Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
704 PM EST Thursday Dec 12 2013
heavy lake effect snows will continue east of both eastern Great
Lakes tonight as a very cold air mass lingers across the Great Lakes
region. A cold front dropping southward tomorrow will Carry Lake
snows southward...and substantially decrease the snows by Friday
night. However any widespread accumulating snowfall will reach the
eastern Great Lakes region Saturday and Saturday night.
Near term /through Friday/...
radar imagery showing a narrow and very intense band of lake effect
snow off Lake Erie extending into the Buffalo metropolitan are and western
Genesee County. The band has shown some signs of drifting south over
the past 45 minutes...and this trend will continue with the band
sinking back into the southern and eastern suburbs through 8pm.
Snowfall rates of 2-3 inches per hour within this band. The band
will also move onshore along the Lake Erie shore of southern Erie
and Chautauqua counties by 8pm with rapidly deteriorating travel
Of Lake Ontario a band of heavy snow extends through southern
Jefferson and west central Lewis County with 2-3 inch per hour
snowfall rates. Recent radar trends suggest the band may sneak a few
miles farther north through 8 PM. After that...it should stay in
place then drift back south across the Tug Hill overnight.
off Lake Erie...
Expect an additional 6 to 12 inches of snow overnight in the most
persistent bands from the Buffalo area down into the southern tier.
Winds will veer to a little more westerly later this evening and the
snow band will begin to drop southward back through the
southtowns...and into ski country overnight. Southwesterly winds up
to 40 knots in the 925 to 850 hpa layer will bring inland extent of
the band of snow to metropolitan Rochester briefly this early evening
before dropping southward. Also these winds will likely bring over
half a foot into western Genesee County and will upgrade this County
to a warning for the event.
Off Lake Ontario...
the long fetch...good moisture and cloud microphysics should
continue to produce prolific snowfall rates overnight with 2-4
inches per hour at times across the Tug Hill. If the band is able to
remain in once place long enough...overnight snow totals may
approach 20 inches in a few spots on the tug...with a foot or so at
lower elevations closer to the lake.
Later overnight a cold front...that is currently over the upper
Great Lakes will begin to drop southward over Lake Ontario. In
addition to the lake snows a sharp wind shift will bring a ribbon of
enhanced low level convergence...and with the still good moisture in
the lower levels expect a burst of snow along the frontal boundary
later overnight. This cold front will drop the snows to along and
southeast of Lake Ontario by tomorrow morning...and then snows
dropping southward of Lake Ontario through the day on Friday. It is
possible that this burst of snow could drop a quick inch or so of
snow within a hour or less time period...even in areas not typically
prone to lake effect snows.
By late Friday afternoon expect snow showers to be diminishing with
accumulating snow largely confined to higher terrain south of Lake
Expect another chilly night with below normal temperatures. Lows
will again drop down into the teens...with single digits likely
across interior southern tier and north country. In the typical
colder spots of the north country temperatures will again drop below
Tomorrow highs will only recover into the high single digits or
lower teens across the Eastern Lake Ontario region behind the cold
front...while south of Lake Ontario highs in the upper teens to
around 20 are likely. Behind the cold front temperatures will likely
remain steady or drop through the afternoon hours.
Wind chills tonight will drop down into the single digits across the
region...and down to -5 to -10f below zero inland across the
southern tier and north country. Through the day Friday wind chills
will remain in the single digits or lower.
Short term /Friday night through Sunday night/...
the focus for this period will be on the potential widespread snows
across western and north central New York. Latest model data...
although the NAM which seems to be an outlier...converging on
similar solutions for this weekend. Models continuing to advertise
the northern stream wave diving southeast across the Great Lakes...
while the southern stream wave ejects northeast from the lower
Mississippi Valley. As both upper waves approach the region
isentropic lift/warm advection ahead of a weak low level wave
lifting northeast from the Ohio Valley along with an inverted trough
will support a broad area of snow spreading into the area by early
Saturday. The isentropic lift and warm air advection look to
continue during the day Saturday as the surface wave tracks into the
lower lakes...although will be weakening as it does. The southern
stream surface reflection looks to become the dominant feature near
or off the East Coast into Saturday night as shortwave energy and
height falls crossing the Appalachians will Transfer energy to the
coastal low. As a result...confidence is increasing that at least
several inches of synoptic snow can be expected across the area
through the weekend...especially in the Saturday and Saturday night
time frame...we will therefore issue a Winter Weather Advisory at
this point to cover the anticipated threat.
