Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1008 am EST Friday Dec 6 2013
generally cloudy skies and colder conditions will prevail the rest
of today. A wave of low pressure will lift northward along a nearly
stationary frontal boundary to our east. This will bring another
round of light snow starting tonight. Cold conditions will remain
in place through the upcoming weekend.
Near term /through tonight/...
the upper level pattern this morning shows an expansive polar low
centered over James Bay extending westward across the southern
prairie provinces to down along the US/Canadian border. A large
upper high is in place over the Gulf of Mexico with an enhanced
southwest flow that extends from central Texas to New England.
Water vapor satellite imagery shows an atmospheric river of
moisture embedded within this southwest flow. At the surface a
cold front stretches from the mouth of the Mississippi River
northeast off the New England coast.
The main upper level jet is passing by to the north this morning
with little lift overhead. As the rear entrance region of the jet
moves in to the region later this afternoon and evening...more
lift is expected with a weak surface low developing well southeast
of the region along the slow moving frontal boundary. This should
set up a fairly tight gradient of snow over western New York...with
little or no snow over Niagara County but up to about 6 inches
over far southeast Allegany County tonight.
Will adjust the Winter Weather Advisory for timing...removing most
of today and restarting the advisory at 4pm this
afternoon/evening. Will draw the line roughly along Route 20a into
the western Finger Lakes region...with the highest amounts focused
along the southern tier. Forecast soundings support all snow so
will remove any mention of mixed precipitation.
Snow should start to taper off from west to east later tonight as
the surface wave shifts off the middle-Atlantic coast. The cold air
aloft...850mb temperatures dropping to around -12c will allow for a
limited response from the lakes toward the early morning hours of
Short term /Saturday through Monday/...
colder air advecting into the region will make for a chilly day on
Saturday with highs only topping out in the upper 20s to lower 30s
and generate enough of a lake response for lingering lake effect
showers the first half of the day before increasing middle-level dry
air/anticyclonic flow kill off activity off Lake Erie by mid-day.
The longer fetch off Lake Ontario may allow light snow showers to
linger through the rest of the day and into Sat night...though by
late Sat night weakening flow as surface high pressure moves
overhead should bring an end to any activity. The aforementioned
area of high pressure will bring light winds Saturday
night...however lingering lake induced cloud cover should limit
radiational cooling across many areas...keeping lows in the 20s.
Portions of the southern tier and north country should still see
enough clearing to manage to drop into the teens overnight.
Look for a quiet day Sunday as high pressure drifts off to the east
across New England. Increasing southerly flow ahead of an
approaching warm front will bring increasingly cloudy skies from the
south during the day.
Isentropic uplift along the warm front lifting north across the
region ahead of a developing surface low over the central Great
Lakes will generate widespread precipitation across the region starting
near the PA border Sunday evening and working its way into the north
country after midnight. At this point general consensus among models
is that the best dynamics/DPVA will remain over Canada while deeper
moisture advection will be found to our east across central and
eastern PA/New York on the northern periphery of a secondary coastal low.
Therefore...expect precipitation to remain relatively light with only a
tenth of an inch or two at best. Regarding precipitation type...expect
precipitation to initially start out as light snow in the evening before
changing over to freezing rain as the warm nose aloft makes its way
over the area before changing over to rain as the boundary layer
warms above freezing towards morning. Given the expectation that
precipitation will be relatively light and the fact the temperatures
should warm above freezing...thus keeping the window for icing
rather small...will hold off on an advisory at this point...though
should the axis of deeper moisture wind up farther west this may
change. Nonetheless...motorists should be prepared for a period of
slick Road conditions...particularly across the southern
The bulk of the precipitation will taper off from southwest to northeast
on Monday as the warm front lifts into New England. Temperatures
will top out in the upper 30s to near 40 the axis of warmest air
crosses the area before temperatures fall back into the 30s during
the afternoon as the cold airmass currently over the northern plains
begins to filter across the Great Lakes. However...temperatures
should stay just warm enough to prevent lake effect from getting
going until Monday night.
Long term /Monday night through Thursday/...
latest GFS and European model (ecmwf) runs continue to show a deep middle level longwave
trough centered near Hudson Bay Monday night...with broad cyclonic
westerly flow developing across the Great Lakes region. The airmass
becomes plenty cold enough to support a lake response...with about
-16c at 850mb on Tuesday and perhaps a few degrees colder than that
Wednesday. The synoptic scale pattern fits the analog for
significant lake effect snow east of the lakes. The pattern would
suggest numerous small scale shortwaves traversing the mean west-northwest flow
aloft. Current guidance shows the most notable of these passing
just north of the lakes Tuesday night. Each of these waves can
result in subtle low level flow changes which can move lake bands
around and also modulate intensity and organization.
While the details cannot be predicted with any confidence at this
lead time...the pattern nonetheless appears very favorable for
significant lake snows east of the lakes. Stay tuned.
It appears most if not all of the snow Tuesday through Thursday will
be lake effect...so outside of lake effect areas expect just partly
As far as temperatures go...it will turn well below average by
midweek with highs only in the low to middle 20s and lows in the
teens...with single numbers possible in the normally colder
Aviation /15z Friday through Tuesday/...
VFR conditions today...then...a wave of low pressure well to the
southeast of New York will spread light to moderate snow with IFR conditions
over the southern tier to western Finger Lakes tonight. This will
mainly impact an area from about kjhw-to about or south of kfzy.
Then improving conditions toward daybreak Sat with the exception
of some limited lake effect on a northwest flow.
Saturday...VFR/MVFR with a chance of snow showers southeast of
Sunday night and Monday...VFR/MVFR with snow and rain likely.
Tuesday...mainly VFR but IFR with lake effect snow east of the lakes.
expect winds and waves to subside through today and generally
remain below advisory levels through the weekend as only a weak to
modest pressure gradient will be in place across the lower lakes
New York...Winter Weather Advisory from 4 PM this afternoon to 4 am EST
Saturday for nyz012>014-019>021-085.
Marine...Small Craft Advisory until 2 PM EST this afternoon for loz044-