave approaches. Eventually lake
effect snow watches may be needed downwind of the lakes for a
several day event which could run through late Thursday. Outside of
the lake effect bands a brisk westerly flow with temperatures
limited to the 20s will make for a very chilly day. Wind chills will
linger in the teens all day.
Long term /Wednesday through Saturday/...
in the extended portion of the forecast...the center of the deep
upper level trough will only slowly drift from Hudson Bay into
northern Quebec Wednesday and Thursday...before ejecting eastward
into the Canadian Maritimes Friday and Saturday. Through at least
Thursday...this feature will maintain a broad cyclonic westerly
flow of cold air across the Great Lakes...with 850 mb temperatures
falling to as low as -18c/-20c by Thursday. Coupled with what
should be Richer/deeper moisture and a higher overall capping
inversion...this pattern will produce an environment favorable for
potentially significant lake effect snows to the east of the Great
Lakes...with their exact placement and intensity remaining
dependent on subtle smaller-scale shortwave features rippling east
through the larger scale upper trough and causing subtle
undulations in the low-level flow.
By the latter portions of the period...the medium range guidance
shows increasing discrepancies with both the timing and amplitude of
the next noteworthy surface trough...behind which a more northerly
flow of colder air appears poised to spread across the area at the
end of the week. Given the resultant increase in forecast
uncertainty...have elected to trend snow shower chances lower and
increasingly more broadbrush in nature for the latter portions of
the week. One thing that appears more certain is temperatures will remain
below average...with daytime highs remaining locked in the 20s
through the end of the week...and nighttime lows generally in the
single digits to middle teens each night.
Aviation /10z Sunday through Thursday/...
for the 06z tafs VFR flight conditions will prevail...except for
southeast of the lakes where bands of light lake effect snow
continues with MVFR...and even IFR southeast of Lake Ontario
continues. These bands of snow will impact the kjhw taf site
overnight...and later as the winds back some possibly near the kart
airfield tomorrow. Dry air will continue to weaken the lake bands
through the night and day tomorrow east of Lake Ontario. There will
be a brief quiet spell of VFR as winds become light and variable
before increasing in strength from the east.
With the easterly winds low clouds will wane...but middle and high
level clouds will increase through the day. Precipitation will reach
the southern tier early Sunday evening from a storm system lifting
through the Mississippi Valley and into the central Great Lakes.
Expect precipitation to remain all snow through 06z as it spreads
northward to taf sites south of Lake Ontario.
Sunday night and Monday...VFR/MVFR with snow and rain likely.
Tuesday through Thursday...mainly VFR but IFR with lake effect
snow east of the lakes.
advisory or near advisory level west-northwest winds will persist
through the night for many of the nearshore waters...especially
along Lake Ontario due to good over lake instability and a tight
enough pressure gradient. A brief return to lighter winds will
develop Sunday...before low pressure passes through the region
Sunday night and Monday. That feature will usher in another surge of
stronger winds...cold air and renewed marine headlines for an
extended period next week.
New York...Winter Weather Advisory from 11 PM this evening to 2 PM EST
Monday for nyz006>008.
Lake effect Snow Advisory until 10 am EST this morning for
Winter Weather Advisory from 9 PM this evening to 11 am EST
Monday for nyz001>005-010>014-085.
Winter Weather Advisory from 7 PM this evening to 1 PM EST
Monday for nyz019>021.
Marine...Small Craft Advisory until 7 am EST this morning for