After this...a broad west northwest flow will develop which will
result in the redevelopment of lake snows by later Sunday. Over-lake
instability looks to be more than sufficient...but moisture and
shear profiles not overly favorable for significant accumulations.
Long term /Monday through Thursday/...
northwest flow lake effect will likely be ongoing at the start of
the period. However...high pressure nosing down from central Canada
and the northern Great Lakes will likely limit significant
accumulations as drier air looks to greatly diminish favorable
dendritic snow growth region...with rather Low Lake equilibrium
levels. Lake snows should wind down later Monday as shear profiles
increase and warm air advection picks up. Medium range models in
fairly close agreement in bringing a clipper low across the region
in the Monday night through Tuesday night time frame with warm air
advection driven snows working across the region within this time
frame. Behind this clipper low there looks to be another shot of
modified Arctic air which may reinvigorate lake snows across the
region...but this may be brief as another clipper low arrives across
the region by Thursday.
Aviation /00z Friday through Tuesday/...
heavy lake effect snow bands...and placement will be the focus this
taf cycle. Expect IFR and lower flight conditions within the snow
bands...while outside of snowbands VFR flight conditions will
In the West...Lake snow band will shift southward soon after 00z
and exit the kbuf/kiag/kroc areas. Expect it to settle to the
southern tier and lower MVFR conditions to kjhw after 06z and as
winds shift to northwest and northerly conditions will deteriorate
to IFR/LIFR after 11z through 19z. This will also bring some lake
snow off Lake Ontario into the Niagara Frontier with MVFR
conditions at kiag and kroc during the afternoon.
East of Lake Ontario...a full lake fetch snow band is just south
of kart with occasional excursions affecting the airfield with IFR
conditions through 04z. The snow band will sag south of the area
after midnight and remain over northern Oswego County through the
night with MVFR ceilings at kart. A cold front will bring a final
burst of snow and veer winds from westerly to northwest to northerly
on Friday morning.
Friday afternoon...improving to VFR.
Saturday and Sunday...MVFR/IFR with snow...tapering off early Sunday
Monday...MVFR with a chance for snow showers. IFR with lake effect
snow likely southeast of the lakes.
Tuesday...MVFR with a chance of snow showers.
with a deep pool of cold air over the eastern Great Lakes right into
the weekend...and passage of several surface waves/low pressures
across the Great Lakes solid advisory-level conditions will persist
through the end of the week. The exception will be the eastern half
of Lake Ontario where winds will become border line gale strength
overnight tonight and into the morning hours Friday. Will issue a
Gale Warning for the eastern half of Lake Ontario to cover for this
potential. Will also place small crafts on the Niagara River for
late this afternoon through the overnight time period.
New York...Winter Weather Advisory from 6 am Saturday to 6 am EST Sunday
Lake effect snow warning until 1 PM EST Friday for nyz007-008-
Winter Weather Advisory from 10 am Saturday to 10 am EST
Sunday for nyz006>008.
Lake effect snow warning until 4 PM EST Friday for nyz006.
Lake effect snow warning until 5 am EST Friday for nyz010-011.
Marine...Small Craft Advisory until 7 am EST Friday for lez020.
Small Craft Advisory until 7 PM EST Friday for lez040-041.
Small Craft Advisory until 7 am EST Friday for loz030.
Small Craft Advisory until 7 PM EST Friday for loz042.
Gale Warning until 10 am EST Friday for loz043>045-063>065.